June 15, 2012 — Bisphenol A, or BPA – a chemical that commonly leaches into food and drink from cans and plastic containers – can alter the behavior of mice for generations after exposure, research led by the University of Virginia School of Medicine shows.
The researchers exposed female mice to the compound prior to and during pregnancy, feeding them sufficient doses to create a BPA level in the blood equivalent to what is typically found in humans. The researchers then examined the genetic effects on subsequent generations. They found that the initial BPA exposure continued to affect gene expression and shape social behavior in the fourth generation – the last examined – though there had been no additional exposure to the chemical.
The researchers believe BPA has trans-generational effects in people the same as it does in mice. "Based on our data, and the results from others, it is clear the effects of this chemical are going to be with us for a long, long time," said Emilie F. Rissman, the study's lead investigator and a professor of biochemistry and molecular genetics at the School of Medicine.
BPA is an endocrine disruptor, meaning it interferes with the body's hormone system. The man-made chemical is commonly used in polycarbonate plastics, and it is often found in can linings and food and drink packaging. Because BPA is water-soluble, it can leach into food and drink, especially when the container gets hot or if the food is acidic. This is the primary way people are exposed to BPA.
A survey conducted by the Centers for Disease Control and Prevention in 2003-04 found detectable levels of BPA in 93 percent of 2,517 urine samples taken from Americans age 6 and older.
In examining the trans-generational effects of BPA, the researchers looked at the social interactions between pairs of juvenile mice in the generations after exposure to BPA. They evaluated the amount of time the mice spent exploring their environment and the amount of time they spent engaged in social activities. They also conducted targeted genetic testing to determine BPA's effects on genetic expression patterns in the brain.
The researchers found that the mice exposed to BPA while in the womb were less social than mice that had not been exposed. By the third subsequent generation, the behavior had flipped: Mice descended from the BPA-exposed mouse were more social than the control group.
The researchers' conclusion: "Exposure to a low dose of BPA, only during gestation, has immediate and long-lasting, trans-generational effects," they write in a paper published online in the journal Endocrinology.
While the researchers believe BPA may have trans-generational effects in humans as well, the effects may manifest differently.
"While we certainly observed behavioral changes that were passed from generation to generation with subsequent exposure, I cannot say for sure these effects would be the same in humans," Rissman said. "However, as fellow mammals with a 99 percent similarity in their genomes, mice are a good laboratory model for investigations like these, which simply cannot be done in people. While work in humans is correlational, it is important and worth examination."
The researchers next plan to examine the mechanism by which BPA is affecting genes.
– by Josh Barney
June 15, 2012