Johnson explained to Hansen that one of the company’s fluorochemicals, PFOS — short for perfluorooctanesulfonic acid — often found its way into the bodies of 3M factory workers. Although he said that they were unharmed, he had recently hired an outside lab to measure the levels in their blood. The lab had just reported something odd, however. For the sake of comparison, it had tested blood samples from the American Red Cross, which came from the general population and should have been free of fluorochemicals. Instead, it kept finding a contaminant in the blood.
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In subsequent weeks, Hansen and her team ordered fresh blood samples from every supplier that 3M worked with. Each of the samples tested positive for PFOS.
In the middle of this testing, Johnson suddenly announced that he would be taking early retirement.
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What Hansen didn’t know was that 3M had already conducted animal studies — two decades earlier. They had shown PFOS to be toxic, yet the results remained secret, even to many at the company. In one early experiment, conducted in the late ’70s, a group of 3M scientists fed PFOS to rats on a daily basis. Starting at the second-lowest dose that the scientists tested, about 10 milligrams for every kilogram of body weight, the rats showed signs of possible harm to their livers, and half of them died. At higher doses, every rat died. Soon afterward, 3M scientists found that a relatively low daily dose, 4.5 milligrams for every kilogram of body weight, could kill a monkey within weeks. (Based on this result, the chemical would currently fall into the highest of five toxicity levels recognized by the United Nations.) This daily dose of PFOS was orders of magnitude greater than the amount that the average person would ingest, but it was still relatively low — roughly comparable to the dose of aspirin in a standard tablet.
In 1979, an internal company report deemed PFOS “certainly more toxic than anticipated” and recommended longer-term studies. That year, 3M executives flew to San Francisco to consult Harold Hodge, a respected toxicologist. They told Hodge only part of what they knew: that PFOS had sickened and even killed laboratory animals and had caused liver abnormalities in factory workers. According to a 3M document that was marked “CONFIDENTIAL,” Hodge urged the executives to study whether the company’s fluorochemicals caused reproductive issues or cancer. After reviewing more data, he told one of them to find out whether the chemicals were present “in man,” and he added, “If the levels are high and widespread and the half-life is long, we could have a serious problem.” Yet Hodge’s warning was omitted from official meeting notes, and the company’s fluorochemical production increased over time.
Hansen’s bosses never told her that PFOS was toxic. In the weeks after Johnson left 3M, however, she felt that she was under a new level of scrutiny. One of her superiors suggested that her equipment might be contaminated, so she cleaned the mass spectrometer and then the entire lab. Her results didn’t change. Another encouraged her to repeatedly analyze her syringes, bags and test tubes, in case they had tainted the blood. (They had not.) Her managers were less concerned about PFOS, it seemed to Hansen, than about the chance that she was wrong.
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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 ’50s, 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 ’70s, both products were ubiquitous. Restaurants served French fries in Scotchban-treated packaging. Hansen’s mother sprayed Scotchgard on the living-room couch.
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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.
She found an answer in data from lab rats, which also appeared to have fluorochemicals in their blood. Rats that had more fish meal in their diets, she discovered, tended to have higher levels of PFOS, suggesting that the chemical had spread through the food chain and perhaps through water. In male lab rats, PFOS levels rose with age, indicating that the chemical accumulated in the body. But, curiously, in female rats the levels sometimes fell. Hansen was unsettled when toxicology reports indicated why: Mother rats seemed to be offloading the chemical to their pups. Exposure to PFOS could begin before birth.
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There was nothing wrong with her equipment or methodology; PFOS, a man-made chemical produced by her employer, really was in human blood, practically everywhere. Hansen’s team found it in Swedish blood samples from 1957 and 1971. After that, her lab analyzed blood that had been collected before 3M created PFOS. It tested negative. Apparently, fluorochemicals had entered human blood after the company started selling products that contained them. They had leached out of 3M’s sprays, coatings and factories — and into all of us.
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Newmark, a collegial man with a compact build, told Hansen that, more than 20 years before, two academic scientists, Donald Taves and Warren Guy, had discovered a fluorochemical in human blood. They had wondered whether Scotchgard might be its source, so they approached 3M. Newmark told her that his subsequent experiments had confirmed their suspicions — the chemical was PFOS — but 3M lawyers had urged his lab not to admit it.
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The executives seemed to view her diligence as a betrayal: Her data could be damaging to the company. She remembers defending herself, mentioning Newmark’s similar work in the ’70s and trying, unsuccessfully, to direct the conversation back to her research.
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After that meeting, Hansen remembers learning from Bacon that her job would be changing. She would only be allowed to do experiments that a supervisor had specifically requested, and she was to share her data with only that person. She would spend most of her time analyzing samples for studies that other employees were conducting, and she should not ask questions about what the results meant. Several members of her team were also being reassigned. Bacon explained that a different scientist at 3M would lead research into PFOS going forward.
