For 40 years, Dupont and 3M knew PFAS chemicals posed a danger to human health — but they hid the evidence from regulators, employees and the public so they could continue selling their toxic products.

According to the authors of the new study in the Annals of Global Health, "the chemical industry used the tactics of the tobacco industry to delay public awareness of the toxicity of PFAS and, in turn, delayed regulations governing their use."

During the decades the two companies hid their own scientists' research on the health risks of per- and polyfluoroalkyl substances' (PFAS), the so-called "forever chemicals" — which take hundreds of years to break down in the environment — became ubiquitous in the water, air, soil and human bodies.