A study published this week in the journal Pediatrics found a link between levels of bisphenol-A in pregnant moms and behavioral problems such as anxiety and hyperactivity in their daughters at age 3. No such effects were seen in boys. BPA has estrogen-like activity and can lead to developmental and behavioral problems in animals—but whether or not it does the same in humans, and at what dosages, is a subject of considerable debate. This study won't settle the debate but highlights the need to answer some basic questions about BPA that remain surprisingly unclear. What's the Context:
Bisphenol-A is used in many types of plastics like polycarbonate, linings of metal cans, and in receipts (even some labeled "BPA-free"). It shows up in the urine of the vast majority of Americans.
Since BPA mimics estrogen in the body, it may effect mental and sexual development, especially if it is present very early in life. For this reason it has been explicitly banned from being used in baby bottles in several European countries, and BPA manufacturers say they don't sell the chemical to makers of baby bottles.
Animal studies show fetal or early-life exposure to the chemical can interfere with mental development and behavior, like hyperactivity and impaired sociality.
How the Heck:
244 pregnant women from Cincinnati, Ohio, had levels of BPA in the urine tested at weeks 16 and 26 of pregnancy, and again within 24 hours of giving birth. BPA levels were also tested in the urine of their children at ages 1, 2, and 3.
Behavioral problems were measured by two surveys filled out by parents when the children were 3 years old. The tests sought to identify problems in executive function, depression, anxiety, and attentional deficits.
Levels of BPA in the children were not linked to behavioral problems. However, the average level of BPA found in the urine at weeks 16 and 26 did appear related to behavioral issues in the girls (but not boys), namely increased levels of depression, anxiety, and hyperactivity.
Researchers don't know why BPA may impact girls more than boys. They speculate that it may disrupt early neural processes that give rise to behavioral differences between males and females, like aggression and anxiety.
Not So Fast:
Critics of this study rightly point out that BPA is quickly metabolized in the body; a 2002 study found its half-life to be about 6 hours. However, a more recent study found that BPA may be metabolized more slowly and that there are significant non-food sources of the contaminant.
Another study found that people who ate food with high levels of BPA showed very low levels of it in their blood.
It remains unclear exactly how much BPA is absorbed into the bloodstream and how BPA may accumulate in fat stores within the body.
Given this uncertainty, measuring urine levels of BPA only twice during pregnancy may not be a good indicator of a fetus' total BPA exposure. It would be better to measure blood levels of the chemical more often and earlier in the pregnancy.
The Future Holds:
Despite the uncertainties in this study, it may make sense for pregnant women to try to limit BPA exposure during pregnancy, especially early on—this can be done by avoiding packaged foods and eating fresh fruits and vegetables, etc.---which is healthy anyway.
The FDA says it's still "looking into" the health effects of BPA, although it remains legal in almost all food containers.
There's enough evidence to curtail our use of BPA, at least in products aimed at pregnant women and infants. This is, of course, easier said than done, considering how cheap, useful, and ubiquitous the chemical is.
Reference: Joe M. Braun, Amy E. Kalkbrenner, Antonia M. Calafat, Kimberly Yolton, Xiaoyun Ye, Kim N. Dietrich, Bruce P. Lanphear. Impact of Early Life Bisphenol A Exposure on Behavior and Executive Function in Children. Pediatrics, Published online Oct. 24, 2011. DOI: 10.1542/peds.2011-1335
Image: katerha / Flickr
