EWG's Tap Water Database — 2019 UPDATE

picture of test tube and beaker in laboratory


October 2019


PFAS, also known as per- and polyfluorinated substances, are a family of chemicals used in hundreds of products – from nonstick pans to stain repellent clothing, wire coatings and firefighting foam. The entire group, numbering more than 3,000 synthetic chemicals, is concerning, because even at low levels, exposure to some of these chemicals may result in serious health effects, including cancer, endocrine disruption, accelerated puberty, liver damage, and immune system and thyroid changes. These chemicals are persistent in the environment and they accumulate in people.

Nationwide tests for six PFAS chemicals detected contamination in water served to more than 16 million people. Working in collaboration with researchers at Northeastern University in Massachusetts, EWG scientists identified over 700 PFAS contamination sites in 49 U.S. states, as of July 2019. Based on published PFAS test results, EWG estimated that up to 110 million Americans could have PFAS-contaminated drinking water.

EWG has developed a health guideline of 1 part per trillion, or ppt – equivalent to 0.001 part per billion, or ppb – for each PFAS detected in drinking water. This guideline is based on studies of PFOA and PFOS and the chemical and toxicological similarity of many PFAS chemicals.

Legacy of pollution

The most infamous family member, PFOA, is a carcinogen that severely polluted the drinking water near a DuPont manufacturing plant in Parkersburg, W.Va. A decade of studies documenting the health impacts of PFOA-linked exposure to testicular and kidney cancer, thyroid disease, ulcerative colitis, high cholesterol, and pregnancy-induced hypertension and preeclampsia. Subsequent studies have linked exposure to endocrine disruption and developmental health impacts, as well as reduced effectiveness of vaccines.

In an initial step toward potential regulation, between 2013 and 2015 the EPA required drinking water utilities across the country to test for six different PFAS chemicals. The results greatly underestimate the extent of contamination, because the reporting limits were 10 times higher than could be detected in water, and the EPA only required reporting of six PFAS, even though the test method detected 14 different PFAS.

Is there a safe level of PFOA or other PFAS in water?

The short answer is no – you do not want any PFAS in your water. The EWG’s health guideline for PFAS is based on evidence of reduced effectiveness of vaccines, and the impact of PFOA and PFOS on mammary gland development. This health guideline is below the reporting level that the EPA mandated in its testing, which means for every positive test we indicated, the result was above the health guideline.

There is growing agreement among scientists that the entire class of PFAS chemicals may be harmful to human health. For exposure to PFOA, government scientists in New Jersey and Germany indicate that a safe level in drinking water may be zero, a figure based on the widespread exposure already occurring from other sources, such as food. There is also growing awareness that replacement chemicals for PFOA, PFOS and the other PFAS are harmful to human health and the environment. And a peer-reviewed study released in 2019 refutes claims by the chemical industry that the next generation of PFAS is safer than PFOA and PFOS. The chemical that DuPont is using to replace PFOA, GenX, has also been linked to cancer in lab animals.

How can I protect my family from PFAS?

For home water filtration options, both reverse osmosis and activated carbon filters can reduce or eliminate PFOA and other PFAS contaminants. Active carbon filters are less effective at removing the shorter-chain replacement chemicals, but we don’t know the extent of water contamination by these replacement chemicals.

Exposure to PFAS chemicals is not limited to water and may also occur through food and food packaging. EWG recommends reducing exposure to fast food wrappers, often coated in PFAS, by preparing meals at home and avoiding the use of paper tableware and microwave popcorn.

Read EWG's guide for more tips on avoiding PFAS.


A. Blum et al. The Madrid Statement on Poly- and Perfluoroalkyl Substances (PFASs). Green Science Policy Institute. 2014. Republished in Environmental Health Perspectives, May 2015. Available at

Danish Ministry of the Environment. Perfluoroalkylated Substances: PFOA, PFOS and PFOS A Evaluation of Health Hazards and Proposal of a Health Based Quality Criterion for Drinking Water, Soil and Ground Water. Environmental Project No. 1665, 2015. Available at

Danish Veterinary and Food Administration. Ministry of Environment and Food of Denmark. Fluorinated Substances in Paper and Board Food Contact Materials (FCM). 2015.

DuPont GenX. 8(e) Filings with EPA, 2010–2013. Available at See also: Sharon Lerner, New Teflon Toxin Causes Cancer in Lab Animals. The Intercept, 2016. Available at

Environmental Working Group. Teflon Chemical Harmful at Smallest Doses. 2016. Available at

EWG. Scientist in N.J., Germany Support ‘No Safe Level’ of Teflon Chemical in Drinking Water. 2016. Available at

New Hampshire Department of Environmental Services. In-Home Water Filtration Options for PFCs in Household Drinking Water. 2016. Available at

New Jersey Drinking Water Quality Institute. Health-Based Maximum Contaminant Level Support Document: Perfluorooctanoic Acid (PFOA). 2016. Available at

New Jersey Department of Environmental Protection. Draft Technical Support Document: Interim Specific Ground Water Criterion for Perfluorononanoic Acid (PFNA, C9). 2017. Available at

L. Schaider et al. Fluorinated Compounds in U.S. Fast Food Packaging. Environmental Science & Technology Letters, 2017, 4(3). Available at See also: EWG, Many Fast Food Wrappers Still Coated in PFCs, Kin to Carcinogenic Teflon Chemical. 2017. Available at

X. Hu et al. Detection of Poly- and Perfluoroalkyl Substances (PFASs) in U.S. Drinking Water Linked to Industrial Sites, Military Fire Training Areas, and Wastewater Treatment Plants. Environmental Science & Technology Letters, 2016, 3(10). Available at

Z. Wang et al. A Never-Ending Story of Per- and Polyfluoroalkyl Substances (PFASs)? Environmental Science and Technology, 2017, 51(5). Available at