Study links BPA to birth defects, miscarriage

A new study has found ‘compelling’ evidence that the plastic additive bisphenol A (BPA) may negatively impact women’s reproductive systems and cause chromosome damage, birth defects and miscarriages.

Researchers from Washington State University and the University of California, Davis, found that rhesus monkeys exposed to BPA in utero suffered serious reproductive abnormalities that increased their risk of giving birth to offspring with Down syndrome or other birth defects – or even having a miscarriage.

Prior studies done in worms and rodents have shown similar effects, but because rhesus monkeys have the most human-like reproductive system, this study “hits much closer to home,” Dr. Patricia Hunt, a geneticist and professor of molecular biosciences at Washington State University, told FoxNews.com.

BPA is a low-grade estrogen that until recently was found in certain plastic bottles—typically marked with the number ‘7’ inside a recycling symbol.  It is still found in the linings of aluminum cans and heat-activated cash register receipts.

A 2003-2004 National Health and Nutrition Examination Survey (NHANES) found BPA exposure is “nearly ubiquitous” in the U.S. population, with 92.6 percent of people over the age of 6 having detectable levels of BPA in their urine.

The chemical has also been associated with obesity, cardiovascular disease, diabetes, breast cancer, prostate cancer and neurological disorders.  While the U.S. Food and Drug Administration recently banned BPA from sippy cups and baby bottles, it did not extend the ban to other products.

This latest WSU study found when pregnant monkeys were given either a single daily dose of BPA or low-level continuous doses – meant to mimic exposure levels in humans – it led to changes in the cells that would become eggs in the developing fetus.

Therefore, once the offspring were ready to reproduce themselves, the egg cells were not able to divide properly, meaning the fertilized egg had the wrong number of chromosomes.  This can cause various birth defects, including Down syndrome, and can even lead to miscarriage.

“The really stunning thing about the effect is we're dosing grandma,” Hunt said in a released statement. “It's crossing the placenta and hitting her developing fetus, and if that fetus is a female, it's changing the likelihood that that female is going to ovulate normal eggs.”

Furthermore, in the monkeys that were continually exposed to BPA, the researchers found the fetal eggs were not packaged the right way in follicles, which is where they develop.  Eggs must be packaged properly in order to grow, develop and mature, according to the researchers.

“This means [the monkeys] will probably end up with a lot fewer eggs to work with, because a female is born with all the eggs she’s going to have,” Hunt said. “Her reproductive lifespan may be shorter.”

While the experiment’s results are worrisome, Hunt said it is nearly impossible to set up a study establishing a concrete cause-and-effect relationship between BPA and reproductive issues in humans, and even correlational findings would take a while to become evident.

“The problem for both of these effects is we would have to wait a generation to see results of fetal exposure in utero. What happens when they grow up and make babies?” she said.

However, she added that it was “compelling evidence” that three different experimental models in worms, mice and monkeys all showed similar effects.

In response the study findings, Steven Hentges, of the American Chemical Society’s Polycarbonate/BPA Global Group released a statement critiquing the study's small sample size and said it was "of unclear relevance to humans."

"In the second test protocol, the monkeys were injected with BPA under the skin, which is of very little relevance to the minute BPA exposures that occur in humans through the diet," he added, "...Because of the way BPA is processed in the body, it is very unlikely that BPA could cause health effects at any realistic exposure level."

The study was published Monday in the Proceedings of the National Academy of Sciences.