For the first time, a study in humans suggests that a controversial, estrogen-like chemical in plastic may be related to conditions that reduce men's fertility.
Men with higher levels of BPA, or bisphenol A, were two to four times more likely than others to have problems with sperm quality and quantity, the study shows.
In particular, men with high levels of BPA in urine and semen were more likely to have fewer sperm overall, fewer live sperm and poor semen quality. Their sperm also had more problems swimming, according to a study of 514 Chinese workers, published today by doctors from Kaiser Permanente in Fertility and Sterility.
Earlier studies by the same researchers also linked higher BPA levels with sexual functioning problems, such as low libido or impotence, says author De-Kun Li of the Kaiser Foundation Research Institute in Oakland.
Those problems can make men less fertile, says Tracey Woodruff of the University of California-San Francisco. The study has several strengths, Woodruff says. For example, measures such as sperm count provide more solid evidence of BPA's effects, unlike subjective measures such as men's rating of their libidos.
The men studied, some of whom worked in factories that exposed them to BPA, had levels that were within the range allowed by the Environmental Protection Agency, Li says. The Centers for Disease Control and Prevention has found BPA -- in many plastic bottles, the lining of metal cans and other consumer products -- in the urine of more than 90% of Americans.
A growing number of researchers and consumer advocates are concerned about BPA, which acts like the female hormone estrogen and can block male hormones, such as testosterone. It has been shown to cause harm in hundreds of animal studies, including effects on male reproductive organs such as the testes and prostate, says University of Missouri researcher Frederick vom Saal.
Now, studies are beginning to confirm some of the same effects on people, Li says.
The American Chemistry Council, an industry group, says BPA has been safely used for 50 years. "Government agencies worldwide have examined the science on BPA ...and concluded that low doses of BPA are not a risk to human health," says council spokesman Steven Hentges.
The National Institute for Environmental Health Sciences says animal studies link BPA with infertility, weight gain, behavioral changes, early puberty, prostate and breast cancer and diabetes.
The Food and Drug Administration has expressed "some concern" about BPA's effects on the brain, behavior and prostate gland in fetuses, infants and children, although it has not taken steps to reduce the average person's exposure to BPA.
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