High levels of occupational exposure to the controversial chemical bisphenol A, more commonly known as BPA, causes erectile dysfunction, loss of desire and difficulty ejaculating, U.S. and Chinese researchers reported today. Similar problems have been reported in rodents, but this is the first study to show such effects in humans, and the findings are likely to further inflame the debate over the chemical.
BPA was first developed in the 1930s as a synthetic estrogen analog, similar to diethylstilbestrol, but it soon came to be used in the manufacture of plastics, particularly polycarbonates. It is now found in a wide variety of products, including baby bottles, water bottles and the linings of cans used for food and beverages. Some of the chemical is known to seep out of such products, and more than 90% of Americans have BPA in their urine. Consumer Reports published a study recently showing that high levels of BPA were found in many food products, but that study has been heavily criticized.
The Food and Drug Administration recently decided tentatively that BPA was safe at levels now found in the population, but that conclusion was refuted by its science advisory board. Nonetheless, many localities have banned BPA in baby bottles, and manufacturers have said they will take it out of products meant for infants.
A variety of BPA animal studies has suggested that the chemical has many health effects, including infertility, weight gain, behavioral changes, early onset of puberty, cancer and diabetes. "Critics dismissed all the animal studies, saying, 'Show us the human studies,' " said Dr. De-Kun Li, a reproductive endocrinologist at Kaiser Permanente's Division of Research in Oakland and the lead author of the new study. "Now we have a human study, and this can't just be dismissed."
Li and his colleagues in the U.S. and China studied 634 workers in Chinese factories: 230 of them were exposed to high levels of BPA on their jobs, and 404 worked in factories where there was no exposure. The team measured air levels of BPA, ingestion and other measures of contamination, and monitored urine levels as well. They also questioned the workers about their sexual experiences.
The team reported online in the journal Human Reproduction that, on average, the workers exposed to BPA had a greater than fourfold increased risk of erectile dysfunction, a fourfold risk of low sexual desire, and a more than sevenfold increased risk of ejaculation difficulties. On average, the men had about 50 times the average urinary BPA concentration of American males, but the team found that the frequency of problems rose with increasing levels of the chemical.
"Because the BPA levels in this study were very high, more research needs to be done to see how low a level of BPA exposure may have effects on our reproductive system," Li said. "This study raises the question: Is there a safe level for BPA exposure, and what is that level? More studies like this, which examine the effects of BPA on humans, are critically needed to help establish prevention strategies and regulatory policies."
The study was funded by the U.S. National Institute of Occupational Safety and Health.
-- Thomas H. Maugh II
Photo: Baby bottles have been among the most controversial products containing BPA. Credit: Don Bartletti / Los Angeles Times