Pyrethroid insecticide exposure and semen quality of young Japanese men

• Environmental pyrethroid insecticide exposure has been considered cause of poorer semen quality in previous epidemiologic studies.
• Urinary concentration of pyrethroid insecticide (3-PBA) was measured and semen parameters were measured for 322 Japanese university students.
• Multiple regression analysis did not extract urinary 3-PBA as a significant variable to explain semen parameters.
• Exposure to pyrethroid insecticide at environmental levels was indicated not to affect semen quality.

The present study aimed at assessing the relationship between exposure to pyrethroid insecticides and semen quality in 323 university students recruited in a population-based manner in Metropolitan Tokyo. Urinary concentrations of pyrethroid insecticide metabolite, 3-phenoxybenzoic acid (3-PBA), were measured by LC/MS/MS and semen parameters were measured by following internationally harmonized protocols. Median urinary 3-PBA concentration was 0.641 ng/mL (specific gravity-adjusted, n = 322). Median values of semen volume, sperm concentration, motility, total number of sperm, and total number of motile sperm were 2.5 mL, 56 × 106/mL, 61%, 141 × 106, and 82 × 106, respectively. Urinary concentration of 3-PBA was not selected as significant in multiple regression models indicating, in contrast to previous findings, that environmental exposure to pyrethroid insecticides did not affect semen quality. This inconsistency may be related to exposure to different pyrethroid insecticides and/or levels of exposure as well as to survey design (hospital- vs population-based subject recruitment).