Researchers have long known people can be exposed to bisphenol A (BPA), a chemical commonly found in plastic packaging from receipts to the lining of food cans and believed to disrupt human hormones. But a new study has found people also can be exposed to the chemical just by breathing.

Published in May 2015 by researchers at the University of Missouri, the study found high concentrations of BPA in both air and water near industrial sites, indicating that people may be exposed to much larger quantities of the chemical than previously thought.

The finding undermines the arguments behind US Food and Drug Administration’s long held stance on BPA. For years, the administration has maintained that BPA primarily enters the body via food or beverages, making it a negligible health risk because orally ingested BPA breaks down and is eliminated from the body fairly quickly. The FDA doesn’t regulate the chemical, which it says is safe at the levels used in food and consumer products.

“The stance the FDA’s had for a number of years is probably narrow sighted,” says Christopher Kassotis, lead researcher on the University of Missouri study. “A number of studies looking at the BPA on receipt paper have revealed that large amounts of the chemical enter the bloodstream from just holding a receipt, and now our studies and a few others have found that there’s significant aerial exposure as well.”

Both exposure from touch and from air can have more of a biological effect than oral ingestion, he claims. “Knowing what we do now, I think the FDA needs to rethink its approach,” he says. “We cannot say a level of exposure is safe or not until we’ve adequately explored all of the exposure routes.”

In May, Health Canada – the Canadian government’s public health department – published updated research that questions the long held but previously untested assumption that BPA is harmlessly metabolized by the liver. The Canadian researchers found that the liver converts BPA into a compound called BPA-gluconide, which has been linked to obesity in human and animal studies.

While it’s still unclear whether or how airborne BPA affects human health, the University of Missouri study’s findings are concerning. These exposures, which can’t be avoided, greatly add to the overall levels of the chemical people are being exposed to on a regular basis. The levels of BPA detected around plastic manufacturing sites in particular were far higher than recommended safe levels for human exposure.

“Even at the sites that were essentially our background baseline sites, we measured 30 nanograms per liter – that’s higher than levels known to cause sexual differentiation issues in snails and some amphibians,” Kassotis says. “And at the aerial release sites, there was 10 times that amount.”

Kassotis and five other University of Missouri researchers collected samples of surface water from six sites throughout the state, including four sites where wastewater was the source of contamination and two where aerial release of endocrine-disrupting chemicals was the source. The team analyzed the samples for estrogenic and androgenic activity, and looked closely at the levels of two endocrine-disrupting chemicals: BPA and ethinylestradiol, a common chemical component of oral contraceptives that’s often found in municipal wastewater.

The researchers found far less ethinylestradiol than expected, which the authors suggest might be due to the need for more sensitive measuring tools, but far more BPA than expected, particularly in the sites near plastic manufacturing plants.

Those levels will certainly affect wildlife, Kassotis says, but their impact on human health remains unknown. Ultimately, the study of airborne BPA is in its infancy. Only a handful of studies have looked at the health impacts of inhaling endocrine disrupting chemicals in general, and fewer still have looked specifically at BPA. A global air sampling study in 2010 found that the chemical was present in the air all over the world, including in the Antarctic, but said that health implications remained unknown.

The team also found estrogenic activity in their surface water samples that could not be pinned on BPA or ethinylestradiol, particularly in sites impacted by wastewater.

Aside from further study, next steps will be to look at how much BPA is being discharged from factories and calculate the distance the chemical traveled to make it into the surface water sample; the amount of BPA that then shows up in the water; and the overall percentage of BPA emissions that ultimately reach nearby water resources.

More research on the impacts of BPA in the air and in surface water is necessary to understand any potential human health impacts, Kassotis says. Chemicals that are inhaled are likely to have a greater bioactive concentration, meaning they are more likely to have a biological effect. People may also be taking in surface water from their skin and mouths.

“People are potentially swimming in, playing in, fishing in these rivers,” Kassotis says. “Maybe they clean their clothes in the water. More than half the drinking water in this country comes from surface water, too, and we know that our treatment processes are not designed to remove the majority of endocrine-disrupting chemicals from water, so there’s certainly potential for them to end up in drinking water. So we’re potentially talking about the full spectrum of exposure here, and right now, the health effects? That’s anyone’s guess.”