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After years of reporting on forever chemicals, ProPublica reporter Sharon Lerner had one question that still nagged at her. She knew that a handful of 3M scientists and lawyers had learned in the 1970s that the chemical PFOS had seeped into the blood of people around the country and that company experiments around that time had shown that PFOS was toxic. But the company kept making the compound until 2000. How, she wondered, had 3M kept its dark secret for decades? For years, no one who knew what had happened inside the company had spoken publicly. Then last year, a former 3M chemist reached out to Lerner. Here are nine takeaways from the investigation published by ProPublica and The New Yorker.
In the late 1990s, a 3M scientist found the company’s forever chemicals in almost every human blood sample she analyzed.
In the late 1990s, 3M chemist Kris Hansen tested samples from dozens of blood banks around the country and found PFOS in every sample. For decades, the company had used chemicals that break down into PFOS in its top-selling fabric coating, Scotchgard, and in a grease-proof coating for food packaging. It also sold PFOS and firefighting foam that contained it. The only blood that didn’t contain PFOS, Hansen found, had been collected either before 3M began selling these products or in rural China, where items containing the fluorochemicals weren’t widely used.
When told about Hansen’s findings, 3M supervisors repeatedly questioned her work.
Hansen said her managers tried to convince her there was something wrong with the testing. Some suggested that her equipment was tainted. Rather than accept her results, they purchased more scientific equipment — machines that each cost more than a car — and even had Hansen repeat her tests at the offices of the company that made the machines. Her managers’ skepticism caused Hansen to sometimes doubt her own work.
Hansen discovered that she was not the first 3M scientist to find one of the company’s fluorochemicals in human blood, and that the company had kept this past discovery secret.
In the late 1990s, Hansen learned that two academic researchers had contacted 3M more than two decades earlier; they’d found a fluorochemical in human blood and wondered whether Scotchgard might be the source. A 3M scientist named Richard Newmark confirmed their suspicions, but Newmark told Hansen that 3M lawyers had urged his lab not to admit it, according to notes that Hansen took at a meeting with Newmark.
A chance to present her findings to 3M’s CEO didn’t go as planned.
In 1999, Hansen was invited to present her PFOS research to top 3M executives, including CEO Livio D. DeSimone. She said that she was immediately pelted with skeptical questions from those in attendance: Why did she do this research? Who directed her to do it? Whom did she inform of the results? Meanwhile, she said, DeSimone appeared to have fallen asleep during her presentation.
Soon after, she learned her job would be changing: A different scientist was going to lead 3M’s PFOS research, she recalled her boss telling her, and she was to spend most of her time analyzing samples for other scientists and not ask questions about the results. She felt like she was being punished.
When 3M told the public that it had found its fluorochemicals in blood bank samples, executives downplayed the risks.
The company’s medical director told The New York Times in May 2000 that the presence of the chemical in human blood “isn’t a health issue now, and it won’t be a health issue.” 3M stopped making PFOS by 2002 but replaced it with PFBS, another forever chemical that persists in the environment and accumulates in people.
The company didn’t reveal that experiments it had conducted in the 1970s had shown PFOS to be toxic.
What Hansen’s bosses didn’t tell her or the public was that 3M had conducted animal studies on PFOS in the 1970s and that those tests had shown PFOS was toxic. The results had remained secret, even to many at the company. In one animal study, 3M scientists found that a relatively low daily dose of PFOS (4.5 milligrams for every kilogram of body weight) could kill a monkey within weeks. While that daily dose was orders of magnitude greater than the amount a typical person would ingest, the results show the chemical would currently fall into the highest of five toxicity levels recognized by the United Nations.
Lerner identified another 3M scientist, Hansen’s former boss, who said he had confirmed the presence of PFOS in the blood of the general public in the 1970s.
Jim Johnson, Hansen’s former boss, said in an interview that he knew “within 20 minutes” that PFOS wouldn’t break down in nature and that he had identified the chemical in a sample he obtained from a blood bank in the 1970s. He also determined back then that the chemical binds to proteins in the body, causing it to accumulate, and found it in the livers of animals that were exposed to the company’s products. Yet he didn’t disclose this information to Hansen before he gave her the assignment that led her to find PFOS in the blood of the general public almost 20 years later. Johnson told Lerner that he knew that Hansen would discover — and thoroughly document — the presence of PFOS in the blood of the general public. “It was time,” he said.
The EPA has begun to reckon with the ubiquity of these toxic chemicals.
In April, the Environmental Protection Agency set drinking water limits for six forever chemicals, including PFOS and PFBS. The agency noted that PFOS is “likely to cause cancer” and that no level of the chemical is considered safe.
3M produced tens of millions of pounds of PFOS and compounds that degrade into it after learning that PFOS was toxic and accumulating in people. In 2022, 3M said that it would stop making the broader group of forever chemicals known as PFAS and would “work to discontinue the use of PFAS across its product portfolio” by the end of 2025. (PFOS and PFBS are PFAS compounds.) In a written statement, a 3M spokesperson said that the company “is proactively managing PFAS” and that its approach to the chemicals has evolved along with “the science and technology of PFAS, societal and regulatory expectations, and our expectations of ourselves.”
“We’re reducing public health on an incredibly large scale.”
Recent studies have linked PFAS to an increased risk of some cancers, developmental effects in children, reduced immune function, interference with hormones and other health harms. Virtually everyone now has at least one PFAS compound in their blood, according to the Centers for Disease Control and Prevention. Because of their ubiquity, the chemicals are “reducing public health on an incredibly large scale,” according to an environmental chemist from Harvard University.
