Lawyers for DuPont knew the Food and Drug Administration had a serious concern that the company’s new food packaging product might be toxic.

Beagles and rats that were fed DuPont’s grease-resistant coating for paper wrappers had enlarged livers after three months, a report showed.

The year was 1966.

Inside FDA, toxicologists were irritated. “The petition is not acceptable for filing,” they wrote in an internal memo. The scientists wanted a two-year health study of the nonstick coating and the unfamiliar chemicals it was made of.

A key chemical in that mixture is now infamous: PFOA, a notorious polluter of U.S. water supplies.

The DuPont product, Zonyl RP, entered the picture as the nation was transforming its food system. Americans wanted eating to be fast, easy and cheap. At supermarkets, paper and plastic containers were delivering more food options to millions of people. Fast-food restaurants wrapped burgers and fries for working families.