Chronic exposure to the chemical bisphenol A (BPA) may lower testosterone levels in men, a new study from China suggests.
In the study, men who were exposed to BPA because they worked in a chemical plant for at least six months had lower levels of testosterone in their blood compared with those who worked in a tap water factory.
Specifically, chemical plant workers had reduced levels of "free" testosterone, which is the form thought to have the greatest influence on the body. (Most testosterone in the body is not "free," but is bound to a protein.)
The findings provide even more evidence that BPA may change men's sex hormone levels, said study researcher Dr. De-Kun Li, a senior research scientist at Kaiser Permanente's Division of Research in Oakland, Calif.
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Previous studies, also conducted on Chinese factory workers, have suggested that BPA may lower sperm counts as well as increase the risk of sexual dysfunction in men — health effects that are controlled in part by sex hormones.
BPA is similar to the female hormone estrogen, meaning that it could have effects on the human body. The effect of BPA on men may be more immediate and easier to detect than the effect on women, because men have very low levels of estrogen to begin with, Li said. [See Is BPA Really a Health Hazard?]
However, whether similar effects would be seen in the general population at lower exposure levels is not known, and need to be studied further. BPA is found in some plastics, canned food containers and other food packaging, and most people in the U.S. have the chemical in their urine.
Heather Patisaul, an associate professor at North Carolina State University who studies the effects of BPA, noted that the study looked at BPA in the blood, rather than the urine. BPA levels in the blood are thought to be a better measure of chronic exposure to the chemical, but are typically very low, and could be influenced by environmental contamination, Patisaul said.
Men who don't work in a chemical factory would likely have BPA levels in their blood that are too low to detect, Patisaul said. In the study, about 70 percent of men who worked in the chemical plant had detectable levels of BPA in their blood, while the same was true of 5 percent of those who worked in the water factory.
"This data should not raise alarm bells for men who don't work in chemical factories," Patisaul said.
Patisaul said that the new study was small and did not do a great job of accounting for differences in hormone levels that might be due to the time of day samples were collected.
The study was published online May 6 in the journal Fertility and Sterility.
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