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.

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1950

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

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1956

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

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1962

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

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1963

3M technical manual deems PFAS toxic.

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1965

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

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1966

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

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1966

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

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1973

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

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1975

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

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1975

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

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1977

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

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1977

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

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1978

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

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1978

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

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1979

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

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1981

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

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1981

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

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1984

3M documents rising fluorine levels in workers’ blood.

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1984

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

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1987

3M PFOA animal study finds tumors.

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1989

3M study finds elevated cancer rates among PFAS workers.

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1992

DuPont study finds elevated cancer rates among workers.

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1992

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

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1995

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

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1997

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

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1998

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

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1998

3M provides EPA evidence that PFAS accumulates in blood.

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1998

3M animal study finds liver damage from PFAS exposure.

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1999

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

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2003

Chemical industry consulting firm urges DuPont to prepare defense strategy for the unfolding PFOA scandal in Parkersburg, W. Va., including EWG’s investigations.

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