Mice exposed to the chemical bisphenol A (BPA) via their mothers during pregnancy and while nursing have an increased risk of liver tumors, new research shows.
“We found that 27 percent of the mice exposed to one of three different doses of BPA through their mother’s diet developed liver tumors and some precancerous lesions,” says lead author Caren Weinhouse, doctoral student in the department of environmental health sciences at the University of Michigan. “The higher the dosage, the more likely they were to present with tumors.”
Mice whose mothers received the highest dosage, 50 mg of BPA per kg diet, were seven times more likely to have tumors than those whose mothers were not exposed to BPA.
More research is needed to determine the implications for human health, Weinhouse says. “This current study showing liver tumors in mice says let’s take another look at BPA and cancer in humans.”
Researchers will next look for biomarkers in the mice genes that may signal risk for disease before it develops, and then try to see if similar characteristics are found in humans.
BPA, is a chemical most commonly found in plastics, cash register receipts, and the lining of food cans. It once was used in hard plastic bottles, including baby bottles, but many companies have removed it as concerns about health effects have been raised in recent years. Studies have estimated that at least 90 percent of Americans have some level of BPA in their bodies.
Gender doesn’t matter
Previous research has found precancerous lesions associated with BPA exposure but the new study, published online in the journal, Environmental Health Perspectives, is the first statistically significant finding of clinically evident tumors in any organ, says Dana Dolinoy, assistant professor of environmental health sciences and senior/corresponding author of the study.
Specifically, the researchers found that adult offspring of exposed mothers had an increase in liver tumors.
The study also shows that in this case, tumor development doesn’t discriminate by sex, Dolinoy says. “In general, females are at lower risk of spontaneous development of liver cancer. That distinction was erased in this study, with both males and females showing tumors.”
The researchers fed 6-week-old female mice diets containing one of three environmentally relevant doses of BPA prior to mating, then throughout pregnancy and nursing. They then took one male and one female from each litter and followed them through to 10 months.
Another point of interest in the research is that most other small animal studies have involved direct exposure to BPA. In this research, it was the mothers who were exposed before conception. The offspring, therefore, were exposed as developing fetuses and pups, not as adults.
“A previous study that exposed adult mice to much higher doses of BPA did not show the same link to cancer development,” Dolinoy says. “This tells us the timing of exposure and the dosage are extremely critical in evaluating study outcomes.”
One year ago, researchers found BPA in human fetal liver tissue, demonstrating that there is considerable exposure to the chemical during pregnancy.
In that study they also found a proportionately higher concentration of free BPA—as opposed to conjugated forms modified by the body for elimination—showing that the ability to flush the chemical from the body is not the same in fetuses as in adults.
The Michigan Nutrition Research Obesity Center, National Institutes of Health, National Institute of Environmental Health Sciences Core Center of Excellence, Children’s Environmental Health Formative Center, and an NIEHS Institutional Training Grant supported the research.
Researchers from Penn State contributed to the study.
Source: University of Michigan