WEDNESDAY, Nov. 11 (HealthDay News) -- Exposure to high levels of the controversial plastics chemical bisphenol A (BPA) significantly raised the risk of sexual dysfunction, including impotence and low sex drive, among Chinese factory workers, a new study has found.
The researchers stressed that the workers were exposed to BPA levels about 50 times higher than what most Chinese or Americans would be exposed to in everyday life.
Even so, they said the study adds to a growing body of research that shows that the ubiquitous chemical may be harmful to humans. BPA, used to make polycarbonate plastic (hard, clear plastic) and epoxy resin, is found in electronic and medical equipment, cars, sports safety equipment, and food and drink containers, including plastic bottles and the lining of cans.
"We found that male workers who had high exposure to BPA in the workplace had a much higher risk of male sexual dysfunction compared to other workers in the same city who were matched for age and other factors," said lead study author Dr. De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, Calif. "A caveat here is those workers did have a much higher BPA exposure than most Americans or Chinese in the general population."
The study is published in the Nov. 11 online edition of Human Reproduction.
In the study, Li and colleagues examined 230 workers in four Chinese factories near Shanghai that either manufactured BPA or used BPA to manufacture epoxy resin. The men worked as packagers, technical supervisors, laboratory technicians and maintenance workers.
The workers were compared to 404 workers in factories that made products ranging from textiles to machinery, in which there was no heightened BPA exposure. The workers from the two groups were matched by age, education, gender and employment history.
Workers in the BPA factories were four times more likely to report erectile dysfunction, reduced sexual desire and overall dissatisfaction with their sex life. They were also seven times more likely to have ejaculation difficulties.
BPA workers were also more likely to report reduced sexual function within one year of beginning employment at the factory, the researchers found.
Researchers measured BPA exposure levels by taking air samples, reviewing factory records and interviewing workers about personal hygiene habits, use of protective equipment and exposure to other chemicals. Levels of BPA in the urine was also tested for a subset of workers.
Among BPA workers, the higher the exposure, the more likely they were to have sexual difficulties.
Most human exposure to BPA occurs when the chemical leaches into food and drink from packaging. Earlier this month, Consumer Reports announced that tests showed BPA in nearly all of 19 brand-name canned foods, including soups, juice, tuna and green beans.
In recent years, concern about the effects of BPA, particularly on fetuses and young children, have been growing. Animal studies have shown that BPA can cause reproductive abnormalities in both males and females by disrupting the endocrine system, according to background information in the study.
Other research has linked BPA to an increased risk of diabetes, cancer and heart arrhythmias. Male sexual dysfunction may be an early indicator of BPA-related problems that take longer to develop, Li said.
One chemicals industry representative took issue with the findings. Steven Hentges, executive director of the American Chemistry Council's Polycarbonate/BPA Global Group, said the occupational exposure of these factory workers far exceeds what the average person would ingest. Furthermore, the study did not make clear if the factories or the workers were following adequate worker-protection measures, such as wearing gloves and face masks and having proper ventilation.
"It is important to note that the study has little relevance to average consumers who use products that contain trace levels of BPA," said Hentges.
Dr. Hugh Taylor, director of the division of reproductive endocrinology and infertility at Yale University School of Medicine, said the findings are "very suggestive" but do not prove cause and effect.
"The results of the study are probably important for people who are working at BPA factories, but the results don't support condemning BPA based on what people are exposed to at normal levels," Taylor said.
Yet Taylor recommends that pregnant women and children in particular avoid BPA. Well-controlled animal studies have shown the chemical is linked to reproductive harm that may be irreversible during critical stages of development. In response to such concerns, some countries have banned the sale of baby bottles made with BPA.
"The totality of the literature suggests BPA has terrible consequences for human health," Taylor said. "I tell my patients to stay away from hard plastics and canned goods while pregnant."
More information
There's more on bisphenol A at the U.S. National Institute of Environmental Health Sciences.
TUESDAY, Sept. 8 (HealthDay News) -- A new study tightens the suspected link between a virus and prostate cancer, and raises the possibility that infection with the virus could be an indicator of aggressive tumors that require swift treatment.
"We're not making any causal association at this moment," stressed Dr. Ila R. Singh, an associate professor of pathology at the University of Utah, lead author of a report on the virus, known as xenotropic murine leukemia virus-related virus (XMRV).
"There probably are multiple causes of prostate cancer, but for the first time we have analyzed prostate cancer and normal prostate tissue and found cancers are much more likely to have [the virus]," Singh said.
The research is published in this week's issue of Proceedings of the National Academy of Sciences.
A link between XMRV and prostate cancer was first reported two years ago by researchers at the Cleveland Clinic and the University of California, San Francisco. They found the virus in cells around tumors.
The new study, involving more than 300 prostate cancer specimens, found that 27 percent of them carried the virus.
"It was also more likely to be present in more aggressive tumors," Singh said. "We found it in 20 percent of the least aggressive tumors and over 45 percent of the most aggressive tumors."
So, a test for presence of XMRV could be at least a partial solution to the major problem facing doctors who treat prostate cancer: distinguishing the minority of virulent, life-threatening cancers from the majority of tumors which grow so slowly that "watchful waiting" may be enough.
Prostate cancers now are diagnosed by a test for prostate-specific antigen (PSA), a protein produced by the gland. However, PSA tests cannot single out aggressive cancers, and there is a major debate on whether widespread use of these tests leads to overdiagnosis and overtreatment.
"I don't know yet if this is the better test, but it might be linked to more aggressive prostate cancers," Singh speculated.
Robert A. Silverman, a professor of cancer biology at the Cleveland Clinic, was one of the researchers who first reported the association of XMRV with prostate cancer. He called the new study "very exciting."
"Finding it in cancer cells makes it easier to reconcile with the idea of a cancer-causing virus than in our prior study," Silverman said. "The prior study found the virus in cells surrounding the cancer. We can't say with certainty that XMRV is a cause of cancer, but it still is a candidate for a cancer-causing virus."
Even if causation is not proved, "XMRV could be a marker for aggressive tumors," Silverman said.
His group has continued research on the virus, one of which indicates that human semen promotes the activity of XMRV, Silverman said.
The new study also overturns a previously reported association between XMRV infection and a genetic variation carried by a small percentage of men. "We don't find any such association," Singh said. So, the new research appears to expands the population at risk from the virus to all men -- whether they carry the genetic variant or not.
Singh and her colleagues are expanding their research on XMRV. "We don't know if women have the virus, and we are looking at cervical cells from Pap smears," she said. "We are looking at seminal fluid from men and also at tissues other than the prostate. We have two large series of autopsies of male and female organs. We are also looking for antibodies to the virus in serum as a way to detect infection."
More information
Find out more about prostate cancer at the U.S. National Cancer Institute.