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Last Edited: 9/6/2002

What is risk assessment?

The process of assessing the likelihood that a given hazardous material may contribute to a particular disease or ill health. This process is often used to set regulations for the protection of the public from hazards in our air, water, food or other aspects of our environment. It may also be used to determine how much clean up is necessary when contamination already exists. The process is based on the available science at the time of the risk assessment and may change over time, as more information becomes available. There are very few studies available about the hazards from levels of contamination people may be exposed to in community settings from sources such as nearby hazardous waste sites, industrial sources or area sources such as traffic. Therefore, most risk assessments are based on studies of people exposed to higher levels of contamination in workplace settings, industrial accidents, poisonings or on information from animal studies. Because there is often some uncertainty as to how these other studies relate to more general population exposures, regulations based on risk assessment often incorporate "uncertainty" of "safety" factors. In California many risk assessments used for regulations are performed by the Office of Environmental Health Hazard Assessment (OEHHA) and other agencies in the California Environmental Protection Agency. For a simple description of how this works check out this educational link from OEHHA:

For more information on how risk assessments are used or for specific risk assessment information go to:

California: or

U.S. Environmental Protection Agency: or