Prenatal Chemical Exposure Linked to Abnormalities in Adult Sperm

An estimated 7% of all men are affected by infertility. Multiple animal studies indicated that exposure to persistent environmental chemicals in early life can negatively impact male reproductive health, and now a human study suggests the same. Environmental health epidemiologist Melissa Perry and a dedicated research team (see full list of authors below) have conducted one of first human studies suggesting prenatal childhood chemical exposure was associated with sperm abnormalities.  

Semen quality plays a critical role in reproductive outcomes and healthy sperm have 23 chromosomes (i.e. human genetic materials). Researchers found extra chromosomes in the sperm of participants who were exposed to chemicals early in life. Abnormal, poor sperm quality increases the risk of miscarriages and congenital birth defects, such as Klinefelter Syndrome.  

"These findings provide new evidence that fetal and subsequent chemical exposures can have an enduring influence into adulthood on the genetic integrity of sperm,” said Perry, dean of the College of Public Health at George Mason University. 

Perry and the team examined semen samples from men aged 22-24 years whose mothers provided blood samples during pregnancy from 1986 to 1987. Forever chemicals, including polychlorinated compounds (PCBs) and perfluorinated compounds (PFASs), were measured in the mother’s blood. The same boys were tested again for chemicals in their blood at ages 7 and 14. Decades later, the men provided sperm, which were assessed in this study. Fetal and early life exposure to higher levels of PCBs and PFASs (found through maternal blood samples and blood in childhood) was associated with sperm containing additional chromosomes in adulthood. 

Normal sperm contain either an X (i.e., the designated chromosome for females) or Y (i.e., the one present in males) chromosome. PCB concentration in blood samples was associated mainly with having an additional Y chromosome, while PFAS exposure was consistently associated with both extra Y and X chromosomes. 

Researchers theorize that PCB exposure could be from a maternal diet of contaminated seafood. PFAS exposure was likely due to environmental pollutants in food, water, and air. 

“Chemical exposure is a public health issue, and there are strong associations with declining sperm concentration and quality. We really need to look toward policy solutions that prevent these chemicals from entering our environment and prevent related harms,” Perry said.