COLUMBIA — MU scientists warn that there is likely more bisphenol A circulating in the human bloodstream than previously believed.
In a new study, Cheryl Rosenfeld and a group of researchers at the Bond Life Sciences Center were the first to simulate a realistic intake of BPA in people through a BPA-supplemented diet fed to mice. The scientists found significantly higher levels of the chemical in animals exposed to BPA through regular diet than in the subjects that ingested a one-time dose.
Scientists in various fields have warned that the effects of BPA — an endocrine disruptor commonly found in household plastics — could cause a catalog of health problems such as reproductive disorders, learning and memory difficulties, and problems with the immune system.
“It can affect estrogen, thyroid and testosterone function, and might cause genetic mutations,” Rosenfeld said.
Despite an ever-growing list of studies demonstrating adverse effects of the chemical, BPA proponents assert there is not enough evidence to discontinue or even issue warnings on the chemical. These arguments, Rosenfeld said, are bolstered by one-dose studies that don't reflect human intake of BPA through normal diet.
The MU study is groundbreaking because previous research had used unrealistic conditions to test the effects of BPA. Consequently, human exposure was presumably underestimated.
“A previous study administered a single, one-time, liquid-dose exposure,” Rosenfeld said, which did not mirror the way people accumulate BPA by exposure to small amounts of the chemical on a regular basis in food.
The team instead created a mouse feed laced with radioactive BPA. After consuming the diet for a week, researchers found the biologically active BPA had accumulated in the mice’s systems, and was significantly higher than the measurement done after mice ate the feed for 24 hours.
The study also showed that the initial increase of BPA in the bloodstream was greater when administered through diet — akin to human intake.
“The liver has to metabolize BPA,” Rosenfeld said. She explained that BPA is introduced to the bloodstream quicker when paired with food, because the liver has to handle the food taken in as well as the chemical.
“This route of exposure potentially overwhelms the capacity of the liver to metabolize the food and the foreign substance,” she said.
Rosenfeld said this study and others that reflect realistic human exposure should be brought to the table in the heated BPA debate that's prompted legislative action and caused some manufacturers to seek out alternatives.
Rosenfeld said she hopes policymakers consider her findings when dealing with legislation to reduce and potentially ban BPA production.
“I would like them to become aware of these studies,” she said. “Single-time point measurements are probably not the most accurate method to measure BPA exposure in humans and animal models.”
BPA is widely used to harden many common plastics. It is rough and durable, and additionally used as a relatively cheap coating inside of almost all food and beverage cans.
More than 8 billion pounds are produced every year, and the study notes that more than 90 percent of people in the U.S. have “measurable amounts of BPA in their bodies.”
Rosenfeld said pregnant women in particular should take measures to reduce their exposure to BPA.
Babies have “even less ability to metabolize BPA and it can disrupt the growth of organs that are normally governed by sex steroid hormones,” she said. “Even sometimes low-dose exposure to BPA can lead to striking effects.”