A hand holding a plastic water bottle.

The way scientists usually measure bisphenol A (BPA) may drastically underestimate our exposure to the chemical, concludes a new analysis published in The Lancet Diabetes & Endocrinology.

Some studies have linked BPA to an elevated risk of health issues, such as fertility problems and certain cancers, but it remains widely used to harden plastic, prevent metal corrosion, and coat paper. The substance is often found in the linings of food cans, on receipts, in medical equipment, and in hard-plastic water bottles.

Currently, our exposure to BPA is generally measured—by the Centers for Disease Control and Prevention, among others—using what’s known as an indirect method (more on that below). The new study suggests that this method may not be accurate and reports that a newer technique found levels of BPA many times higher than expected.

“If the conclusions are true and can be generalized to other populations, then the research and regulatory communities around the world have systematically underestimated the health risks posed by BPA, perhaps by a rather large margin,” says Jonathan Martin, Ph.D., a professor in the department of environmental science and analytical chemistry at Stockholm University, who was not involved in the new study.

But he urged caution in interpreting the results of the new study, which was quite small. “The extent of the problem shown here may not be widely generalizable,” Martin says. “I’m reserving judgment until results like these can be replicated in other labs with other samples.”

Here’s what you need to know about the risks of BPA, the findings of the new study, and how you can minimize your exposure

What Do We Know About BPA Risks?

BPA is what’s known as an endocrine disruptor, which means that it can interfere with or mimic the actions of your hormones. Such disruptions can have effects throughout the body.

More on Plastics

The FDA and its counterparts in Canada and the European Union say that BPA used in food packaging and containers poses no risk to consumers. (The European Food Safety Authority is currently reviewing the most recent research on BPA and may update its recommendations in 2020.)

These conclusions from regulatory authorities are based in part on what has been found by the CDC and others—that though BPA is ubiquitous, most people are exposed only at very low levels (PDF).

Many experts, however, say that even in small amounts, endocrine disruptors can be harmful to our health over time.

The Endocrine Society, a professional group representing thousands of physicians and scientists who specialize in hormone-related disorders, says that dozens of studies in large populations have linked low levels of BPA and similar chemicals to problems with reproduction, metabolism, and behavior. The American Academy of Pediatrics has cautioned that BPA “can act like estrogen in the body and potentially change the timing of puberty, decrease fertility, increase body fat, and affect the nervous and immune systems.”

The FDA declined to comment on the record.

What the New Study Found

When your body is exposed to BPA, it begins to break it down rapidly. That means most of what is found in human urine—which is often used to monitor exposure—is not BPA itself. Instead, what’s found are metabolites, or what BPA is broken down into.

Until recently, researchers could not measure those metabolites directly. Instead, the only way they could determine human levels of exposure was indirectly, by converting the metabolites back into BPA.

But within the past several years, new, direct methods began to emerge, so that “in one sweep, you measure BPA and its metabolites,” says Roy Gerona, Ph.D., an assistant professor in the School of Medicine at the University of California San Francisco who runs UCSF’s Clinical Toxicology and Environmental Biomonitoring Laboratory. These methods have not yet been widely adopted, however.

Gerona, the lead author on the new paper, has been working on a direct method for measuring BPA metabolites for years. In the new study, he and his collaborators wanted to compare this new technique to one similar to the indirect approach used by the CDC.

They used both techniques to analyze samples of urine collected from 29 pregnant women, five nonpregnant women, and five men. The new direct method found levels of BPA almost 19 times higher than those detected using the indirect method. And it seemed that the greater the concentration of BPA, the more the indirect method underestimated it.

(The CDC said it could not comment on outside research but confirmed that its latest monitoring studies use an indirect method for measuring BPA.) 

Next Steps

The researchers checked and rechecked their results, and corroborated their findings with a lab at the University of Missouri. 

“We were very skeptical of our results,” Gerona says. “I would like other people to be skeptical and critical as well. That’s really the only way it can be verified.”

Other experts agree. “The new study highlights an urgent need for laboratories that are currently using the indirect analytical method to conduct a thorough evaluation of this method for bias,” says Tunde Akinleye, a chemist in Consumer Reports’ food safety division. “The result of that evaluation could have serious implications for how regulatory agencies currently assess the risks posed by BPA.”

If the results found in the new Lancet analysis are replicated in large numbers of people, the current assumption that human exposure is low may need to be reexamined.

“The indirect measurement has the effect of making it look like everyone is in this low-exposure range, which we’ve assumed is the human exposure range. Regulatory decisions have been based on the assumption that our exposure is relatively low,” says Patricia Hunt, Ph.D., an author of the new study and a professor at Washington State University’s School of Molecular Biosciences in Pullman. But the new results suggest “some people are much more highly exposed.”

Confirmation of the new study’s results could also change the way scientists and regulators interpret past studies of BPA exposure, and ultimately, the agreed-upon methods for measuring BPA, as well as other concerning chemicals—such as phthalates and parabens.

“When you think about all the epidemiological studies that have come out showing an association between BPA and various adverse health impacts—those studies used the old approach [for measuring BPA],” says Pete Myers, Ph.D., founder and chief scientist of the nonprofit Environmental Health Sciences and an adjunct professor of chemistry at Carnegie Mellon University in Pittsburgh. “What does [this new study] mean for those results? If you use this new approach, the associations that were already present may become stronger.”

What You Should Know

BPA is no longer used in baby bottles, sippy cups, or infant formula packaging. And that’s in part because consumers put pressure on the marketplace to change. Many experts we spoke to expressed hope that the new study might encourage regulators to consider wider-reaching regulations on the other uses of BPA.

“The FDA’s safety standards for many chemicals in food are far too weak, both when it comes to how rigorously companies must demonstrate safety and how quickly the FDA must take action to protect the public when new data puts safety into question,” says William Wallace, manager of safety policy at Consumer Reports.

But while you may see plastic products labeled BPA-free, be aware that these often contain replacement chemicals that may carry similar risks, Myers says.

Still, there are several “safe and simple steps to limit these exposures that are in the hands of consumers,” said Leo Trasande, M.D., the director of the NYU Center for the Investigation of Environmental Hazards and the author of “Sicker Fatter Poorer” (Houghton Mifflin Harcourt, 2019), a book about endocrine-disrupting chemicals.

For the moment, it seems wise to reduce your use of canned foods and your handling of thermal paper receipts, he says.

And take care with plastic. “Never put plastic in the microwave or dishwasher,” Hunt says. “Heat is an invitation for chemicals to leach out.”

You can find additional tips for reducing your exposure to plastic in this previous article


How to Eat Less Plastic

Some researchers believe the average person consumes about 5 grams of plastic per week. On the "Consumer 101" TV show, Consumer Reports expert Kevin Loria offers six tips for reducing your exposure to microplastics.