Scientists have found liver tumours in mice exposed to Bisphenol A (BPA) - a chemical found in certain plastics. In one of the first studies to show a significant association between BPA and cancer development, University of Michigan School of Public Health researchers have found liver tumours in mice exposed to the chemical via their mothers during gestation and nursing.
Previous research has found precancerous lesions associated with BPA exposure but the new study is the first statistically significant finding of clinically evident tumours in any organ, said Dana Dolinoy, the John G Searle Assistant senior/corresponding author of the study.
Specifically, the researchers found that adult offspring of exposed mothers had an increase in liver tumours.
Dolinoy said another interesting finding in their research is that tumour development didn't discriminate by sex.
"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 tumours," she said.
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 their research, Dolinoy said, 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 foetuses 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 said.
"This tells us the timing of exposure and the dosage are extremely critical in evaluating study outcomes," she said.
Earlier, Dolinoy's lab found BPA in human foetal 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 foetuses as in adults.