Is pre- and postnatal exposure to dioxins and per- and polyfluoroalkyl substances (PFAS) associated with parameters of semen quality in young adulthood? – Results from a longitudinal birth-cohort study

Background Dioxin and per- and polyfluoroalkyl substances (PFAS) exposure in fetal life and early infancy may be harmful for the male reproductive system. Objectives We investigated the associations between pre- and postnatal dioxin/PFAS exposure and semen quality in young adulthood. Methods The Ulm Birth Cohort Study is a population-based longitudinal birth cohort study (recruited 11/2000-11/2001). Maternal serum was collected shortly after delivery (mostly taken within the first two days) and maternal milk 6 weeks postpartum, immediately aliquoted, and stored at -80 ⁰C. Concentrations of dioxins (PCDDs, PCFDs and dioxin-like PCBs) were analyzed in milk in the year 2022 and PFAS in maternal serum in the year 2023. Semen provided by male offspring in 2021/22 was analyzed according to the 2010 WHO manual. Multivariable linear regression models were used to analyze the associations of (1) maternal dioxin/PFAS concentrations and of (2) cumulative dioxin/PFAS exposure with semen quality. Results Semen was available for n=98 males (age 20.4 ± 0.4 years; 86% were breastfed at 6 weeks). Median WHO 2005 -PCDD/F+PCB-TEQ concentration was 0.516 pg/g milk (n=77, IQR 0.296-0.715), median serum PFAS level (EFSA sum) was 10.8 µg/L (n=92, IQR 8.3-13.8). In adjusted analyses, we found no associations between concentrations of dioxin on a continuous scale with various measures of semen quality. For the continuous analysis of PFAS, a positive association with sperm concentration was seen in the partly adjusted cumulative exposure model, which was, however, not present after full adjustment. The mutual adjustment for dioxins and PFAS in statistical analysis revealed a significant negative association between dioxin levels in milk with sperm concentration and %-progressive motility and a significant positive association between PFAS levels in postpartum serum and sperm concentration. Conclusion While our data do not suggest an adverse association between early PFAS exposure and semen quality in adulthood, an adverse association with early dioxin exposure cannot be excluded. The small sample size and potential sources of bias or confounding call for cautious interpretation.