A recent study published in the “Proceedings of the National Academy of Sciences” found that Bisphenol A (BPA) can adversely affect fetal development in rhesus monkeys. The study’s findings raise concerns regarding BPA exposure and human health consequences. BPA is a common chemical used to make polycarbonate plastic, which is used in beverage containers, compact discs, impact-resistant safety equipment, automobile parts, toys and other products. BPA epoxy resins also are used as protective linings in food cans, dental sealants and other products. There has been growing concern regarding BPA because human exposure to BPA is widespread. The Centers for Disease Control and Prevention found detectable levels of BPA in 93 percent of Americans in a 2003-2004 survey. People are primarily exposed to BPA from food packaging, according to the U.S. Environmental Protection Agency.
For more than 15 years, there has been debate over whether BPA has an adverse toxicological effect on humans. BPA binds to certain estrogen receptors in the body and it is considered to be an endocrine (hormone system) disruptor that can mimic estrogen. Yet, expert opinions vary regarding the health effects of BPA. Some studies have concluded that BPA poses no health risks while other studies have concluded that BPA is linked to a number of adverse health effects. Although there have been hundreds of studies on the effects of BPA on rodents, there have been very few studies of BPA in primates. Given the physiological similarities between humans and primates, studies on BPA in primates may have more direct implications for human health.
Dr. Patricia Hunt, a geneticist at Washington State University, led the recent study on the effects of BPA on 19 pregnant rhesus monkeys. Rhesus monkeys share 95 percent of their DNA with humans and have been recognized as “a superior model for human reproductive physiology.” In the study, the monkeys were fed or given low doses of BPA at levels similar to which humans are routinely exposed. Hunt found that BPA caused adverse effects at two points during the pregnancy.
First, BPA disrupted the key events of meiotic prophase. Meiosis is a special type of cell division necessary for sexual reproduction. Hunt found that in the earliest stage of the egg development, the egg cell failed to divide properly. Hunt opined that such damage could lead to miscarriage or to birth defects. Second, Hunt found that BPA caused problems later in pregnancy by disrupting follicle formation. BPA caused eggs to be improperly packaged in the follicles in which they developed. Hunt concluded that improper follicle packaging could limit the number of viable eggs, thereby limiting the reproductive lifespan of the exposed female.
According to some scientists, the small size of the study makes its significance to human health unclear. Thus, the debate regarding BPA and human exposure risks will continue. The U.S. Food and Drug Administration, in cooperation with the National Toxicology Program, currently is pursuing additional studies to better understand the risks associated with human exposure to BPA.