High Exposure to BPA Means Low Sperm Count

Two weeks ago, Canada added the much-maligned bisphenol-A (BPA) to its list of toxic substances, lending support to the accumulating evidence that it poses a health threat to humans.  BPA has shown to be harmful in the laboratory animals, but the chemical industry claims that our exposure levels are too low to matter. But are they?

Part of the problem in answering that question is that it's impossible to examine the exact cause and effect of BPA in humans without exposing them to large doses and measuring the outcome. However, a recent study did just that. Chinese factory workers exposed to high occupational levels of the chemical were found to have low sperm counts and low-quality sperm.

Conducted by researchers at Kaiser Permanente Division of Research, it was the first human study to tie the endocrine disruptor to lowered semen quality, and could further implicate the chemical in serious health problems.

Most of us are exposed to BPA, which is used to strengthen plastics, by way of consumer products -- receipts; soda, beer and food cans; hard plastic bottles; and dental sealants. As a result, most humans have measurable amounts of BPA in their urine.

To be sure, the Chinese workers were exposed to much higher levels than the average consumer. The study looked at 130 Chinese factory employees that dealt directly with materials containing BPA and compared them with 88 workers that had normal routes of exposure.

The study found a nice dose-response with BPA:

men with detectable levels of BPA in their urine were more likely to have low sperm counts and low sperm quality. The lowest sperm counts were in men with the highest levels of BPA.

What's more, even in men that didn't work with the chemical, BPA was linked with lower-quality semen quality.

BPA is an endocrine disruptor, meaning it can mimic and disrupt the body's own hormones. In the lab, BPA has been linked to mammary and prostate cancers, infertility, and other reproductive problems in animals. Last year, a similar study of Chinese factory workers found that BPA exposure resulted in an increase in sexual dysfunction.

Evidence of problems at high doses doesn't necessarily correspond with problems at low doses. That's the whole argument behind industry groups and regulators, who have yet to ban the substance. But do we know what's safe? The recommended limit of exposure is 0.05 mg of BPA per kg of body weight per day. But as noted on the Body Politic blog, "the EPA doesn't know what happens to animals (let alone humans) who are exposed to 0.05 mg/kg of BPA per day. They've never tested it. They arrived at this limit by testing what happened to rats exposed to 5 mg/kg per day; then they divided by 100 and assumed that the resulting level would be absolutely safe."

With an arbitrary limit for what's safe, numerous routes of exposure and evidence that, at least in high doses, it can negatively affect human health, we shouldn't have to wait for regulators to finally conclude that it causes even more reproductive problems in humans. We have alternatives to BPA. Why not use them?

Photo credit: eutrophication&hypoxia