Occurrence and Profile Characteristics of the Pesticide Imidacloprid, Preservative Parabens, and Their Metabolites in Human Urine from Rural and Urban China

Knowledge of human exposure to imidacloprid, the most extensively used insecticide, and para-hydroxybenzoic acid esters (parabens), the most extensively used preservative, is insufficient. In this study, 295 urine samples collected from subjects in rural and urban areas in China were analyzed for imidacloprid and four parabens (namely, methyl paraben, ethyl paraben, propyl paraben, and butyl paraben) as well as their major metabolites (namely, 6-chloronicotinic acid (6-ClNA) and para-hydroxybenzoic acid (p-HB)). Imidacloprid was detected in 100% of the urine samples from rural Chinese subjects and 95% of the urine samples from urban Chinese subjects. Concentrations of urinary imidacloprid detected in rural Chinese subjects (geometric mean (GM) = 0.18 ng/mL) were slightly higher than those detected in urban Chinese subjects (GM = 0.15 ng/mL) when the effect of pesticide spraying was excluded. However, concentrations of urinary imidacloprid detected in rural adults increased significantly in the subsequent days of pesticide spraying (GM = 0.62 ng/mL), which could return to the normal levels within 3 days. In contrast, concentrations of urinary parabens detected in rural Chinese subjects (GM = 6.90 ng/mL) were lower than that in urban Chinese subjects (GM = 30.5 ng/mL). In addition, the metabolism characteristics of imidacloprid to 6-ClNA and parabens to p-HB were discussed preliminarily.