3M internal study confirms PFOS bioaccumulates in blood and is toxic; executives suppress findings

3M scientists conduct toxicology studies on rats and monkeys, discovering that PFOA and PFOS bioaccumulate in blood and cause liver damage and immune suppression. Minutes from a 1978 internal meeting record that the compounds "should be regarded as toxic," yet eight executives vote not to report the findings to the EPA, concluding the toxicity "does not constitute a substantial risk." The research is withheld from regulators for more than 20 years.