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November 2011 www.defra.gov.uk
Revised Departmental Guidance
Prepared by Defra and the
Collaborative Centre of Excellence
in Understanding
and Managing Natural and
Environmental Risks, Cranfield
University
Guidelines for Environmental Risk Assessment
and Management
Green Leaves III
Authors
Áine Gormley, Simon Pollard, Sophie Rocks
Collaborative Centre of Excellence in Understanding and Managing Natural and Environmental Risks,
Cranfield University, Bedfordshire, UK.
Edgar Black Department for Environment, Food and Rural Affairs, UK
Editorial board
Jens Evans Environment Agency, UK.
Daniel Galson Galson Sciences Ltd., UK.
Emma Hennessey Department for Environment, Food and Rural Affairs, UK
Case study contributors
Daniel Galson Galson Sciences Ltd., UK
Andy Hart Food and Environment Research Agency, UK
Phil Longhurst, Joe Morris, Simon Pollard, Mick Whelan School of Applied Sciences, Cranfield University,
Bedfordshire, UK
Joseph Lovell Department for Environment, Food and Rural Affairs, UK
Peter Bailey, Cath Brooks, Anna Lorentzon, Ian Meadowcroft Environment Agency, UK
Edmund Peeler Centre for Environment, Fisheries and Aquaculture Science, UK
Jonathan Smith Shell Global Solutions, UK
Acknowledgements
The Department for Environment, Food and Rural Affairs (Defra) commissioned the Collaborative Centre
of Excellence in Understanding and Managing Natural and Environmental Risks at Cranfield University
to redraft these guidelines. The work was executed via an editorial panel representing Government,
academia and consultancy.
This Risk Centre is a strategic partnership between Cranfield University; Defra; the Engineering and
Physical Sciences Research Council (EPSRC); the Economic and Social Research Council (ESRC); the Living
With Environmental Change (LWEC) programme; and the Natural Environment Research Council (NERC).
We are grateful to members of these organisations for their support.
The authors and editorial board thank the peer reviewers of the draft Guidelines for their helpful
comments.
© Crown copyright 2011
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1
I am pleased to present “Green Leaves III”, the latest edition of our Guidelines for
Environmental Risk Assessment and Management.
When the Department of the Environment, Transport and the Regions and the
Environment Agency published the previous edition in 2000, it provided guidance in
risk assessment and risk management, along with risk communication, as essential
elements of structured decision making processes across Government.
Over a decade later, publication of this revised, peer-reviewed guidance emphasises
not only developments in scientific knowledge and information that supports risk
assessment, but also improves the relevance of risk assessment through case studies
that demonstrate good practice.
The assessment and management of environmental risk is central to the environmental vision and operational
activity of the Department for Environment, Food and Rural Affairs (Defra). At a strategic level, Defra
recognises the need to manage our activities in a way that minimises the risks of environmental damage,
while at the same time ensuring economic growth and social progress. Across our regulatory remit, we
are increasingly challenged to supply the scientific rationale for decision making in a timely manner. In
response, we facilitated the establishment of the Collaborative Centre of Excellence in Understanding and
Managing Natural and Environmental Risks (the Risk Centre) as part of a strategic partnership between
Cranfield University and the Research Councils. We have collaborated with the Risk Centre in preparing
these revised and improved guidelines.
Developments in the field of risk assessment and management are reflected in this revision. These include
pre-assessment considerations that help formulate the risk management question, tools and techniques
to deal with uncertainty, and the identification of a broader range of options to manage the risk as a
continuing process. This work is part of a wider set of actions to build a network of risk practitioners
and to encourage a more consistent approach to environmental risk assessment and management
within Defra.
Whilst the specific requirements of individual legislation will take precedence over this guidance,
I trust you will find it a valuable document and useful starting point for your work in this field.
Professor Robert Watson
Chief Scientific Adviser
Department for Environment, Food and Rural Affairs
Foreword
2
Executive Summary
This document provides generic guidelines for the assessment and management of environmental risks.
The guidelines supersede earlier versions published in 1995 by the Department of the Environment, and in
2000 by the Department of the Environment, Transport and the Regions and the Environment Agency. This
revision brings the guidelines in England and Wales in line with current thinking in the field of environmental
risk management. Methods are described for estimating the probability of harm to, or from, the environment,
the severity of harm, and uncertainty are described. The guidelines focus on generic principles, rather than
domain-specific risks, such as from river flooding, animal disease or hazardous wastes.
A cyclical framework for environmental risk management is provided to offer structure in what would otherwise
be a complex array of considerations for the decision-maker. The framework also offers a mechanism through
which the process of environmental risk assessment and management can be explained to stakeholders,
and acts as a valuable aide-mémoire to multidisciplinary teams conducting risk assessment. This framework
identifies four main components of risk assessment: (1) formulating the problem; (2) carrying out an assessment
of the risk; (3) identifying and appraising the management options available; and (4) addressing the risk
with the chosen risk management strategy. Each component has a dedicated chapter in the document that
provides guidance for completing that stage. The importance of iteration, communication and learning is
woven throughout the guidelines and reinforced in the closing chapter.
Essential components of environmental risk assessment and management that are conveyed in the
document can be summarised as follows. Risk questions are best informed by a range of stakeholders.
When a risk problem is highlighted, the source, pathways and receptors under potential threat should be
recognised. An assessment plan is then needed to outline the data requirements for assessment and the
methods needed for data collection and synthesis. Resources for the assessment can be allocated following
initial risk screening and prioritisation. Identifying the hazard at the beginning of the assessment should
clearly define the harm to the environment that is of concern. An estimation of the potential consequences
of the hazard being realised and an evaluation of the probability of impact can then be carried out.
This evidence collected is used to provide judgement as to the significance of the risk.
It is advisable to employ suitable techniques to analyse and understand uncertainties within the risk assessment
when possible. The risk management options should then be considered in terms of their positive and negative
effects according to technical and economic factors, environmental security, social issues and organisational
capabilities. The chosen strategy will usually involve terminating, mitigating, transferring, exploiting or
tolerating the risk. The implemented strategy should be monitored to ensure the risk is controlled to an
acceptable level. If this is not the case, iterations of the risk assessment and management processes should
proceed as necessary. In all the above, a clear organisational and people framework is required to ensure
accountabilities are understood. Each component should include openness and transparency, and involve
stakeholders when feasible. When communicating the risk management strategy to the public, it is essential
to highlight that the public have a responsibility to take reasonable care.
Case studies are provided throughout and used to illustrate key concepts. A comprehensive bibliography
is provided, followed by appendices on definitions, legislation, risk management at the institutional level,
and the types of uncertainty in risk assessment.
As with previous versions, we expect these guidelines to be consulted widely by environmental risk practitioners
across the UK Government and their agencies, by practitioners providing risk advice to Government, and by
other stakeholders with an interest in how environmental risks are assessed and managed.
3
Contents
Foreword ………………………………………………………………………………………………………………………….. 1
Executive Summary …………………………………………………………………………………………………………… 2
CHAPTER 1 ………………………………………………………………………………………………………………………… 5
Introduction to the Guidelines ………………………………………………………………………………………………… 5
1.1 Background ………………………………………………………………………………………………………………….. 5
1.2 Purpose and scope ……………………………………………………………………………………………………….. 5
1.3 Key definitions …………………………………………………………………………………………………………….. 6
1.4 A structured approach to risk management ………………………………………………………………………. 8
1.5 Outline of the guidelines ……………………………………………………………………………………………….. 9
CHAPTER 2 ………………………………………………………………………………………………………………………. 10
Formulating the Problem ……………………………………………………………………………………………………… 10
2.1 The importance of good problem definition …………………………………………………………………….. 10
2.2 Framing the question ………………………………………………………………………………………………….. 11
2.3 Developing a conceptual model …………………………………………………………………………………….. 12
2.3.1 Source-pathway-receptor (S-P-R) …………………………………………………………………………… 12
2.3.2 Factors controlling the hazard ………………………………………………………………………………. 13
2.3.3 Scenario building ……………………………………………………………………………………………….. 15
2.4 Planning the assessment ………………………………………………………………………………………………. 15
2.4.1 Stakeholder and public participation and engagement ……………………………………………… 15
2.5 Screening the risks ………………………………………………………………………………………………………. 17
2.6 Prioritising the risks …………………………………………………………………………………………………….. 19
2.7 Summary …………………………………………………………………………………………………………………… 21
CHAPTER 3 ………………………………………………………………………………………………………………………. 22
Assessing the Risk ………………………………………………………………………………………………………………. 22
3.1 Features of the risk assessment ……………………………………………………………………………………… 22
3.2 A staged approach to risk assessment …………………………………………………………………………….. 23
Stage I: Identify the hazard(s) ………………………………………………………………………………………… 23
Stage II: Assess the consequences ………………………………………………………………………………….. 24
Stage III: Assess their probabilities ………………………………………………………………………………….. 27
Stage IV: Characterise risk and uncertainty ………………………………………………………………………. 30
3.3 General issues in risk assessment …………………………………………………………………………………… 32
3.3.1 Direction, strength and weight of evidence …………………………………………………………….. 32
3.3.2 Expert elicitation ………………………………………………………………………………………………… 35
3.3.3 Dealing with uncertainty ……………………………………………………………………………………… 38
3.4 Summary …………………………………………………………………………………………………………………… 40
4
CHAPTER 4 ………………………………………………………………………………………………………………………. 41
Appraising the Options ……………………………………………………………………………………………………….. 41
4.1 Introduction ………………………………………………………………………………………………………………. 41
4.2 Structured decision making ………………………………………………………………………………………….. 42
4.3 Considerations in decision making …………………………………………………………………………………. 43
4.3.1 Reducing risks …………………………………………………………………………………………………… 43
4.3.2 The relevance and use of precautionary approaches …………………………………………………. 44
4.3.3 Environmental security ………………………………………………………………………………………… 44
4.3.4 Economic considerations …………………………………………………………………………………….. 46
4.3.5 Multi-criteria decision analysis ………………………………………………………………………………. 46
4.3.6 Involving stakeholders and the public ……………………………………………………………………. 47
4.4 Summary …………………………………………………………………………………………………………………… 49
CHAPTER 5 ………………………………………………………………………………………………………………………. 50
Addressing the Risk …………………………………………………………………………………………………………….. 50
5.1 Implementing the risk management strategy …………………………………………………………………… 50
5.2 Responsibility for residual risk ……………………………………………………………………………………….. 52
5.3 Reporting the risk management strategy ………………………………………………………………………… 52
5.4 Surveillance and monitoring of residual risk …………………………………………………………………….. 52
5.5 Contingency planning …………………………………………………………………………………………………. 53
5.6 Summary …………………………………………………………………………………………………………………… 55
CHAPTER 6 ………………………………………………………………………………………………………………………. 55
Cross-Cutting Aspects of Risk Management ……………………………………………………………………………. 55
6.1 Introduction ………………………………………………………………………………………………………………. 55
6.2 Learning ……………………………………………………………………………………………………………………. 55
6.3 An iterative approach ………………………………………………………………………………………………….. 55
6.3.1 Problem formulation …………………………………………………………………………………………… 56
6.3.2 Risk assessment …………………………………………………………………………………………………. 56
6.3.3 Options appraisal ……………………………………………………………………………………………….. 56
6.3.4 The risk management strategy ……………………………………………………………………………… 56
6.4 Communication …………………………………………………………………………………………………………. 56
6.4.1 The frequency of reporting ………………………………………………………………………………….. 57
6.5 Summary …………………………………………………………………………………………………………………… 58
REFERENCES …………………………………………………………………………………………………………………….. 59
Appendix 1: Definitions ……………………………………………………………………………………………………. 71
Appendix 2: Legislative requirements for risk assessment ………………………………………………….. 74
Appendix 3: Endocrine-disrupting chemicals ……………………………………………………………………… 76
Appendix 4: Classifications of uncertainty …………………………………………………………………………. 77
Appendix 5: Risk management at the institutional level ……………………………………………………. 78
CHAPTER 1
Introduction to the Guidelines
1.1 Background
This document contains generic guidelines for the assessment and management of environmental risks.
An original set of guidelines was published in 1995 by the Department of the Environment (DoE).
In 2000 the Department of the Environment Transport and the Regions (DETR), the Environment Agency
(EA), and the Institute of Environment and Health (IEH) published revised Guidelines for Environmental
Risk Assessment and Management. This new document replaces the earlier versions and brings
the guidelines in England and Wales in line with current thinking in the field of environmental risk
management. It has been peer reviewed and revised in light of comments received.
As with previous versions, we expect these guidelines to be consulted widely by environmental risk
practitioners across the UK Government and their agencies, by practitioners providing risk advice to
Government, and by other stakeholders with an interest in how environmental risks are assessed
and managed.
1.2 Purpose and scope
This document is intended to guide policy and regulatory staff in Government and its agencies, those
assessing and managing environmental risks for Government, and other parties in the principles of
managing environmental risks. The document assumes little prior knowledge and focuses on generic
principles rather than domain-specific risks such as those from river flooding, animal disease or hazardous
wastes. It is recognised that certain environmental risks (for example radioactive waste, flooding and
animal disease) have their own technical language, conventions and individual approaches to risk analysis
(Linkov et. al. 2006; Lundgren and McMakin, 2009). In these cases, additional guidance exists elsewhere
in the literature. However, specific guidance is not available for many kinds of environmental risks, and it is
intended that these guidelines may assist in setting out the general expectations and approach required.
The guidelines promote a structured approach to environmental risk management and provide advice
and information that is consistent with good practice. Guidance on the scientific aspects of risk
assessment is brought up-to-date where necessary. Methods for estimating the probability of harm to,
or from, the environment, and the severity of harm, and for evaluating uncertainty are described. The
guidelines promote the use of a generic framework to reach a decision on managing environmental risk.
Recent developments in environmental risk management referred to in this document include:
a) the structuring of scientific evidence that informs decisions on environmental risk;
b) practical experiences of deliberative and participatory decision-making;
c) an increased focus on the governance of risk, including the organisational and human aspects,
especially in light of the requirements for risk-informed regulation; and
d) developments in strategic and comparative environmental risk assessment.
This 2011 revision also provides an opportunity to furnish the guidelines with recent case studies and
exemplars from within and outside Government that illustrate good practice.
5
6
1.3 Key definitions
Several key definitions pertaining to environmental risk assessment and management are detailed below.
Appendix 1 provides a more exhaustive list.
s Decision-making: The process of identifying the likely consequences of decisions, establishing the
importance of individual factors (Figure 1) and selecting the best course of action to take to manage
an environmental risk.
s Environmental security: An environment protected from harm or adverse effects from natural or
human processes so that resources are sustained for future generations.
s Exploiting risk: Adopting a strategy to increase the likelihood of exploiting unexpected positive
effects (Hillson, 2001). Rather than hoping for an identified potentially positive effect to result from a
chosen strategy, exploiting the risk can involve making an identified opportunity happen.
s Governance: On a national scale, governance refers to the structure and processes for decision
making that involve non-governmental and governmental actors (Nye and Donahue, 2000). On a
global scale, governance represents an organised structure of regulation encompassing state and
non-state actors that bring combined decision making without the presence of one superior authority
(IRGC, 2005).
s Hazard: A situation or biological, chemical or physical agent that may lead to harm or cause
adverse affects.
s Risk: The potential consequence(s) of a hazard combined with their likelihoods/probabilities.
s Risk assessment: The formal process of evaluating the consequence(s) of a hazard and their
likelihoods/probabilities.
s Risk management: The process of appraising options for responding to risk and deciding which
to implement.
s Stakeholders: Individuals who are interested in, or affected by, an issue or situation.
s Uncertainty: Limitations in knowledge about environmental impacts and the factors that influence
them. Uncertainty originates from randomness (aleatory uncertainty) and incomplete knowledge
(epistemic uncertainty).
7
Figure 1: Assessing a risk involves an analysis of the consequences and likelihood of a hazard being realised.
In decision-making, low-consequence / low-probability risks (green) are typically perceived as acceptable and
therefore only require monitoring. In contrast, high-consequence / high-probability risks (red) are perceived
as unacceptable and a strategy is required to manage the risk. Other risks (amber) may require structured risk
assessment to better understand the features that contribute most to the risk. These features may be candidates
for management (HM Treasury, 2004).
In the public domain, the language of risk is often less precise. It may be thought of in at least five ways:
s activities that can be a source of risk, such as oil exploration;
s specific hazards that pose a threat, such as an oil spill;
s exposure to hazards, such as oil adhering to wildlife after a spill;
s the harm that might result from exposure, such as bleeding in the stomach if oil is ingested; and
s a loss of value placed on these consequences by society, such as temporal bird population declines
from exposure.
Also, emerging risks often generate public concern because they are usually assumed to be
uncontrollable, not well understood or not competently managed. Therefore, it is important to strive for
an environment of ‘no surprises’ and to consider social issues during all stages of risk assessment and
management so that the process helps to secure beneficial outcomes. These issues are discussed within
each chapter of the guidelines.
Likelihood

Medium	High	High
Medium	Medium	High
Low	Medium	Medium

Consequences
8
1.4 A structured approach to risk management
Risk management ‘frameworks’ have been developed in many countries and organisations, and are
used to act as route maps for decision-makers. The purpose of any framework is to offer some structure
to what would otherwise be a complex array of considerations for the decision-maker. Frameworks
are a guide rather than a rigid set of instructions. They can be useful in explaining to stakeholders the
process of environmental risk assessment and management and can be a valuable aide-mémoire to
multidisciplinary teams progressing with a risk assessment.
One example of a structured approach to environmental risk management is provided in Figure 2.
A cyclical approach suggests that environmental risk management is not a single, one-off exercise,
but a dynamic process. This framework identifies four main components:
(1) formulating the problem;
(2) carrying out an assessment of the risk;
(3) identifying and appraising the management options available; and
(4) addressing the risk with the chosen risk management strategy.
Each of these four components is illustrated in Figure 2 with additional considerations shown as
banners adjacent to each component. Some cross-cutting features are also shown in the middle of
Figure 2. Decision-makers should expect to have to reconsider their analyses and decisions as new
information comes to light (iteration), to communicate early and often, and to make arrangements for
implementing the learning that comes from assessing risks, so as to ensure a preventative approach to
risk management.
Not all risks require comprehensive and detailed assessment. Solid problem formulation should allow
decision-makers to evaluate the extent of subsequent analysis required. The level of effort put into
assessing each risk should be proportionate to its significance and priority in relation to other risks, as
well as its complexity, by reference to the likely impacts. Consideration should be given to stakeholders’
perceptions of the nature of the risk.
9
Figure 2: A framework for environmental risk assessment and management. The dashed line between the
‘formulate problem’ and ‘assess risk’ stages on the figure indicates the strong interdependencies between these
two stages.
1.5 Outline of the guidelines
In the remainder of this document, each component in Figure 2 has a dedicated Chapter (2-5) that
provides guidance for completing that stage. The importance of iteration, communication and learning
(shown in Figure 2) is woven throughout the guidelines and reinforced in the closing Chapter (6).
The document is structured as follows: Formulating the Problem (Chapter 2); Assessing the Risk
(Chapter 3); Appraising the Options (Chapter 4); Addressing the Risk (Chapter 5); and Iterating,
Communicating and Learning (Chapter 6).
Relevant case studies are provided throughout and used to illustrate key concepts. A comprehensive
bibliography is provided, followed by appendices on definitions, legislation, risk management at the
institutional level, and the types of uncertainty in risk assessment.
FORMULATE
PROBLEM
ASSESS
RISK
APPRAISE
OPTIONS
ADDRESS
RISK
Stages
within risk
assessment:
1.
Identify the
hazard(s)
2.
Assess the
consequences
3.
Assess their
probabilities
4.
Characterise
risk and
uncertainty
Mitigate,
terminate,
transfer
or accept
Report
strategy
Reduce
uncertainty
Monitor
and
survey
Frame
the problem
Plan the
assessment
Develop
conceptual
model
Screen
and
prioritise
risks
ITERATE
COMMUNICATE
LEARN
Economic
Technological Organisational
Environmental security
Social issues
CHAPTER 2
Formulating the Problem
10
2.1 The importance of good problem definition
Clearly setting out the problem at hand and the boundaries within which
any decisions on environmental risk are made is important for effective risk
management. It may be tempting to omit the formal definition of the problem,
particularly where there is pressure to complete a risk assessment quickly
or to apply numerical data readily at hand. However, failure to formulate
the problem clearly could result in a loss of focus and, consequently, in an
inappropriate output. Formulating the problem in clear and unambiguous
terms will assist in selecting the level and types of assessment methodology
used, and improve the risk management decision. It is also necessary to enable
risk and uncertainty to be assessed because likelihoods should not be assigned
to ambiguously defined outcomes. Therefore, if the risk decision is challenged
or audited, a firm rationale for the process can be provided.
Stakeholders have an important role to play in formulating the problem and, when feasible,
their early involvement will tend to make risk management decisions more effective and durable.
Environmental risk assessments completed by reference to legislation (for example, environmental
permits and environmental safety cases) may have quite specific requirements that should be discussed
with regulators in advance. Most environmental risks relate to specific hazards and environmental
components, are spatially and temporally determined and can often have wider consequences.
Consider a theoretical chemical incident (accident) on the banks of the River Mersey, which results
in large scale chemical releases into the river. This may have consequences for people living in the
immediate locality, but also for the wider north west of England, depending on the type and nature of
releases. There could also be national implications for the risk assessment of similar facilities across the
UK. Additionally, if there was a risk of this chemical contamination reaching the Irish Sea this could have
international implications for both the UK and the Republic of Ireland. If the evidence was that there was
no significant risk to the Irish Sea, it would still be helpful to communicate this to relevant stakeholders
in the Republic of Ireland. Horizon scanning techniques can also be used to complement risk assessment
of potentially wider consequences by helping to identify low probability, high impact events, which are
often termed ‘unknown unknowns’ or ‘wild cards’(Petersen, 2008), or rare, extreme impact events with
retrospective predictability, which are often termed ‘black swans’ (Taleb, 2007).
A critical early need is to establish basic information about the risk, including ‘what’, ‘to whom’ (or which
part of the environment), ‘where’ (location) and ‘when’ (in time) (Figure 3). For example, framing a risk
assessment for a discharge to a surface water body will require early agreement about which discharge
point is to be considered, over what period in time, to which receiving water body, affecting which
receptors or outcome measures.
FORMULATE
PROBLEM
ASSESS
RISK
APPRAISE
OPTIONS
ADDRESS
RISK
11
Figure 3: The components of the problem formulation stage, which require dialogue with stakeholders.
2.2 Framing the question
Risk assessments are generally employed where the outcome of a given activity is uncertain. The
aim of the risk assessment is to evaluate the significance of the risk by reference to a societal norm,
standard or view on its acceptability, and then make organisational and individual arrangements for its
active management. Risk assessments frequently provide greater understanding of the features of an
environmental issue and aim to identify those aspects that contribute most to the risk. In this sense they
may be diagnostically useful, as well as estimating the significance of the risk. Examples of specific risk
questions include:
s What is the risk of an environmental release from an engineered, contained process (e.g. from a
system designed to treat waste contaminated with hazardous compounds)? What areas does this
affect? For how long may they be at risk?
s What is the likelihood of environmental effects from the use of engineered nanomaterials in consumer
products in the UK? What is the time frame for potential effects being realised?
s How likely is an incursion of an exotic fish disease in the UK, what are its potential consequences,
and how long may they persist?
s What is the likelihood of a disruptive coastal flood event on the South Coast, and for how long may
the disruption last?
Risk questions are best informed by a range of stakeholders. Increasing public awareness of risks and
greater opportunities to access risk information result in both organised stakeholders and individual
members of the public wanting to influence risk decisions more directly. For this to happen, they need
to be able to participate in decision processes early so that they can understand and question the risk
assessments being undertaken. The best decisions about environmental risks require both the best
science and the best decision processes. The best decisions are those informed by people’s knowledge
and concerns (expert and lay), and are understood and supported by the people who may be directly
affected by them.
Framing the
problem: the
‘risk of what to
whom, where
and when’
Developing
a conceptual
model
Planning the risk
assessment
Screening and
prioritising
the risks to be
assessed
12
2.3 Developing a conceptual model
One way to formalise these aspects is by developing a conceptual model – that is, a representative
schematic of the boundaries of the problem under consideration. Adverse consequences (harm, loss of
function, detriment) cannot occur unless that environmental feature we wish to protect (for example,
a top grade salmon river or a heathland) suffers exposure to a hazard. Hence there is merit is setting out
the relationships between hazards, exposure and environmental features before we go on to analyse
them in depth. Equally, if the risk management options are to be evaluated (e.g. the impact if there is
a change in legislation) it is helpful for the options to be specified within the conceptual model. This
ensures that the risk assessment is designed so that the options can be evaluated.
The level of detail required in the conceptual model will differ depending on the complexity of the risk
assessment. A conceptual model can be highly specific and concentrate on just one facet of a large
project, or it may be possible to embody the entire risk in one model. For example, for a single chemical
affecting a single receptor, the conceptual model will probably be simple; in the case of multiple sources
and multiple receptors (e.g. catchments) the model will be more complex. Conceptual models work
particularly well for physical features present in environmental settings (Case Study Box 1).
It is desirable, wherever possible, that consensus is secured with both the decision-maker and
stakeholders on what is included, and what is outside the scope of the assessment. Agreement on the
scope of the assessment can be influenced by:
s the purpose of the assessment;
s legislative and regulatory requirements;
s boundaries of ownership;
s changes to the layout of a facility; and
s international, national, regional and local environmental aspects.
Examples of the European Directives and UK statutory instruments that require an environmental risk
assessment to be carried out are provided in Appendix 2.
2.3.1 Source-pathway-receptor (S-P-R)
Conceptual models present the hypothesised relationships between the source (S) of a hazard,
the pathways (P) by which exposure might occur, and the receptors (R) – those features of the
environment that we value and that could be harmed (S-P-R). Existing or potential linkages between
these components of a risk can be set out in tabular form with reference to a schematic or conceptual
model, which summarises those relationships visually (Pollard, 2008). Table 1 provides an example of
identifying and representing the S-P-R linkages regarding leakage from an underground gasoline storage
tank containing benzene as a component of fuel. The intention is to represent the scope of the problem,
clarify the environmental components at risk and set the boundaries of the risk assessment
(Case Study Box 1).
13
Table 1: An example of identifying and representing the S-P-R linkages regarding leakage from an underground
gasoline storage tank that contains benzene.

Hazard	Source	Pathway	Receptor	S-P-R linkage
Benzene	Underground gasoline storage tank	Leaching Groundwater supply	Groundwater supply Public water supply	Yes Yes

The S-P-R approach has proven flexible across a wide range of environmental risks. An alternative
conceptual framework used in assessing and managing environmental risks especially at the policy level is
the D-P-S-I-R model (Drivers-Pressures-State-Impacts-Responses). The drivers are the forces that increase
or mitigate pressures on the environment (e.g. changes in land use). Pressures are the stresses that an
activity, situation or agent places on the environment (e.g. waste disposal). State is the condition of the
environment (e.g. land productivity decline). Impacts are the consequences or effects of environmental
degradation (e.g. crop yield decline). Responses are those made by society to the environmental situation
(e.g. conservation and rehabilitation). The D-P-S-I-R concept is similar to that of S-P-R, but it is important
to specifically consider the likelihood of the impacts occurring when characterising the nature of hazards
and evaluating the response options (The World Bank, 2006).
2.3.2 Factors controlling the hazard
When developing a conceptual model it is important to be aware of engineered, natural, and human
events and processes that affect the risk. For example, factors such as soil moisture, chemical concentration
and population growth can control the timing, intensity, spatial extent and duration of hazardous events.
If influencing factors are not considered at an early stage, difficulties may arise in conducting meaningful
assessments and selecting practical options. In relation to flooding, for example, factors such as the
prevailing meteorological conditions, the condition of flood defence assets, the soil moisture deficit,
and hydraulic capacity of the flood channel will all influence the magnitude of the hazard to some extent.
Equally, plant operator performance, levels of investment, training and staff morale can be important
factors in managing hazardous activities at process facilities.
Case Study Box 1
Response to an accidental release of fuel to groundwater
Shell Global Solutions, Chester, UK
A conceptual model was used to plan the risk assessment and associated collection of relevant data regarding an accident
at a service station that resulted in the release of petrol to groundwater. The law and corporate procedures both require
that a release is managed to ensure there is no unacceptable risk to human health or the environment. Risk management
goals needed to be achieved in a safe and timely manner, using effective, practicable and sustainable techniques. Problem
formulation required the assessor to determine the likelihood of damage from this spill, whether the damage would be
unacceptable, and if so, what remedial actions were necessary. A risk assessment and management process was adopted.
Initial steps were to:
s stop any continuing release; and
s identify and undertake any emergency response necessary to prevent unacceptable exposure of humans or
environmental receptors.
Once imminent risks were controlled, the next stages were to further define the constraints within which risks should be
assessed and managed. Typical steps in the process were:
s development of a Conceptual Site Model (CSM), including identification of plausible
source-pathway-receptor (S-P-R) linkages and constituents of potential concern (COPCs) (Figure 4);
s assessment of the fate and transport of COPCs along each S-P-R linkage in order to predict the likely exposure of each
receptor, and evaluate the associated risks;
s defining appropriate remediation objectives, e.g. reducing COPC concentrations at a certain receptor to defined values
(such as environmental criteria), in order to reduce risk; and
s appraising alternative remediation options, considering factors such as technical feasibility and effectiveness, cost,
constraints on time and physical space on site, and sustainability criteria.
Figure 4: Illustration of conceptual model of fuel release to groundwater (copyright SNIFFER, 2005).
14
2.3.3 Scenario building
The utility of futures research methods – most especially scenario building – as a complement to the
development of a risk assessment conceptual model is now beginning to be assessed. Scenarios are
plausible descriptions of how the future may develop and enable envisioning of alternative evolutions of
whole systems rather than individual entities. Scenarios are based on a coherent and internally consistent
set of assumptions about key relationships and driving forces concerning the issue(s) being researched.
Scenario construction can be used to explore future risks, opportunities, strengths and weaknesses
of current strategy and policy approaches, and to provide a long-term vision independent of political
timetables. Done well, scenario building exercises can help to identify critical decision points and strategic
options, but also develop a clear context for future strategies and polices (Finger et. al., 2007).
2.4 Planning the assessment
The assessment plan outlines the data requirements for risk assessment and the methods needed for
data collection and synthesis. Each assessment should start with research into existing legislation and
guidance relevant to the assessment. Risks can be assessed quantitatively and/or qualitatively. Both
qualitative and numerical data are appropriate and one should not necessarily be valued above the other.
The selection of assessment endpoints should also be considered, such as a quantitative measurement
of the abundance of a species in relation to an environmental stress. The time period and spatial scale
should be defined to make the assessment endpoint unambiguous.
A decision should also be made on which data are important for the analysis. For example, collecting
data on a plant species that is known to be susceptible to a certain environmental stress is a higher
priority than assessing the effects on species in distant taxonomic groups. In turn, planning facilitates the
effective use of resources, which are best focused at collecting data essential to characterising the risk
(Nickson, 2008). An assessment plan may also describe more sophisticated assessment techniques that
could be conducted depending on the results of initial work.
Effective planning can help to answer hypotheses at an early stage in the assessment. If the information
collected (or already present) is adequate and indicates that a stressor has no known toxicity or
reasonable mechanism to be toxic to the plant species, further analysis may be unnecessary.
2.4.1 Stakeholder and public participation and engagement
As awareness of environmental problems has grown and people have become more concerned about
risks to the quality of the environment and to their health, so demands have increased for more and
better engagement in environmental decision-making.
Traditionally, environmental legislation requires increasingly that neighbours, local residents,
national and local interest groups are consulted about the activities and developments that may impact
on the environment. In practice, consultation has often been rather late in the decision process and some
(e.g. Petts and Brooks, 2006) have argued that there has been little opportunity for people to actually
influence the decision. The result has sometimes been public frustration and opposition, with demands
for more information and consequential delays to decisions (Few et. al., 2007). These difficulties have led
to the adoption of analytical-deliberative decision processes in the UK and overseas (Stern et. al., 1996),
which allow for public discussion, debate and reflection about the risk assessment itself alongside the
analysis of risk (often also known as participatory risk assessment).
15
Participatory risk assessment has been recognised as a valuable method to support public engagement.
In planning a risk assessment, public engagement should be provided for if:
s stakeholder and the public’s input and views can be taken into account in the decision;
s there is, is likely to be, or has been, concern about the risk issue; and
s support is needed for the decision from stakeholders and the public.
A participatory risk assessment process engages people through a bottom-up approach that aims to
involve stakeholders and the public in problem formulation, appraising preferred management options
and proposing solutions to particular risk problems. In planning a participatory risk assessment,
key elements include:
s communicating information transparently and using a non-technical or domain – specific language;
s defining issues that need to be addressed and the questions that need answered – scoping the
problem and framing the questions;
s identifying the data and information needed to deal with the questions;
s identifying the sources of data; and
s deciding how to deal with uncertainty.
The most effective participatory risk assessments use small discussion groups (10-20 people) and allow time
(usually more than one meeting) for people to become familiar with technical issues, to read background
material and to build confidence to take part in discussion and to ask questions (Petts et. al., 2010). Formal
methods involving small groups include citizens’ juries, community advisory committees or consensus
panels. The general literature on participation provides more information on these (e.g. Petts and Leach,
2000). They are particularly appropriate for policy and plan-making (e.g. flood risk management) processes
where more time is available, and where people from a broad range of interests and perhaps different
areas of the country or region may need to be involved. However, these methods can be expensive
(often in excess of £20k and can be over £100k). For a site-specific decision – such as relating to the design
of a flood risk management scheme, or a decision on remediation of a contaminated site – it may be
appropriate to form a discussion group(s) or workshop(s). These might meet on two or three evenings
(at least 2-3 hours each time) or at weekends, in order to learn about the risk decision that has to be made,
to scope the problem and to discuss information needs for the risk assessment.
There is an extensive literature on stakeholder and public participation and engagement (including
Renn, 2006; Petts et. al., 2010). While this document focuses on presenting a generic approach to
assessing and managing risk, further details on the subject of stakeholder and public participation and
engagement are provided in Case Study Box 4, Chapter 4 and Chapter 6.
16
2.5 Screening the risks
In practice, some initial screening of risks will usually accompany development of the conceptual model.
Screening can be used to determine which risks should be investigated in greater detail using techniques
suitable to the nature of the risk and quality of the evidence base. If effective, screening should also
identify those features that will not receive further analysis. Prioritisation allows for the efficient allocation
of resources. Justifying and recording the accompanying rationale for screening risks is valuable.
At this stage, risk assessors may develop an early view as to whether they have sufficient data to
support a quantitative assessment of the risk if this is deemed necessary, or whether additional data and
evidence to support such an assessment might be required. Quantitative risk analysis (QRA) is an expert
discipline, expensive to undertake, and requires substantive data and analysis. This may include formal
mathematical modelling. Not all risks will require QRA however, either because they are deemed to be
insignificant on the basis of the evidence already assembled, or because the risk manager is already
confident about their significance and can progress to deciding how to manage the risk.
Risk screening is useful, therefore, for highlighting those risks where uncertainty could affect the
management decision and their success in managing outcomes. Such risks may need to be analysed in
greater detail with more sophisticated methods. Risk screening can also:
s rationalise why some risks may not be investigated further; and
s identify risks for immediate action, without need for further investigation.
Case Study Box 2 illustrates a process for screening a series of risks that have the potential to cause harm
to animals, humans or the environment. Here, three ‘filters’ were used to prioritise significant hazards for
further investigating.
A wide range of risk screening tools exist. Most are qualitative or semi-quantitative. Usually the focus is on
screening out those risks deemed insignificant, so those of higher priority or with significant uncertainty
can be examined in more detail. Risk screening may rely on the following (Bradford-Hill, 1965):
s the plausibility of linkages between the source of a hazard and a receptor;
s the relative potency of a hazard, availability of a pathway, or vulnerability of a receptor;
s the likelihood of an event, on the basis of historic occurrence or of changed circumstances; or
s a view on the performance of current risk management measures that, if they were to fail, may
increase the potential for future harm.
Risk screening tools may also adopt qualitative reasoning, belief nets (Ray, 2010), or qualitative systems
tools to explore the interaction between hazards and receptors. Some risk ranking tools, used with
or without weightings (Marcomini et. al., 2010), are used to generate classes of risks of different
significance and priority. Usually, screening assessments are designed to be precautionary in that, where
uncertainty remains about the probability and consequences of harm, risks are escalated to the next tier
of analysis as a precaution.
17
Case Study Box 2
Screening exposures during carcass disposal
Collaborative Centre of Excellence in Understanding and Managing Natural and Environmental Risks, Cranfield University,
Bedfordshire, UK
The screening of hazardous agents (biological, chemical and nuisance) that were released during the disposal of animal
carcases that have the potential to cause harm to animals, humans, or the environment was carried out to identify a subset
of risks for prioritising further efforts. By reference to the conceptual model (source-pathway-receptor) developed during
problem formulation (risk of what to whom, where and when?), the intent was to decide which risks should be within the
risk assessment and which could be excluded.
This process often necessitates multi-stakeholder
discussion because the constraints of the risk assessment
may not be widely appreciated. For example, certain
statutory risk assessment requirements are narrow in
scope, whereas the requirements used to support an
environmental management system may be openended and broad in scope. The context of application
and views of the end user of the risk assessment are
therefore often critical to risk screening.
In this case, given the large number of possible
combinations of hazardous agents, exposure pathways
and receptors that could be affected, the study
(Pollard et. al., 2008) considered those risks that
could result in hazardous agents evading destruction
in the environment and presenting concentrations of
concern to receptors. A structured series of filters was
adopted to screen potential exposures accordingly
(Figure 5). The outcome of the screening exercise was
to reduce the scope of the prioritisation that followed,
dramatically reducing the onward processing effort
during prioritisation. Setting rules for risk screening has
important implications because risks screened out
are unlikely to be revisited until a revised conceptual
model is considered or the basis for the risk
assessment revised.
Figure 5: Screening potential exposures prior to
the risk assessment of significant hazards during
carcass disposal (Pollard et. al., 2008).
18
Principal hazards to public health,
animal health and the environment
Serious effects or impacts
Serious effects or impacts; and likely to
evade destruction
Serious effects or impacts; likely to
evade destruction; and likely to present
at concentrations of concern
Pooled list of
chemical,
biological and
amenity hazards
Filter 1
does the hazard pose potentially
serious health effects, animal
health effects or environmental
impacts?
Filter 2
for hazards posing potentially
serious effects or impacts, are they
likely to evade destruction if not
contained
Filter 3
for those hazards posing
serious effects and impacts that may
evade destruction, could they be
present at a point of exposure in a
sufficient quantity to be
of concern?
2.6 Prioritising the risks
Beyond establishing the plausibility of a risk, the risk analyst may seek to prioritise some risks above
others, where there is supporting evidence.
Prioritising the risks needs to be transparent because of the challenge of comparing different risks and
the weightings analysts may apply. Given the wide variety of uses, there is no single prioritisation system
appropriate to all applications. Some ranking systems focus on: the relative condition of assets that
might fail (condition assessments, e.g. National Audit Office, 2007); the relative potencies of different
chemical hazards (e.g. Whaley et. al., 1999); the relative availability of exposure pathways to receptors
(e.g. Delgado et. al., 2010); or the likelihood of harm should exposure occur (e.g. Richards, 2008). Many
approaches used within environmental risk assessment seek to rank the relative feasibility of exposure
by considering the viability of exposure pathways from source to receptor. These qualitative approaches
evaluate source-pathway-receptor relationships by working through a conceptual model, exploring
whether exposures may be direct or indirect, and determining the integrity of the barriers in place to
minimise environmental exposure. Usually, high priority risks are considered for further analysis or direct
or immediate risk management.
Some scientific communities have developed highly structured approaches to screening and prioritising
risks. These are of particular value where there are a large numbers of S-P-R relationships as, for example,
exist for combined surface and sub-surface environments. Case Study Box 3 illustrates how an analysis
of the potential consequences of radiological impacts allowed the analyst to prioritise risks for more
detailed analysis. Here the environmental features, events and processes (FEPs) inherent to a radioactive
waste disposal facility are evaluated using a structured technique to explore which combinations would
merit further in-depth analysis.
It is important that risks identified as being of low priority are not discarded entirely from the remainder
of the process. Risks screened out may need to be revisited because of the inter-relationships that exist
between risks. For example, inter-relationships exist between the impact of climate change on other risks,
such as water availability, exotic animal disease, air quality and human health. A future risk management
option targeted at high-priority risks may also reduce lower-priority risks through their interdependency.
Equally, some risk management options may increase lower-priority risks.
2.7 Summary
Most environmental risks are spatially and temporally determined, so a critical early need is to establish
the risk of what (is happening) to whom (or which part of the environment), where (location) and when
(in time). Formulating the problem in clear and unambiguous terms will assist in selecting the level
and types of assessment methodology used and improve the risk management decision. Stakeholders
have an important role to play in formulating the problem and, when feasible, their early involvement
tends to make decisions more effective and durable. It is important to recognise, early on, whether
there is a need for public engagement and whether it is feasible. Development of a conceptual model
can help to present in visual or written form the hypothesised relationships between the source (S) of a
hazard, the pathways (P) by which exposure might occur and the receptors (R). The S-P-R relationship
conceptualises the receptors at risk of exposure to the hazard. Risk screening can be used to identify
what should or should not be investigated in more detail, while risk prioritisation typically provides a list
of main concerns for further action. Both screening and prioritisation facilitate the effective allocation of
resources. This process, whereby the problem is formulated and scoped, may need to be revisited as the
assessment proceeds (see Chapter 6).
19
Case Study Box 3
Radioactive Waste Disposal Case Study
Galson Sciences Ltd. Oakham, Rutland, UK
Radioactive waste disposal facilities in the UK require an Environmental Safety Case (ESC), supported by environmental safety
assessments. All such disposal programmes face the problem of determining which phenomena and components of the
disposal system can and should be represented in the quantitative safety assessment. This problem is referred to as “scenario
development,” and the phenomena and components of the system are referred to as environmental FEPs, i.e. features, events
or processes.
Figure 6: The ISAM assessment
20
Assessment Context
Describe System
Develop and Justify
Scenarios
Formulate and
Implement Models
Run Analyses
Interpret Results
Rejection
Adequate Safety
Assessment?
Compare with Safety
Criteria
Review and
Modification
Yes
Yes
No
No
Effective to Modify
Assessment?
Acceptance
The proposed new Low-Level Waste (LLW) Facilities at Dounreay used an environmental safety assessment methodology
developed in the Improving long-term Safety Assessment Methodologies (ISAM) coordinated research project of the
International Atomic Energy Agency (IAEA) (Figure 6).
The approach to scenario development followed four structured steps:
1. identification and classification of FEPs potentially relevant to the disposal system’s performance;
2. elimination of FEPs from the performance assessment (PA) modelling according to well-defined screening criteria;
3. identification or formation of scenarios relevant to the performance of the disposal system; and
4. specification of scenarios for consequence analysis.
The FEPs were then evaluated and prioritised according to the likelihood and potential consequence of radiological impacts,
ensuring that the assessment was proportional to the hazard of the waste that is, the assessment needed to be sufficiently
comprehensive to support decision making, while not unduly burdensome to conduct or overly detailed. The prioritisation
was then used to develop a subset of potential exposure scenarios, from which screening decisions can be made. As
illustrated in Figure 7, each FEP can be either excluded from the assessment because they are outside the scope, screened
out on the basis of a low probability and/or consequence, accounted for in the undisturbed performance scenario, or
included in the calculations of disturbed performance.
Figure 7: FEP screening and scenario development process for the Run 3 environmental safety assessment used to
support the ESC for the proposed New LLW Facilities at Dounreay. Note that FEPs screened into the Undisturbed
Performance scenario are generally also considered in the modelling of the Disturbed Performance scenarios.
21
FEPs to be Screened
Undisturbed Performance
(also included in Disturbed Performance
modelling until time of disruption)
Disturbed Performance
FEPs to be modelled in Run 3
Category O
Screened Out of Run 3
Outside Scope
Category SO-P
Screened Out of Run 3
Low Probability
Category SO-C
Screened Out of Run 3
Low Consequence
Yes
No
Yes
Yes
No
Yes
Could FEP bypass or
eliminate one or more
disposal system
barriers?
Runs 1 & 2 No
No
Is FEP significant
to performance of
disposal system?
Does FEP have a
low probability of
occurrence?
Is FEP within
scope of PA?
3.1 Features of the risk assessment
Risk assessment is the formal process of evaluating the consequences of a
hazard and their probabilities. The assessment itself typically involves four
stages: (1) identifying the hazard(s); (2) assessing the potential consequences;
(3) assessing the probability of the consequences; and (4) characterising the
risk and uncertainty (Figure 8). In this sense, the risk assessment addresses the
so-called ‘risk triplet’; i.e. (a) what can go wrong; (b) what the consequences
are; and (c) how likely the consequences are. The risk triplet is a favoured
approach to assessing the risks from engineered systems (Pham, 2003).
A similar approach (Figure 8) is commonly applied to situations in which a
hazard exists in the environment and the risk it poses needs to be evaluated.
Both approaches have elements in common, particularly with respect to
environmental exposure. However, it is important to note that in cases of
animal health risk assessment, hazard identification is part of risk analysis and
not the official assessment process (OIE, 2010).
Social questions such as the significance of the risk are usually addressed separately to the assessment
required, to estimate the magnitude of the risk. However, in some cases, it may be inappropriate to
separate the magnitude of the risk from the significance of the risk, especially where the outcomes
have a significant social component (e.g. equity issues). This issue should be recognised in the problem
formulation stage (Chapter 2).
Figure 8: The primary stages of environmental risk assessment that sit within the overarching framework for
environmental risk assessment and management (Figure 2). The assessment stages that precede characterising the
risk and uncertainty address the ‘risk triplet’; i.e. (a) what can go wrong; (b) what the consequences are; and (c)
how likely the consequences are. Uncertainty should be considered at every step of the process.
22
CHAPTER 3
Assessing the Risk
FORMULATE
PROBLEM
ASSESS
RISK
APPRAISE
OPTIONS
ADDRESS
RISK
IDENTIFY THE HAZARD(S)
FORMULATE PROBLEM
ASSESS THE CONSEQUENCES UNCERTAINTY
ASSESS THEIR PROBABILITIES
CHARACTERISE RISK AND UNCERTAINTY
Risk assessment approaches can be broadly categorised as qualitative, quantitative, and semiquantitative. A vast array of tools and techniques exist. Qualitative methods include S-P-R analysis,
ranking methods and qualitative event trees. These methods can be simple and cost-effective to execute,
but are inevitably more subjective than quantitative methods.
The operation and outputs of qualitative methods may also be subject to ambiguity, because there is no
way to know how similar one person’s interpretation of qualitative inputs or outputs is to another’s. This
makes qualitative measures less useful for characterising the magnitude of the risk. Qualitative methods
have value in establishing a sound logic for subsequent analysis, which may be a full quantitative risk
assessment, if this is required.
Quantitative methods include quantitative exposure assessments, quantitative fault-tree analysis,
simple deterministic risk estimation and Monte Carlo simulation techniques. These can be based on
inputs derived by data or by expert judgement. Even when based on large datasets, they need not be
resource intensive for the end-user, if the model is made available as software and requires simple inputs
for each new assessment. However, quantitative methods are reliant on the selection or manipulation of
the data.
Semi-quantitative methods include ranking, scoring, indexing, causal criteria and logic-based systems.
These methods often offer a consistent and systematic approach when risk prioritisation is required.
However, these methods are also subjective, akin to fully qualitative methods. As with all tools and
techniques, the assumptions used and a justification of the data applied, and its reliability, needs to be
communicated with the assessment. Often the design and operation of the approach influences the
outcome of the analysis and so there is a continued need to ensure judgements about risk have a basis in
scientific evidence.
3.2 A staged approach to risk assessment
Irrespective of whether the risk assessor applies qualitative or quantitative methods, there are similarites
in the stages followed to estimate the magnitiude of the risk before evaluating its significance.
Considering the ‘risk triplet’ and Figure 8 above, the risk assessment must understand the environmental
consequences posed by a specific hazard, evaluate the consequences that may arise if the hazard is
realised, and then evaluate the likelihoods of these consequences.
Stage I: Identify the hazard(s)
These guidelines define a hazard as a situation or biological, chemical or physical agent that may,
under specific conditions, lead to harm or cause adverse affects (Chapter 1). This could include the
bioaccumulation of endocrine-disrupting chemicals (EDCs) in fish (Appendix 3), a tidal surge along a
stretch of the coast, the introduction of an invasive species, a dry summer leading to low river flows, or
the planting of a genetically modified crop. Where a risk assessment is to be applied at the policy level,
the hazard may be as broad as the adverse impacts of road transport on the environment or of induced
climate change from the contribution of fossil fuel-derived carbon dioxide emissions.
The identification of the hazard will have an important bearing on the scope of the overall assessment.
One common pitfall is to overlook secondary hazards that may also arise. For example, during a river
flood, sediments may be deposited on agricultural land in the flood plain. If these sediments were to
be contaminated, they may pose an additional hazard. Secondary hazards need consideration during
problem formulation when the scope of the risk assessment is being agreed.
23
Stage II: Assess the consequences
The potential consequences that may arise from any given hazard are inherent to that hazard. The full
range of potential consequences must be considered at this stage. For example, while the potential
consequences of a discharge of high levels of nitrates and phosphates from a point source to surface
waters may be self-evident, a flood may have additional, non-obvious consequences, such as pollution
arising from an over-stretched sewerage system, or loss of habitats due to river scouring.
The consequences of a particular hazard may be actual or potential harm to human health, property,
the natural environment or dependent valued services (the issue of probability of occurrence is covered
below). The magnitude of such consequences can be determined in a number of ways, depending
on whether they are being considered as part of a risk screening process or as part of a more detailed
quantification of risk. At all stages of risk assessment the spatial and temporal scale of the consequences
and the time to onset of the consequences need to be considered. In some cases the focus will be
on estimating the social and economic impact of an environmental risk (Williams et. al., 2008). For
example, Case Study Box 4 illustrates how the Environment Agency (EA) used the Building Trust with
Communities approach in order to assess the consequences that odours from a factory would have on
a local community. The Building Trust with Communities approach involves working with communities
early on, to understand their concerns, interests and priorities so that the solution will have considered all
potential consequences (EA, 2007).
Case Study Box 4
Tackling odours with a partnership approach – Crown Pet Foods
Environment Agency, UK
The Building Trust with Communities approach was used to assess the social consequences of odours from Crown Pet
Foods factory in Castle Cary, Somerset. The Building Trust approach is used by Environment Agency staff to work with
communities early on to understand their concerns, interests and priorities (Figure 9).
Crown Pet Foods produce dry pet food kibbles from proteins, fats, vitamins and minerals. It has an Environmental Permit,
granted in September 2006. In eight months over 2007-08 more than 1600 complaints were made about odours from the
factory. Over 300 households were affected and the public demanded the problem be immediately resolved. Local residents
were concerned about the consequences the odours would have on their quality of life, the environment, house prices,
and the image of Castle Cary.
Using the Building Trust with Communities approach (Figure 9), the Environment Agency local area team produced
regular newsletters, used websites, got involved in the site liaison group and visited the homes of local people who were
concerned about the consequences of the odour problem. Staff explained the Environment Agency’s role in regulating the
site, the action taken and the role the community could play.
24
Figure 9: The Building Trust with Communities approach to dealing with a site with ongoing complaints
and concerns.
In parallel, a strong open relationship was built with the operator, using a transparent approach to gain trust. Although
the company was working within the conditions of the permit, the insights and evidence gained from working with local
residents, as well as from monitoring, combined to form a case for action beyond the requirements of the permit to ensure
quality of life for local people. The managing director of the site was able to use this evidence to persuade the board to
invest £1million in odour abatement technologies, improving quality of life for 350 homes. The odour issues have been
resolved, complaints reduced from 50 a day to 2 in the last 10 months and the Area team now enjoy a positive relationship
with the local community.
Case Study Box 5 illustrates an approach to consequence assessment using a toxicity exposure ratio (TER)
in the assessment of pesticide risks to birds. The information in Case Study Box 5 is developed further in
Case Study Box 11 where probability density functions are used to evaluate uncertainties in elements of
the TER calculations.
25
Has a breach occurred?
Complaint received
Discuss issue with operator
Carry out necessary work to establish
whether the breach has occurred
Engage with the local community, using the
Building Trust with Communities approach to
clarify their concerns and explain how we will
manage the issue. Use existing methods, such
as a site liaison group, where appropriate.
Keep the community engaged – at least by
keeping them informed about progress in
investigating the issue
Keep the community engaged – at least by
keeping them informed about progress in
resolving the issue
No
Consider whether any further action is
needed e.g. review or vary the permit
Work with operator to
resolve the problem
Issue resolved
Community engagement activity
Yes
Communicate outcome to community and
operator.
Manage expectations and provide reassurance.
Consider whether continued engagement might
be appropriate and, if so, what?
Resolving pollution affecting
communities
Case Study Box 5
Consequence assessment of pesticide risks to birds
Food and Environment Research Agency, UK
The flow chart below shows a model for the consequence assessment of acute risks of pesticides to birds. The box at the far
right shows the assessment endpoint: this is a ratio of toxicity (measured by the LD50) to exposure (TER), as specified under
current EU regulations for this type of risk assessment. The rest of the chart shows factors that may influence this risk, and
how they combine to determine the TER.
Factors that are considered when calculating the TER fall into four main groups: (1) factors used to estimate the daily food
requirement of birds; (2) aspects of bird behaviour and diet; (3) factors influencing the concentration of pesticide on foods
eaten by birds; and (4) the toxicity of the pesticide.
Some factors (indicated by dashed lines) are acknowledged as influencing risk but, for various reasons, are not included
when calculating the TER (Figure 10). Therefore the potential influence of these factors should be considered when
evaluating uncertainties affecting the assessment outcome.
Figure 10: Model for the consequence assessment of acute risks of pesticides to birds
(adapted from Hart et. al., 2006).
26
BW: body weight
DEE: daily energy
expenditure
GE: gross energy
content of food

FIR: Food intake per day (wet wt) PT: Fraction of diet obtained in treated areas PD: Fraction of food type in diet C: Peak concentration on food AV: Avoidance –

TER: Toxicity –
exposure ratio
omitted
M: moisture content
of food
AE: assimilation
efficiency
AppRate: application
rate
RUD: residue per
unit dose
Napp: number of
spray applications
MAF: Multiple
application factor
ftwa: Time weightedaverage factor
LD
50
(mg/kg bw)
Metabolism – omitted
Non-dietary routes of
exposure – omitted
Dietary exposure
(mg/kg bw/day)
Stage III: Assess their probabilities
With the range of potential impacts (which could be qualitatively or quantitatively described), the
likelihood that they will occur may be expressed as a probability or frequency. It is important to assess
probability with some degree of confidence as the credibility of the risk assessment is undermined if
the probability presented appears to be wholly subjective or, conversely, indefensibly precise. Indeed,
using data to define probabilities for discrete and rare events is more difficult than for those that can be
readily observed. It is therefore best to consider how relevant the data is to the problem. These issues
are also discussed in Chapter 2.1 and Chapter 5.6. Generally, risk assessors consider three aspects of the
likelihood of consequences being realised.
a) The probability of the initiating event occurring
The probability of the occurrence of an event can be expressed as a fraction from 0 to 1. Events that
are unlikely will have a probability near 0, and events that are likely to happen have probabilities near 1.
Many environmental risks are manifest because engineered systems fail. Process engineers have therefore
used fault trees, sometimes supported by quantification of contributing failure modes, to estimate the
probability of a so-called ‘top event’ occurring. This might be an accidental release. More broadly, process
risk analysis tools that estimate the probability of an initiating event may be used for the breakthrough of
filters or landfill liners, for example, in the analysis of barrier failure, where multiple barriers protect the
environment from a hazardous release; and where a sequence of events may occur to result in exposure
(e.g. the progressive deterioration of flood defence assets). Sophisticated quantitative fault tree software
and tools are in wide application within engineering systems. Case Study Box 6 provides an example of a
logic sequence for an initiating event. The impact of uncertainty can also be investigated by carrying out
further analysis or ‘what if’ scenarios within quantitative models (Regan et. al., 2003).
27
Case Study Box 6
The introduction of an exotic fish virus to the UK through imports of live fish vector
Centre for Environment, Fisheries and Aquaculture Science, Weymouth, UK.
The UK enjoys freedom from a number of notifiable fish diseases including epizootic haematopoietic necrosis virus (EHNV).
EHNV affects perch and rainbow trout in Australia, thus no live imports of these species from Australia to the UK is
permissible. However, other species can be traded, and large specimen carp for recreational angling have been imported.
The import of species not recognised as susceptible, may introduce the virus (i.e. in the gut, on the skin or in mucous) and
this was qualitatively assessed for a consignment of 30 carp (Peeler et. al., 2009). A scenario tree of events necessary for
the introduction was developed (Figure 11). A wide range of data (e.g. epidemiology and biophysical properties of EHNV,
fish population distribution in Australia) was used to qualitatively assess
(from negligible to high) the likelihood and uncertainty of each step; the qualitative assessments were combined using a
matrix to produce a conditional likelihood. The likelihood that a consignment of carp would introduce the virus was judged
to be low. There was a high level of uncertainty around the likelihood that contact between the carp and an infected fish
would result in contamination of the carp with the virus. The virus is only likely to establish when water temperatures are
above 12°C. Assessment of the water temperatures in rivers in southern England indicated that on average the water
temperatures were permissive for 14 weeks during the summer.
Figure 11: Release pathway for the introduction of an exotic pathogen via imports of a vectors species (vs).
28
vector sp. (vs) sourced from
catchment / zone containing
susceptible species and the hazard
susceptible species are infected with
the hazard
susceptible species shed the hazard
release of pathogen occurs
Step 5
Step 4
Step 3
Step 2
Step 1
yes
yes
yes
yes
yes
yes
no
no
no
no
no
stop
stop
stop
stop
stop
consignment contaminated with
hazard
Vectors selected
for shipment
Exporting zone, region
or country
Definitions:
Effective: contamination
results in infection of ss
or contamination of vs
Contamination: carriage
of the hazard (e.g. on
skin or in gut) without
multiplication
hazard remainsviable during
transport
effective contact made between
susceptible species and vector
species, or vector species and
environmental reservoir
b) The probability of exposure to the hazard
Risk assessors also have an interest in what happens should a release occur. Usually, hazardous agents are
released to the wider environment and may travel some distance to receptors. Consider the releases of
bioaerosols from large composting facilities, for example, or the transboundary distributions of persistent
organic pollutants at a global level, or the hydrogeological transport of contaminants in an aquifer.
Here, the assessor must characterise the temporal and spatial distribution of hazardous agents from
the point of release to the so-called ‘exposure point’. A wide variety of environmental dispersion tools
exist to characterise contaminant transport, for example. These are sometimes coupled to exposure
assessment tools that estimate the likely ‘dose’ at the exposure point.
c) The probability of the receptors being affected by the hazard
Should exposure to a hazard occur, the risk analyst is then interested in the likelihood of harm that may
result from the exposure. The likelihood of harm depends on the susceptibility and vulnerability of a
receptor to the hazard, on the potency of the hazard itself, and on the amount or extent of exposure.
For chemicals and pathogens, this is often simplified in terms of a dose–response relationship, which
relates exposure to the expected magnitude of harm for certain receptor types. In flood damage
assessment, for example, standard depth–damage curves can be used to relate the depth of flood waters
to the damage sustained by a building or its contents, again according to the extent of exposure to the
flood waters and property type.
Often the risk analyst is interested in all three probabilities above – from the likelihood of the initiating
event through to the likelihood of harm. The three probabilities can be assessed together (e.g. as part of
a single model), or the later steps can be assessed conditional on the outcome of earlier steps (e.g. if a
landfill liner leaks, what will be the down gradient consequences for an abstraction borehole?).
That is, various risk scenarios may need to be set up and then explored in detail (Finger et. al., 2007).
In pathogen hazards, for example, the approach is typically to describe a range of outbreak scenarios
with different likelihoods.
29
Stage IV: Characterise risk and uncertainty
Risk characterisation pulls together the information from the previous three stages. It is concerned with
determining the qualitative and, if possible, quantitative likelihood of occurrence of the known and
potentially adverse effects that an activity or agent presents to a given receptor under defined exposure
conditions, along with acknowledging the assumptions and uncertainties (OECD, 2011). Here we are
concerned with the significance of the risk. Risk characterisation can be achieved through reference to
some pre-existing measure, such as an environmental quality standard or a flood defence standard, or by
reference to pre-established social, ethical, regulatory or political standards.
A variety of methods can be used to characterise the risk. A basic approach might involve comparing
contaminant concentrations in lake water with guideline values and deciding what this means in terms
of how likely it will be that adverse consequences will be realised. Considerations may also include how
valid the guideline values are for the site of concern and whether further investigations were necessary in
order to justifiably characterise the risk (Davis, 2002).
In many ecotoxicological risk assessments, for example, the ratio of the measured or estimated
environmental exposure concentrations to the predicted no-effect concentration (PNEC) can be used
to evaluate the significance of the risk for target ecosystems. The dose level at which no critical effect
is found and the lowest dose at which the effect is found may be identified from studies in human
populations or data from studies in experimental animals and other test systems, where a benchmark
dose (Setzer and Kimmel, 2003) may be used as an alternative. This information is then used to derive a
standard considered to represent a level of exposure or intake at which it is believed there is little,
if any, likelihood of developing ill-health effects. This standard is then compared directly with the
measure or estimate of exposure. This approach also requires a consideration of the uncertainties in
exposure estimates when interpreting the ratio (Case Study Box 7).
Different approaches are adopted by different regulators but often a safety factor or safety margin
is included in the risk characterisation process to allow for uncertainty. For example, using the no
observable adverse effects level (NOAEL) approach to pesticide risk assessment normally includes a
safety factor of 100 times to ensure that the maximum possible exposure will be less than the NOAEL,
by at least 100 times (Cao et. al., 2011). The uncertainty within the exposure estimates can result from
inappropriate species/strain, gender differences, the safety factors assumed and used to predict the end
result, and/or possible combinations with other chemical compounds.
Further guidance on characterisation of the risk based on the strength and weight of evidence,
expert elicitation and dealing with uncertainties is provided in the following sections.
30
Case Study Box 7
Assessing ecotoxicological risks for “down-the-drain” chemicals in surface waters
Cranfield University, Bedfordshire, UK
Environmental risk assessments for chemicals are generally based on comparing exposure with an effect threshold (Predicted
No Effect Concentrations: PNEC). For so-called “down-the-drain” chemicals (such as pharmaceuticals and the ingredients
used in household cleaning products), exposure assessments (i.e. calculations of Predicted Environmental Concentration:
PEC) are usually based on a simple ratio of per capita consumption and per-capita domestic water use, which is then
adjusted for removal during sewage treatment and for dilution in the receiving environment using a generic dilution factor
(e.g. 10). One problem with this procedure is that it does not take into account spatial and temporal variability in dilution
which changes with the relative magnitude of point-source loads and river discharge at the point of emission.
Higher tier exposure models such as GREAT-ER (Geography-referenced Regional Exposure Assessment Tool for European
Rivers: Koormann et. al., 2006) can be used to predict the statistical distribution of river-reach-specific concentrations
(Figure 12), accounting for time varying emission and in-stream dilution and degradation. These predictions can be
compared with effect thresholds or integrated with distributions of effect end-points in a range of organisms (species
sensitivity distributions) to identify risk “hot spots” or predict overall risk. This approach has been employed to assess the
aquatic risks associated with triclosan (an antimicrobial substance used in soap and toothpaste) for urbanised catchments
(Capdevielle et. al., 2008) and whole regions in the UK (Price et. al., 2010). These assessments suggest that although local
exposure can be high, particularly under low flow conditions, overall risks are generally acceptable,
especially when toxicity adjustments are made for pH dependent speciation of triclosan.
Figure 12: Higher-tier triclosan (TCS) exposure assessment using GREAT-ER example PEC distributions in the
Aire-Calder catchment.
31
Simulated 90th percentile TCS concentrations in the Aire-Calder catchment
Measured data from
Environment Agency
of England and Wales
Aire-Calder catchment
-2056 km2, 1.1 million
people, includes many
urban centres (e.g.
Leeds, Bradford,
Huddersfield) –
considered a “worst
case” example in the UK
Keighley
Esholt
(Bradford)
Knostrop
(Leeds)
Huddersfield
Use rate: 1 g/capita/year
Rate Constant (River): 0.21 h-1
Removal in STWs: 90-98%
Key Assumptions
River Aire
River Calder
90th %ile PEC (ng/L)
Higher-tier TCS exposure assessment using GREAT-ER
Example PEC distributions in the Aire-Calder catchment
0
20
40
60
80
100
120
140
160
180
200
0 20 40 60 80 100
Distance downstream (km)
Concentration (ng/L)
mean mod
90 %ile
mean meas
5 %ile
0
0.0 – 6.233
6.233 – 15.975
15.975 – 70
> 70
River Aire

3.3 General issues in risk assessment
3.3.1 Direction, strength and weight of evidence
Rarely does all the evidence on an issue support the conceptual model on whether and how a hazard
might be realised. Conclusions are formulated using different data and lines of evidence that vary in the
degree to which they support or contradict the conceptual model. In deciding whether evidence supports
the risk assessment, the risk assessor will need to consider the direction of evidence (does the evidence
offer support for or against the plausibility of the relationship between cause and effect), its strength
(how confident is the assessor that individual lines of evidence support the plausibility of the causal
relationship) and the overall weight (given other possible competing theories, what is the overall balance
of evidence?). For example, the conditions needed to establish a causal relationship between two items
can be based on (Bradford-Hill, 1965):
s analogy – if a similar agent exerts similar effects, it is more likely for the association to be causal;
s consistency – the more studies finding similar results, the more likely it is to be causal;
s coherence – a coherence between empirical and laboratory evidence suggests more causality,
however the absence of coherence cannot nullify the findings;
s experimental evidence – an association from experiments may be enough to show causation;
s strength – the stronger the association, the stronger the likelihood of causation;
s specificity – the more specific the association between a cause and effect is, the larger the probability
of a causal relationship;
s plausibility – a plausible mechanism between cause and effect is helpful, but may be limited by
current knowledge;
s temporality – the cause must precede the effect; and
s biological gradient – greater exposure should generally lead to greater incidence, frequency or
magnitude of the effect, i.e. dose-response.
The use of different lines of evidence raises the issue of how best to assess their degree of independence
and the quality of the underlying content. This is important because estimates of risk are fundamentally
determined by the origin, quality and provenance of the evidence that supports them (Suter II and
Cormier, 2011).
Table 2 shows one example of a set of quality indicators for scientific evidence. Additional measures
are offered using the pedigree analysis approach, which is part of the NUSAP (numbers unit spread
assessment pedigree) system for uncertainty assessment (van der Sluijs et. al., 2005).
32
Table 2: Example of quality indicators for scientific evidence (after Bowden, 2004).

Indicators of evidence quality
Quality rank	Theoretical basis	Scientific method	Auditability	Calibration	Calibration	Objectivity
Very high	Well established theory	Best available practice: large sample; direct measure	Well documented trace to data	An exact fit to data	Independent measurement of sample variable	No discernable bias
High	Accepted theory; high degree of consensus	Accepted reliable method; small sample; direct measure	Poor documented but traceable to data	Good fit to data	Independent measurement of high correlation variable	Weak bias
Moderate	Accepted theory; low consensus	Accepted method; derived or surrogate data; analogue; limited reliability	Traceable to data with difficulty	Moderately well correlated with data	Validation measure not truly independent	Moderate bias
Low	Preliminary theory	Preliminary method of unknown reliability	Weak and obscure link to data	Weak correlation to data	Weak indirect validation	Strong bias
Very low	Crude speculation	No discernable rigour	No link back to data	No apparent correlation	No validation presented	Obvious bias

In addition, there is an argument for explicitly addressing the question of data availability and quality (EFSA,
2009). Table 3 suggests a generic means of scoring the data available, which in turn can provide a measure
of epistemic uncertainty, i.e. when uncertainty is brought about by a lack of knowledge (Section 3.3.3).
Table 3: Scoring system for addressing the question of data availability regarding epistemic uncertainty
(taken from EFSA, 2009).

Score	Description
Low (1)	s Solid and complete data available; strong evidence in multiple references with most authors coming to the same conclusions; or s considerable and consistent experience from field observations.
Medium (2)	s Some or only incomplete data available; evidence provided in small number of references; authors’ or experts’ conclusions vary; or s limited evidence from field observations; or s solid and complete data available from other species which can be extrapolated to the species being considered.
High (3)	s Scarce or no data available; evidence provided in unpublished reports; or s few observations and personal communications; and/or s authors’ or experts’ conclusions vary considerably.

Assessing the quality, reliability and relevance of experimental or empirical evidence, and the underpinning
conceptual model, is an important part of risk assessment and management. It is as necessary when
considering a single line of evidence as it is when multiple sources are used. Case Study Box 7 provides an
example of evaluating the direction and magnitude of the impact of different uncertainties. Likewise,
the appropriateness of the techniques/methods used in the risk assessment should be reviewed by internal
or external risk assessors, or other experts who can comment on the data used within the risk assessment
and the validity of the results. A helpful review of the use of multiple conceptual models, assessment of
their pedigree and reflection on their reasonability is provided in Refsgaard et. al. (2006).
33
Case Study Box 8
Qualitative evaluation of uncertainties in pesticide risks to birds
Food and Environment Research Agency, Defra, UK
The Webfram models of pesticide risks to birds (Case Study Box 10) quantify some uncertainties probabilistically. However,
it is important to consider how other uncertainties, which remain unquantified, might change the assessment outcome.
This was done using ‘uncertainty tables’, a qualitative method for evaluating uncertainties that has since been taken up in
guidance for REACH (ECHA, 2008). To construct an uncertainty table, the user lists sources of uncertainty together with an
evaluation of their impacts on the assessment outcome, represented by symbols indicating the direction and magnitude by
which the ‘true’ risk might differ from the estimated value (Table 4).
For example, ‘+/- – -’indicates an uncertainty that could alter the true risk in either direction, from a little higher (+) to a lot
lower (- – -). The user then evaluates the combined effect of all the uncertainties and expresses this using symbols and also
in a narrative form to be included in the conclusion of the risk assessment. For more information on uncertainty tables, see
Hart et. al. (2010).
Table 4: An ‘uncertainty table’ used to evaluate the impact of uncertainties in an assessment of pesticide risks
to birds.

Source of uncertainty	Direction and magnitude
General uncertainties
Distribution choice is always somewhat uncertain, and goodness of fit is questionable or not testable (due to insufficient sample sizes) for some parameters. Raw data were unavailable for some.	+/-
Measurement uncertainty applies to all variables but not quantified for any.	+/-
Exposure assessment
Not all cereal fields will be treated with the pesticide under assessment.	– –
Those cereal fields that are treated, will not all be treated on the same day.	-/- –
Uncertainty about estimation of diet composition and seed preference is represented by running models with different combinations of assumptions. True values are likely to be intermediate.	+/-
Assimilation efficiency data for leaves and seeds represent variation between sites and may underestimate variation between individual animals.	+/-
Assimilation efficiency data for arthropods are for different species and there is uncertainty in extrapolating to the species of concern.	+/-
Variance of gross energy for dicot leaves may be over-estimated	–
Moisture content of dicot leaves estimated from crop plants, weed foliage may have lower moisture content.	–
Insect residues are estimated from data on forage and small seeds and the extrapolation is very uncertain. Recent research appear to show some possibility of higher values but more of lower values.	+/- –
Animals, radiotracked, may not represent a sample of population visiting cereal fields. Time spent active in field may not be a good surrogate for proportion of diet obtained in field, and may vary between months.	+/-
Non-dietary routes of exposure are omitted. Could increase total exposure by 2-5 fold.	++
Effects assessment
Differences between pesticides in the degree of between-species variation, and uncertainty in its estimation.	+/-
Variation of standard deviation of dose response slope between pesticides, and uncertainty in its estimation.	+/-
Uncertainty extrapolating from toxicity in lab to field conditions (for same species)	++/- –
Avoidance response (if applicable to pesticide under assessment)	-/- – –
Metabolism and depuration of pesticide under assessment. If %mortality is low, exposure probably requires most of a daily intake of food, and provides a period for depuration and metabolism to reduce internal dose.	-/- – –
Overall: There are many factors which may decrease or increase the true risk. We consider that the balance of the identified factors is likely to decrease risk; i.e. the true risk is likely to be lower than estimated, especially for the pesticides with substantial avoidance responses and rapid metabolism. For pesticides with little or no avoidance and slow metabolism, the models are likely to underestimate risk.	+/- – –

34
3.3.2 Expert elicitation
Expert judgement is always required in risk assessment, whether concerned with how representative the
conceptual model is, with the elicitation of specific data from a selection of possible choices, or with the
plausibility of specific exposure scenarios. It can also be used to estimate quantities for which data is lacking,
or to quantify uncertainties. Judgement can be used informally, such as a single expert working in an office
estimating and documenting the data for a parameter value for use in a model. Or it can be elicited from
one or more experts, using a formal, structured procedure such as an expert opinion workshop.
Often the complexity of the risk problem is such and the uncertainties are so large that a formalised
approach is adopted using a range of experts from many disciplines. Good examples exist in the
hydroelectric dam risk assessment and radiological waste literature (e.g. Rashad and Hammad, 2000).
Here the consequences of poor decision-making are often substantial, so the operators of hydroelectric
dams and radioactive waste facilities have developed and employ highly structured approaches for
the selection and use of evidence. Formal expert elicitation is a structured practice to elicit beliefs on
generated risk scenarios. At this level of sophistication, expert elicitation is a complex activity on which
there is an extensive literature and multiple contrasting approaches and schools of thought. O’Hagan
et. al. (2006) provide a comprehensive overview.
Expert judgement methods may be used to elicit: a) distributions; b) preferences, rankings or pair
comparisons; c) qualitative information (links, interrelationships); d) point values (most likely, minimum,
maximum, quantiles); or e) probabilities. For example, the following steps describe how probabilities
(of defined events) can be elicited (after Vanrolleghem, 2010):
1) identify and select experts;
2) explain the nature of the problem and the elicitation procedure to the experts;
3) chose a scale and unit familiar to the experts for defining the quantity;
4) discuss and document the sources of current knowledge and evidence, its relevance to the problem,
its strengths and weaknesses;
5) elicit and assess extremes of the distribution;
6) elicit and specify the distribution;
7) confirm that the distribution represents the experts’ beliefs; and
8) decide if the distributions elicited from different experts should be aggregated and, if so,
how (Bedford and Cooke, 2001).
Examples in which expert elicitation methods were used are provided in Case Study Box 9 and 10.
Case Study Box 9 describes the study structure of an assessment that used expert elicitation related to
qualitative categories, while Case Study Box 10 provides an example of a formal elicitation approach
relating to quantitative information.
35
Case Study Box 9
Anaerobic digestion [AD] risk assessment and residue hazards
Centre for Energy and Resource Technology, Cranfield University, UK.
Market confidence is central to the use of organic waste materials in UK agriculture. A thorough and independently
traceable process of risk assessment is needed for assurance that processed waste materials can be used safely. This process
often requires the combination of both existing evidence and expert knowledge from the sector. Waste material processing
brings together stakeholders from a wide range of expertise. These include farmers, process operators, waste management
contractors, land management specialists and food supply-chain representatives, such as food standards and supermarket
representatives. The project team was tasked with drawing together the available evidence on the hazards present for all
wastes allowed into AD processes as a feedstock. In addition, expert knowledge from members of the steering groups was
sought to ensure that operational and agricultural practices could be taken account of within the assessment. Figure 13 shows
the sequence of evidence gathering and analysis which draws on key reference documents as well as expert stakeholder input.
Figure 13: Overview of risk assessment method for the safe use of AD residue.
In excess of 38 million potential combinations of; waste types, hazards, process types, viable pathways, end user groups, and
exposure risks made up the series of range scale combinations to be considered. Spreadsheet-based modelling techniques were
used to collate key decisions from stakeholders and, in turn, to relate stakeholder decisions to each stage in the sequence (e.g.
exposure pathways).
Release of hazardous agents including; human and animal pathogens, plant pathogens, potentially toxic elements [PTEs],
persistent organic pollutants [POPs], physical hazards and odour, along the processing and end-use pathway to unacceptable
concentrations would erode market confidence in AD biofertiliser use. Agricultural land-use for this residue would be
closed-off and the resulting reduction in land bank available for disposal would raise the cost of AD processes and
potentially return materials to landfill in order to assure the protection of animals, humans or the wider environment.
Assuring a transparent, documented, evidence-based process was central to developing and maintaining market confidence.
36
Key
Shapes:
Process
Data
Document
Master list
or hazards
Master list
of exposure
pathways
End uses for AD
products
Wastes
categorised
as a hazard
profile
AD processes of
products
Key
reference
documents
Make link between
end uses and
exposure
pathways
Master list of
waste types
Hazard screening Waste type
screening
Waste typeprocess typeproduct typescreening
Categories of
waste type – AD
type with similar
hazard profiles
Principle
hazards
Compilation of
waste-processproduct-end use
permutations
Exposure
assessment of
waste-processproduct-end uses
Ranked risk
matrix
Project
team work
Export
stakeholder
input
Shading
Exposure
pathways linked to
end use
Case Study Box 10
Eliciting expert judgments about the future cost of livestock diseases
Food and Environment Research Agency, Defra, UK.
As part of a public consultation on animal health in 2009, Defra published estimates of the average annual cost of future
outbreaks of exotic animal diseases. The estimates were made by Defra vets and economists who were expert in the field, but it
was recognised that the estimates were highly uncertain and thus ‘illustrated very roughly the possible scale of outbreak costs’.
For a revised assessment in 2010, formal methods of expert elicitation were used to help the Defra vets and economists
express their uncertainty about each element of the calculation underlying the estimated costs. They were asked in a
structured group discussion to provide upper and lower estimates as well as central figures for each element, which were
used to construct probability distributions representing their uncertainty. These distributions were then combined using
Monte Carlo simulation to estimate a probability distribution for the total costs.
The results were presented in a table of estimated costs, similar to that in the 2009 assessment but, this time, adding ranges to
show the uncertainty (Table 5). This provides a picture of the how different the true costs might be, which was previously lacking.
When the results are plotted as a cumulative distribution, it is possible to estimate the chance that the average annual
cost will fall below any given value. For example, there is a 60% chance that the average annual cost excluding unknown
diseases will be less than £20 million – and therefore a 40% risk it will exceed £20m (see Figure 14). This type of information
could help decision makers consider what financial provisions to make for future costs.
Sensitivity analysis was used to identify which parts of the calculation contributed most uncertainty: these might be priorities
for data collection or modelling to reduce the uncertainty of future estimates.
Table 5: Extract from results of expert elicitation, for the average annual cost to government for one disease.
Similar results for multiple diseases were combined to estimate a total (Defra, 2010).

Disease	Main species affected	Average interval between outbreaks	% probability that outbreak is major	Incidence cost £m if outbreak is minor	Incidence cost £m if outbreak is major	Average cost per outbreak £m	Average annual cost £m
Foot-and mouth disease	Cattle, sheep, pigs	25 (10,59)	5 (2.3,7.9)	50 (18,125)	400 (90,3200)	76 (30,227)	3.1 (0.86,12)

Figure 14: Graph showing the uncertainty expressed by experts in estimating the average annual cost of known
exotic livestock diseases in England (government costs only).
37
100%
80%
60%
40%
20%
0%
0 10 20 30 40 50 60 70 80
Average annual cost excluding unknown diseases (£m)
Cumulative probability (as %)

e.g b

. approx. e sufficien

60% chanc t to cover

e that £20 known exo

m p.a. wo tic disease

uld s

3.3.3 Dealing with uncertainty
Uncertainty is associated with every component of risk assessment (Section 3.1). Rarely, in environmental
science can uncertainties be quantified with precision. The uncertainties present can be defined as
epistemic, where their existence is brought about by a lack of knowledge; or aleatory, which relates to
the inherent variability of any natural system. Classifications within each of these types of uncertainty are
detailed in Appendix 4.
Identifying uncertainties is the first step towards quantifying them. Whilst only epistemic uncertainties can
be reduced, clear recognition of all uncertainties can help improve the quality at every stage.
For example, data may be incomplete (e.g. data may be lacking on the times series of emissions from a
certain incinerator, the total emissions over a defined period, or the precise nature of the emissions). Also,
data may be subject to rounding-off (e.g. 0.342 may have been recorded as 0.3); specified only
as a maximum permitted level of emission; poorly specified (e.g. instead of the electricity use of a
80-l boiler in France in 2007, one may have data for a 75-l boiler in Germany in 2006); erroneous
(e.g. measurement errors or mistakes in recorded units); subject to sampling variability (e.g. a small number
of incinerators surveyed); sampling bias (e.g. in selection of incinerators surveyed); or extrapolation
(e.g. from incinerators in a country where data are available to another country which lacks data).
Multiple techniques exist for dealing with uncertainty within environmental risk assessments. Selection
of the most appropriate method depends largely on the type(s) of uncertainties identified. Below is an
outline of the most commonly used techniques.
s Further research
The collection of information enhances knowledge and understanding and reduces uncertainty.
Situations in which data are sparse, imprecise, or uncertain in some other way will benefit from further
research and development (Aven and Steen, 2010). This should in turn reduce the uncertainties
associated with subsequent processes such as modelling and decision making.
s¬ Uncertainty factors
Uncertainty factors (also called safety factors) are often used to take account of uncertainty
(OECD, 1995). They may be thought of as providing a margin of safety: they attach a factor-based
correction to the data being used which is designed to reflect the level of uncertainty within it. Some
uncertainty factors are used to take account of extrapolation uncertainties, for example, the standard
uncertainty factors used to take account of species differences in toxicology and ecotoxicology.
s¬ Probability density functions
Many methods have their focus on computational modelling processes. One such technique is the use
of Probability Density Functions (PDFs), a technique based on Bayesian probability theory that is used to
estimate unknown model parameters based on the degree of belief about these parameters (Bolstad,
2007). In practice, Bayesian probability theory is applied mainly to situations such as noise in data where
no unique solution exists (Neil and Bretthorst, 1993). All the relevant information is summarised in a PDF,
which may then be used in the modelling process to present a risk as a spectrum of possible outcomes
with a distribution of frequencies or probabilities for each (also known as a risk curve). Modelling the risk
in this way can be done with various tools including Monte-Carlo simulation or Latin Hypercube sampling.
Case Study Box 11 describes the use of PDFs to quantify variability and uncertainty within the calculations
carried out in the risk assessment of pesticide risks to birds that was illustrated in Case Study Box 4.
38
Case Study Box 11
Probabilistic modelling of pesticide risks to birds
Food and Environment Research Agency, Defra, UK
The ‘Webfram’ projects developed a suite of probabilistic models for assessing environmental risks of pesticides. The completed
models were implemented as web-based software and are available for online use at www.webfram.com. The approach for
acute risks to birds and mammals is based on the same conceptual models as are used for deterministic assessment (see Case
Study Box 5) but using probability distributions to represent variability and uncertainty affecting different elements of the
calculation, as illustrated in the diagram below (Figure 15). Probability distributions show the range and relative likelihood of
possible values for each input and output, and thus provide a fuller picture of the possible outcomes.
Figure 15: Illustration of a probabilistic model for assessing acute risk of pesticides to birds.
The user enters information on the application rate and toxicity of the pesticide. The models then estimate dietary exposure
using the best available data on the diet and feeding behaviour of relevant species in UK conditions. The output is a
distribution estimating the variability of the toxicity-exposure ratio (TER, as used in current deterministic assessments) in the
population of animals that visit the treated crop on the day of pesticide application.
The models quantify some important types of uncertainty: ‘sampling’ uncertainty that is caused by having only limited
amounts of data for each model input, and uncertainty about the extrapolating from toxicity for species tested in the
laboratory to those exposed in the wild. The effect of these uncertainties is shown by distributions or confidence intervals
for the model outputs, showing how different the “true” TERs could be. Other types of uncertainty, which were not
quantified, were considered in a qualitative way (see Case Study Box 8). More details are available online at
www.webfram.com and in Hart et. al. (2006).
39
0.1
0.08
0.06
0.04
0.02
0
3025 35 40 45 50 55 60
Male BW
2.6
2.4
2.2
2
1.8
1.6
1.2 1.4 1.6 1.8 2
log10 DEE [kJ / g]
log10BW [g]
Best Fit
95% Prediction Interval
Data
0.35
0.2
0.25
0.3
0.15
0.1
0.05
0
18 2220 24 26 28 30
Gross Energy Insects [kJ/g]
6 5 4 3 2 1 0
2.5
3
3.5
1.5
1
0.5
0
0 0.2 0.4 0.6 0.8 1
Moisture Content Insects
Probability Density
2 Frequency
1.8
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
0 0.2 0.4 0.6 0.8 1
4
3.5
3
2.5
2
1.5
1
0.5
0
AE Plants
Probability Density
Frequency
1.6
1.4
0.8
1
1.2
0.6
0.4
0.2
0
10 20 100 200
RUD Insects
Probability Density

100% 80% s 1.5 1 0.5 0 0 0.2 0.4 0.6 0.8 1 2 1.5 1 0.5 0 PD Insect – May Probability Density Frequency food intake per day (wet wt) fraction of food type in diet fraction of diet obtained in treated areas concentration on

60%
40%
20%
0
210 543
FIR / BW
0 1 2 3 4 5 6 7 % of skylark25
30
20
10
15
5 0
0 0.40.2 0.6 0.8 1
PT
Probability Density
3 Frequency
2.5
2
3.5
3
2.5
100%
80%
60%
40%
20%
0
0.0001 0.001 1 100 100000 106 108
Dose [mg / kg BW / d]
% of species
Mallard Duck
Bobwhite Quail
100%
80%
60%

40% 20% 0 0.01

1 100 1000
Toxicity Exposure Ratio (TER)
% of skylarks
100%
80%
60%
40%
20%
0
0.01 0.1 1 10 100
Exposure [mg / kg BW / d]
% of individuals
body weight
daily energy
expenditure
gross energy
content of food
mositure content
of food
assimilation
efficiency
pesticide
application rate
residue per unit
dose
food
LD
50
(mg/kg)
ToxicityExposure
Ratio
exposure
(mg/kg/day)
s¬ Bayes linear methods
Unlike PDFs, which describe uncertainty in terms of probability, Bayes linear methods describe uncertainty
by expectation. By making expectation the fundamental quantity for the quantification of uncertainty,
demands for probability specifications are lifted to allow for a partial analyses in terms of the limited
beliefs that can be specified (Goldstein and Wooff, 2007). These methods are therefore useful if the
problem formulated is too complex to allow a full prior specification, or if the analysis is too difficult
because of the full prior specification (Coolen et. al., 2001). It is for these reasons that the Bayes linear
approach is sometimes viewed as a generalisation or simple approximation to the full Bayes approach
(Randell et. al., 2010). An overview of the Bayes linear approach is provided in Goldstein (1999).
s¬ Sensitivity analysis
Sensitivity analysis is used to determine which uncertainties have the largest impact on assessment
performance measures. It is good practice to conduct sensitivity analysis as an early step in model design,
to identify which factors are important to include, as well as at the end of the assessment. Sensitivity
analysis is of diagnostic value because it can usually highlight which aspects of the system being assessed
contribute most to the risk (Saltelli et. al., 2008). Depending on the degree of control one has over these
higher contributors, these features may then become priorities for management control.
A sensitivity analysis also enables the uncertainty in the output of a mathematical model to be attributed
to different sources of variation in the input of the model. This can provide an understanding of how
robust a model is. Sensitivity analysis can help to identify the significance of uncertainties in the model in
order to highlight areas that require further research or data collection. A useful overview and qualitative
comparisons of available sensitivity analysis methods, including mathematical, statistical and graphical
methods, is provided in Fray and Patil (2002).
3.4 Summary
Risk assessment involves four stages: (1) identifying the hazard(s); (2) assessing the potential
consequences; (3) assessing their probabilities; and (4) characterising the risk and uncertainty. The
output of this structured process provides a judgement as to the presence likelihood of the risk and its
significance, along with details on how the risk was assessed and where assumptions and uncertainties
exist. The evidence required to provide judgements and subsequently characterise a risk in this way can
be qualitative, quantitative, or semi-quantitative. Either way, for each problem, appropriate tools must
be employed. Where data is lacking or inaccessible, elicitation provides a formal method for obtaining
expert judgement. Uncertainty is always present when conducting each stage of an environmental risk
assessment. The techniques available to analyse, understand and manage these uncertainties include the
collection of more data, the use of trusted sources, probability density functions, Bayes linear methods,
and/or sensitivity analysis.
40
4.1 Introduction
Risks deemed unacceptable require management to lower them to a
tolerable level of residual risk. Usually, the decision-maker has access to a
range of risk management options to reduce, eliminate or exploit risk.
Zero risk is usually unachievable.
Options appraisal is the process of identifying and selecting the most
appropriate risk management strategy given the constraints of the
decision-maker (HM Treasury, 2003). This may involve scoring, weighting
and/or reporting different risk management options. Various criteria are
used for identifying the ‘best’ option, according to context, but a common
framework is to seek to maximise some long-term definition of human
well-being such as environmental security, net social benefit or value for
money (risk reduction per unit cost). Key inputs for this process are the
controlling factors for each risk identified during the problem formulation
stage (Chapter 2). For instance, if a controlling factor is the level of investment in monitoring and control
equipment, then risk management options can be identified that focus on those issues immediately.
It is important to identify the risk management options as a distinct preliminary step because ill-considered
risk management strategies may otherwise result in wasted effort and expenditure (HM Treasury, 2004).
The risk management options available usually take one of the following forms (Figure 16):
s terminate the source of the risk where possible;
s mitigate the effects by improving environmental management techniques or engineered systems;
s transfer the risk through new technology, procedures or investment;
s exploit the potential benefits of the risk by embracing new opportunities; or
s accept the risk by not intervening with new or existing situations.
To select the preferred option, the potential positive and negative effects associated with each option
may be considered under the following headings (Figure 16):
Technical factors: whether the options were likely to reduce the risk, by how much, and how difficult it
would be to implement the option; for example, the extent of required research and development.
Economic factors: the cost of implementing the option (to the organisation, affected businesses,
exposed groups or society as a whole).
Environmental security: the potential impacts of the options on the health and sustainability of
environmental resources including the impact to existing habitats.
Social issues: the social impacts of the risk, such as the potential costs or other losses to the community,
jobs or house prices, life expectancy and/or amenities.
Organisational capabilities: considering the risk management capability within the organisation or
body, or the capability of society or exposed groups.
41
CHAPTER 4
Appraising the Options
FORMULATE
PROBLEM
ASSESS
RISK
APPRAISE
OPTIONS
ADDRESS
RISK
Figure 16: Identifying the optimal risk management technique involves consideration of the effects associated
with economic and technical factors, environmental security, social issues and organisational capabilities
(after Aon Corporation, 2011).
Combining these elements permits a systematic comparison of options for risk management.
A recommended decision-making process is outlined in Section 4.2, and factors that should be
considered when identifying the available options are detailed in Section 4.3.
4.2 Structured decision making
Regarding the systematic methods that can be used for comparing and evaluating risk management
options; there is no universal method suitable for all circumstances. Rather, selection or adaptation of an
existing methodology or development of a new methodology will often be necessary.
All good decisions rely on the effective analysis of alternative options. A systematic appraisal is important
to ensure that the decision-maker is clear about the objectives and how to decide where the balance
lies between the benefits from the reduction of the risk and the costs and implications for society of
introducing potential control measures. A systematic appraisal of options will be the process of identifying,
quantifying and weighting the costs and benefits of the measures which have been identified as means of
implementation. This process must include all implications of the potential options, and not just those that
can be quantified. A common framework can be envisaged consisting of the following steps:
42

Terminate

 

Mitigate

Preventative Corrective

 

Transfer

Insurance Contract transfer

 

Exploit

 

Accept

Eliminate
the source
of risk
Explore
opportunities
in the risk
approach
Make a
conscious
decision to
tolerate the risk
Directive
Social issues
Hybrid
POSITIVE AND NEGATIVE ENVIRONMENTAL EFFECTS OF STRATEGIES CONSIDERING:
Economic
factors
Technical
factors
Environmental
security
Organisational
capabilities
RISK MANAGEMENT STRATEGIES:
1. Identification of the objective, ensuring a clear and common understanding of what is the
desired outcome.
2. Identification of the options. In most cases there will be options that are obvious to the decision-maker.
Some will be less applicable than others and it will be necessary to identify those that have the potential,
either in whole or part, to meet the objective.
3. Clarify the decision criteria, the implications of change, and the social, economic and
environmental benefits.
4. The options identified will need to be implemented using various tools, such as policy instruments,
economic measures or regulations. Consideration should be given to the selection of those most
appropriate while recognising that they will not be mutually exclusive and a combination of one or
more may be appropriate for one or more options.
5. Identification of the impacts of the options. This will require collection of data from those stakeholders
who will be affected by potential measures. Close consideration should be given to the implications of
changes in working methods (good and bad) to meet the objective.
6. Compare the advantages and drawbacks for each option including the trade-off between quantified
and qualitative data to draw conclusions.
When the required risk response becomes clear, the effectiveness of the chosen risk management action
is then checked during the monitoring and review phases (Chapter 5).
4.3 Considerations in decision making
4.3.1 Reducing risks
Where the focus is on what the best strategy is to mitigate the assessed risks (Figure 16), consideration
should be given to the risks that will remain after the chosen management option is implemented. This is
commonly referred to as the ‘residual risk’. As described in Section 1.3 and detailed in Appendix 2, there is
a substantial amount of regulation that may constrain or enable an activity with uncertain consequences.
In some cases it may be appropriate to strike a balance between risk reduction and cost, such as required
under the regulatory principles of ALARP (As Low As Reasonably Practicable) and BAT (Best Available
Technique) in England and Wales (Environment Agency, 2010).
The ALARP principle is from a specific regulatory framework that applies when risk needs to be reduced
to as low as reasonably practicable. Adoption of the principle implies that any further reduction in the
risk beyond ALARP can be achieved only at grossly disproportionate cost and that the benefits afforded
by accepting the risk are judged to outweigh the costs.
The application of BAT means that the estimation of the risk associated with a particular activity
can change over time as new techniques and technologies are developed, and the costs of existing
techniques vary. Such changes may warrant another iteration of the risk assessment process. BAT relies
not only on technological solutions, but includes other approaches such as environmental management
systems and staff training.
43
4.3.2 The relevance and use of precautionary approaches
If a preliminary scientific evaluation shows that there are reasonable grounds for concern that a particular
activity might lead to damaging effects on the environment, or on human, animal or plant health,
which would be inconsistent with the protection normally afforded to these within the European
Community, the precautionary principle may be invoked.
The precautionary principle states that ‘In order to protect the environment, the precautionary approach
shall be widely applied by States according to their capabilities. Where there are threats of serious or
irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing
cost-effective measures to prevent environmental degradation’ (Principle 15 of Agenda 21).
If the precautionary principle is adopted, decision-makers determine what action is necessary,
taking into account the potential consequences of taking no action, the uncertainties inherent in the
scientific evaluation, and consulting interested parties on the possible ways of managing the risk.
The adopted measures should be proportionate to the level of risk and to the desired level of protection.
They should be provisional in nature, pending the availability of more reliable scientific data.
Research into the use of the precautionary principle (EEA, 2001) identified that the following issues
should be considered: the acknowledgement of ignorance; the requirement for long-term monitoring;
ensuring that real-world conditions are accounted for in regulatory appraisal; consideration of benefits
as well as risks; ensuring the use of lay and local knowledge as well as specialist expertise; and avoiding
‘paralysis by analysis’ by acting to reduce potential harm when there are reasonable grounds for concern.
4.3.3 Environmental security
In appraising risk management options, the relationship between protecting and enhancing our
environment and allowing economic sustained growth in the long term should be explored
(Defra, 2010). Environmental security aims to achieve a better quality of life for everyone now, and for
generations to come. The overall aim is to ensure that economic and environmental benefits are available
to everybody.
Recently there has been much work developing sustainability appraisal methods to support contaminated
land risk management decisions. In the UK this work has been led by the Sustainable Remediation
Forum (SuRF-UK) and their framework guidance is now available (CLAIRE, 2010). Others in Europe
(NICOLE, 2010) and the USA (SURF, 2010) have been doing similar work within their policy environments.
It has also been recognised that achieving environmental security requires collective partnership
approaches to decision-making for environmental protection. Environmental management strategies
must therefore consider economic demands and social needs, with the capacity of the environment to
cope with discharges, pollution and other perturbations, and to support human and other life
(Case Study Box 12).
44
Case Study Box 12
UK Climate change risk assessment – across a range of sectors
Climate Change Risk Assessment Project, Defra, UK
The Climate Change Act (2008) requires Government to implement policies to adapt to climate change – and to inform
this, to lay before Parliament assessments of the risks posed to the UK by the impacts of climate to the year 2100. The risk
assessment will be complemented with an Adaptation Economic Assessment (AEA) which will assess options for dealing
with the largest risk, based on their costs and benefits.
The method for this first Climate Change Risk Assessment uses a tiered risk assessment to consider the risks posed to the
UK by impacts cause by climate across a range of sectors (such as Health, Transport, Agriculture, etc). Analysis will be both
quantitative and qualitative depending on the evidence and data available for each type of risk. To do this the following
process has been used (Figure 17):
Identify and characterise the impacts:
through literature reviews, workshops and
systematically mapping cross-sector impacts.
Assess vulnerability: As well as looking
at possible future climate changes, this
step of the method considers exposure
to the risks through an assessment of
the adaptive capacity of major sectors
at the organisational level, an analysis
of government policy, and uses a social
vulnerability checklist to characterise impacts
that have particular equity issues.
Identify main risks: A subset of risks with
relatively higher magnitude and likelihood,
and those where urgent decisions are needed
will be selected for further analysis.
Assess risks to 2100: We will project
future consequences using risk metrics
to create qualitative, or sometimes
quantitative, “response functions” that relate
consequences to climate variables. Climate
projections combined with socio-economic
assumptions can assess the magnitude of
possible future consequences. Accounting for
the effects of autonomous adaptation and
existing policies will provide an estimate of
the ‘residual’ consequences.
Report on risks: using the assessment of
impacts and vulnerability together, a report
will be created to help Government identify
priority areas for action, geographic variations
and compare different risks where possible.
Inform the second CCRA (in 2017):
by including a learning process within
the project so that the expertise gained
is retained in government and the wider
research community.
45
Define problem/
Decision criteria
4. Cross sector links
15. Choose
detailed sector
1. Literature
review and other inputs
11. Anticipated adaptation
Retain all risks for report
Assess
Risk to 2100
Assess
Vulnerability
Identify &
Characterise
Impacts
Report
on
Risks

7. Risk 12. Mon 8. Assess how vary wit 13. Repor and t 10. Incorporate cha 9. Scale w change p
metrics etisation risk metrics h climate ts, maps ables socio-economic nge ith climate rojections main risks	3. Identify

14. Report outputs
6. Adaptive capacity
2.Policy risk mapping
5. Consider equity
Figure 17: Framework for monitoring future climate change impacts.
4.3.4 Economic considerations
Economic factors can have a significant influence on the decision-making process and may affect
the acceptability of a given option. In the case of flooding, for example, there are construction and
maintenance costs associated with any flood risk management scheme; there may also be costs in terms
of damage to the environment by habitat removal or alteration. An example of estimating flood damage
cost to agriculture is provided in Case Study Box 13.
The best option is likely to be the one with the greatest excess of benefits over costs. The benefits are
those accruing from protection (e.g. the damage or loss of property, materials, crops, human health and
environmental assets that is avoided) taking account of the likelihood that these benefits will be realised.
The costs are those social, regulatory and private costs of the control options, including construction,
maintenance and environmental damage. This should include both those benefits and costs that can
be monetised and those that cannot (or for which robust monetary valuations are not readily available)
– the latter need to be assessed in physical and qualitative terms. As monetary values can more readily
be assigned to some impacts than others, care is needed to ensure that adequate consideration is given
in any decision-making to all non-monetised items that may be thought significant, relative to the
monetised elements. Agreement should be sought at the problem formulation stage over what
non-monetised metrics are acceptable to decision-makers. Where there are multiple endpoints,
benefits and associated criteria, multi-criteria decision analysis may help discriminate the different
benefits associated with different risk management options.
4.3.5 Multi-criteria decision analysis
Environmental decisions can be complex, largely due to the inherent trade-offs between social,
environmental and economic factors. The selection of an appropriate risk management strategy often
involves additional criteria, such as the distribution of environmental impacts or costs and benefits
(Steele et. al., 2009). Research in the area of multi-criteria decision analysis (MCDA) has enabled the
development of practical ways to compare decision options when there are multiple criteria for assessing
those options (Kiker et. al., 2005). MCDA brings together criteria and performance scores, usually in
matrix form, to provide a basis for integrating risk and uncertainty levels. In this way, it is possible to
perform an evaluation (ranking) of the alternatives. The main advantage of MCDA is its capacity to draw
attention to areas of conflict between stakeholders and decision-makers). However, the need to attempt
to first reach a consensus on criteria and weightings in discussion with stakeholders can bring limitations
to the use of MCDA methods (Section 4.3.6). Participants may initially be unready to relinquish their own
subjective views, but through the use of MCDA, a deeper understanding of the values held by others is
possible (Paruccini, 1993).
A basic example of a decision matrix is provided in Table 6 which can be used to describe a MCDA
problem. The level of risk determined in the risk assessment process can be used to parameterise the
decision matrix. Streamlining the factors against which the options are assessed can be a two-stage
affair. First, how each option would affect the problem being considered is shown in terms of its positive
and negative impacts on the three core elements: environment, society and the economy. Next, it can
be helpful to consider if what appears to be the ‘best’ option is worth pursuing given the ‘delivery’ risks
associated with this (e.g. organisational capability, complexity of implementation). This is where the
“balancing of risk” comes to the fore. For example, the decision matrix in Table 4 shows that option 3 is
most efficient from a risk reduction point of view but it is also expensive. Depending on the
decision-maker’s opinion of the budget, a decision-maker may select option 3 or a cheaper option 2,
46
which may still result in an appropriate level of risk reduction (Kiker et. al., 2005). Details on executing
more technical and specific MCDA methods (e.g. aggregated indices randomisation method; analytic
hierarchy process; the evidential reasoning approach; value analysis) are available in the literature
(e.g. Higgins et. al., 2008; Tam et. al., 2006; Chan and Tong, 2007).
Table 6: Example of a decision matrix showing how each option under consideration will affect the economic,
environmental and social risks identified.

Option 1 Do nothing	Option 2 Mitigate	Option 3 Terminate
Economic	?	¤	¤
Environmental	¤	¤	¤
Social	¤	¥	¤
Key: ¤ Level of risk decreases ¥ No significant impact on the risk ¤Level of risk increases ? Not enough information or too much uncertainty to judge the impact

4.3.6 Involving stakeholders and the public
As detailed in Chapter 2.4.1, in some cases it may have been necessary and feasible to involve
stakeholders and the public in the risk assessment and management process. While it may not be
necessary to involve the same people in all elements of the process (e.g. it might be appropriate to
involve members of the local public in the scoping of the risk issues and framing of questions),
certain groups may take on active roles within the decision-making process. It is also likely that those
who were involved in the planning of the risk assessment will want to be involved in the post-assessment
stages. This can be beneficial, as good decisions are often informed by the knowledge and concerns
of stakeholders and the public, and are understood and supported by the people who may be directly
affected by them (e.g. a new genetically-modified sugar beet trial; the assessment of coastal flooding;
the design of a new flood control scheme; the licensing of an extension to a landfill; and the remediation
of a contaminated site).
Involving stakeholders and the public in appraising options can result in positive outcomes, such as the
resolution of conflict, social learning (e.g. Bull et. al., 2008), integration of a broader knowledge base and
community support (e.g. Weber et. al., 2001). However, there may be multiple decision-makers
(for example, planning authorities and environment agencies) that need to be involved in appraising the
options. In this case, it is important to make clear to those involved the objectives and the limits of what
can be achieved. For example, it may not be possible to change a land-use planning decision, but it may
be possible to place conditions upon what is built and how it is operated. If people have expectations
about what their engagement might achieve that are not fulfilled, the credibility of the process,
the organisation and the decision can all be lost (Petts, 2008). These issues are discussed further in
Chapter 6.
47
Case Study Box 13
Estimating flood damage cost to agriculture to inform risk assessment
School of Applied Sciences, Cranfield University, Bedfordshire, UK
Exceptional rainfall during the summer of 2007 caused widespread flooding and economic damage in England
(Chatterton et. al., 2009). Over 42,000 hectares of farmland were seriously affected, at the time of year when crops were
approaching harvest and grasslands were being grazed or cut for winter feed (Figure 18). The 2007 floods provided a useful,
albeit unfortunate, opportunity to assess the economic impact of large scale flooding on farming. This is required to inform
the appraisal of flood risk management and investment options, whether to justify protection of high value agricultural land
or to assess the cost of temporally storing flood waters on farm land to alleviate urban damage downstream.
A personal visit survey of 78 farmers affected by flooding in the 2007 event was carried out in the West Midlands,
Oxfordshire and Yorkshire, covering about 14% of the total agricultural area flooded (Posthumus et. al., 2009). The
method used is summarised in Figure 19.
Average flood damage costs were estimated at £1200 per hectare flooded, highest on horticultural and vegetable crops
and lowest on grassland. Over 80% of flood damage costs were associated with losses of output and additional production
costs, and the rest concerned damage to farm assets such as machinery, property and infrastructure.
At a total of £50 million, the costs to agriculture were only about 2% of the total estimated economic cost of the 2007
Summer Floods in England. At the farm level, flood damage costs (excluding household property) averaged about £80,000,
with a median value of £43,000. Only about 5% of agricultural flood damage costs were insured compared with around
80% in the urban sector.
This case study serves three main purposes: (i) it provides evidence-based estimates of flood damage costs of summer
flooding on farm land, (ii) it helps to refine the methods for estimating flood damage costs for benefit assessment of
flood risk management options involving farmed areas (Penning-Rowsell et. al., 2005) and (iii) it confirms the vulnerability
of farming to extreme events and reveals how farmers might manage flood risks associated with future climate change,
including the possible use of insurance.
Figure 18: Flooding on the River Avon, near Tewksbury, in July 2007 caused extensive damage to high value crops.
48

* **	Relative to situation ‘without’ this type of flood event. Probability of an event of this type occurring within the next 12 months.

*** Average annual damage costs associated with an event of this type and probability (i.e. flood risk).
Figure 19: Procedure for assessing flooding risks
4.4 Summary
Evaluating risk management options involves identifying and considering a range of potential
risk management techniques. The risk management options available are to terminate, mitigate,
transfer, exploit or tolerate the risk. To select the preferred option, the potential positive and negative
impacts associated with each option are considered according to technical factors, economic factors,
environmental security, social issues and organisational capabilities. The decision-making process can be
complex, owing to trade-offs between these factors, and because the consideration of one issue often
has to take its place within a portfolio of concerns (i.e. the finite and limited money available often
needs to be distributed across a portfolio of risks). Multi-criteria decision analysis (MCDA) provides a
practical way to compare decision options when there are multiple criteria for assessing those options.
Involving stakeholders and the public in appraising options can result in positive outcomes, but there may
be multiple decision-makers that need to be involved and, therefore, it is important to be clear about
the objectives and the limits of what can be achieved. If unsustainable environmental degradation is
preventable, a lack of full scientific certainty should not be used as a reason for postponing cost-effective
preventative measures. The best option is likely to be the one with the greatest excess of benefits over
detriments, compared to the other possible options. The required response is about finding a balance
within the boundaries of what is tolerable and justified by reference to the residual risk.
49
Farm type
Impact of floods on:*
Area, season, duration,
depth, water quality
Crop outputs,
inputs and values
Livestock outputs,
inputs and values
Flood
damage costs
Average annual
damage cost of
flood event***
Farm assets and
infrastructure costs
Other costs, e.g.
clean up, relocation
Characterisation
of flood event
Annual
probability**
Land use
5.1 Implementing the risk management strategy
Addressing the risk involves undertaking any action, procedure or operation to
fulfil the objectives of the risk management strategy identified at the options
appraisal stage (Chapter 4). If a risk needs to be terminated, then all or part
of an activity should cease. This may include the decision not to proceed with
a new proposal or contracting out of an existing project. When a risk needs
to be mitigated to an acceptable level, the treatment can often be built into
operational activities. For example, Case Study Box 14 shows how the risk
of flooding is managed in high-risk areas in England and Wales where flood
defence schemes and improvements are being considered. If a decision was
made to transfer a risk, risk managers could look to:
s¬ use insurance;
s¬ ¬ amalgamate the risk with another that is already managed to an acceptable
level (hybrid risk transfer);
s¬ arrange partnerships; or consider
s¬ ¬ outsourcing. In practice however, risk can rarely be outsourced in its entirety. Even when liabilities are
contractually transferred, reputational impacts may return to the origination of the risk.
Care should be taken that the risk is actually transferred and details of this are recorded. In addition,
some risks (e.g. reputation) cannot be transferred. For example, whilst contract clauses might protect
an institution against the less responsible operations and practices of outsourced parties, in practice
these risks may still return to ‘bite’ the contracting organisation. Further details on operational risk
management at the institutional level are provided in Appendix 4.
If the opportunity that a risk presents is to be exploited, the event should be made to happen in a
measured, informed, calculated and monitored fashion. It may also be possible to increase the probability
and therefore maximise the benefits.
To accept a risk generally means implementing a reactive approach without taking explicit actions.
When implementing this strategy, it is important to clearly acknowledge acceptance of the risk(s)
and monitor the effectiveness of the strategy (Section 5.8).
50
CHAPTER 5
Addressing the Risk
FORMULATE
PROBLEM
ASSESS
RISK
APPRAISE
OPTIONS
ADDRESS
RISK
Case Study Box 14
National flood risk assessment (NaFRA)
Environment Agency, UK
The National Flood Risk Assessment (NaFRA) was developed to provide information on flood risk. This was a key part of
the move to planning flood management on the basis of risk, rather than reacting to flood hazard. NaFRA is a generic
quantitative risk assessment using a standard model designed for nationwide application. NaFRA results are available
throughout the floodplain in England and Wales. Detailed quantitative flood risk assessments are used to appraise options
at specific sites, particularly for high risk areas where flood defence schemes and improvements are being considered.
How the assessment works
The process used to create the national flood risk assessment is as follows:
1. The flood outline is split into impact zones that are 50m x 50m in size.
2. Information on flood defences; i.e. their location, standard of protection and condition are linked with the impact zones
to identify which defences affect which impact zones. Information about the height of the natural banks affecting each
impact zone is also added.
3. Predicted flood water levels are then compared to the height of the natural banks and the defences to calculate the
likelihood of flooding by defences and natural banks overtopping for each impact zone.
4. The same predicted flood water levels are then compared to the condition of defences to calculate the likelihood of the
defences failing and the effect that this would have on each impact zone.
5. The overall likelihood of flooding for each impact zone is calculated by combining the figures above.
6. The flood likelihood results are then put into three categories:
Significant – where the likelihood of flooding is greater than 1.3% (1 in 75) in any one year
Moderate – where the likelihood of flooding is between 1.3% (1 in 75) and 0.5% (1 in 200) in any one year
Low – where the likelihood of flooding is less than 0.5% (1 in 200) in any one year.
How the risk is managed
Outcome measures have been set for the Environment Agency (EA) and other operating authorities managing flood risk.
The five outcome measures appear in Table 7. The targets show what the capital programme, i.e. spending on flood
defence upkeep and improvement projects – is expected to contribute to these measures until 2011.
Table 7: Outcome measures of NaFRA for the EA and other Operating Authorities (EA, 2009).

Outcome measures until 2011	Definition	Minimum target
Economic benefits	Average benefit cost ratio across the capital programme.	Five to one average with all projects having a benefit cost ratio greater than 1.
Households protected	Number of households with increased protection against flooding or coastal erosion risk.	145,000 households of which 45,000 are at significant or greater flood risk.
Deprived households at risk	Number of households in the 205 most deprived areas for which the likelihood of flooding reduces from significant or greater risk.	9,000 of the 45,000 households above.
Nationally important wildlife sites	Hectares of sites of special scientific interest (SSSI) land where there is a programme of measures.	24,000 hectares.
UK Biodiversity Action Plan habitats	Hectares of priority Biodiversity Action Plan habitat including intertidal, created by March 2011.	800 hectares of which at least 300 hectares should be intertidal.

51
5.2 Responsibility for residual risk
Whether the risk management strategy terminated, mitigated, transferred, exploited or accepted the
inherent risk, residual risks may remain. The responsibility for addressing the residual risk is either shared
by society (e.g. societal risk), remains with the individuals involved in developing or implementing the risk
management strategy (e.g. private risk) or it is transferred further (e.g. to insurers).
5.3 Reporting the risk management strategy
Reporting risk management strategies is an important part of addressing the risk, particularly regarding
decisions on addressing the most serious risks, and needs to be quickly and effectively communicated to
the appropriate level and the appropriate individual within an organisation (Cooper et. al., 2005). It is
essential to be aware of accountability at both the organisational and individual levels (National Research
Council, 2009).
At a time of crisis, the public generally expect the Government to provide a strong lead and to take
charge of events and manage situations, thereby protecting the public. Where there is a need for
leadership and reassurance, or a need for accountability and justification of decisions, the public will
often look to governing authorities to deliver clear messages on how risks are being managed.
When reporting a risk management strategy to the public, communicating the importance of
self-responsibility to the public should not be forgotten. The actions of an individual may exacerbate
an outcome (either for themselves or for others) and, if the public are not aware that they also have a
responsibility to take reasonable care, the fault may be unduly proportioned to other organisations.
A number of cross-cutting aspects relating to communicating the risk management process are detailed
in Chapter 6. These should be referred to and considered prior to communication.
5.4 Surveillance and monitoring of residual risk
Surveillance implies an active evaluation of changing circumstances. Perhaps the residual risk is
sensitive to some external influence that requires active monitoring. For example, a change in
European environmental legislation may initially have no impact, but may have an impact over time as
environmental attributes change and, therefore, the implemented risk management strategy requires
monitoring (Case Study Box 13).
The emergence of new risks may be the result of a diverse set of risks such as climate change,
increasing urbanisation, demographic changes, changes in social attitudes towards risk acceptability,
and advances in technologies available to reduce risk. This can result in a new set of conditions against
which existing risks should be compared and altered if necessary. The implication is that environmental
risk assessments need to be living documents rather than static one-off reports. This issue of reviewing
the entire risk management process is detailed further in Chapter 6.
52
5.5 Contingency planning
High-impact events with a low probability, such as certain animal disease outbreaks, severe flooding
or natural disasters, are often addressed with the development of an emergency plan and a business
continuity plan that ensure essential business activities can continue in the face of serious disruption as a
result of these events (Defra, 2007). In general, regulatory bodies have strategies in place for contingency
planning. For example the Environment Agency has in place a flood warning system to provide sufficient
warning to those living in flood risk areas. The Health Protection Agency has a handbook for recovery
options following a radiation incident (Nisbet et. al., 2008). Water UK has a guide for effective control
of water-based contamination incidents (Water UK, 2003). The Food and Environment Research
Agency (Fera) produced guidance on the decontamination of buildings exposed to chemical, biological,
radiological or nuclear materials (Fera, 2011). Also, some environmental risks (e.g. Case Study Box 14)
are part of the National Risk Assessment and therefore the National Risk Register (Cabinet Office, 2010).
Likewise, the scale of risks and whether local, national or international intervention is required should
be considered. It is important to look at the potentially wider consequences of a risk so that decisions
based on a local situation are appropriate on a national and international scale, mitigating the potential
for conflict and environmental damage or harm. If this happens in advance, then decision-making in
a crisis of international proportions is likely to happen faster and with greater justification and public
satisfaction. Effective public engagement is vital for the success of such strategies (Chapter 2 and 6).
5.6 Summary
Addressing the risk involves undertaking any action, procedure or operation in order to meet the
objectives of the risk management strategy. The risk management strategy needs to have a documented
rationale; it is important to be explicit and clear about the actions that you will undertake in support of
the risk management strategy. Reporting risk management strategies is an important part of addressing
the risk and can benefit one or a number of stakeholders.
53
Case Study Box 15
Did a change in legislation increase the likelihood of Gyrodacytlus salaris introduction to the UK?
Centre for Environment, Fisheries and Aquaculture Science), Weymouth, UK
An assessment was carried out on the
risk posed to UK salmon by allowing
the movement of Atlantic salmon
from coastal sites in countries where
an Atlantic salmon parasite exists.
Import risk assessments are generally
undertaken in response to a proposed
new trade. The rules governing trade
in live fish within the EU is determined
by European legislation. The European
Commission proposed a change in
legislation to allow movement of live
Atlantic salmon from coastal sites in
countries where the Gyrodactylus salaris
(a monogenean ectoparasite of Atlantic
salmon) was present but where the
salinity does not drop below 25 % (parts
per thousand) to territories which were
officially free of the parasite. Potentially
this increased the probability that G.
salaris would be introduced to the UK
and a risk assessment was undertaken
(Peeler et. al., 2006). A scenario tree of
events, necessary for the introduction
and establishment of the parasite
was constructed (Figure 20); relevant
information was identified, and the
probability of each step qualitatively
assessed. Salinity was shown to be
the key environmental determinant of
parasite survival; at 25 % the parasite
survives for approximately 22 hours.
The change in legislation did not create
routes with a higher level of risk of G.
salaris introduction per consignment of
fish, compared with existing routes (i.e.
from approved G. salaris free freshwater
zones). Thus, based on the equivalence
principle of the SPS agreement of
the World Trade Organisation, there
was no basis to challenge the change
in legislation. However, as a result
of allowing imports of salmon from
coastal sites the total volume of live fish
imports increases, and thus the absolute
probability of G. salaris introduction,
may too increase.
54
Freshwater smolt
unit is infected
Wild fish in river are infected
Wild fish infected with parasite
migrate to proximity of
coastal site
Parasite survives migration
Living parasite detaches
from fish
Parasite attaches to susceptible
fish at coastal site
Consignment of fish
is infected
Parasite survives transport to
coastal site
Coastal site is infected on date of
transport
Consignment contains infected
fish P10
Parasite survives transport by wellboat/ lorry/
helicopter
Parasite survives and establishes at receiving
coastal site
Infected fish escapes
Infected fish swims to river near
destination site
Parasite survives transport
to freshwater site
G. salaris established in resident susceptible
population
G. salaris survives journey to
freshwater
Living parasite detaches
from farmed fish and infects
wild/feral host species P14
Consignment for f/w site
contains infected fish
Figure 20: Scenario tree for the introduction of G. salaris from
coastal sites to uninfected areas.
CHAPTER 6
Cross-Cutting Aspects of Risk Management
55
6.1 Introduction
As risks are dynamic in space and time, and the context in which they may be
realised changes, managing a risk effectively can thus require regular ongoing
monitoring, iteration of the previous analysis (Chapter 2 to 5), deliberation,
and constructive communication and learning during the processes.
Such activities strengthen the evidence base that supports the risk
management strategy and ultimately help to reduce the uncertainties that
surround the risk problem. This is particularly the case for those risks that
might be deemed marginal in their magnitude or, because of their specific
characteristics, are sensitive to change. Examples include where the progressive
erosion of cliffs increases the risks to people and property over time, or
where changes to international border controls influences the likelihood of
exotic animal disease agents entering a country. Reporting risk management
strategies is therefore an important part of addressing the risk and can benefit
one or a number of stakeholders.
This Chapter serves to reinforce the general cross-cutting aspects to consider during the environmental
risk assessment and management process.
6.2 Learning
Here learning refers to the gaining an awareness of knowledge, expertise, information, skills, values,
expectations, failures and successes as a result of the risk assessment and management process.
Learning as such is often inevitable, but should nonetheless be sought and acknowledged. Particularly as
awareness of environmental problems has grown and people have become more concerned about risks
to the quality of the environment and to their health; demands have increased for better engagement
in environmental risk assessment and management. Sharing information and learning through
communication and iteration are discussed in the following sections.
6.3 An iterative approach
Adaptive management aims to reduce uncertainty in the risk management process by taking an iterative
approach. An iterative approach includes all stages as described below (Section 6.2.1 to 6.2.4). Put
simply, iterations address whether the original concern (e.g. groundwater protection, the environmental
release of chemicals, the effectiveness of flood gates) is still the main concern, and whether the
environmental setting (source of hazard, exposure pathways, position and number of receptors) has
altered since the original risk assessment. Frequently, new information comes to light during a risk
assessment; either through research commissioned or by newly discovered or volunteered data.
Risk analysts need to be open to revisiting earlier assumptions, redoing calculations on risk estimates,
altering the conceptual model as new data comes to light, and exploring alternative scenarios.
Often, local knowledge can be supplied by the public, stakeholders or other parties.
FORMULATE
PROBLEM
ASSESS
RISK
APPRAISE
OPTIONS
ADDRESS
RISK
6.3.1 Problem formulation
It is important to review the process whereby the problem was formulated, specifically the conceptual
model of exposure (Chapter 2), which is unlikely to be static. Also, the problem formulation stage may
need to be completed more than once in order to complete planning for the risk assessment.
For example, a more sophisticated risk assessment may be necessary if preliminary screening indicates
that an unacceptable risk could be associated with a particular action or event. The more sophisticated
risk assessment would require either new data or more detailed models.
6.3.2 Risk assessment
The risk assessment process is by nature iterative (Chapter 3). An iterative risk assessment may be carried
out even when a chosen risk management action is in place. If initial assessment indicates that the
desired or necessary goals may not be reached, further iterations proceed until the goals are reached.
Care should be taken that attempts to gather ever more information do not clash with the need to make
a timely decision (so-called ‘paralysis by analysis’).
6.3.3 Options appraisal
Reappraisal of the options should not just be a review of what has already been considered. Each risk
management option should be reassessed through the risk assessment process to determine whether it
reduces the risks to an acceptable level.
6.3.4 The risk management strategy
A principal question for reviewing the risk management strategy is: are the measures in place (still)
effective? Technological, organisational and economic solutions for risk reduction may also change
with time. New institutional arrangements may be put in place that alters the accountabilities for risk
management (e.g. legislation, contracting out operations). The technological performance of engineering
systems (e.g. treatment plant) will deteriorate over time. Also, the financial support for continued risk
management activity may dry up or become harder to justify in time, especially if it is perceived to be
effective. In other words, an absence of failures may be used as a rationale for relaxing investment
in risk management. It is possible that social attitudes to risk may also change and that demands for
the level of risk reduction require tightening or relaxing. As the appropriateness and effectiveness of
risk management actions are influenced by scientific and technical analysis as well as the opinions of
stakeholders, iterations should include these opinions until competence, fairness and efficiency are
ensured. Section 6.4 provides further guidance on the communication process.
6.4 Communication
Effective and well-planned risk communication can improve the reputation of the risk owner,
and can help to implement the risk management strategy efficiently, control cost, and reduce stigma
(Ash and Leone, 2006). The Cabinet Office (2003) state that understanding risk is important for:
crises prevention; making better decisions on how to handle risk; smoother implementation of policies
set out to manage risk; reassuring and empowering the public; and building trust in scientists,
the Government and the media.
56
57
The following list gives examples of important elements to bear in mind when attempting to improve
public involvement in risk-related decision-making:
s¬ risk is complex and inherently uncertain;
s¬ outrage shapes risk perceptions and behaviours;
s¬ effective communication must be a two-way process;
s¬ effective communication is necessary but not sufficient;
s¬ trust and credibility are both essential;
s¬ credibility is based on more than scientific and technical competence;
s¬ expectations need to be managed;
s¬ what works well in one context might fail in another; and
s¬ differing viewpoints might be irreconcilable.
The success of any engagement effort and its impact on decision outcomes is not only dependent on
the quality of the involvement opportunities offered to local communities, but is equally shaped by the
motivations, ambitions and capacities of the individuals and groups engaged in the process.
When feasible, the benefits of public engagement include:
s¬ ensuring that the decision reflects local circumstances and priorities;
s¬ providing a form of ‘quality control’ by opening expert assessment to questioning and challenge;
s¬ highlighting the uncertainty inherent in risk decisions;
s¬ providing assurance that legitimate concerns have been addressed;
s¬ promoting transparency in decision making;
s¬ promoting consensus on the best option;
s¬ resolving potential conflict early;
s¬ enhancing public trust in decisions; and
s¬ potentially ensuring that people are not exposed to actual or perceived risks.
In a democratic society, there will be diverging views about the merits and risks of many activities
(Stern and Fineberg, 1996). Reasonable and effective public processes cannot expect unanimity, but it
is equally certain that conflict will arise if decisions are made and imposed on parties who reasonably
consider themselves to be directly affected and who have authentic concerns.
6.4.1 The frequency of reporting
The frequency of reporting on the risk assessment and management process should reflect how dynamic
the changes in the underlying context are. For example, a national climate change risk assessment may
be reviewed on a 5-yearly basis (Case Study Box 12) whereas changes to risk at a rapidly expanding
integrated refinery may require annual review. When reporting on a risk management strategy,
it is important to realise that the outcome of assessments on new or emerging risks are sometimes
contradictory. For example, studies have highlighted how the use of a genetically-modified (GM) plant
of cotton by Mexican and Indian farmers improved their living conditions. Yet, contrasting studies
emphasise its potential negative impacts, such as the development of pests resistant to controls,
reduced biodiversity, and the pollution of non-GM crops with GM material. This highlights the need for
iteration in order to strengthen the evidence base for justifying and subsequently communicating a risk
management strategy. In turn, this provides an effective learning base for future risk assessments
and iterations.
6.5 Summary
Recognising the dynamic nature of environmental risk places a requirement on risk assessors and those
that commission risk assessments to monitor the outcome of the risk management strategy and to iterate
the process when necessary. A critical factor here is whether or not the risk management strategies in
place continue to control the risk to the level of acceptable residual risk. Therefore, it is as important to
review the problem formulation process, each stage of the risk assessment and the risk management
options identified. Perhaps the original risk problem is no longer the main concern, or the environmental
setting has changed since the initial risk assessment, or what constitutes the acceptable level of risk
has shifted. As awareness of environmental problems grows and people have become more concerned
about risks to the quality of the environment and to their health, demands have increased for more and
better engagement in environmental risk assessment and management. However, consideration should
be given to whether public involvement could violate the principle of fairness. Throughout the process,
learning should be acknowledged and maintained as an exchange between those involved in or affected
by the risk assessment and management process.
58
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Appendix 1
71
Definitions
Accountability Obligation to account for activities and disclose results in a
transparent manner.
Aleatory uncertainty Uncertainty that stems from the inherent variability of any natural system.
Assessment endpoints An expression of the environmental value that is to be protected,
operationally defined by an entity and its attributes. For example, a
freshwater lake is a valued ecological entity; the flux of nutrients from
its tributaries is an important attribute. Together, lake productivity and
nutrient flux can form an assessment endpoint.
Assurance An evaluated opinion, based on evidence gained from review,
on the organisation’s governance, risk management and internal
control framework.
Benchmark dose An alternative to the LOAEL (lowest observed adverse effect level) and
NOAEL (no observed adverse effect level) for setting regulatory levels such
as acceptable daily intakes. The approach provides a more quantitative
way of obtaining regulatory levels for health effects assumed to have a
nonlinear low dose–response relationship (Setzer and Kimmel, 2003).
Decision-making The process of identifying the likely consequences of decisions,
working out the importance of individual factors, and choosing the best
course of action to take.
Delayed effect A long time of latency between the initial event and the actual impact
of damage.
Engagement Where the public and/or stakeholders are asked to directly and actively
take part in decision processes, but a public agency/authority is still
responsible for the decision.
Environmental security An environment protected from harm or adverse affects caused by natural
or human processes so that resources are sustained for future generations.
Epistemic uncertainty Uncertainty that originates from a lack of knowledge.
Expert An individual widely recognised by their peers as a source of
information/skills within a specific domain.
Exploiting risk Adopting a strategy to increase the likelihood of exploiting unexpected
positive effects (Hillson, 2001). Rather than hoping for an identified
potentially positive effect to result from a chosen strategy, exploiting the
risk can involve making an identified opportunity happen.
72

Exposure

The nature and level of a situation or biological, chemical or physical agent that an environmental component (landscape, water body, animal, etc.) may be subjected to intentionally or non-intentionally. Negative consequences of human activities or events. On a national scale, governance refers to the structure and processes for decision making that involves non-governmental and governmental actors

Extent of damage Governance

(Nye and Donahue, 2000). On a global scale, governance represents an
organised structure of regulation encompassing state and non-state actors
that bring combined decision without the presence of one superior authority
(IRGC, 2005).

Hazard	A situation or biological, chemical or physical agent that may lead to harm or cause adverse affects. Systematic activity designed to identify, as early as possible, indicators of changes in risk. The effect that a risk would have if it happens. The risk arising from a specific hazard before any action has been taken to manage it. The temporal extension of potential damages. Where there are threats of serious or irreversible damage, lack of full scientific certainty should not be used as a reason for postponing cost-effective measures to prevent environmental degradation. Lay members of the public, with or without a defined interest or expertise; can be individuals or groups. Those risks that affect any part of society and for which Government is expected to respond.
Horizon scanning
Impact Inherent risk
Persistency Precautionary principle
Public
Public risk

Qualitative risk assessment Describes the probability of an outcome in terms that are by their very
nature subjective as the assessment typically assigns relative values to
assets, risks, controls and effects.
Quantitative risk assessment A methodology used to organise and analyse scientific information to
estimate the likelihood and severity of an outcome. In this approach,
objective numeric values are calculated for each component gathered
during a risk assessment.

Residual risk	The exposure arising from a specific risk after action has been taken to manage it and making the assumption that the action is effective. The duty or obligation to satisfactorily perform or complete a task.
Responsibility
Reversibility	The possibility to restore the situation to the estate before the

damage occurred.
73
Risk The consequence(s) of a hazard(s) being realised, and their
likelihoods/probabilities.
Risk analysis The process of determining what decisions are appropriate to protect a
system or environment from harm or adverse affects. This encompasses
problem formulation, risk assessment, risk management and risk
communication.
Risk appetite The amount of risk that an organisation is prepared to accept, tolerate,
or be exposed to at any point in time.
Risk assessment The formal process of evaluating the consequence(s) of a hazard(s) being
realised and their likelihoods/probabilities.
Risk characterisation The process of providing an unbiased estimate of the level of risk being
considered.
Risk management The process of analysing exposure to risk before determining how best to
handle the situation.
Risk owner The person who has overall responsibility for ensuring that the strategy for
addressing the risk is appropriate and who has the authority to ensure that
the right actions are being taken.
Risk profile The documented and prioritised assessment of the range of specific risks
faced by the organisation.
Risk rating A classification (e.g. high, medium, low or very low) given to a risk,
based on its likelihood and potential impact.
Risk strategy An organisational approach to risk management, which should be
well-documented and accessible.
Semi-quantitative A numerical risk estimate based on a mixture of qualitative and
risk assessment quantitative data.
Scenario building Scenario building provides a structured way to think about and plan for
future uncertainties, and explores plausible pathways of how more than
one possible future might develop.
Stakeholders Individuals who are interested in or affected by an issue or situation.
Susceptibility A condition that increases the likelihood that an environmental
component will be exposed to a particular hazard.
Uncertainty Limitations in knowledge about environmental impacts and the factors
that influence them. It originates from randomness (aleatory uncertainty)
and incomplete knowledge (epistemic uncertainty).
Vulnerable groups Those who are prone to show more adverse responses than other groups,
given the same exposure.
74
Legislative requirements for risk assessment
The obligation to carry out environmental risk assessments arises from a range of European Directives and UK
Statutory Instruments. For example, under the EU Directives on environmental impact assessment (97/11/EC)
and strategic environmental assessment (2001/42/EC), practitioners are required to manage the aggregation
of environmental effects past, present and in the reasonably foreseeable future by means of a cumulative
effects assessment (CEA). Some pieces of legislation that specifically require a risk assessment include:
s Environmental Permitting Regulations (England and Wales) 2010;
s Directive 97/11/EC amending Directive 85/337/EEC on the assessment of the effects of certain public
and private projects on the environment;
s Directive 2001/42/EC on strategic environmental assessment;
s Directive 2000/60/EC on establishing a framework for community action in the field of water policy;
s Directive 79/409/EEC on the conservation of wild birds;
s Directive 99/92/EC on explosive atmospheres (ATEX 137);
s Nitrate Pollution Prevention Regulations 2008;
s Climate Change Act 2008;
s Control of Substances Hazardous to Health Regulations 2002 (COSHH);
s Control of Asbestos at Work Regulations 2002;
s Control of Lead at Work Regulations 2002;
s Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR);
s Water Resources Act 1991;
s Chemicals (Hazard Information and Packaging for Supply) Regulations 2009;
s Environmental Protection Act 1990 Part II – Waste Management;
s Waste Electrical And Electronic Equipment Regulations 2006 – Updated 2009;
s Hazardous Waste Regulations 2005;
s Town and Country Planning Act 1990; and
s EU REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) legislation (EC 1907/2006).
In addition, legislation exists to ensure public participation in the process of environmental risk assessment
and management. Following the signature of the Aarhus Convention by the Community on 25 June
1998, the Community adopted in May 2003 Directive 2003/35/EC providing for public participation in
respect of the drawing up of certain plans and programmes relating to the environment and amending
with regard to public participation and access to justice Council Directives 85/337/EEC and 96/61/EC.
Chemicals considered under REACH legislation
Chemicals with production or importation levels between 1 tonne/year and 10 tonnes/year must initially
be considered within the EU REACH (Registration, Evaluation, Authorisation and restriction of CHemicals)
legislation. For those species not covered by REACH (e.g. polymers, species under customs supervision or
radioactive species) the risk assessment methodologies described above come into use. For non-isolated
intermediates, for example, those species produced only within a chemical reaction and that are not
released separately, no further hazard assessments are available.
Appendix 2
75
Figure 21: A flow chart demonstrating the systematic approach to assembling either a Chemical Safety Assessment or Chemical Safety
Report for chemicals that come under the REACH legislation (i.e. those with production or importation levels between 1 tonne/year and
1000 tonnes/year). The diagram shows that the level of detail varies with particular weight and information triggers throughout the process
(from Rocks et. al., 2008).
STOP
STOP
Y

Y

 

N

N
Is substance a non-isolated
intermediate, under customs supervision,
radio active, or a polymer?
Substance
Psychochemical
properties Toxicological
information

Substance state Boling point Vapour Pressure Water solubility Flammability

Melting freezing point Relative density Surface tension Flash-point Explosive properties

Self ignition temperature
Oxidising properties Granulometry
Partition coefficient n-octanol/water
>100 tonne/year?
>1 tonne/year?
>10 tonnes/year?
>10 tonnes/year?
Y

Y

Y Y Y Y Y N >100 tonnes/year? >1000 tonnes/year? Positive result o >100 tonnes/year? >1000 tonnes/year? 2-generation reproductive study Carcinogenicity study Identification of degradatio products Further degradation testing Bio concentration (fish) Long-term toxicity on Long-term toxicity (sediment organisms) Long-term/reproductive toxicity (birds)

Y Y

Y

Y
Y
N

N

N

 

N

 

N

N
N
Stability in organic
solvent
Dissociated constant
Viscosity
Chemical Safety Assessment
Chemical Safety Assessment
Skin irritation/corrosion
Assessment of:
human/animal data
acid or alkaline reaction
Eye imitation
Assessment of:
human/animal data
acid or alkaline reaction
Mutagenicity
In vitro gene mutation
In vitro cytogenicity
In vitro gene mutation
Acute toxicity
Oral/dermal/inhalation route
Short-term repeated dose toxicity
Sub-chronic toxicity study
Reproductive toxicity screening
Developmental toxicity study
Toxicokinetics
Corrosive, strong acid/
base, flammable, very toxic, or
skin irritant; and >10
tonne/year?
Relevant in vivo study
Positive result o
>100 tonnes/year?
>10 tonnes/year?
>100 tonnes/year?
In vivo mutagenicity
studies
Ecotoxicological
information
Aquatic toxicity
Short-term toxicity testing
(Daphnia)
Long-term toxicity testing
(Daphnia)
Long-term toxicity testing
(fish)
Further studies on adsorption/desorption
Short-term toxicity to earthworms/plants
Effects on soil microorganisms
earthworms/plants/soil invertebrates
<10 tonnes per/year
and insoluble or does not
cross biological
membranes?
Growth inhibition study (algae)
Short-term toxicity testing (fish)
Activated sludge respiration
inhibition testing
Ready biodegradability
Degradation in surface water
Soil simulation testing
Sediment simulation testing
Hydrolysis as a function of pH
Environmental fate/behaviour
Adsorption/desorption
Other available
psychochemical
toxicological and
ecotoxicological information
Methods of detection and
analysis

76
Appendix 3
Endocrine-disrupting chemicals
Endocrine-disrupting chemicals (EDCs) are exogenous substances or mixtures that alter the function
of the endocrine system and, consequently, cause adverse health effects in an intact organism, or its
progeny or (sub) populations. The EDCs of greatest concern in the environment include various persistent
organic pollutants (POPs), pesticides, phthalates, metals, and other compounds such as bisphenol A
(Welshons et. al., 2006). Due to the resistance of these chemicals to degradation, they have been
distributed in small quantities throughout the world. Once they enter natural waters, they bioaccumulate
in phytoplankton, zooplankton and fish (Figure 22), and may biomagnify up the food chain resulting in
potential widespread human exposure to these chemicals.
Studies have associated exposure to EDCs with human and animal health impacts such as on brain
structures involved in cognition and mental health (Lupien et. al., 2009), adult ovarian dysfunction,
the injury of salmonid olfactory tissue, and by extension, contribute to the threatened and endangered
status of many salmonid stocks (Tierney et. al., 2008). As a result, the Department for Environment,
Food and Rural Affairs (Defra), the water industry, the Water Services Regulation Authority (Ofwat)
and the Environment Agency (EA) have been working collaboratively to design an Endocrine-disrupters
demonstration programme (EDDP) to help prevent these adverse effects of EDCs. In addition, concerns
have been raised as to whether these chemicals should be considered as single compounds or whether
they should be grouped together via endpoint or mechanism of action for a true representation of their
effects, and consequently the assessment of the risk such chemicals have.
Figure 22: The biogeochemical cycle of EDCs at the cathment scale.
Transpiration
Evaporation
Loss to
outflow:
As phytoplankton,
zooplankton and/or
fish:
In dissolved form:
As particles:
Removal by sedimenting particles:
Diffuse and
point sources of
chemicals
Catchment erosion
of contaminated
sediment
Flushing from
heavy rainfall
.
POPs (PCBs,
PBDEs etc.)
.
Pesticides (DDT,
lindane etc.)
.
’
.
(!(’
.
(&
$”%$)#’
.
’
.
'(s
.
(!(’
.
(!s
.
(&
$”%$)#’
.
’
.
'(s
.
(!(’
.
(!s
.
(&
$”%$)#’
.
’

.
'(s
.
(!(’

.
(!s
.
(&
$”%$)#’
.
'(’
.
(!’
.
Phthalates (BBP,
DEP etc.)
.
Other compounds
(e.g. Bisphenol A)
.
(!’
(Cd, Hg, As,
Pb, Cr, Cu,
Ni)
Not to scale
.
’
.
(!(’
.
'(’
.
(!’
.
(&
$”%$)#’
77
Appendix 4
Classifications of uncertainty
A number of classifications of uncertainty within environmental risk assessment and management
processes are listed below.
s Data – pertaining to the level of confidence associated with its truth and correctness. Associated issues
may relate to its availability, accuracy, or general trustworthiness.
s Language – its use is both unavoidable and necessary, and connected uncertainties primarily stem
from a lack of clarity. For example, terms may be underspecific or ambiguous.
s System – relating to a lack of knowledge about the causes, processes, and effects within
investigated systems.
s Variability – the inherent unpredictability of any human or natural system. It may be quantified and
sources and factors contributing to the variability identified through statistical methods.
s Analytical – concerns the variability within processes employed, such as sampling or interpretive
techniques, and therefore a change in procedure or sampling environment may alter the results of
the analysis.
s Model – concerning the representation of real-world processes in model form.
s Decision – where doubt surrounds an optimal or preferred course of action, often in the face of
differing objectives.
Identifying uncertainties is the first step towards quantifying them. Whilst only epistemic uncertainties
can be reduced (i.e. data, language, system), clear recognition of all uncertainties can help improve the
quality at every stage of the risk assessment process. The question “how safe is safe enough” must be
answered even when considerable uncertainty exists in new technology in order to enable society to
function. Where unknowns are significant, the precautionary principle can be used to enable
decision-making.
Risk management at the institutional level
Environmental risk management is an important function at the institutional or organisational level and it
has grown in prominence over the last 15 years. The interface between corporate and environmental risk
management is a particular area of debate. The Strategy Unit (2002) described a hierarchy of institutional
risk (Figure 23). Strategic risks are associated with corporate priorities; programme or tactical risks are
associated with institution-wide activity delivering to strategic priorities; and project or operational risks
are localised and specific to individual projects. On occasion, risks to or from the environment may
feature among the strategic risks of an organisation – for example, the possibility of floods overwhelming
some critical infrastructure, resulting in the threat of a major outage of power or water supply with
subsequent service loss to customers including vulnerable groups. In these cases, environmental risks
must be considered alongside other strategic business risks within an integrated, enterprise-wide risk
management framework.
Figure 23: Strategic, programme and operational risks (after Strategy Unit, 2002).
Environmental risk versus business risk
Some of the key issues for consideration in comparing environmental risks with other business risks
include the observations that:
s environmental impacts are not easily monetised and are often difficult to express in quantitative terms.
This should not detract from their importance;
s environmental risks are frequently newsworthy events that pose considerable knock-on reputational
impacts to organisations;
s environmental impacts may be felt over timescales well beyond conventional business planning cycles
(decades, centuries);
s outsourced operations may incur environmental risks through the less responsible operations and
practices of contracted parties. Whilst contract clauses might guard against these impacting on the
institution, in practice these risks may still return to ‘bite’ the contracting organisation;
78
Appendix 5
Strategic decisions about
corporate priorities
Decisions transferring
strategy into action
Decisions
required for
implementation
Strategic
Programme
Operational and project
79
s being concerned with open, heterogeneous systems, environmental risks frequently harbour more
uncertainty that those associated with closed, engineered systems;
s regulatory risk is often greater for environmental impacts because of the rapidly developing nature of
environmental legislation; and
s regulators increasingly view corporate responsibilities to managing environmental risks as a surrogate
for corporate social responsibility and good risk governance in general.
Internal auditing
Internal audit will verify compliance with the requirements of the risk management goals and explore
the elements involved in identifying, assessing and addressing risks. Auditing should encompass the
quality of available data, suitability of assigned responsibilities and the timescales for action. By assessing
and auditing the internal risk management capabilities of the organisation, and comparing these with
external organisations in similar sectors, institutions have sought to gauge where improvements can
be made to their own processes. Some 10 years of benchmarking practice in risk management have
revealed the importance of organisational culture, leadership on risk issues, the necessity of discussing an
institution’s appetite for risk and the management of risk knowledge as critical components of a
well-developed risk management capability (Figure 24).

Leadership and Strategy Integrity and Ethical Values s Leader creates ethical workplace s Personal ethical practices Communicate Mission and Objectives s Policies and procedures s Top-down alignment of strategy	People and Communication Commitment to Competence s Employee competence s Training Information and Communication s Information quality s Top-down communication s Communication across processes
Accountability and Reinforcement Assignment of Authority and Responsibility s Assignment of ownership s Demonstrated accountability Human Resource Policies and Practices and Performance Measurement s Performance indicators s Incentives and discipline	Risk Management and Infrastructure Identify and Assess Risk s Risk assessment practices s Risk tools and processes Establish Processes and Controls s Process reliability and efficiency s Control effectiveness and efficiency s System access and security

Figure 24: Components of good risk governance (after PriceWaterhouseCoopers, 2005).
Climate change
One example where the requirements of environmental and business risk management are increasingly
close is that of climate change. Through a range of statutory and other mechanisms, businesses
are being expected to demonstrate to those who are affected by, or interested in, risk how they are
considering the future impacts of climate change within their strategic business planning. For some
sectors, especially those operating essential infrastructure (water companies, power utilities, waste
companies, highways and rail network providers), future climate risks are likely to be a key consideration.
Other examples of strategic environmental risks may include the continued use of production chemicals
that are becoming increasingly obsolete under revised legislation and supply-chain risks associated with
the extraction of minerals at source.
Ethical risks
In addition to these technical environmental risks, institutions may also face ethical risks posed
by contentious developments, activities or future proposals. In countries where native indigenous
populations have accepted rights over specific natural resources, organisations may be required to
manage corporate risks initiated by perceived threats to cultural practices, spiritually significant land and
ways of life. These issues have been historically underplayed whilst organisations focused on establishing
corporate risk frameworks, risk committees and champions, and risk registers. We have learnt in
practice that the cultural and business process elements of good risk management are critical. This infers
the importance of the organisational and people framework alongside the competent application of
technical tools and process.
80
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