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.
1965
DuPont rat study shows increased liver and kidney weight and increased spleen size.
1966
The Food and Drug Administration rejects a DuPont petition to use PFAS chemicals as a food additive, citing liver studies.
1970
3M warns Fire Journal, the magazine of the National Fire Protection Association, that PFAS is toxic to fish.
1977
3M finds PFOS, the PFAS chemical in the company’s Scotchgard fabric treatment, “more toxic than anticipated.”
1978
3M concludes that PFOS and PFOA, a PFAS chemical used to make DuPont’s Teflon, “should be regarded as toxic.”
1979
DuPont survey of employees in its Parkersburg, W.Va., Teflon plant finds possible evidence of liver damage.
1981
3M and DuPont reassign female workers after animal studies reveal PFAS damages the eyes of the developing fetus.
1983
3M identifies PFAS’ potential harm to the immune system as a cause for concern.
1984
DuPont detects PFAS in the tap water in Little Hocking, Ohio, but does not alert the local water utility.
1990
3M study finds risk of testicular cancer from exposure to PFOA, also known as C8.
1992
Former 3M scientist finds male PFOA workers more likely to die from prostate cancer.
1997
DuPont study finds heightened cancer rates among workers at the Parkersburg plant.
