Federal agencies will have to significantly change the way they regulate a class of potentially toxic nonstick chemicals if a defense bill that just passed the Senate becomes law.

The Senate’s annual defense authorization bill, S. 1790, passed the chamber on a 86-8 vote on June 27. It includes by far the most sweeping language yet considered by either chamber of Congress to address per- and polyfluoroalkyl substances, or PFAS.

These chemicals are used in nonstick coatings, firefighting foams, and some food packaging. They’re especially valuable as a protective coating because of their resistance to breaking down in...