Pesticide residues in urine of adults living in the United States: Reference range concentrations

We measured 12 analytes in urine of 1000 adults living in the United States to establish reference range concentrations for pesticide residues. We frequently found six of these analytes: 2,5-dichlorophenol (in 98% of adults); 2,4-dichlorophenol (in 64%); 1-naphthol (in 86%); 2-naphthol (in 81%); 3,5,6-trichloro-2-pyridinol (in 82%); and pentachlorophenol (in 64%). The 95th percentile concentration (95thPC) for 2,5-dichlorophenol (indicative of p-dichlorobenzene exposure) was 790 mu g/liter; concentrations ranged up to 8700 mu g/liter. 2,4-Dichlorophenol concentrations ranged up to 450 mu g/liter, and the 95thPC was 64 mu g/liter. 1-Naphthol and a-naphthol (indicative of naphthalene exposure) had 95thPCs of 43 and 30 mu g/liter, respectively; concentrations of l-naphthol ranged up to 2500 mu g/liter. Chlorpyrifos exposure was indicated by 3,5,6-tricholoro-2-pyridinol concentrations of 13 (95thPC) and 77 mu g/liter (maximum observed). Pentachlorophenol had a 95thPC of 8.2 mu g/liter. Other analytes measured included 4-nitrophenol (in 41%); 2,4,5-trichlorophenol (in 20%); 2,4,6-trichlorophenol (in 9.5%); 2,4-dichlorophenoxyacetic acid (in 12%); 2-isopropoxyphenol (in 6.8%); and 7-carbofuranphenol (in 1.5%). The 95thPCs of these analytes were <6 mu g/liter. p-Dichlorobenzene exposure is ubiquitous; naphthalene and chlorpyrifos are also major sources of pesticide exposure. Exposure to chlorpyrifos appears to be increasing. Although pentachlorophenol exposure is frequent, exposure appears to be decreasing. These reference range concentrations provide information about pesticide exposure and serve as a basis against which to compare concentrations in subjects who may have been exposed to pesticides.