By MALCOLM RITTER, AP Science Writer
Male factory workers in China who got very high doses of a chemical that’s been widely used in hard plastic bottles had high rates of sexual problems, researchers reported Wednesday.
Heavy exposure to BPA, or bisphenol A, on the job was linked to impotence and lower sexual desire and satisfaction, according to the study, which adds to concerns about BPA’s effects on most consumers.
The men in the study experienced BPA levels about 50 times higher than those faced by typical American men, said researcher Dr. De-Kun Li. “We don’t know” whether more typical doses have similar effects, he said.
The U.S. government recently announced new funding for research into BPA’s effects.
Li is lead author of the latest study, published online Wednesday by the journal Human Reproduction. The work was financed by the National Institute of Occupational Safety and Health.
BPA is used in a wide variety of consumer products, including some hard plastic bottles and metal food or beverage cans. Several makers of baby bottles recently said they had stopped using the chemical. Some 90 percent of the U.S. population carries detectable levels in the urine.
Scientists are concerned that BPA exposure might harm the reproductive and nervous systems, and possibly promote prostate and breast cancers. Last year, a preliminary study linked BPA to possible risks for heart disease and diabetes.
The Food and Drug Administration concluded last year that trace amounts of BPA that leach out of bottles and food containers are not dangerous. But the FDA is now reviewing that stance after criticism from its scientific advisers.
For the new research, Li and colleagues studied 164 factory workers in China who were exposed to high levels of BPA on the job. They were compared to 386 other men in the same town who either worked at other factories or were married to factory workers.
The scientists measured BPA exposure through air sampling, and interviewed the workers about their sexual functioning.
Compared to the other workers, men with high BPA exposure were about four times as likely to report trouble achieving erections, about seven times as likely to say they had difficulty ejaculating, and about four times as likely to report low sex drive or low satisfaction with their sex lives.
The effects are dramatic and “pretty clearly related to the exposure,” said Linda Birnbaum, director of the National Institute of Environmental Health Sciences, who was not involved in the research.
The finding fits in with animal studies and should be followed up by research in the general population, she said. Her institute said last month it will spend more money on BPA-related research, bringing the total to $30 million over two years.
Li said the workers probably were exposed not only through inhalation and skin contamination but also by swallowing BPA powder that contaminated their food. He said he didn’t know which route was most prominent in the Chinese factories.
Adapted from materials provided by The Endocrine Society
Bisphenol A Exposure In Pregnant Mice Permanently Changes DNA Of Offspring
Exposure during pregnancy to the chemical bisphenol A, or BPA, found in many common plastic household items, is known to cause a fertility defect in the mother’s offspring in animal studies, and now researchers have found how the defect occurs. The results of the new study will be presented June 13 at The Endocrine Society’s 91st Annual Meeting in Washington, D.C.
The study, funded partly by the National Institutes of Health, joins a growing body of animal research showing the toxic health effects of BPA, including reproductive and developmental problems. Last August the U.S. Food and Drug Administration found BPA to be safe as currently used but later said more research on its safety is needed. BPA is used to make hard polycarbonate plastic, such as for baby bottles, refillable water bottles and food containers, as well as to make the linings of metal food cans.
BPA has estrogen-like properties and in pregnant animals has been linked to female infertility.
“The big mystery is how does exposure to this estrogen-like substance during a brief period in pregnancy lead to a change in uterine function,” said study co-author Hugh Taylor, MD, professor and chief of the reproductive endocrinology section at Yale University School of Medicine.
To find the answer to that question, Taylor and his co-workers at Yale injected pregnant mice with a low dose of BPA on pregnancy days 9 to 16. After the mice gave birth, the scientists analyzed the uterus of female offspring and extracted DNA.
They found that BPA exposure during pregnancy had a lasting effect on one of the genes that is responsible for uterine development and subsequent fertility in both mice and humans (HOXA10). Furthermore, these changes in the offspring’s uterine DNA resulted in a permanent increase in estrogen sensitivity. The authors believe that this process causes the overexpression of the HOXA10 gene in adult mice that they found in previous studies.
The permanent DNA changes in the BPA-exposed offspring were not apparent in the offspring of mice that did not receive BPA injection (the controls). This finding demonstrates that the fetus is sensitive to BPA in mice and likely also in humans, Taylor said.
“We don’t know what a safe level of BPA is, so pregnant women should avoid BPA exposure,” Taylor said. “There is nothing to lose by avoiding items made with BPA—and maybe a lot to gain.”
Adapted from materials provided by Yale University
Chemical Present In Clear Plastics Can Impair Learning And Cause Disease
Low doses of the environmental contaminant bisphenol–A (BPA), widely used to make many plastics found in food storage containers, including feeding bottles for infants, can impair brain function, leading to learning disabilities and age–related neurodegenerative diseases, according to Yale researchers and colleagues.
“These data heighten concerns about the potential long–term consequences of human BPA exposure,” said Neil J. MacLusky of Helen Hayes Hospital, who conducted the study with Csaba Leranth, M.D., professor in the Department of Obstetrics, Gynecology & Reproductive Sciences and in the Department of Neurobiology at Yale School of Medicine.
Leranth’s group, which also included Tibor Hajszan, M.D., a research scientist at Yale, found that low doses of BPA in female rats inhibit estrogen–induction of synaptic connections in the hippocampus, an area of the brain involved with expression of sexually differentiated behaviors, as well as with formation and retention of memory.
Although estrogen is best known as one of the principal hormone products of the ovary, a number of studies over the last twenty years have shown that estrogen is also synthesized in the brain, where it contributes to the development and function of the hippocampus.
MacLusky said that high concentrations of BPA have been reported in the blood of some pregnant women and that BPA contamination could adversely affect human hippocampal development, with long–term effects on children’s learning ability. Also, when the ability to make estrogen is impaired, as in old age, exposure to BPA could adversely affect hippocampal function and contribute to age–related neurodegenerative diseases such as Alzheimer’s disease, in which hippocampal function is impaired.