Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)

Introduction

What Are PFAS?

Per- and polyfluoroalkyl substances (PFAS) are a large, complex group of synthetic chemicals that have been used in consumer products around the world since about the 1950s. They are ingredients in various everyday products. For example, PFAS are used to keep food from sticking to packaging or cookware, make clothes and carpets resistant to stains, and create firefighting foam that is more effective.

PFAS molecules have a chain of linked carbon and fluorine atoms. Because the carbon-fluorine bond is one of the strongest, these chemicals do not degrade easily in the environment.

PFOA, also known as C8, has 8 carbons.

How Are People Exposed to PFAS?

Human exposure to PFAS is widespread but variable by geography and occupation. PFAS are used in the aerospace, automotive, construction, and electronics industries. Over time, PFAS may leak into the soil, water, and air.

People are most likely exposed to these chemicals by consuming PFAS-contaminated water or food, using products made with PFAS, or breathing air containing PFAS. Because PFAS break down slowly, if at all, people and animals are repeatedly exposed to them, and blood levels of some PFAS can build up over time.

One report by the Centers for Disease Control and Prevention, using data from the National Health and Nutrition Examination Survey (NHANES), found PFAS in the blood of 97% of Americans. ¹ Another NHANES report suggested blood levels of PFOS and PFOA in people have been reduced since those chemicals were removed from consumer products in the early 2000s. However, new PFAS chemicals have been created and exposure to them is difficult to assess.

NIEHS conducts or funds research that aims to understand more about PFAS exposures and any subsequent health effects.

Fact Sheets

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Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS)

Why Be Concerned About PFAS?

Multiple health effects associated with PFAS exposure have been identified and are supported by different scientific studies. Concerns about the public health impact of PFAS have arisen for the following reasons:

• Widespread occurrence. Studies find PFAS in the blood and urine of people, and scientists want to know if they cause health problems.
• Numerous exposures. PFAS are used in hundreds of products globally, with many opportunities for human exposure.
• Growing numbers. More than 9,000 PFAS have been identified.
• Persistent. PFAS remain in the environment for an unknown amount of time.
• Bioaccumulation. People may encounter different PFAS chemicals in various ways. Over time, people may take in more of the chemicals than they excrete, a process that leads to bioaccumulation in bodies.

Because there are many types of PFAS chemicals, which often occur in complex mixtures and in various everyday products, researchers face challenges in studying them. More research is needed to fully understand all sources of exposure, and if and how they may cause health problems.

What Is NIEHS Doing?

What We Have Learned So Far

When looking for possible human-health effects of chemical compounds, it is important to understand that they are hard to study, especially with thousands of variations in PFAS chemicals. Much PFAS research has been supported or led by NIEHS.

The research conducted to date reveals possible links between human exposures to PFAS and adverse health outcomes. These health effects include altered metabolism, ²   fertility, ³  reduced fetal growth and increased risk of being overweight or obese, ⁴ increased risk of some cancers, and reduced ability of the immune system to fight infections. ⁵

While knowledge about the potential health effects of PFAS has grown, many questions remain unanswered. Therefore, NIEHS continues to fund or conduct research to better understand the effects of PFAS exposure.

National Toxicology Program

The National Toxicology Program (NTP) is an interagency testing program headquartered at NIEHS. In 2016, based on evidence from prior studies, NTP concluded that PFOA and PFOS were a hazard to immune system function in humans. ⁶

NTP is leading multi-faceted toxicology studies to evaluate and identify the adverse effects of PFAS chemicals, such as:

• A systematic literature review of six PFAS chemicals—PFNA, PFHxS, PFHxA, PFDA, PFOS, PFBS—to determine whether they weaken the body’s response to vaccinations.
• Animal studies, including a two-year study on PFOA and 28-day studies on these seven PFAS chemicals: PFBS, PFHxS, PFOS, PFHxA, PFOA, PFNA, PFDA.

NIEHS-funded Research

NIEHS also awards many grants to external organizations, particularly research universities, across the U.S. to conduct PFAS studies, including:

• Time-sensitive studies such as PFAS exposures in residents near Colorado Springs whose water was contaminated with the PFAS known as perfluorohexane sulfonate (PFHxS), and contamination of the Cape Fear River in North Carolina by GenX.
• Long-term epidemiological studies of health effects of PFAS exposures, some beginning before birth, including a study on more than 300 children in the Faroe Islands. ⁷
• In children’s environmental health research, a study examined associations between prenatal and childhood PFAS exposure with cognitive test results in children. The findings were inconsistent highlighting need for further research on the ways in which PFAS may act on the developing brain. ⁸
• Another long-term study showed a link between PFAS exposure and increased risk of Type 2 diabetes in women. ⁹
• Researchers are also studying the health effects of PFOA and a PFOA replacement (GenX) on the offspring of exposed mice. ¹⁰

NIEHS Superfund Research Program

The Superfund Research Program (SRP) funds the search for practical applications to protect the public from exposures to hazardous substances. Examples include:

• The Sources, Transport, Exposure, and Effects of PFASs (STEEP) project, at the University of Rhode Island, is identifying sources of PFAS contamination, assessing human health effects, and educating communities on ways to reduce exposure. ¹¹
• The Michigan State Superfund Research Center is developing energy-efficient nanoreactors capable of breaking the carbon-fluorine bond that keeps PFAS from degrading.
• Scientists at the University of California, Berkeley, are working on options to contain aqueous film-forming foams used for firefighting, a major source of PFAS contamination.
• The Brown University Superfund Research Center has developed databases that exploit land use data to identify cities and towns at high risk for PFAS exposure. ¹²
• Small Business Innovation Research (SBIR) grantee CycloPure, Inc., has developed a new way to remove hazardous PFAS from water. The water pitcher-based filters should be an affordable option for people concerned about PFAS exposure where they live or work.
• A team at the North Carolina State University SRP Center is studying alligators living in PFAS-contaminated water to understand possible effects on the immune system. They also developed a new high-throughput tool to quickly characterize how PFAS may be transported within the body and potentially cause harm.
• Another SBIR project by EnChem Engineering, Inc. is developing an innovative technology to speed up removal of PFAS at Superfund sites.
• SRP-funded small business AxNano developed a portable tool that relies on nanoparticles to quickly detect PFAS in samples. Their method is more affordable and efficient than traditional mass spectrometry.

Why Research Collaboration Is Important

PFAS contamination is a complex issue that no organization can address alone. NIEHS and NTP are actively coordinating efforts with other government agencies on understanding the ways in which PFAS may affect human health.

• NTP collaborates with EPA on the Responsive Evaluation and Assessment of Chemical Toxicity (REACT) program, which is developing a new approach to screen more than 100 PFAS to identify common and overlapping patterns of toxicity.
• NIEHS works closely with the U.S. Food and Drug Administration on PFAS-related food safety, and the Centers for Disease Control and Prevention on monitoring PFAS exposure levels.
• Known as the Zurich Statement, NIEHS co-authored a commentary on PFAS ¹⁵ calling for more collaboration among organizations researching, regulating, and using PFAS. It was developed at a November 2017 workshop in Zurich, Switzerland.
• Some state agencies review collective PFAS research findings to assess and evaluate the effects of these chemicals on human health in their communities.

Further Reading

Stories from the Environmental Factor (NIEHS newsletter)

• Alligators Exposed to Elevated Levels of PFAS Show Signs of Immune Disruption (December 2022)
• NIEHS Influences National Efforts to Understand, Solve PFAS Problems (September 2022)
• PFAS Water Filter Developed Through NIEHS Funding (April 2022)
• Air Pollution and Forever Chemicals Continue to Pose Health Risks (March 2022)
• More Monitoring of Breast Milk Needed, New Research Suggests (March 2022)
• Complexities of PFAS Research Focus of Congressional Hearing (February 2022)
• Effort to Remove PFAS From Water Earns Grad Student Wetterhahn Award (January 2022)
• PFAS Exposure May Increase Diabetes Risk in Latina Adolescents (October 2021)
• Focusing on Solutions Makes Research More Relevant to Public, Expert Says (September 2021)
• PFAS Research Shared at Federal Workshop Hosted by NIEHS (October 2020)
• Virtual Workshop Explores Newest PFAS Research (September 2020)
• Mauge-Lewis Researches Replacement PFAS in Firefighting Foams (May 2020)
• GenX Affects Function of Proteins That Protect the Brain (April 2020)
• Replacement Chemicals May Put Pregnancies at Risk (February 2020)
• PFOA Evaluated for Cancer Links by NTP Expert Panel (January 2020)

Additional Resources

• Agency for Toxic Substances and Disease Registry
• Biden-⁠Harris Administration Combatting PFAS Pollution to Safeguard Clean Drinking Water for All Americans (June 2022) - The White House describes plans to deliver clean water across America and mobilize federal, state, and local investments to confront contamination, protect public health, and advance environmental justice.
• Estimating Levels of PFAS in Your Blood - Web-based tool developed by the Centers for Disease Control and Prevention and the Agency for Toxic Substances and Disease Registry.
• National Academies Sciences Engineering Medicine Consensus Study Report Highlights - Guidance on PFAS Exposure,Testing, and Clinical Follow-Up. NIEHS, and the Agency for Toxic Substances, and Disease Registry (ATSDR) supported this study to evaluate the most current evidence on the human health effects associated with PFAS exposure and to provide information for ATSDR to consider in their advice for clinicians about PFAS testing and how test results should inform clinical care.
• PFAS Collection 2022 - Published between 2018 and 2022, these Environmental Health Perspectives papers demonstrate the diverse areas where skillfully designed PFAS-related epidemiological research and modeling is occurring.
• PFAS Contamination Map - A nationwide map of PFAS contamination created by the Environmental Working Group (EWG)
• PFAS Strategic Roadmap: EPA's Commitments to Action 2021-2024 - PFAS contamination poses unique challenges. The problem of “forever chemicals” will not be solved by tackling one route of exposure or one use at a time. Cumulatively, the actions outlined in the roadmap will build upon one another and lead to more enduring and protective solutions.

Related Health Topics

• Endocrine Disruptors
• Safe Water and Your Health
• Toxicology