BACKGROUND: The association of exposure to endocrine disrupting chemicals in the peripubertal period with subsequent sperm DNA methylation is unknown. OBJECTIVE: We examined the association of peripubertal serum 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) concentrations with whole-genome bisulfite sequencing (WGBS) of sperm collected in young adulthood. METHODS: The Russian Children's Study is a prospective cohort of 516 boys who were enrolled at 8-9 years of age and provided semen samples at 18-19 years of age. WGBS of sperm was conducted to identify differentially methylated regions (DMR) between highest (n=4) and lowest (n=4) peripubertal TCDD groups. RESULTS: We found 52 DMRs that distinguished lowest and highest peripubertal serum TCDD concentrations. One of the top scoring networks, "Cellular Assembly and Organization, Cellular Function and Maintenance, Carbohydrate Metabolism", identified estrogen receptor alpha as its central regulator. CONCLUSION: Findings from our limited sample size suggest that peripubertal environmental exposures are associated with sperm DNA methylation in young adults.

BACKGROUND: There is little research investigating exposures that occurred during war or conflict and the resulting influence on semen quality. We examined the associations between military service and semen quality among U.S. Veterans of Operation Enduring Freedom, Operation Iraqi Freedom, and Operational New Dawn. METHODS: U.S. Veterans (n = 714), who sought fertility treatment and were participants of the Department of Veterans Affairs Women Veterans Cohort Study were included in the current study. Semen quality parameters (semen volume, total sperm count, sperm concentration, and percentage of total motile sperm) measured at fertility clinics in Veterans Affairs Healthcare System were analyzed. FINDINGS: The median values of Veterans were 2.7 mL for semen volume, 55.3 x 10(6) for total sperm count, 22.0 x 10(6)/mL for sperm concentration, and 55% for total motile sperm. No significant differences among Veterans were found between military-specific variables evaluated and sperm quality. In multivariate models, Veterans > /=46 years of age had lower semen volume (beta = -0.10 +/- 0.05; p < 0.05) and lower percent total motile sperm (beta = -18.45 +/- 7.0; p = 0.009) than Veterans 18 to 25 years of age. Black and Hispanic Veterans had lower sperm concentrations as compared to White Veterans (beta = -0.17 +/- 0.07; p = 0.01 and beta = -0.20 +/- 0.06; p < 0.001, respectively). Finally, Veterans diagnosed with post-traumatic stress disorder or major depression had lower total sperm motility (beta = -0.10 +/- 0.03; p = 0.004 and beta = -0.09 +/- 0.04; p < 0.05, respectively). DISCUSSION: Veterans who were older, Hispanic or Black, or diagnosed with post-traumatic stress disorder or major depression were more likely to have lower sperm quality. Longitudinal studies are needed to better characterize the influence of military-specific exposures on semen quality parameters.