Science  /  Longread

How 3M Discovered, Then Concealed, the Dangers of Forever Chemicals

The company found its own toxic compounds in human blood—and kept selling them.

Fluorochemicals had their origins in the American effort to build the atomic bomb. During the Second World War, scientists for the Manhattan Project developed one of the first safe processes for bonding carbon to fluorine, a dangerously reactive element that experts had nicknamed “the wildest hellcat” of chemistry. After the war, 3M hired some Manhattan Project chemists and began mass-producing chains of carbon atoms bonded to fluorine atoms. The resulting chemicals proved to be astonishingly versatile, in part because they resist oil, water, and heat. They are also incredibly long-lasting, earning them the moniker “forever chemicals.”

In the early fifties, 3M began selling one of its fluorochemicals, PFOA, to the chemical company DuPont, for use in Teflon. Then, a couple of years later, a dollop of fluorochemical goo landed on a 3M employee’s tennis shoe, where it proved impervious to stains and impossible to wipe off. 3M now had the idea for Scotchgard and Scotchban. By the time Hansen was in elementary school, in the seventies, both products were ubiquitous. Restaurants served French fries in Scotchban-treated packaging. Hansen’s mother sprayed Scotchgard on the living-room couch.

Hansen grew up in Lake Elmo, Minnesota, not far from 3M’s headquarters. Her father was one of the company’s star engineers and was even inducted into its hall of fame, in 1979; he had helped to create Scotch-Brite scouring pads and Coban wrap, a soft alternative to sticky bandages. Once, he molded some fibres into cups, thinking that they might make a good bra. They turned out to be miserably uncomfortable, so he and his colleagues placed them over their mouths, giving the company the inspiration for its signature N95 mask.

Hansen never intended to follow her father to the company. She spent her childhood summers catching turtles and leopard frogs at the lake and hoped to have a career in environmental conservation. Her first job after earning her chemistry Ph.D. was on a boat, which took her to remote parts of the Pacific Ocean. But the voyage left her so seasick that she lost twenty pounds, and she soon retreated to Minnesota. In 1996, at her father’s suggestion, Hansen applied for a position in 3M’s environmental lab.

After Hansen started her PFOS research, her relationships with some colleagues seemed to deteriorate. One afternoon in 1998, a trim 3M epidemiologist named Geary Olsen arrived with several vials of blood and asked her to test them. The next morning, she read the results to him and several colleagues—positive for PFOS. As Hansen remembers it, Olsen looked triumphant. “Those samples came from my horse,” he said—and his horse certainly wasn’t eating at McDonald’s or trotting on Scotchgarded carpets. Hansen felt that he was trying to humiliate her. (Olsen did not respond to requests for comment.) What Hansen wanted to know was how PFOS was making its way into animals.