Companies use Per- and polyfluoroalkyl substances, better known as PFAS, in everything from nonstick pans to fast-food wrappers. The man-made chemicals don’t break down in the environment, which is why they’re building up in soils and waterways across the world.

When PFAS-laced items end up in landfills, they can leech into groundwater supplies, including those used for drinking water. The U.S. Geological Survey (USGS) found that up to 95 million people rely on contaminated sources of water in both urban and rural areas.

That includes more than 3.7 million people in the Mountain West. The largest population of people exposed is in New Mexico (1.1 million people), followed by Utah (830,000), and Idaho (800,000). Hundreds of thousands of people are also vulnerable in Nevada (600,000), Colorado (320,000) and Wyoming (120,000).

Andrea Tokranov, USGS research hydrologist and lead author of the study, said many states test their groundwater supplies for PFAS.

“But,” she continued, “it's not necessarily equal across all states. And also domestic well owners or private well owners are oftentimes not having the same access to testing as people who are on public supply.”

Tokranov noted the contamination detected by the USGS is before the groundwater is filtered and treated as a safety measure. But PFAS could remain in drinking water at low levels, posing a health concern.

This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNR in Nevada, KUNC in Colorado and KANW in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.