THURSDAY, Oct. 28, 2010 (HealthDay News) -- Men with high amounts of the controversial plastics chemical bisphenol-A (BPA) in their urine also tend to have impaired semen quality, a new study of factory workers in China reveals.
The research, funded by the U.S. National Institute of Occupational Safety and Health, found high urine levels of BPA to be significantly associated with a drop in sperm concentration, overall sperm count, sperm vitality and sperm motility.
Although prior work with mice and rats had uncovered troubling associations between BPA exposure and damage to the male reproductive system, the current finding is the first drawn from research involving people.
"Compared with men without detectable urine BPA, those with detectable urine BPA had more than three times the risk of lowered sperm concentration and lower sperm vitality, more than four times the risk of a lower sperm count, and more than twice the risk of lower sperm motility," study lead author Dr. De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, Calif., said in a news release from the organization.
BPA was not found, however, to have an impact upon either the shape of sperm or its volume, Li noted.
Li and his colleagues report their observations Oct. 28 in the journal Fertility and Sterility.
BPA is commonly found in industrial settings involved in the manufacturing of a wide array of items including baby bottles, plastic containers, food and beverage container linings, and even dental sealants.
Responding to recent reports, in January the U.S. Food and Drug Administration and other U.S. health agencies pledged $30 million toward short- and long-term research aimed at clarifying the health effects of the chemical.
The current report is the third released by Li and his team over the past year. Their first study indicated that exposure to high amounts of BPA in the work environment is linked to a higher risk for impaired sexual function among men, while a second report found evidence that as urine levels of BPA rise, male sexual function dips.
The latest report is based on a five-year study of 218 Chinese factory workers who provided researchers with both urine and semen samples.
Even after accounting for a host of other potentially influential factors, such as smoking and drinking history, chronic disease background, job history, prior exposure to other chemicals and heavy metals, and a prior history of fertility issues, the study authors determined that the association between high BPA urine levels and poor semen quality endured.
Li said his team's work suggests that BPA appears to have a consistent and potent negative impact on male reproductive health.
What's more, the research team said their findings could have implications beyond the factory setting.
"Similar dose-response associations were observed among participants with only environmental BPA exposure at levels comparable to men in the general United States population," Li noted.
But not everyone agreed with that notion.
Steven Hentges is executive director of the Polycarbonate/BPA Global Group with the American Chemistry Council, an industry trade organization based in Arlington, Va. The new findings are "likely to have limited relevance to consumers," he said.
"This study is a little bit lean on details, but what's clear is that it wasn't designed to examine the potential effects of BPA on consumers," Hentges stressed. "It focused on workers. And from what they report we can be sure that some workers were exposed to extraordinarily high amounts of BPA. Thousands of times higher than the average American," he added.
"And in fact, in recent years government agencies around the world have examined the science around BPA, and have concluded that low doses are not a risk to human health," Hentges continued. "The European Food Safety Authority, which is like the FDA in Europe, and whose primary focus with respect to BPA was on reproductive health, released a very comprehensive update on safety issues in September and reaffirmed their previous conclusions that BPA low-dose exposure isn't a risk to human health."
For more on BPA, head to the U.S. National Institute of Environmental Health Sciences.