The Environmental Protection Agency warned Wednesday that a group of human-made chemicals found in the drinking water, cosmetics and food packaging used by millions of Americans poses a greater danger to human health than regulators previously thought.

The new health advisories for a ubiquitous class of compounds known as polyfluoroalkyl and perfluoroalkyl substances, or PFAS, underscore the risk facing dozens of communities across the country. Linked to infertility, thyroid problems and several types of cancer, these “forever chemicals” can persist in the environment for years without breaking down.