Biologically based pesticide dose estimates for children in an agricultural community

Current pesticide health risk assessments in the United States require the characterization of aggregate exposure and cumulative risk in the setting o f food tolerances. Biologic monitoring can aggregate exposures from all sou rces and routes, and can integrate exposures for chemicals with a common me chanism of action. Its value was demonstrated in a recent study of organoph osphorus (OP) pesticide exposure among 109 children in an agricultural comm unity in Washington State; 91 of the children had parents working in agricu lture. We estimated individual OP pesticide doses from urinary metabolite c oncentrations with a deterministic steady state model, and compared them to toxicologic reference values. We evaluated doses by assuming that metaboli tes were attributable entirely to either azinphos-methyl or phosmet, the tw o OP pesticides used most frequently in the region. Creatinine-adjusted ave rage dose estimates during the 6- to 8-week spraying season ranged from 0 t o 36 mu g/kg/day. For children whose parents worked in agriculture as eithe r orchard applicators or as fieldworkers, 56% of the doses estimated for th e spray season exceeded the U.S. Environmental Protection Agency (EPA) chro nic dietary reference dose, and 19% exceeded the World Health Organization acceptable daily intake values for azinphos-methyl. The corresponding value s for children whose parents did not work in agriculture were 44 and 22%, r espectively. The percentage of children exceeding the relevant reference va lues for phosmet was substantially lower (< 10%). Single-day dose estimates ranged from 0 to 72 mu g/kg/day, and 26% of these exceeded the EPA acute r eference dose for azinphos-methyl. We also generated dose estimates by adju stment for total daily urine volume, and these estimates were consistently higher than the creatinine-adjusted estimates. None of the dose estimates e xceeded the empirically derived no-observable-adverse-effect levels for the se compounds. The study took place in an agricultural region during a perio d of active spraying, so the dose estimates for this population should not be considered representative of exposures in the general population. The fi ndings indicate that children living in agricultural regions represent an i mportant subpopulation for public health evaluation, and that their exposur es fall within a range of regulatory concern. They also demonstrate that bi ologically based exposure measures can provide data for heath risk evaluati ons in such populations.