Appendix A: Risk-Benefit Analysis
The methodology of risk-benefit analysis is fundamentally an integration
of two methodologies: risk assessment and cost-benefit analysis. The first
method, risk assessment, is employed to evaluate risk resulting from both
hazardous technologies and toxic health threats. Although the principles
are the same, the assessment procedures are applied somewhat differently,
depending on whether the focus is on technology or health. Because the
discussions about risk-benefit analysis in this book primarily refer to toxic
emissions from hazardous wastes, the methodology presented here applies
to toxic exposure (Covello 1993).
The goal of risk assessment is to accurately predict the health implica-
tions of a hazard before or after it exists and to establish valid safety stan-
dards to protect the exposed population. The methodology typically spec-
ifies four interrelated steps (1) a process of hazard identification (e.g., Does
a waste incinerator emit dioxins or heavy metals?); (2) an assessment of
human exposure (e.g., Can the various routes of the toxin to the affected
population be traced and how much of it enters the human body?; (3) the
modeling of the dose responses (e.g., What is the empirical relationship of
the exposures to the chemical under investigation and the frequency of
adverse impacts?); and (4) a characterization of the overall risk (e.g., How
does the data as a whole provide an overall evaluation of the toxic implica-
tions for human health, most commonly defined in terms of cancer?). In an
effort to err on the conservative side of safety, risk assessors most often use
‘‘worst case scenarios.’’ The overall risk is generally expressed as the proba-
ble number of cancers per million people who are exposed over the course
of a standard life expectancy.
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