You've probably noticed that more and more of your friends and co-workers are switching from the once ubiquitous plastic water bottle to stainless steel or glass water bottles. Most likely, they made the switch because they're concerned about the effects those plastic
bottles have on their health.

Over the last decade or so, we have come to understand that plastic is not the innocuous and stable material it appears to be.  Bisphenol A (BPA), a molecular building block of many 
polycarbonate plastics and epoxy resins, can leech out of materials and contaminate the surrounding environment. Animal studies have provided us with several examples of the potentially harmful effects of BPA exposure on development and behavior. In the first study
on the effects of BPA exposure on human behavior, scientists have connected BPA exposure in the womb to more aggressive behaviors in  girls¹.

BPA is a widely used compound that can be found in items like water bottles, food containers, and medical devices as well as in the linings of aluminum cans used for food storage.  BPA mimics  the hormone estrogen and can bind to and activate estrogen receptors. In a growing fetus, this estrogen mimic could disturb delicately-balanced, hormonally-driven developmental processes. Over the last decade or so, animal studies have shown that prenatal BPA exposure does indeed affect development and can lead to physiological and behavioral changes in young animals. For example, young male mice exposed to BPA in utero exhibited increased aggressive behavior as well
as a reduced testis size².

The first study on prenatal BPA exposure and human behavior, headed by Bruce Lanphear, director of the Cincinnati Children's Environmental Health Center, suggests that prenatal BPA exposure is associated with an increase in externalizing behaviors in two-year-old girls. Negative externalizing behaviors include hostile, defiant, and aggressive actions.

The study's participants began as 249 expectant mothers in the Cincinnati area.  The women gave three urine samples, one at 16 weeks of gestation (early second trimester), one at 26 weeks of gestation (end of second trimester) and one at the time of delivery. At each time
point, there were detectable levels of BPA in samples from 90% of women. Once the children reached the age of two, parents scored their behavior with the Behavior Assessment System for Children (BASC-2), a widely-used clinical rating-scale system that assesses many aspects of
behavior, both positive and negative.

Looking across the entire dataset for an association between prenatal BPA levels and behavior, researchers found no significant correlation.  However, when they split the data into mother-daughter and mother-son pairs, they did see a significant association between average prenatal BPA levels and higher externalizing-behavior scores in girls.  In particular, it was the level of BPA at the earliest timepoint of gestation, 16 weeks, that was correlated with the externalizing behaviors in girls. Daughters of women who had the highest BPA concentrations at time of delivery (top two quartiles) had externalizing scores similar to males. The researchers will continue to follow the children through 5 years of age to monitor the persistence
of these behaviors. 


These results suggest that BPA in a mother's body can affect the neurodevelopmental processes of her children and that the sex of the child can modulate these effects. It should be noted that this study was based upon a relatively small number of participants and that the children were very young, which might make it difficult to accurately qualify their behavior.  However, the fact that prenatal BPA exposure has been shown to affect behavior in other animals raises my confidence in the author's conclusions. I don't know if it is more alarming or more astounding that a material so intertwined with our everyday life, especially with food and water, could be the source of a developmentally-disrupting toxin found in over 90% of Americans³. We trust that materials found in grocery aisles and hospitals are safe, but unfortunately, some are "safe-until-proven-otherwise." 

Although the jury may still be out on the safety of BPA, this initial foray into the effects of BPA exposure on human development and behavior has nonetheless convinced me it is time to be serious about minimizing my exposure to this compound.

References

1) Braun J, et al. Prenatal Bisphenol A Exposure and Early Childhood Behavior. Environmental Health Perspectives, online. doi:10.1289/ehp.0900979; 2009.
2) Kawai K, et al. Aggressive Behavior and Serum Testosterone Concentration during the Maturation Process of Male Mice: The Effects of Fetal Exposure to Bisphenol A. Environmental Health Perspectives: Vol. 111 (2); 2003. 
3) Calafat AM, et al. Exposure of the U.S. Population to Bisphenol A and 4-tertiary-Octylphenol: 2003-2004. Environmental Health Perspectives: Vol. 115 (12); 2007.