Cumulative exposure assessment of neonicotinoids and an investigation into their intake-related factors in young children in Japan.

Exposure levels of neonicotinoids (NEO) in young children remain unknown, despite their widespread use and the plausible vulnerability of toddlers to environmental toxicants. Herein we aimed to clarify the exposure levels and sources of NEOs in young Japanese children. Disposable diapers were collected from 1036 children (16-23 months old) participating in an adjunct study of the Japan Environment and Children's Study between 2015 and 2016. Six NEOs and one metabolite in urine extracted from a diaper from each child were analyzed using high-performance liquid chromatography-tandem mass spectrometry. A relative potency factor approach was used to assess the cumulative exposure to NEOs equivalent to dinotefuran levels (DIN). The 95th percentile urinary concentration of DIN was 157 μg/L and 380 μg/g creatinine (Cr). Receiver operating characteristic curve analyses for the propensity scores of the possible exposure-related factors revealed that the discriminatory powers determining whether Cr-adjusted and Cr-unadjusted DIN concentrations exceeding the 95th percentile values were higher for the amount of each foodstuff ingested on the survey day (areas under the curve were 0.62 and 0.75, respectively) than for the exposure-related behaviors (0.60 and 0.71, respectively) or for mothers' attitudes toward food selection and preparation (0.54 and 0.57, respectively). Use of a mosquito coil, insect repellent, and mothproof net for a screen door, and playing on a lawn were associated with increased urinary NEO levels (odds ratio [OR]: 2.0-2.9), while care about the child's nutritional balance by mothers reduced urinary NEO levels (OR: 0.23-0.41). To the best of our knowledge, this is the first study that dealt with urinary concentrations and possible exposure sources of NEOs in a large number of young children. Attention to the children's behavior and diet might result in the reduction of a high exposure to NEOs in young children.