BPA mimics the body's own hormones and may lead to negative health effects, say critics of the chemical.
BPA is most commonly used to make plastics and epoxy resins used to line food and beverage cans, and people are exposed primarily through diet, although other routes are possible such as exposure through the skin when handling paper used to print cash register receipts.
Bisphenol A is found in the linings of canned food. (Photo by Oak Grove Library)
Globally, more than six billion pounds of BPA are produced each year.
"Much of the focus for BPA is on the exposures in utero or in early life, which is of course extremely important, but this suggests exposure may also be a concern for adults," said the study's lead author, John Meeker, assistant professor of Environmental Health Sciences at the University of Michigan School of Public Health.
"Research should focus on impacts of exposure throughout multiple life stages," Meeker said.
Russ Hauser, a professor of reproductive physiology at Harvard School of Public Health, contributed to the research along with colleagues at Massachusetts General Hospital and the U.S. Centers for Disease Control and Prevention, a government agency.
The study is published in the current issue of the journal "Reproductive Toxicology."
Meeker and Hauser recruited 190 men through a fertility clinic. All gave spot urine samples and sperm samples the same day. Subsequently, 78 of the men gave one or two additional urine samples a month apart.
Researchers detected BPA in 89 percent of the urine samples.
Researchers measured sperm concentration, sperm motility, sperm shape and DNA damage in the sperm cell.
"We found that if we compare somebody in the top quartile of exposure with the lowest quartile of exposure, sperm concentration was on average about 23 percent lower in men with the highest BPA," Meeker said.
Results also suggested a 10 percent increase in sperm DNA damage.
Several previous studies have documented adverse effects of BPA on semen in rodents, but this is the first to report the effects of BPA on semen in humans.
The results are consistent with a previous study by Meeker and Hauser suggesting that certain hormones - follicle-stimulating hormone and Inhibin B - are elevated or decreased in relation to BPA, respectively, a pattern consistent with low sperm production and development.
Due to the study's relatively small sample size and design, the scientists say their results are "preliminary and more study is needed."
"The study from which these data came is currently in progress," Hauser said. "With a larger sample size and enhanced study design, we will be able to more definitively investigate this preliminary association in the near future."
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