Temporal variability of organophosphate insecticide metabolites over one year in Chinese adults.

Organophosphate (OP) insecticides widely used worldwide are a class of non-persistent pollutants with a short biological half-life. Most OP insecticides are rapidly metabolized in the human body to six dialkyl phosphate metabolites (DAPs), of which urinary concentrations are usually used to assess OP insecticide exposures. In this study, to understand the reliability of a single measurement of OP insecticide metabolites in representing a true longer-term average exposure, we investigated the temporal variability of urinary DAPs over one year in 114 Chinese adults aged 18-30. The detection rates for all six DAP metabolites exceeded 98%. The intraclass correlation coefficients (ICCs) of DAPs indicated poor (ICC < 0.4) to fair (ICC = 0.4-0.75) reproducibility in spot urine samples over one week, month, or year. Log-transformed DAP metabolites requested 2-12 spot urine samples per subject to offer a reliable estimate of OP insecticide exposures over several months or one year. The sensitivity and specificity for predicting subjects with the one-year average OP insecticide exposure in the highest tertile with one, two, or three urine samples varied from 0.25 to 0.991, 0.491 to 0.966, respectively. We recommend at least 3 spot urine samples for the assessment of one-year OP insecticide exposure by using log-transformed DAPs. This study offers a reference for an appropriate evaluation of a relatively long-period exposure to OP insecticides in biomonitoring and epidemiological studies.