The challenge of assessing children's residential exposure to pesticides ELAINE A. COHEN HUBAL, LINDA S. SHELDON, MARIA J. ZUFALL, JANET M. BURKE AND KENT W. THOMAS National Exposure Research Laboratory, U.S. EPA, Research Triangle Park, North Carolina 27711 In implementing the Food Quality Protection Act (FQPA) the U.S. Environmental Protection Agency (USEPA) has adopted a policy that the exposure factors and models used to assess and predict exposure to pesticides should generally be conservative. Some elements of exposure assessments for FQPA are screening level Ð they are both uncertain and conservative. If more realistic assessments are to be conducted, then research is required to reduce uncertainty associated with the factors and models used in the exposure assessments. To develop the strategy for conducting this research, critical exposure pathways and factors were identified, and the quality and quantity of data associated with default assumptions for exposure factors were evaluated. Then, based on our current understanding of the pathways that are potentially most important and most uncertain, significant research requirements were identified and prioritized to improve the data available and assumptions used to assess children's aggregate exposure to pesticides. Based on the results of these efforts, four priority research areas were identified: (1) pesticide use patterns in microenvironments where children spend time, (2) temporal and spatial distribution of pesticides following application in a residential setting, (3) dermal and nondietary ingestion exposure assessment methods and exposure factors, (4) dietary exposure assessment methods and exposure factors for infants and young children. The National Exposure Research Laboratory (NERL) research strategy in support of FQPA is designed to address these priority research needs. Journal of Exposure Analysis and Environmental Epidemiology (2000) 10, 638±649. Keywords: aggregate exposure, children, exposure assessment, exposure pathways,FQPA, pesticide exposure. Introduction In response to amendments to the pesticide laws contained in the Food Quality Protection Act (Public Law 104±170, Aug. 3, 1996), U.S. Environmental Protection Agency (USEPA) is upgrading the risk-assessment procedures for setting pesticide-residue tolerances in foods. Under FQPA, USEPA can establish or leave in effect a tolerance (the legal limit for a pesticide chemical residue in or on a food) only if it is determined to be ``safe.'' FQPA defines ``safe'' as ``a reasonable certainty that no harm will result from aggregate exposures to the pesticide's chemical residue from all anticipated dietary sources as well as all exposures from other sources for which there are reliable information.'' FQPA requires USEPA to give special consideration to infants and children by requiring ``that there is a reasonable certainty that no harm will result to infants and children from aggregate exposure to the pesticide's chemical residues ...'' FQPA instructs USEPA that in ``the case of threshold effects... an additional 10-fold margin of safety for pesticide residues and other sources of exposure shall be applied for infants and children to take into account ... completeness of data with respect to exposure ... to infants and children.'' The law further provides that ``the Administrator may use a different margin of safety for the pesticide chemical residue only if, on the basis of reliable data, such margin will be safe for infants and children.'' In implementing these provisions of FQPA, EPA has generally followed a policy that the more uncertain the exposure factors and models used to assess and predict exposure (i.e., the more significant the knowledge and data gaps associated with these), the more conservative they should be to protect infants and children. Some elements of EPA's exposure assessments for FQPA are screening level. They are both uncertain and conserva- tive. If more realistic assessments are to be conducted, then research is required to reduce uncertainty associated with the factors and models. To produce more realistic exposure assessments, the following questions need to be addressed. o What are all the pathways for children's residential (i.e., home, day care, school) exposure to pesticides? o Which are the pathways of potentially highest exposure? o What are the default assumptions used to estimate exposure by each pathway? o Are the assumptions too conservative, or not conserva- tive enough? Address all correspondence to: Dr. Elaine A. Cohen Hubal, MD, U.S. Environment Protection Agency, National Exposure Research Laboratory, HEAB (MD-56), Research Triangle Park, NC 27711. Tel.: +1-919- 541-4077. Fax: +1-919-541-0905. E-mail: hubal.elaine@epamail.epa.gov Received 19 November 1999; accepted 17 July 2000. Journal of Exposure Analysis and Environmental Epidemiology (2000) 10, 638±649 # 2000 Nature America, Inc. All rights reserved 1053-4245/00/$15.00 www.nature.com/jea