Claire Bugos is a New York City-based health and science reporter and writer.

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Exposure to perfluoroalkyl and polyfluoroalkyl  substances (PFAS) is known to cause an array of health issues. Now, researchers have found that these toxic “forever chemicals” are linked to liver damage, and may be associated with non-alcoholic fatty liver disease.

In an analysis published in Environmental Health Perspectives, researchers reviewed more than 100 studies and found that PFAS exposure is largely correlated with an increase in enzymes that indicate liver disease.

Nonalcoholic fatty liver disease—characterized by a build-up of fat in the liver—affects about a quarter of the world’s population. About a third of all U.S. adults may have the disease by 2030, according to a 2018 study.

Factors like diet and lifestyle cannot fully explain this uptick in incidence of this liver disease, said Sarah Rock, a PhD student in the department of population and public health sciences at the University of Southern California and a lead author on the study. Research so far shows that environmental factors play a key role.

Sometimes called “forever chemicals,” PFAS can persist in the environment and our bodies for thousands of years. Known for their water, grease, and heat-resistant properties, this class of chemicals is used in a wide range of products, including nonstick cookware, rain jackets, cosmetics, and fast-food wrappers.

Most Americans have been exposed to PFAS, as the chemicals may contaminate drinking water, food, indoor and outdoor air, and even breast milk. Scientists have found links between PFAS exposure and health outcomes like thyroid and heart disease, developmental deficiencies, immune suppression, and certain cancers.

“The major takeaway from this review is the comprehensive evidence across animal, population, and occupational studies that exposure PFAS is linked to liver damage,” Rock said in an email to Verywell. “These findings contribute to the growing evidence that PFAS may play a role in development of multiple diseases.”

The researchers analyzed a selection of all the studies published on two databases through November 2021 for people or animals exposed to PFAS between 1951 and 2016. This included 85 rodent studies and 24 epidemiological studies, primarily of people in the U.S.

Animal studies are useful because they allow scientists to control the level of PFAS exposure and see its direct effect by dissecting the animal and studying its tissue. The same experiment is much more difficult to do in humans, said Abby Mutic, PhD, MSN, CNM, director of the Southeast Pediatric Environmental Health Specialty Unit at Emory University, who was not involved with the study.

Finding a correlation between a chemical exposure and a change in certain biomarkers or symptoms indicates that PFAS exposure is, indeed, harmful to human health. But to get a full sense of exactly how much PFAS is necessary to cause liver damage, Mutic said researchers need to document how changes in biomarkers relate to actual tissue damage, in addition to symptoms.

The review focused on liver damage associated with the most studied legacy PFAS, namely PFOA, PFOS, and PFNA. But PFAS is a class that includes more than 4,000 chemicals, all with slightly different properties. Manufacturers may replace legacy PFAS with less understood regrettable substitutes—chemicals that are slightly different from the more common PFAS, but are likely just as harmful to health and the environment.

The available evidence presents inconsistencies in the relationship between various non-legacy PFAS and signs of liver injury, the authors write.

“There is some evidence to suggest that the substitutes have similar effects, but not enough to say definitively,” Rock said. “We need more research on the effects of these newer chemicals, and a better understanding of how exposure to multiple PFAS might affect health.”

PFAS act as endocrine disruptors, meaning they interfere with hormone systems. Due to their chemical structure, they can also harm the body by mimicking fatty acids.

“It’s possible that PFAS activate some of the same receptors that fatty acids do, which could lead to fat accumulation or inflammation in the liver in a similar way that an unhealthy diet would,” Liz Costello, MPH, a PhD student in epidemiology at the University of Southern California and co-author of the paper, told Verywell in an email.

Scientists usually test for nonalcoholic fatty liver disease by measuring alanine aminotransferase (ALT) in the blood. Epidemiological studies showed that in addition to ATL, exposure to PFAS is linked to other biomarkers of fatty liver disease, like cholesterol, triglycerides, and uric acid.

Costello said that while this study importantly analyzes the data that is currently available, there’s still a lot that scientists don’t yet know about how, exactly, PFAS and the liver interact.

A 2019 study indicates that while PFAS played a role in increasing lipid levels in pre-diabetic adults, these changes could be mitigated with lifestyle changes, such as eating a healthier diet and exercising.  

Over a lifetime of using products that contain PFAS, the toxins may build up and cause long-term damage. But because it’s so difficult to know when and where one might be exposed to PFAS, Mutic said it’s important to make lifestyle choices that are within one’s control.

“We think our homes, our workplaces, our environments are safe. We don’t think about all these unseen chemicals that we’re breathing in or drinking every day,” Mutic said.

The responsibility should be on producers and regulators to only sell clean products, rather than on the consumer to minimize their toxin exposure through everyday items, she added.

“I get frustrated with constantly feeling like you’re having to convince consumers that it matters what they choose to buy,” Mutic said.

Costello said researchers are working to learn more about the relationships between PFAS and the liver through longer studies and those that use imaging and biopsies to see the toxins’ effects.

In the meantime, environmental advocacy organizations are pointing to existing research to encourage legislators to regulate the class of chemicals and companies to stop manufacturing them.

“PFAS exposure is ubiquitous and almost everyone is exposed. It’s difficult for people to avoid PFAS on their own, so the focus is really on regulation and remediation in our environment: removing existing PFAS and limiting exposure to new ones,” Costello said.

PFAS are pervasive in our environment and can be difficult to avoid. To minimize your exposure, you can opt for products that are labelled “PFAS-free” or are not marketed as water- or stain-resistant. If you are at risk for developing liver disease, certain lifestyle changes may minimize the liver damage associated with PFAS exposure.

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Costello E, Rock S, Stratakis N, et al. Exposure to per- and polyfluoroalkyl substances and markers of liver injury: a systematic review and meta-analysis. Environ Health Perspect. 2022;130(4):46001. doi:10.1289/EHP10092

Estes C, Razavi H, Loomba R, Younossi Z, Sanyal AJ. Modeling the epidemic of nonalcoholic fatty liver disease demonstrates an exponential increase in burden of disease. Hepatology. 2018;67(1):123-133. doi:10.1002/hep.29466

Centers for Disease Control and Prevention: Agency for Toxic Substances and Disease Registry. PFAS in the U.S. population.

Lin PD, Cardenas A, Hauser R, et al. Per- and polyfluoroalkyl substances and blood lipid levels in pre-diabetic adults—longitudinal analysis of the diabetes prevention program outcomes study. Environ Int. 2019;129:343-353. doi:10.1016/j.envint.2019.05.027

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