Aug. 26, 2010 -- Men who are exposed to high levels of the controversial plastic chemical bisphenol A (BPA) may show a small, but significant increase in blood levels of the male sex hormone testosterone, a study shows. These testosterone levels still remained within the normal range.
The study is published in Environmental Health Perspectives.
Some preliminary research has linked elevated testosterone to an increased risk for heart disease and certain cancers, but whether BPA significantly affects testosterone and whether this has any effect on health remains unproven.
BPA is an ingredient found in the liners of some food cans, feeding cups, and baby bottles. Growing numbers of companies now offer BPA-free bottles. Citing "potential health concerns," the FDA has called for more study on BPA.
In the CHIANTI Adult population study, researchers measured BPA levels in the urine of 715 Italian men and women aged 20 to 74 over a 24-hour period. There were detectable levels of BPA in more than 95% of the men.
The average daily exposure was more than 5 micrograms of BPA per day, which is slightly higher than levels seen in U.S studies. Men who had the highest levels of BPA in their urine showed an increase in the amount of testosterone in their blood, the study showed.
"BPA is what's known as an anti-androgen. That means that it blocks the normal action of testosterone in the body and what we might be seeing is the body making more testosterone to overcome this," says study researcher Tamara Galloway, PhD.
Galloway is a professor of ecotoxicology at the University of Exeter, U.K. "The levels we saw in our study group were still within the normal range for healthy men, so we can't say for sure what the effects might be," she says in an email.
"Small fluctuations in endocrine function could have a lot of consequences, some which may not have been characterized yet," says John Meeker, ScD, an assistant professor of environmental health sciences at the University of Michigan School of Public Health in Ann Arbor, who has conducted studies on BPA and testosterone.
The new study "is adding to a small, but growing body of literature that background exposures to BPA could have potential health implications for people in the general population," he tells WebMD. "Human studies are limited, but there are a number underway so we should know a bit more about the human health risks of BPA exposure in the near future."
Meantime, Meeker, along with the FDA and other groups, suggest limiting exposure to BPA.
Some urge caution in drawing any conclusions based on the new findings.
"The bio-monitoring data represents exposure only over the last 24 hours. The study cannot establish a cause-effect relationship for any biological event that occurs at an earlier time," says Steven G. Hentges, PhD, of the Polycarbonate/BPA Global Group of the American Chemistry Council, a trade group in Arlington, Va.
"The small changes in testosterone levels appear to be within normal ranges and there is no indication that these changes are associated with any health effect," he tells WebMD in a written statement. What's more, testosterone levels are known to vary significantly throughout the day and seasonally.
Elizabeth Whelan, ScD, MPH, the president of American Council on Science and Health, a nonprofit that receives industry funding as well as funding from other sources, agrees. "It is no surprise that BPA was measurable in urine, but as to BPA being causally related to an increase in testosterone, the authors note that their evidence does not prove causation," she says. "There is no reason to believe that trace environmental exposures to BPA would affect testosterone levels any more than eating a meal consisting of natural soy, which is a potential natural endocrine modulator."
Concerns About BPA
Others aren't willing to take any chances regarding BPA.
Calling this an "important study," Robin M. Whyatt, DrPH, a professor of clinical environmental health sciences and the deputy director of the Columbia Center for Children's Environmental Health in New York City, says that "these findings are a clear indications that BPA is an endocrine disruptor and the effects on testosterone levels are of concern."
“This compelling new study is another piece of evidence that everyday exposures to BPA are affecting human health," says Sonya Lunder, MPH, a senior analyst at the Environmental Working Group, a nonprofit organization that advocates for public health issues. "The finding bears more follow-up, especially to determine the overall effects of this short-term alteration in hormone levels. However, it points to the immediate need to reduce BPA exposures, not just for infants and children, but for all age groups," she says in an email.