A former DuPont facility, the Washington Works plant in Parkersburg, West Virginia produces PFAS.

Opinion: What Industry Knew About the Perils of PFAS

A document analysis shows that manufacturers knew for decades about the chemicals’ toxicity but kept promoting them.

For decades, the chemical industry has shown a pattern of promoting its products to the public without disclosing their harms. We have now found that for chemicals known as PFAS, this industry practice has been harming our health once again.

Per- and polyfluoroalkyl substances, known as PFAS, have been produced since the 1940s and are used in consumer products such as nonstick cookware, stain-resistant carpets, and waterproof clothing. Many studies have shown that PFAS persist in the environment and have contaminated drinking water, soil, and peoples’ bodies. The early producers of PFAS — 3M and DuPont — promoted them as a miracle of modern science. They have made billions of dollars producing millions of pounds of these chemicals. But these companies knew something long before the public did: PFAS are highly toxic.

Thanks to a groundbreaking lawsuit filed in 1999, scientists and regulators learned about the harms these chemicals cause, which we now know can include increasing the risks of kidney and testicular cancers, autoimmune disease, adverse impacts on pregnancy, and birth defects. The lawsuit (Tennant v. E.I. du Pont de Nemours & Company) was brought by attorney Robert Bilott and eventually settled in 2001. The settlement established that DuPont dumped more than 7,100 tons of sludge laced with perfluorooctanoic acid, or PFOA, adjacent to the plaintiff’s property, where the chemical seeped into the ground and entered local water sources, including the Ohio River.

As environmental health scientists working with government and communities to prevent harmful chemical exposures, we have been studying what the industry knew about these harmful chemicals and when it knew about them.

We can determine the timeline from internal industry documents donated to the Industry Documents Library hosted at the University of California, San Francisco, a publicly available and searchable archive of material collected through Freedom of Information Act requests, subpoenas, and litigation. The most recent set we analyzed were uncovered in Bilott’s litigation against PFAS manufacturers, which showed industry knew about the adverse health effects of these chemicals decades before they were made public. Many of the documents were marked “confidential,” and in some cases, were explicit that the document should be returned “for destruction.” (Bilott’s story was featured in the 2019 film “Dark Waters” and in his book, “Exposure: Poisoned Water, Corporate Greed, and One Lawyer’s Twenty-Year Battle against DuPont.”)

We believe our study, published in Annals of Global Health, represents the first time that scientists have analyzed PFAS industry documents based on methods developed to expose tactics the tobacco industry used to cover up the dangers of their products.

In 1961, DuPont’s own testing showed that some components of Teflon had “the ability to increase the size of the liver of rats at low doses,” and advised that “contact with the skin should be strictly avoided.”

We were able to compare internal memos and industry scientists’ reports to public archives of the scientific literature. By doing so, we showed that many significant health hazards, including concern for reproductive toxicity and liver damage, were kept out of the public domain for decades. Research into these hazards is now growing rapidly, as the environmental damage of these chemicals has become more apparent.

In this set of documents, we found that, in 1961, DuPont’s own testing showed that some components of Teflon had “the ability to increase the size of the liver of rats at low doses,” and advised that “contact with the skin should be strictly avoided.” According to a 1970 internal memo, the DuPont-funded Haskell Laboratory for Toxicology and Industrial Medicine found C8, a form of PFOA and one of thousands of PFAS, to be “highly toxic when inhaled and moderately toxic when injected.” And in a 1979 private report for DuPont, the Haskell Lab found that two dogs who were exposed to a single dose of PFOA “expired within 48 hours.” Despite these examples, DuPont’s confidential internal memos downplay their harms, with one employee stating that C8 “has a lower toxicity like table salt.”

In 1981, DuPont learned from 3M that C8 caused birth defects in the offspring of pregnant rats exposed to it. The company produced an internal memo notifying workers of the study and its plans to move female employees away from PFAS manufacturing areas, stating, “We know of no evidence of birth defects caused by C-8 at Du Pont.” However, an internal document dated the same month, April 1981, shows that the company learned that two of eight pregnant employees who had worked in C8 manufacturing gave birth to children with birth defects. No case reports were published in the medical literature describing the findings. We also found no public notification or further employee notifications of these findings.

The PFAS story is one that has played out over and over again, with similarities to industry hiding health harms from tobacco, lead, PCBs, and DDT. In each case, companies knew about the harms of their products long before scientists and the public, suppressed the truth, and delayed much-needed regulations to protect people and communities.

So why does this keep happening?

One reason is industry influence on the development and use of science in decision-making. At a 2022 workshop hosted by the National Academies of Sciences, Engineering, and Medicine, or NASEM, scientists presented empirical evidence showing that industry-sponsored research and conflicts of interest among authors are associated with more favorable results and conclusions that for the sponsor, called “funding bias.” Further, studies funded by industry were found to have results that skewed toward industry compared with non-industry-sponsored research. The tobacco and chemical industries not only use similar strategies to influence science, they often use the same consulting and communications firms, resulting in shared marketing tactics.

Researchers at the NASEM meeting recommended that investigators should be independent of the sponsor throughout the research process. Disclosing COIs is not enough; clear policies and procedures are needed to eliminate or mitigate them. Money that comes from vested interests has strings attached. Thus it is critical to prioritize public funding of research, to recognize industry funding as a source of bias, and to accounting for it in government guidelines and risk assessment.

Financial conflicts of interest must also be removed from the regulatory process, and changes are needed at the U.S. Environmental Protection Agency to strengthen chemical regulatory oversight. We convened a group of scientists in 2020 to develop recommendations on how to reduce harmful chemical exposures. In a series of papers, we recommended that EPA change how it measures chemical risks including evaluating chemicals by class rather than one at a time and changing methods to better reflect real-world exposures, such as being exposed to multiple chemicals at a time. PFAS are a great example of the need for this approach, as they represent a class of thousands of molecules with similar properties, but regulations have been limited to just a handful that have been named and studied.

For too long, the EPA has underestimated the risk of health harms. Adopting up-to-date scientific methods that are more inclusive can protect people better, especially those who live in highly impacted communities.

If we want to stop polluting industries from repeatedly lying to regulators and the public about their products, we need a major shift in how we approach chemical regulation and hold industry accountable for their products. Disclosure of internal documents is one way to hold industry accountable and ensure that public health, not polluter profits, drives our regulatory system.

Tracey J. Woodruff is director of the UCSF Program on Reproductive Health and the Environment and the UCSF Environmental Research and Translation for Health (EaRTH) Center. She is a former senior scientist and policy analyst at the U.S. Environmental Protection Agency.

Nadia Gaber is affiliated faculty in the Department of Humanities and Social Sciences at UCSF and a former postdoctoral fellow at the UCSF Program on Reproductive Health and the Environment. She also conducts water safety and affordability research with the community-led nonprofit We the People of Detroit.