Fluorochemicals have been used by 3M, DuPont and other companies to create innovative products for decades. The chemicals now are known to persist in the environment.

1946: DuPont sells the first Teflon products, which are made with fluorochemicals.

1956: 3M begins selling Scotchgard Protector, which contained a fluorochemical that helped it repel stains.

1970: The U.S. Environmental Protection Agency (EPA) is created.

1976: A scientist publishes first evidence that fluorochemicals, which are synthetic, are present in humans.

1986: DuPont begins selling the Teflon-based Stainmaster to protect carpets.

1998: 3M reports to the EPA that low levels of fluorochemicals are widely present in humans based on tests of blood-bank samples.

2000: 3M stops using fluorochemicals in Scotchgard products, and ends manufacturing another fluorochemical that it sold to DuPont to make Teflon and other coatings. Scotchgard is reformulated with a new stain repellent.

2001: In a series of studies, researchers at Michigan State University report low levels of fluorochemicals in polar bears, bald eagles, albatrosses, seals, dolphins, mink and other animals around the world. A 3M study finds traces of fluorochemicals in milk, bread, apples and other supermarket foods.

2003: The EPA issues a preliminary risk assessment of perfluorooctanoic acid (PFOA), the chemical still used by DuPont to make Teflon and other coatings. The EPA says the chemical isn’t known to be harmful to humans or the environment, but animal tests suggest more study is needed.

2004: The EPA alleges that since 1981 DuPont withheld important health information about PFOA, an allegation the company denies. DuPont sets aside $45 million to cover potential losses over PFOA liability.

Source: 3M, DuPont, EPA.