Risk Assessment

Risk assessment is the first step in environmental risk analysis, a tool designed to assist decision makers in making environmental policy decisions. Risk assessment is meant to provide a science-based methodology with clearly defined steps to give decision makers the necessary background on which to base their decisions. Risk assessment is intended to allow decision makers to separate the fact-based elements of environmental issues from [Page 356]“political,” value-based decisions. The extent to which it is able to do this is debated, but risk assessment has been widely adopted by national and international institutions as a model for helping decision makers formulate policy on complex scientific issues.

The classic model for risk assessment was first set out in the United States in a 1983 report, Risk Assessment in the Federal Government: Managing the Process, developed by the National Research Council Committee on Institutional Means for Assessment of Risks to Public Health. This report, widely known as the “Red Book,” defined risk assessment as “the determination of the probability that an adverse effect will result from a defined exposure.” The definition is commonly expressed as an equation, R = H × E E, or risk equals (probability of) hazard times exposure.

This method for determining what degree of hazard may ensue from human activities derives from techniques that were developed by toxicologists for assessing hazards from chemicals and food additives. The National Research Council published the Red Book in response to congressional requests for assistance in applying techniques for decision making about environmental risk in a comprehensive and uniform manner across a range of policy areas and federal agencies.

This type of risk assessment, also called “probabilistic risk assessment,” is meant to define a standardized, step-wise process for solving this equation. The phases of ecological risk assessment include (1) hazard identification, or problem formulation, which involves choosing goals and desired end points, models to be used, and analysis method; (2) measurement and characterization of exposure and effects through dose response assessment and exposure assessment; and (3) risk characterization, which involves describing, integrating, and summarizing the previous steps. Questions for the risk assessor include: Is the risk chronic? How severe is the risk? Who or what is affected, and over what time period? Risk characterization ideally includes a statement of level of confidence, remaining uncertainties, and interpretation of adverse effects.

Techniques used in risk assessment include laboratory studies and field surveys. Laboratory studies, such as animal assays to assess dose-response relationships, are usually more controlled but less applicable to responses in the environment. Field surveys are more difficult to control but allow measurement and analysis of biological responses in the environment. Other techniques include models of varying levels of complexity, categorical rankings, and characterization of exposure and effects data. Some of the issues of concern are what data to use, collect, and fit into models; what statistical techniques to use in the analysis; whether to use indexes (aggregated data); and how long to collect and analyze data.

The goal of risk assessment is to create a tool for regulators that can be broadly used and is not subject to politically driven manipulation. It is meant to create a transparent process for decision making. This was of particular concern at the time of the Red Book's publication, because political interference into environmental decision making had become a major issue during the Reagan administration as a result of widespread concerns about political issues overriding scientifically justified decisions. William Ruckleshaus, head of the Environmental Protection Agency during the Nixon administration, returned to the chief Environmental Protection Agency position and laid out a plan for “science-based” risk assessment.

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