Here's yet another reason to avoid most canned foods, many plastics (those with recycling code number 7) and even cash receipts: The Bisphenol A, or BPA, used to make those products has been linked to fertility problems in men.
The new study of humans, by Kaiser Permanente published in Fertility and Sterility, seems to confirm previous laboratory studies of animals. Men with higher exposure to BPA (as measured by the concentration in urine) had lower quality sperm. They had lower sperm concentrations and counts, and decreased sperm vitality and motility. Men who showed levels of exposure equivalent to those common in the general U.S. population showed signs of sperm stress.
Though not all links are proven by robust human studies, BPA has already been linked to a range of potentially serious health problems, from obesity to cancer. It is believed to have effects at very low levels because it is an endocrine disruptor a synthetic chemical so similar to estrogen that the body mistakes it for a hormone.
Since the waves of scientific evidence questioning the safety of BPA have begun crashing in recent years, the focus of regulations and voluntary industry actions has been to remove BPA from children's products, like baby bottles and early childhood toys. Consumer groups and pediatricians have warned against heating plastics in the microwave, eating a lot of canned foods or using old plastic water bottles.
But as with many chemical exposures, the harm was thought to be most serious to developing fetuses and young children, so the focus of efforts to reduce exposure was put squarely on mothers, pregnant women and parents. This study suggests that grown men, particularly those interested in fathering children, should be concerned, too.
Here's how Kaiser Permanente described the study and its conclusions:
The five-year study recruited 514 workers in factories in China and compared workers who had high urine BPA levels with those with low urine BPA. Men with higher urine BPA levels had 2-4 times the risk of having poor semen quality, including low sperm concentration, low sperm vitality and motility.
This is the first human study to report an adverse association between BPA and semen quality. Previous animal studies found a detrimental association between BPA and male reproductive systems in mice and rats.
This study is the third in a series, published by Dr. De-Kun Li, a reproductive and perinatal epidemiologist at Kaiser Permanente's Division of Research in Oakland, Calif., and his colleagues, that examine the effect of BPA in humans. The first study, published in November 2009 in the Oxford Journals Human Reproduction, found that exposure to high levels of BPA in the workplace increases the risk of reduced sexual function in men. The second study, published in May 2010 in the Journal of Andrology, found that increasing BPA levels in urine are associated with worsening male sexual function.
Funded by the U.S. National Institute of Occupational Safety and Health, this new study adds to emerging human evidence questioning the safety of BPA, a chemical created in the production of polycarbonated plastics and epoxy resins found in baby bottles, plastic containers, the linings of cans used for food and beverages, and in dental sealants...
Despite a markedly reduced sample size in this group of men exposed only to low environmental BPA sources, the inverse correlation between increased urine BPA level and decreased sperm concentration and total sperm count remain statistically significant, the researchers explained...
The researchers explained that BPA is believed by some to be a highly suspect human endocrine disrupter, likely affecting both male and female reproductive systems. This new epidemiological study of BPA's effects on the male reproductive system provides evidence that has been lacking as the U.S. Food and Drug Administration and various other U.S. government panels have explored this controversial topic.
These findings, Dr. Li also points out, may portend adverse BPA effects beyond the male reproductive system. Semen quality and malesexual dysfunction could be more sensitive early indicators for adverse BPA effects than other disease endpoints that are more difficult to study, such as cancer or metabolic diseases.
For this study, workers in participating factories with and without BPA exposure in the workplace were identified and deemed eligible for the study. Among 888 eligible workers, 514 (58 percent) agreed to participate in the study. Of them, 218 participants provided both urine and semen specimens and were included in the final analyses. Through an in-person interview, participants provided information on demographic characteristics; potential risk factors that may influence semen quality including smoking, alcohol use, chronic diseases, history of sub-fertility, exposure to other chemicals and heavy metals; and recent exposure to heat sources such as a steam bath, as well as occupational history.
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