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You are here: Home / Publications / Environmental Risk Assessment - Approaches, Experiences and Information Sources / Introduction to Risk Assessment Concepts

Introduction to Risk Assessment Concepts

Chapter 1: Introduction to Risk Assessment Concepts


This chapter is a general introduction to environmental risk assessment and examines its basic concepts - hazard, risk, risk assessment, risk management, risk perception and risk communication.

The technique of risk assessment is used in a wide range of professions and academic subjects. Engineers "risk assess" bridges to determine the likelihood and effect of failure of components, and social welfare workers "risk assess" their clients to determine the likelihood of the reoccurrence of anti-social behaviour. Risk assessment has become a commonly used approach in examining environmental problems. It is used to examine risks of very different natures. For instance, the approach is used to assess the environmental risks posed by Genetically Modified Organisms (GMOs), chemicals, ionising radiation and specific industrial plants. Definitions in risk assessment are all-important because of the wide range of uses of the approach, and different meanings of terms used by different groups of experts and practitioners.

In this introductory chapter some basic definitions are necessary.

Hazard is commonly defined as "the potential to cause harm". A hazard can be defined as "a property or situation that in particular circumstances could lead to harm" (Royal Society, 1992). Risk is a more difficult concept to define. The term risk is used in everyday language to mean "chance of disaster". When used in the process of risk assessment it has specific definitions, the most commonly accepted being "The combination of the probability, or frequency, of occurrence of a defined hazard and the magnitude of the consequences of the occurrence" (Royal Society, 1992).

The distinction between hazard and risk can be made clearer by the use of a simple example. A large number of chemicals have hazardous properties. Acids may be corrosive or irritant to human beings for example. The same acid is only a risk to human health if humans are exposed to it. The degree of harm caused by the exposure will depend on the specific exposure scenario. If a human only comes into contact with the acid after it has been heavily diluted, the risk of harm will be minimal but the hazardous property of the chemical will remain unchanged.

There has been a gradual move in environmental policy and regulation from hazard-based to risk-based approaches. This is partly due to the recognition that for many environmental issues a level of zero risk is unobtainable or simply not necessary for human and environmental protection and that a certain level of risk in a given scenario is deemed "acceptable" after considering the benefits.

Risk assessment is the procedure in which the risks posed by inherent hazards involved in processes or situations are estimated either quantitatively or qualitatively. In the life cycle of a chemical for instance, risks can arise during manufacture, distribution, in use, or the disposal process. Risk assessment of the chemical involves the identification of the inherent hazards at every stage and an estimation of the risks posed by these hazards. Risk is estimated by incorporating a measure of the likelihood of the hazard actually causing harm and a measure of the severity of harm in terms of the consequences to people or the environment.

Risk assessments vary widely in scope and application. Some look at single risks in a range of exposure scenarios such as the IPCS Environmental Health Criteria Document series, others are site-specific and look at the range of risks posed by an installation.

In broad terms risk assessments are carried out to examine the effects of an agent on humans (Health Risk Assessment) and ecosystems (Ecological Risk Assessment). Environmental Risk Assessment (ERA) is the examination of risks resulting from technology that threaten ecosystems, animals and people. It includes human health risk assessments, ecological or ecotoxicological risk assessments, and specific industrial applications of risk assessment that examine end-points in people, biota or ecosystems.

Many organisations are now actively involved in ERA, developing methodologies and techniques to improve this environmental management tool. Such organisations include OECD, WHO and ECETOC. One of the major difficulties concerning the use of risk assessment is the availability of data and the data that is available is often loaded with uncertainty.

The risk assessment may include an evaluation of what the risks mean in practice to those effected. This will depend heavily on how the risk is perceived. Risk perception involves people's beliefs, attitudes, judgements and feelings, as well as the wider social or cultural values that people adopt towards hazards and their benefits. The way in which people perceive risk is vital in the process of assessing and managing risk. Risk perception will be a major determinant in whether a risk is deemed to be "acceptable" and whether the risk management measures imposed are seen to resolve the problem.

Risk assessment is carried out to enable a risk management decision to be made. It has been argued that the scientific risk assessment process should be separated from the policy risk management process but it is now widely recognised that this is not possible. The two are intimately linked.

Risk management is the decision-making process through which choices can be made between a range of options which achieve the "required outcome". The "required outcome" may be specified by legislation by way of environmental standards, may be determined by a formalised risk-cost-benefit analysis or may be determined by another process for instance "industry norms" or "good practice". It should result in risks being reduced to an "acceptable" level within the constraints of the available resources.

Risks can be managed in many ways. They can be eliminated, transferred, retained or reduced. Risk reduction activities reduce the risk to an "acceptable" level, derived after taking into account a selection of factors such as government policy, industry norms, and economic, social and cultural factors.

It is important to note that although risk assessment is used extensively in environmental policy and regulation it is not without controversy. This is also true for risk management.


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