Starting next year, California water systems must notify residents if their water sources contain potentially toxic levels of cancer-linked chemicals called PFAS under a law Gov. Gavin Newsom signed Wednesday.

The new law, AB 756, will also expand state regulators’ ability to test for per-and polyfluoroalkyl substances, known as PFAS. The compounds can be found in everyday plastics and products like floss and are concentrated in firefighting foam that the military and commercial aviation industry has used for decades.

That foam has seeped into groundwater and wells surrounding military installations and commercial airports, and has been found in drinking water sources at more than 712 locations in 49 states, according to the Environmental Working Group, a nonprofit organization.