Urinary levels of insecticide metabolites and DNA damage in human sperm

BACKGROUND: Members of the general population are exposed to non-persistent insecticides at low levels. The present study explored whether environmental exposures to carbaryl and chlorpyrifos are associated with DNA damage in human sperm. METHODS: Subjects (n 5 260) were recruited through a Massachusetts infertility clinic. Individual exposures were measured as spot urinary metabolite concentrations of chlorpyrifos [3,5,6-trichloro-2-pyridinol (TCPY)] and carbaryl [1-naphthol (1N)], adjusted using specific gravity. Sperm DNA integrity was assessed by neutral comet assay and reported as comet extent, percentage DNA in comet tail (Tail%) and tail dis-tributed moment (TDM). RESULTS: A statistically significant increase in Tail % was found for an interquartile range (IQR) increase in both 1N [coefficient 5 4.1; 95 % confidence interval (CI) 1.9–6.3] and TCPY (2.8; 0.9– 4.6), while a decrease in TDM was associated with IQR changes in 1N (22.2; 24.9 to 0.5) and TCPY (22.5; 24.7 to 20.2). A negative correlation between Tail % and TDM was present only when stratified by comet extent, suggesting that Tail % and TDM may measure different types of DNA damage within comet extent strata. CONCLUSIONS: Environmental exposure to carbaryl and chlorpyrifos may be associated with increased DNA damage in human sperm, as indicated by a change in comet assay parameters. Key words: comet assay/DNA damage/exposure/insecticide