Since the 1940s, companies have been using PFAS – perfluoroalkyl and polyfluoroalkyl substances – to make products easier to use, from Teflon nonstick pots to waterproof rain gear, stain-resistant carpet and firefighting foam.

The chemicals’ resistance to heat, oils, stains, grease and water makes them useful. However, that same chemical stability also makes them linger in the environment – and in the human body. Studies have suggested that some types of PFAS can contribute to health harms, including thyroid disease, liver damage and kidney and testicular cancer.

The U.S. Environmental Protection Agency has concluded that there is no safe level of human exposure for two of the most common PFAS compounds: perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). It set drinking water standards limiting their acceptable levels in water systems in 2024.

However, drinking water isn’t the only way people are exposed to PFAS today.

To better understand the ways people are being exposed to PFAS, we and a team of colleagues examined four exposure pathways – drinking water contamination, food contamination, recreational exposure and industrial emissions, such as from Superfund sites, airports, military bases and manufacturing plants – across three Great Lakes states: Michigan, New York and Pennsylvania.

An interactive map and online dashboard we created lets residents look up their communities’ known PFAS exposure risks. The results offer insights for people across the United States who share similar living environments, dietary choices and lifestyles.

PFAS exposure patterns

The extensive use and improper disposal of products containing these “forever chemicals” have led to their widespread presence in the environment. They have made their way into farm fields, drinking water and water bodies, where fish and shellfish can ingest the chemicals and humans can swim in PFAS-contaminated water.

In an analysis of the three states, we found that the average person consumes about three times more PFAS through food than through drinking water.

We looked at 19 food items in which PFAS have been detected, including seafood, such as clams, crab and shrimp, which have the highest levels of PFAS. Other foods beyond these 19 may also expose people to PFAS, so the totals may underestimate the actual intake.

For water contamination, we found that PFAS had been detected in 1,272 out of 2,593 tested public water facilities in Michigan, New York and Pennsylvania, collectively serving a population of about 23 million people.

We also found distinct patterns of PFAS exposure.

Among the three states, Pennsylvania has the highest risk of PFAS exposure from food and water, while Michigan has the lowest. Michigan’s lower risk likely reflects its significantly lower PFAS contamination in drinking water, which may be due to its PFAS water-testing and regulation.

Notably, our analysis found that most dietary PFAS risk comes from butter, olive oil and shrimp. Seafood typically contains much higher PFAS concentrations than butter or olive oil – polluted rivers bring these chemicals into marine environments, and fish and shellfish gradually accumulate and magnify it through the food chain. However, substantially greater consumption of butter and olive oil makes those products potentially large dietary sources of PFAS.

It’s important to note that not all sources of the foods we examined have the same PFAS risk, and the analysis did not assess the health effects from the PFAS exposure levels detected.

We found that intake of foods that can contain PFAS is higher in Pennsylvania and New York than in Michigan, driven largely by greater seafood and olive oil consumption, likely reflecting the influence of Mediterranean cuisines. Higher seafood consumption there is consistent with proximity to the coast.

Comparing Detroit, Philadelphia and NYC

Zooming in on individual cities offers more insight:

Detroit has an above-average risk of PFAS exposure through food compared with other locations in Michigan, and the highest amount among the three major urban centers we looked at. Ground beef and baked tilapia, two products in which PFAS has been detected in the North Central regional market, contribute to Detroit’s relatively higher food-related PFAS exposure risk compared with cities in other states, in addition to high consumption of bacon, sausage and crab.

Detroit’s public drinking water hasn’t been tested for PFAS, so residents’ risk level from water is unknown.

New York City has minimal PFAS exposure risk from its public drinking water and much lower PFAS levels than surrounding suburban areas. Its risk of dietary intake of PFAS comes primarily from consumption of butter and olive oil.

Philadelphia’s public drinking water has also been found to be at minimal risk, with significantly lower PFAS contamination than in surrounding suburban areas. However, it has relatively high consumption of shrimp, bacon and sausage. We found that the city and its region also have a high risk of exposure to PFAS from recreation on water bodies compared with other regions. Studies are only beginning to understand the risks from PFAS exposure through skin.

Among smaller cities, Rochester, New York, and its surrounding area, particularly along Lake Ontario, also stands out for its higher risks from recreational exposure to PFAS compared with other regions. A 2024 study of PFAS in the Great Lakes found that airborne pollution was contributing to contamination in the five lakes, particularly Lake Ontario, along with PFAS from industry-lined rivers.

How to reduce your PFAS exposure

In general, we recommend several actions to help mitigate PFAS exposure risk.

Households served by public water systems with high levels of PFAS may want to use drinking water filtration systems.

People can also reduce their exposure by adjusting their dietary choices by eating less of those foods with the potential to have PFAS contamination.

Our dashboard also includes a map of recreational sites near PFAS-contaminated water bodies.

The dashboard reflects the goal of our study – not only to inform, but also to empower individuals and communities to make healthier choices. Local governments and advocacy groups can also use the data to prioritize policies to reduce exposure.

Where to learn more

Several official and unofficial resources are also available to help the public understand PFAS contamination across the U.S.

The EPA created an online PFAS Analytic Tool that shows locations of PFAS contamination in natural water, drinking water systems, and industrial emissions through interactive maps. The Environmental Working Group, a science and advocacy group, provides a map highlighting PFAS-contaminated sites and affected public water systems.

These resources offer valuable insights into contamination locations, but they do not directly assess human exposure or individual risk.

As the research on PFAS continues to develop and policies evolve, the need for information becomes increasingly important for public understanding and prevention. We hope our study inspires people to become more informed and more engaged in protecting themselves and their families from environmental pollution exposure.

Jiahui Guo, a Ph.D. student at Penn State, and Yongwang Ren, a postdoctoral researcher at Kansas State University, contributed to this article.

This project is funded by Illinois-Indiana Sea Grant, Grant Number: NA22OAR4170654-T1-01.