Evaluation of Predictive Algorithms Used for Estimating Potential Postapplication, Nondietary Ingestion Exposures to Pesticides Associated with Children's Hand-to-Mouth Behavior

Abstract

Postapplication exposure assessment related to indoor residential application of pesticide products requires consideration of product use information, application methods, chemical-specific deposition, time-dependent availability and transferability of surface residues, reentry time, and temporal location and macro- and microactivity/behavior patterns (Baker et al., 2000). Children's mouthing behavior results in potential postapplication exposure to available pesticides in treated microenvironments through the nondietary ingestion route, in addition to the dermal or inhalation routes. Children's activities and associated behaviors may result in multiple or repeat contact of dermal areas (clothed and unclothed body areas and hands) with treated surfaces, or surfaces that may have indirect sources of residues. Further, some surfaces contacted may have transferable pesticide residues and others may not. Transfer of residues from the indoor residential environment to the dermal surface (e.g., hands) of an individual has been assumed to be linear as a function of time and number of contacts. However, studies suggest that this transfer process to the hands and other body areas may be rapidly saturable. In the most recent U.S. Environmental Protection Agency (EPA), Office of Pesticide Programs (OPP) “Residential Exposure Assessment Standard Operating Procedures” (U.S. EPA, 2012), the input variable for the number of dermal contacts (with treated surfaces) is an exponent, making the relationship nonlinear. Further, removal processes such as hand washing and transfer to untreated surfaces are important to consider. Predictive algorithms for estimating children's hand-to-mouth-related incidental ingestion exposures post pesticide application have been developed by the EPA/OPP and incorporated into probabilistic models. A review of literature addressing variables used to estimate potential incidental ingestion exposure is presented. Data relevant to input variables for predictive algorithms are discussed, including the results of a multiyear, pesticide transferable residue measurement program conducted by the Non-Dietary Exposure Task Force (NDETF) and the associated distributional characterization for this key variable. Sources of conservative bias in current hand-to-mouth, incidental ingestion exposure estimation and the role of biomonitoring to evaluate predicted exposures are discussed.