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EPA-Expo-Box (A Toolbox for Exposure Assessors)

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Aggregate and Cumulative


A number of example assessments are available that demonstrate the application of a combined exposure approach.

Programs Using a Combined Approach to Estimate Exposure and Risk

Aggregate and cumulative assessments are appropriate particularly when an agency with sufficient data is seeking to go beyond a traditional single-stressor, single-pathway assessment. Cumulative assessments of pesticides and residual risks of air toxics by EPA are examples of a how a combined approach is used to better understand the complicated relationships that exist when analyzing multiple chemicals, routes of exposure, and pathways.

Pyrethroids and Pyrethrins Assessment

EPA’s Office of Pesticide Programs conducted a cumulative exposure assessment for the pyrethroid pesticides, a family of chemicals with similar neurotoxic modes of action. EPA considered acute and chronic exposure to residues of pyrethroids in food, water, and other potential residential exposures; oral, dermal, and inhalation exposures were considered. The cumulative risk assessment concluded that estimated risks are not of concern.

Revised Organophosphate Cumulative Risk Assessment (OPCRA)

EPA conducted a cumulative exposure assessment for organophosphate pesticides revising the preliminary cumulative risk assessment conducted in 2001. The preliminary assessment was designed to test and improve method for conducting cumulative risk assessments in the future. The revised assessment evaluated more than 1,000 organophosphate pesticides in food, water, and other potential residential exposures.

OAQPS National Air Toxics Assessments (NATA)

EPA’s National-Scale Air Toxics Assessment (NATA) is a screening tool to prioritize pollutants, emission sources, and locations of interest for further study to gain a better understanding of risks. NATA estimates exposures at census blocks and then estimates risk at the population level, including cancer incidence and number of people estimated to be above certain cancer risk levels. Since 1996, four NATA assessments have been completed to characterize at a national level the chronic cancer risk estimates and noncancer hazards from inhaling air toxics.

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