For Decades, Polluters Knew PFAS Chemicals Were Dangerous But Hid Risks From Public As far back as 1950, studies conducted by 3M showed that the family of toxic fluorinated chemicals now known as PFAS could build up in our blood. By the 1960s, animal studies conducted by 3M and DuPont revealed that PFAS chemicals could pose health risks. But the companies kept the studies secret from their employees and the public for decades. Here is a timeline of internal memos, studies and other company documents detailing the two companies’ history of deception. DOWNLOAD ALL DOCUMENTS

1950 3M mice study reveals that PFAS builds up in blood. DOWNLOAD DOCUMENT

1956 Stanford University study finds that PFAS binds to proteins in human blood. DOWNLOAD DOCUMENT

1961 DuPont toxicologist warns that PFAS chemicals enlarge rat and rabbit livers. DOWNLOAD DOCUMENT

1962 Volunteers who smoke PFAS-laced cigarettes get “polymer fume fever.” DOWNLOAD DOCUMENT

1963 3M technical manual deems PFAS toxic. DOWNLOAD DOCUMENT

1965 DuPont rat study shows increased liver and kidney weight and increased spleen size. DOWNLOAD DOCUMENT

1966 The Food and Drug Administration rejects a DuPont petition to use PFAS chemicals as a food additive, citing liver studies. DOWNLOAD DOCUMENT

1966 3M study finds that PFAS causes “acute oral toxicity” in rats. DOWNLOAD DOCUMENT

1970 3M warns Fire Journal, the magazine of the National Fire Protection Association, that PFAS is toxic to fish. DOWNLOAD DOCUMENT

1970 DuPont scientists say PFAS is “highly toxic when inhaled.” DOWNLOAD DOCUMENT

1973 DuPont study shows liver damage from exposure to PFAS in food packaging. DOWNLOAD DOCUMENT

1975 3M is informed that PFAS builds up in human blood samples. DOWNLOAD DOCUMENT

1975 DuPont warns 3M about “toxic effects” of PFAS in food packaging. DOWNLOAD DOCUMENT

1977 3M tests workers and animals to measure PFAS in blood. DOWNLOAD DOCUMENT

1977 3M finds PFOS, the PFAS chemical in the company’s Scotchgard fabric treatment, “more toxic than anticipated.” DOWNLOAD DOCUMENT

1978 3M animal tests find lesions on spleen, lymph nodes and bone marrow. DOWNLOAD DOCUMENT

1978 3M concludes that PFOS and PFOA, a PFAS chemical used to make DuPont’s Teflon, “should be regarded as toxic.” DOWNLOAD DOCUMENT

1979 DuPont survey of employees in its Parkersburg, W.Va., Teflon plant finds possible evidence of liver damage. DOWNLOAD DOCUMENT

1981 3M and DuPont reassign female workers after animal studies reveal PFAS damages the eyes of the developing fetus. DOWNLOAD DOCUMENT 1

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1983 3M identifies PFAS’ potential harm to the immune system as a cause for concern. DOWNLOAD DOCUMENT

1984 3M documents rising fluorine levels in workers’ blood. DOWNLOAD DOCUMENT

1984 DuPont detects PFAS in the tap water in Little Hocking, Ohio, but does not alert the local water utility. DOWNLOAD DOCUMENT

1987 3M PFOA animal study finds tumors. DOWNLOAD DOCUMENT

1989 3M study finds elevated cancer rates among PFAS workers. DOWNLOAD DOCUMENT

1990 3M study finds risk of testicular cancer from exposure to PFOA, also known as C8. DOWNLOAD DOCUMENT

1992 DuPont study finds elevated cancer rates among workers. DOWNLOAD DOCUMENT

1992 Former 3M scientist finds male PFOA workers more likely to die from prostate cancer. DOWNLOAD DOCUMENT

1995 DuPont scientist expresses concern over long-term PFAS health effects. DOWNLOAD DOCUMENT

1997 DuPont study finds heightened cancer rates among workers at the Parkersburg plant. DOWNLOAD DOCUMENT

1998 3M scientists report that PFAS moves through the food chain. DOWNLOAD DOCUMENT

1998 3M provides EPA evidence that PFAS accumulates in blood. DOWNLOAD DOCUMENT

1998 3M animal study finds liver damage from PFAS exposure. DOWNLOAD DOCUMENT

1999 3M scientist describes PFOS as “the most insidious pollutant since PCB.” DOWNLOAD DOCUMENT

2000 3M animal study finds increased liver size from PFOS exposure. DOWNLOAD DOCUMENT