Heavy exposure to BPA, or bisphenol A, on the job was linked to impotence and lower sexual desire and satisfaction, according to the study, which adds to concerns about BPA's effects on most consumers.
The men in the study experienced BPA levels about 50 times higher than those faced by typical American men, said researcher Dr. De-Kun Li. "We don't know" whether more typical doses have similar effects, he said.
People shouldn't be alarmed by the finding, said Li, a reproductive and perinatal epidemiologist at Kaiser Permanente's research division in Oakland, California. But he said it would be prudent to limit exposure to BPA while scientists look for any effects from lower doses.
The U.S. government recently announced new funding for research into BPA's effects.
Li is lead author of the latest study, published online Wednesday by the journal Human Reproduction. The work was financed by the National Institute of Occupational Safety and Health.
BPA is used in a wide variety of consumer products, including some hard plastic bottles and metal food or beverage cans. Several makers of baby bottles recently said they had stopped using the chemical. Some 90 percent of the U.S. population carries detectable levels in the urine.
Scientists are concerned that BPA exposure might harm the reproductive and nervous systems, and possibly promote prostate and breast cancers. Last year, a preliminary study linked BPA to possible risks for heart disease and diabetes.
The Food and Drug Administration concluded last year that trace amounts of BPA that leach out of bottles and food containers are not dangerous. But the FDA is now reviewing that stance after criticism from its scientific advisers.
For the new research, Li and colleagues studied 164 factory workers in China who were exposed to high levels of BPA on the job. They were compared to 386 other men in the same town who either worked at other factories or were married to factory workers.
The scientists measured BPA exposure through air sampling, and interviewed the workers about their sexual functioning.
Compared to the other workers, men with high BPA exposure were about four times as likely to report trouble achieving erections, about seven times as likely to say they had difficulty ejaculating, and about four times as likely to report low sex drive or low satisfaction with their sex lives.
The effects are dramatic and "pretty clearly related to the exposure," said Linda Birnbaum, director of the National Institute of Environmental Health Sciences, who was not involved in the research.
The finding fits in with animal studies and should be followed up by research in the general population, she said. Her institute said last month it will spend more money on BPA-related research, bringing the total to $30 million over two years.
Steven Hentges, a BPA expert and official with the American Chemistry Council, an industry group, said the work is "probably not very relevant for consumers."
For one thing, the reported 50-fold difference in exposure seems to be an underestimate because of how it was calculated, he said. In addition, he said, the workers inhaled BPA or got it on their skin. Consumers get it through diet instead, which lets the body detoxify it, Hentges said.
Li said the workers probably were exposed not only through inhalation and skin contamination but also by swallowing BPA powder that contaminated their food. He said he didn't know which route was most prominent in the Chinese factories.