How 3M Buried the Truth About PFAS in Human Blood for Decades

PFAS — the so-called ‘forever chemicals’ now detectable in the blood of nearly every person and animal on Earth — were pioneered by 3M, which used them in products like Scotchgard and sold them for use in nonstick cookware, food packaging, cosmetics, firefighting foam, and stain-resistant fabrics. These compounds don’t break down in the environment or the body, and they’re linked to cancers, thyroid and liver damage, immune and developmental effects, and hormonal disruption. ProPublica’s Sharon Lerner spent roughly a decade and some 60 stories establishing that 3M knew these chemicals were toxic and had spread into the public’s bloodstream as far back as the 1970s, yet kept manufacturing them.

The one question Lerner could never answer was how a company of thousands of employees kept that knowledge secret for so long. The break came when Kris Hansen, a chemist who spent 27 years at 3M and worked in its environmental lab in the 1990s handling ‘highly sensitive data,’ emailed after leaving the company. Hansen had known about the contamination long before the public did but had never spoken out, and now wanted to talk.

Her account, told across days of phone calls and an in-person interview in Minnesota, is the spine of ProPublica’s audio series ‘Paper Trail.’ It’s also a study in institutional loyalty: 3M enjoyed near-reverential status in Minnesota as a symbol of American ingenuity — the maker of Post-it Notes, Scotch tape, and N95 masks — which helps explain how a planet-scale contamination that could have been stopped instead stayed quiet for decades.