Ten-year temporal trends (2006-2015) and seasonal-differences in urinary metabolite concentrations of novel, hygiene-used pyrethroids in Japanese children.

Background And Aim: Metofluthrin, profluthrin, tefluthrin, and transfluthrin are pyrethroid (PYR) insecticides increasingly used to control mosquitoes, flies, and moths in households and public places (hygiene-PYRs). Currently, there is limited data available concerning exposure to these novel hygiene-PYRs. The goal of this study was to monitor exposure to these hygiene-PYRs by analysing their urinary metabolites and to investigate the temporal and seasonal trends in the concentrations of these metabolites.

Methods: First morning urine samples were obtained from 50 Japanese children (four-six years old) in October of 2006, 2011, and 2015 (total = 150 children) in order to investigate temporal trends. Additionally, first-morning urine samples were collected from 44 three-year-old children in August-September of 2012 (summer) and in February of 2013 (winter) to investigate seasonal differences. The urinary concentrations of 2,3,5,6-tetrafluorobenzyl alcohol (FB-Al; a specific metabolite of transfluthrin), 4-methyl-2,3,5,6-tetrafluorobenzyl alcohol (CH-FB-Al; a common metabolite of tefluthrin and profluthrin), 4-methoxymethyl-2,3,5,6-tetrafluorobenzyl alcohol (CHOCH-FB-Al; a specific metabolite of metofluthrin), and 2,3,5,6-tetrafluoro-1,4-benzenedimethanol (HOCH-FB-Al; a common metabolite of metofluthrin, tefluthrin, and profluthrin) were measured using GC-MS/MS.

Results: For the investigated years, rapid increases in the detection rates of the hygiene-PYR metabolites were observed. In 2015, FB-Al was identified in 64% of the samples, CH-FB-Al in 46%, CHOCH-FB-Al in 50%, and HOCH-FB-Al in 83%. Significant increasing trends were found for the concentrations of all hygiene-PYR metabolites from 2006 to 2015 (Jonckheere-Terpstra test, p < 0.001). The concentrations of FB-Al and CHOCH-FB-Al were higher in summer than in winter (Mann Whitney-U test, p < 0.05).

Conclusions: These findings suggest that, in Japanese children, exposure to hygiene-PYRs has increased over the past decade, and that children are exposed to higher levels of hygiene-PYRs in summer than in winter.