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Scientists have long suspected that industrial chemicals used in plastic water bottles can disrupt human hormones.
But, to date, evidence has been observational, meaning it shows an association between plastics exposure and certain diseases, but can't prove a causal effect.
Now, a groundbreaking new study shows direct evidence that bisphenol A — or, BPA, a chemical used to package food and drink — can reduce sensitivity to insulin, a hormone that helps regulate blood sugar.
An impaired ability to respond to insulin, known as insulin resistance, can mean chronically high blood sugar levels and a much higher risk of type 2 diabetes.
The researchers, who presented their findings at the 2024 Scientific Sessions of the American Diabetes Association, said this study shows the EPA may need to reconsider the safe limits for exposure to BPA in plastic bottles, food containers, and other containers.
Researchers from California Polytechnic State University studied 40 healthy adults who were randomly assigned to receive either a placebo or a small dose of BPA daily.
After four days, the participants who were given BPA were less responsive to insulin, while the placebo group did not experience any change.
The dose of BPA that participants received, 50 micrograms per kilogram of body weight per day, is an amount currently classified as safe by the EPA.
"These results suggest that maybe the US EPA safe dose should be reconsidered and that healthcare providers could suggest these changes to patients," Todd Hagobian, senior author of the new study and professor at California Polytechnic State University, said in a press release.
The FDA considers BPA to be safe at low levels occurring in food containers, up to 5 mg per kg body weight per day, or 1,000 times the amount the new study found to be risky. Some researchers argue the FDA guidelines are outdated.
Other regulatory agencies around the world have taken a tougher stance on the chemical — the European Commission proposed to ban BPA in products that come into contact with food or beverages by the end of 2024.
The concern about BPA is part of a broader alarm being raised about our everyday exposure to substances that may be harmful to our health.
Other recent research has found microplastics, particles so tiny they can infiltrate human cells, may potentially wreak havoc with our health. They've been found everywhere, from human lungs to reproductive organs.
Understanding how the substances we encounter every day may affect our health long-term could help us make better decisions about how to reduce the risk of chronic illnesses like type 2 diabetes.
"Given that diabetes is a leading cause of death in the US, it is crucial to understand even the smallest factors that contribute to the disease," Hagobian said in the press release. "We were surprised to see that reducing BPA exposure, such as using stainless steel or glass bottles and BPA-free cans, may lower diabetes risk."
