Environmental Risk Analysis

Chapter 6

© 2004 Thomson Learning/South-Western

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Concept of Risk Risk – the chance of something bad

happening Dealing with risk involves two tasks:

Identifying the degree Responding to it

Policymaker must use a systematic assessment of risk before devising a policy response

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Concept of Risk Classifying Risk: Voluntary and Involuntary

Risk Voluntary risk – a risk that is deliberately assume

at an individual level Involuntary risk – a risk beyond one’s control and

not the result of a willful decision

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Concept of Risk Defining Environmental Risk

Environmental risk – the probability that damage will occur due to exposure to an environmental hazard

Hazard – the source of the environmental damage Exposure – the pathways between the source of

the damage and the affected population or resource

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Risk Assessment in Environmental Decision Making Risk assessment – qualitative and

quantitative evaluation of the risk posed to health or the ecology by an environmental hazard

Hazard identification – scientific analysis to determine whether a causal relationship exists between a pollutant and any adverse effects

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Risk Assessment in Environmental Decision MakingFigure 6.1 Risk Assessment Process

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Risk Assessment in Environmental Decision Making

Methods of identifying environmental hazards Case clusters – study based on observation of

abnormal patters of health patterns within some population group

Animal bioassay – a study based on the comparative results of laboratory experiments on living organisms both before and after exposure to a given hazard

Epidemiology – the study of the causes and distribution of disease in human populations based on characteristics such as age, gender, occupation, and economic status

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Risk Assessment in Environmental Decision Making Dose-Response Analysis – a quantitative

relationship between doses of a contaminant and the corresponding reactions

Threshold – the level of exposure to a hazard up to which no response exists

Two types of extrapolations High-to-low dose extrapolation – adjusts for the

high exposure levels used in laboratory or other test conditions

Laboratory-to-natural extrapolation – infers how the effects observed in the laboratory would differ under conditions existing in nature

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Risk Assessment in Environmental Decision MakingFigure 6.2 Hypothetical Dose-Response Relationships

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Risk Assessment in Environmental Decision Making Exposure Analysis – characterizes the

sources of an environmental hazard, concentration levels at that point, pathways, and any sensitivities

Risk Characterization – description of risk based upon an assessment of a hazard and exposure to that hazard Quantitatively identifies magnitude of the risk and a

way to compare one risk to another Qualitatively gives context to the numerical risk

value

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Risk Management in Environmental Decision Making: Responding to Risk Risk Management – the decision-making

process of evaluating and choosing from alternative responses to environmental risk

Two major tasks: Determining what level of risk is “acceptable” to

society Evaluating and selecting the “best” policy

instrument to achieve that risk level

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Risk Management in Environmental Decision Making: Responding to Risk Tasks of Risk Management

Determining Acceptable Risk “Acceptable” risk – the amount of risk determined

to be tolerable for society De minimis risk – a negligible level of risk such that

reducing it further would not justify the costs of doing so

Evaluating and Selecting a Policy Instrument

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Risk Management in Environmental Decision Making: Responding to Risk Risk Management Strategies

Considerations in selection of risk management strategy: The level of risk established The benefits that accrue to society from adopting

the policy The associated costs of implementing the policy

Prevalent risk management strategies: Comparative risk analysis Risk-benefit analysis Benefit-cost analysis

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Risk Management in Environmental Decision Making: Responding to Risk

Comparative risk analysis – an evaluation of relative risk

Risk-benefit analysis – an assessment of risks of a hazard along with the benefits to society of not regulating that hazard

Benefit-cost analysis – a strategy that compares the MSB of a risk reduction policy to the associated MSC