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.