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Assessing Pesticide Cumulative Risk

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Through the pesticide reevaluation program, EPA periodically reviews individual registered pesticides to ensure that they continue to meet statutory standards and can be used without unreasonable risks to human health and the environment. As a result of the Food Quality Protection Act (FQPA), the Agency also must assess the cumulative risks of pesticides that share a common mechanism of toxicity, or act the same way in the body.

EPA has developed a framework for conducting cumulative risk assessments. In assessing cumulative risks, EPA evaluates the potential for people to be exposed to more than one pesticide at a time from a group with an identified common mechanism of toxicity. These cumulative assessments consider exposures from food, drinking water, and residential sources. The Agency also incorporates regional exposures from residential and drinking water sources since this is the most appropriate way to account for the considerable variation in potential exposures across the country. EPA's cumulative assessments, therefore, approximate as closely as possible people's actual exposures and potential risks resulting from current uses of these pesticides in different parts of the country.

The Agency has determined so far that five groups of pesticides each have a common mechanism of toxicity and require cumulative risk assessments because exposure to these pesticide groups may pose potential risks to human health and the environment. The five groups are: the organophosphates, N-methyl carbamates, triazines, chloroacetanilides, and pyrethrins/pyrethroids.

The Agency has determined that two other groups of pesticides, the thiocarbamate and dithiocarbamate pesticides, should not undergo cumulative assessments since chemicals in those two groups do not act the same way in the body. In late 2001 and early 2002, EPA provided an opportunity for the public to comment on the Agency's common mechanism determinations for the thiocarbamates (PDF) (46 pp, 348 KB, About PDF) and dithiocarbamates (PDF) (51 pp, 418 KB, About PDF), which also belong to the carbamate group of pesticides. EPA considered four common effects, including acetyl cholinesterase inhibition, and determined that the thiocarbamates and dithiocarbamates do not share a common mechanism of toxicity.

Through cumulative risk assessment, EPA considers whether the risks posed by a group of pesticides that act the same way in the body meet the safety standard of "reasonable certainty of no harm" established by FQPA. During the development of individual and cumulative risk assessments and subsequent risk management decisions, EPA provides a number of opportunities for input from stakeholders. The Agency's process for public involvement and consultation during EPA's registration review of pesticides is outlined on a separate web page.

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