BPA, an estrogen-mimicking compound found in common products like water bottles, soup cans, and store receipts, is linked to a lot of nasty complications, including obesity and neurological changes. Now, for the first time, researchers have found a direct link between BPA exposure and cancer development while studying mice.

The researchers behind the study, located at the University of Michigan School of Public Health, never set out to find a connection between BPA and cancer. They initially hoped to examine links between BPA exposure and obesity. “We weren’t actually looking for liver cancer at all,” says Caren Weinhouse, a U-M doctoral student and one of the paper’s authors.

This was a surprise finding, but it was fortuitous.

The study, published in Environmental Health Perspectives, exposed mice to BPA in early life via their mothers’ diet during gestation and nursing and then maintained the mice on a controlled diet until they were 10 months old. The mice were then euthanized. That’s when the researchers noticed that a significant proportion of the test subjects had liver tumors. The mice who received the highest BPA dosage were a staggering seven times more likely to have liver tumors than mice whose mothers had not been exposed to BPA. Overall, 27% of the mice exposed to BPA ended up with liver tumors. The more BPA they were exposed to, the more likely they would get tumors.

“This was a surprise finding, but it was fortuitous. It was a fairly conservative model for studying liver cancer,” explains Weinhouse. That’s because the strain of mouse used in the study happens to be fairly resistant to liver tumor development, and still, tumors occurred.

Prior studies have drawn a link between early life exposure to BPA and precancerous lesions, as well as BPA exposure and increased susceptibility to carcinogens. But this is the “first study showing a statistically significant link between early life BPA exposure and later life tumors in any organ when the exposure is to BPA alone,” says Weinhouse.

While more work needs to be done, it appears that timing of BPA exposure could play an important role in tumor development. A previous study, which exposed adult mice to high doses of BPA, didn’t find a direct link to cancer development. “Our approach is to say that this study warrants taking another look at BPA and cancer. We’re looking for biomarkers that may indicate an increased risk in early life in animals before they develop liver tumors,” says Weinhouse.

Researchers need to do analysis of humans before a direct link between BPA and human cancer can be proven. Regardless, with so many other reported side effects, we should already be on the hunt for better, safer alternatives.