In 2010, a five-year Kaiser Permanente Northern California study of more than 500 male Chinese factory workers found that those with high levels of the compound bisphenol A (BPA) in their bodies had decreased sperm concentration, decreased total sperm count, decreased sperm vitality and decreased sperm motility.
This is among the first human studies showing a negative connection between BPA and semen quality. Previous animal studies had already found a negative connection between BPA and male reproductive systems in mice and rats.
BPA is most well known as an ingredient in some polycarbonated plastics and epoxy resins.
De-Kun Li, MD, PhD, MPH, a senior research scientist with Kaiser Permanente Northern California’s Division of Research, led the team whose study appeared in the Oct. 26, 2010 issue of Fertility and Sterility, a peer-reviewed journal of the American Society for Reproductive Medicine.
This study is the third in a series published by Dr. Li and his colleagues that looks at the effect of BPA on humans. Previous studies found that exposure to high levels of BPA in the workplace increases the risk of reduced sexual function in men and that increasing BPA levels in urine are associated with worsening male sexual function.
The five-year study recruited 514 workers in factories in China and compared workers who had high BPA levels in their urine with those with low levels. Urine BPA levels are an indicator of how much BPA got into the men’s bodies. Men with higher urine BPA levels had two to four times the risk of having poor semen quality.
“The consistency of the findings between the current and the previous two studies, despite different exposure measurements (urine BPA levels vs. BPA exposure in the workplace) and end points (semen quality vs. sexual function), strengthens the validity of these findings,” said Dr. Li, a reproductive and perinatal epidemiologist.
“The finding of the adverse BPA effect on semen quality illustrates two points: first, exposure to BPA now has been linked to changes in semen quality, an objective physiological measure,” Dr. Li continued. “Second, this association shows BPA potential potency: it could lead to pathological changes of the male reproductive system in addition to the changes of sexual function.”
Funded by the National Institute of Occupational Safety and Health, this new study adds to emerging human evidence questioning the safety of BPA, a chemical used in the production of polycarbonated plastics and epoxy resins found in baby bottles, plastic containers, the linings of cans used for food and beverages, and in dental sealants.
Dr. Li also suggests that BPA’s adverse effects may extend beyond the male reproductive system. Lowered semen quality and male sexual dysfunction could be coal-mine canaries indicating that BPA exposure could eventually lead to other health risks, such as cancer or metabolic diseases.
BPA is suspected of being a powerful disrupter of the human endocrine system, and probably affects the female, as well as the male reproductive systems. This new study, of BPA’s effects on the male reproductive system, provides evidence that had been lacking as the Food and Drug Administration and other United States agencies explore this controversial topic.