More than 1,000 studies over the past 40 years – some by the U.S. military – show that PFOA and PFOS endanger the planet and public health. They persist in the environment forever and bioaccumulate in animals. In humans, they’re linked to cancer, thyroid disease, reduced immunity, high cholesterol, birth defects and other threats. And manufacturers, the Environmental Protection Agency and the military have looked the other way.

1947: 3M starts mass-manufacturing PFOA, one of the best-known members in a family of thousands of fluorochemicals called PFAS (per- and polyfluoroalkyl substances).

1951: DuPont starts using PFOA to make Teflon.

1953: A close relative of PFOA – a chemical called PFOS – is accidentally spilled on a 3M chemist’s tennis shoe. It leaves a coating that repels oil and water. Scotchgard is born.

1960s: 3M and the U.S. Navy develop “aqueous film-forming foam” (AFFF), a firefighting foam containing PFOS and PFOA. Animal and human studies link the chemicals to liver damage.

1970s: Military sites, civilian airports and firefighting training centers start using AFFF worldwide. Research by 3M finds that the PFOA and PFOS are toxic.

1980s: A U.S. Navy study finds that AFFF has “adverse effects environmentally” and kills aquatic life. Research at 3M proves that employees have PFOA and PFOS in their blood. DuPont discovers that PFOA passes from a mother to her unborn baby via the umbilical cord.

1999: The EPA and 3M find that PFOS contamination is appearing at blood banks around the country. A farmer sues DuPont after scores of his cattle mysteriously die in Parkersburg, West Virginia. It is revealed at trial that the nearby DuPont plant dumped tons of PFOA into a local landfill, poisoning the cattle’s water supply – and the Ohio River, polluting the drinking water of some 80,000 people.

2000: 3M announces it will voluntarily halt production of PFOA and PFOS – technically known as “long-chain” chemicals – and will stop putting them in products by 2002. It starts creating new “short-chain” PFAS formulations that are similarly hazardous, scientists say.

2005: An EPA advisory panel concludes that PFOA is a “likely” human carcinogen.

2006: An EPA program encourages all major manufacturers to stop making long-chain PFAS, citing potential birth defects and other risks. DuPont and others agree to phase out production by 2015; like 3M, they start making new varieties, none proven safe.

2007: PFOS and PFOA are estimated to be in the blood serum of more than 98 percent of Americans.

2009: The EPA issues a non-enforceable “lifetime drinking water health advisory,” recommending a maximum of 200 parts per trillion for PFOS and 400 ppt for PFOA.

2011: The Department of Defense acknowledges the PFAS crisis in an internal study: 594 military sites are likely to have contaminated groundwater, it says.

2012: The EPA directs large public water systems to test for PFAS. The results suggest that as many as 110 million Americans are exposed to PFAS in their drinking water, the Environmental Working Group finds.

2012: A landmark medical study finds a probable link between PFOA exposure and six diseases: testicular cancer, kidney cancer, high cholesterol, ulcerative colitis, thyroid disease and pregnancy-induced hypertension.

2016: The EPA issues a far stricter lifetime health advisory level for PFOA and PFOS in drinking water: 70 ppt.

March 2018: The Pentagon’s 2011 prediction comes true with a vengeance – PFAS contamination is detected at 121 military sites and suspected at hundreds of others. At least 564 drinking-water supplies in nearby communities have PFAS levels that exceed the EPA’s health advisory.

August 2018: Clovis dairy farmer Art Schaap finds out from the Air Force that PFOA and PFOS pollution from Cannon Air Force Base has contaminated his wells, his land, his cows and their milk. One of Schaap’s wells has a concentration of 12,000 ppt, nearly 171 times higher than the EPA health advisory level.

Amy Linn has written about social issues and child well-being throughout her career, starting at the Miami Herald and including work for the Philadelphia Inquirer, San Francisco Examiner and Bloomberg...