ENVR 540 Lecture Notes - Hydrology, Epidemiology

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29 Jan 2013

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Chapter13: The Science of Risk Assessment:
The basic model, partitions risk assessment into four steps: hazard identification,
dose-response modeling, exposure assessment and risk characterization.
Integration of a risk assessment with a cost analysis and other matters to develop
strategies for risk regulations and control often called risk management
Hazard identification uses the input of biologist, chemist and others to determine
whether available data indicate that some compound or exposure should be
considered possible hazards.
Dose-response modeling requires the input of statisticians, epidemiologist and
people expert in developing models that predict adverse response as a function of
Toxicologists are important for understanding mechanism of toxicity and the
relevance of animal data for human exposures.
Exposure measurements often require the input of engineers as well as
hydrologist (for waterborne hazards), meteorologists (for airborne hazards). And
analytical chemists.
The risks associated with exposures to a hazard may be expressed by a variety of
summary satisticans that include individual life time risk, annual population risk,
the percentage or proportion of increase in risk and loss of life expectancy.
Six essential issues arise in risk assessment. First, not every person exposed to a
potential hazard will exhibit an adverse response. In addition, almost every
adverse response to some exposure may occur even without exposure, although
the link between asbestos and mesothelimoa may be a near-exception.
Second, the frequenecy or magnititude of an adverse response geneally depends
on the degree and extent of exposure to a hazard.
Third, people vary intheir response to the same level of dose or exposure.
The risk for any individual may depend on a variety of intrinsic factors such as
age, sex, prior or concurrent exposures to other hazards, and the level of
detoxifying enzymes.
Fourth, data for the direct measurements of human risk are often absent or
seriously inadequate.
Fifth, mayn risks are deemed acceptable, and their acceptability depends on many,
sometimes suprising factors, including the number of people exposed, whether
exposure is voluntary.
Finally, criter are often unclear about the best way to balance risk and benefits to
establish acceptable exposure limits for a hazard.
Risk in Context:
Good risk management requires good risk assessment.
Two strategies are commonly used in quantative risk assessment. One is the
margin of safety approach, in which a scientific team looks for the higest dose
that has produced no effect in animal or human studies, defined as the “no
observed effect level”
Uncertainty in Risk Assessment:
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