In pursuing rulemakings and drafting regulations, decision makers must first be aware of risks facing the public. Decision makers must be able to answer the basic questions about a given risk: Who does it affect? What does it do? Where does it occur? When does it occur? Why does it occur? and How much risk is too much risk? Risk assessments provide scientific answers to these questions.

What is a risk assessment?
Risk assessments may rely on preexisting data, or assessors may acquire new data for purposes of their study. Risk assessments are often scientific (for example, assessing environmental exposure) but may also be technical or analytical (for example, assessing the integrity of physical structures).

A risk assessment is a process, not a document. Risk assessments produce quantified, and often nonquantified, results which decision makers use in pursuing regulatory activity.

For public health issues, the National Research Council (NRC), part of the National Academies of Science, defines risk assessment as, "The use of the factual base to define the health effects of exposure of individuals or populations to hazardous materials and situations."

To deconstruct this definition, the "factual base" is scientific or technical data produced from experiments and studies. The "health effects of exposure" can be adverse or favorable. The "hazardous materials and situations" are often the subjects of federal studies, regulations or proposed regulations.

The risk assessment process contains multiple steps. The NRC states:

Risk assessments contain some or all of the following four steps:

• Hazard identification: The determination of whether a particular chemical is or is not causally linked to particular health effects.
• Dose-response assessment: The determination of the relation between the magnitude of exposure and the probability of occurrence of the health effects in question.
• Exposure assessment: The determination of the extent of human exposure before or after application of regulatory controls.
• Risk characterization: The description of the nature and often the magnitude of human risk, including attendant uncertainty.

How is risk assessment used?
Risk assessments are an integral early step in the rulemaking process. Without knowledge of the risk a hazard poses to the public, decision makers cannot make fully informed policy choices.

Risk assessments are the regulatory tool most tied to science. A good risk assessment relies on rigorous science and subsequently produces scientific conclusions.

Risk assessments are necessary in understanding the consequences of human exposure to certain hazards. Decision makers can better set policy goals and priorities when public risks are assessed.

On a more practical level, decision makers use risk assessments as part of cost-benefit analysis. In order to monetize the potential benefits to society of a regulatory option, cost-benefit analysts must first know the risks or hazards the proposed option would eliminate. For more on cost-benefit analysis as a regulatory tool, click here.

Problems with risk assessment
Risk assessments can be controversial if experts, policy makers or the public or private sectors disagree with the conclusions. Critics may assail the underlying science, or factual base, of an assessment or inferences made by the risk assessors. This kind of criticism can be effective because a risk assessment is only as good as the science upon which it is based. In its seminal 1983 report, the NRC stated, "The basic problem in risk assessment is the sparseness and uncertainty of the scientific knowledge of the health hazards addressed, and this problem has no ready solution." The identification of this problem was not limited to the time and is still applicable today. For this reason, risk assessment is one of several tools decision makers use in developing regulations and setting priorities.

Other regulatory tools