Academic journal article Environmental Health Perspectives

Cumulative Organophosphate Pesticide Exposure and Risk Assessment among Pregnant Women Living in an Agricultural Community: A Case Study from the CHAMACOS Cohort

Academic journal article Environmental Health Perspectives

Cumulative Organophosphate Pesticide Exposure and Risk Assessment among Pregnant Women Living in an Agricultural Community: A Case Study from the CHAMACOS Cohort

Article excerpt

Approximately 230,000 kg of organophosphate (OP) pesticides are applied annually in California's Salinas Valley. These activities have raised concerns about exposures to area residents. We collected three spot urine samples from pregnant women (between 1999 and 2001) enrolled in CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas), a longitudinal birth cohort study, and analyzed them for six dialkyl phosphate metabolites. We used urine from 446 pregnant women to estimate OP pesticide doses with two deterministic steady-state modeling methods: method 1, which assumed the metabolites were attributable entirely to a single diethyl or dimethyl OP pesticide; and method 2, which adapted U.S. Environmental Protection Agency (U.S. EPA) draft guidelines for cumulative risk assessment to estimate dose from a mixture of OP pesticides that share a common mechanism of toxicity. We used pesticide use reporting data for the Salinas Valley to approximate the mixture to which the women were exposed. Based on average OP pesticide dose estimates that assumed exposure to a single OP pesticide (method 1), between 0% and 36.1% of study participants' doses failed to attain a margin of exposure (MOE) of 100 relative to the U.S. EPA oral benchmark [dose.sub.10] (BM[D.sub.10]), depending on the assumption made about the parent compound. These BM[D.sub.10] values are doses expected to produce a 10% reduction in brain cholinesterase activity compared with background response in rats. Given the participants' average cumulative OP pesticide dose estimates (method 2) and regardless of the index chemical selected, we found that 14.8% of the doses failed to attain an MOE of 100 relative to the BM[D.sub.10] of the selected index. An uncertainty analysis of the pesticide mixture parameter, which is extrapolated from pesticide application data for the study area and not directly quantified for each individual, suggests that this point estimate could range from 1 to 34%. In future analyses, we will use pesticide-specific urinary metabolites, when available, to evaluate cumulative OP pesticide exposures. Key words: cumulative dose, exposure, mixtures, organophosphate pesticides, pregnancy, prenatal, risk, urinary metabolites, women. Environ Health Perspect 111:1640-1648 (2003). doi:10.1289/ehp.5887 available via http://dx.do.org/ [Online 16 June 2003]

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Substantial toxicologic evidence suggests that low-level exposure to organophosphate (OP) pesticides affects neurodevelopment and growth in developing animals (Chanda and Pope 1996; Dam et al. 1998; Eskenazi et al. 1999; Gupta et al. 1985; Muto et al. 1992; Schulz et al. 1995; Song et al. 1997; Whitney et al. 1995). Recent biologic monitoring studies, which include pregnant women and children, show that there is widespread OP pesticide exposure in the U.S. population (Berkowitz et al. 2003; CDC 2003; Fenske et al. 2000; Loewenherz et al. 1997; Lu et al. 2000; O'Rourke et al. 2000).

To address concerns about the potential health effects of pre- and postnatal exposure of children to pesticides, the Food Quality Protection Act (FQPA) was passed in 1996, significantly amending the U.S. laws that regulate pesticides: the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Federal Food, Drug, and Cosmetic Act. The FQPA established a stringent health-based standard ("a reasonable certainty of no harm") for pesticide residues in foods to assure protection from unacceptable pesticide exposure and to strengthen health protections from pesticide risks for sensitive populations. In addition, the FQPA required the U.S. Environmental Protection Agency (U.S. EPA) to consider the cumulative effects on human health that may result from exposure to mixtures of pesticides (FQPA 1996). In response, the U.S. EPA Office of Pesticide Programs, in consultation with the FIFRA scientific advisory panel, has developed guidelines for the cumulative risk assessment of pesticides that share a common mechanism of toxicity (U. …

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