Oct. 27, 2010 -- Men with high urinary levels of the controversial chemical bisphenol A (BPA) may have lower sperm quality, which could affect their ability to conceive a child.
The new study, which appears in Fertility and Sterility, is the first to link BPA levels to sperm quality in humans. Other studies with similar results were conducted in animals. Exactly how BPA can affect sperm is not known, but animal studies have shown that BPA may have a negative impact on sperm production.
"The higher the BPA exposure, the worse the semen quality," says study author De-Kun Li, MD, PhD, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland. "The findings add more weight to the evidence about the effects of BPA on sperm quality," he says.
Of 218 men who worked in a factory in China, those with higher levels of BPA exposure had two to four times the risk of poor semen quality, including low sperm count and motility (the ability of the sperm to move toward the egg), compared to their counterparts who had lower levels of urinary BPA or no detectable BPA in their urine. Some of the factory workers were exposed to BPA on the job while others were not.
BPA levels varied among the men, but occupational exposure to BPA was the most significant contribution to higher levels of BPA.
Evidence Against BPA Mounting
Many manufacturers have already taken steps to eliminate the BPA in baby bottles and cups, but the chemical is also found in the linings of canned foods, plastic containers, dental sealants, and cigarette filters. The FDA has called for more study on BPA because of its "potential health concerns," and the Canadian government recently placed BPA on its list of toxic chemicals.
The time is now to take steps to reduce BPA exposure, Li says.
"You don’t have to wait for regulatory agencies to ban BPA," he says. "In most cases, avoiding BPA doesn’t cost much." Simple ways to steer clear of BPA involve not eating canned foods.
"This study clearly shows that BPA exposures adversely affect men in a serious way: by influencing their semen quality, which could have obvious impacts on their ability to have children," Laura N. Vandenberg, PhD, of the department of biology at Tufts University in Boston, says in an email.
"This study also shows that adult men are sensitive to BPA, and even small amounts of the chemical can have pretty drastic effects," she says. "What remains to be seen is whether the effects of BPA on semen quality are permanent after the kinds of low, chronic exposures that most adults experience."
Findings May Not Apply to U.S.
Steven G. Hentges, PhD, of the Polycarbonate/BPA Global Group of the American Chemistry Council, a trade group in Washington, D.C., says the new findings are likely not generalizable to people in the U.S.
"This study wasn't designed to look at consumers, who in contrast to the Chinese workers in this study are exposed to low levels of BPA," he says.
"In the U.S., worker safety programs limit exposure to BPA with proper personal protective equipment," he says. As a result, exposures are likely not as high among U.S. workers.
And "even with extreme high exposures in this study, most of the workers with poor sperm quality still did not meet criteria for infertility as designated by the World Health Organization," he says.