Exposure to Bisphenol A Linked to Reduced Semen Quality

Laurie Barclay, MD

October 28, 2010

October 28, 2010 — Exposure to bisphenol A (BPA) is linked to reduced semen quality and sperm count, according to the results of a study reported in the October 28 issue of the Journal of Fertility and Sterility.

"Compared with men without detectable urine BPA, those with detectable urine BPA had more than 3 times the risk of lowered sperm concentration and lower sperm vitality, more than 4 times the risk of a lower sperm count, and more than twice the risk of lower sperm motility," lead author De-Kun Li, MD, PhD, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, California, said in a news release. "Similar dose-response associations were observed among participants with only environmental BPA exposure at levels comparable to men in the general United States population."

BPA is a chemical created 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 dental sealants. Although previous animal studies showed harmful effects of BPA on the male reproductive systems of mice and rats, this is the first study to report an adverse association between BPA and semen quality in humans. The trial is the third in a series by Li and colleagues evaluating the effects of BPA on human sexual function. The first 2 studies, published in the November 2009 issue of Human Reproduction and the May 2010 issue of the Journal of Andrology, found an association between both high levels of BPA in the workplace and rising BPA levels in urine and worsening sexual function in men.

During this 5-year study, workers in participating factories in China were enrolled in the trial, and those with high urine BPA levels were compared with those with low urine BPA levels. Of 888 eligible workers, 514 (58%) agreed to participate, and 218 participants provided both urine and semen specimens and were included in the final analyses.

In-person interviews collected data on demographic characteristics, occupational history, and potential risk factors thought to affect semen quality, such as smoking, alcohol use, chronic diseases, history of subfertility, exposure to other chemicals and heavy metals, and recent exposure to heat sources such as a steam bath.

Risks for poor semen quality, including low sperm count and concentration and low sperm vitality and motility, were 2 to 4 times greater in men with high urine BPA levels than in those with low urine BPA levels. Urine BPA levels, however, were not associated with semen volume or abnormal sperm morphology.

Even though there was a markedly reduced sample size in the group of men exposed only to low environmental BPA sources, the inverse correlations between increased urine BPA level and lower sperm concentration and total sperm counts remained statistically significant.

Limitations of the study include a high rate of participation decline when subjects learned of the need to provide samples of both urine and sperm. However, it is highly unlikely that the choice to participate or not participate was related to semen quality.

"The consistency of the findings between the current and [2 previous] 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," Dr. Li concluded. "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. 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."

The US National Institute of Occupational Safety and Health supported this study. The study authors have disclosed no relevant financial relationships.

Fertil Steril. Published online October 28, 2010.