In 1953, a paper written for cigarette manufacturer RJ Reynolds detailed possible carcinogens in tobacco, but the document would remain largely ignored by the public for decades. During this time, the tobacco industry told the public: "We do not accept the presence of harmful substances in tobacco."

The chemical companies seem to be taking notice. Just a few years later, DuPont scientists discovered that PFAS had enlarged livers in lab rats and could cause birth defects in workers. However, the company told employees that the compounds linked to cancer were "about as toxic as table salt."

Like the tobacco industry before it, chemical companies have concealed the health risks of PFAS from the public for decades. A new peer-reviewed study dissects the public relations strategies of PFAS producers, offering a damning timeline that includes industry research and comments from DuPont and 3M officials showing they were aware of the dangers but publicly insisted the chemicals were safe.

PFAS foam gathers at Van Etten Creek Dam in the town of Oscoda, Michigan. PFAS have been widely used in consumer and industrial applications.

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"The chemical companies have used tobacco industry tactics to delay public awareness of the toxicity of PFAS and, in turn, to delay regulation of PFAS use," the UCSF authors write. "PFAS are now ubiquitous in the population and the environment."

PFAS are a class of about 15,000 chemicals that are commonly used to make thousands of products that are waterproof, stain-resistant, and heat-resistant. These compounds have been linked to low levels of cancer, thyroid disease, renal insufficiency, birth defects, autoimmune diseases, and other serious health problems. They are called "forever chemicals" because of their long life in the environment.

The public was largely unaware of this health threat until records subpoenaed in a lawsuit against DuPont showed the toxicity of the chemicals and an industry cover-up.

The study used a scientific method previously developed by tobacco industry researcher Stan Glantz to analyze similar documents from cigarette manufacturers. The authors found that PFAS producers and their Allies most often employ two tobacco tactics: withholding internal research that reveals health risks and distorting public discourse.

Glantz said: "All these chemical companies are always years ahead of the public and mainstream scientific community in trying to stop the development of public understanding."