Hundreds of people in the tri-state region have been given the same warning: Don’t drink the water.

The discovery of a chemical that studies linked with cancer and other diseases led to households being given bottled water for drinking and cooking.

The water isn’t contaminated by something you can see, taste or smell. Small water filters may not be effective at removing it. Boiling the water isn’t effective at removing it.

The culprit: A man-made chemical called PFOA.

Its presence in private wells and municipal water systems in southwestern Vermont and Rensselaer County, N.Y., has left residents and public officials at the local and state level scrambling to find answers.

How long has it been there? What are the long-term health affects? And who is responsible?

PFOA, or perfluorooctanoic acid, was a key part of the process to make Teflon — the non-stick, water-repellent coating many people know to be used on cookware. Teflon was used to insulate wires, to coat specialty tapes and foams that would be used.

Most manufacturers have stopped using PFOA — the largest users of PFOA entered an agreement with the federal EPA in 2006 to phase-out its use by 2015 — but scientists say it takes years to degrade in soil and water.

In Hoosick Falls, N.Y., PFOA was first found in fall 2014 after a concerned resident pushed village officials to test for it. Though state and county health officials said consuming the water was fine, it wasn’t until late November that the EPA issued a no-drink order. It also turned up in wells outside the village in the town of Hoosick and in nearby Petersburgh, N.Y.

Across the border in Vermont, officials received a tip from another concerned citizen about a former North Bennington factory, known for years as ChemFab. Tests on water samples ultimately found PFOA in many private wells.

Also affected was a municipal system in Pownal, Vt., although officials don’t believe the levels pose a threat.

In Hoosick Falls and North Bennington, the Saint-Gobain Corporation is being called the “potentially responsible” party. The Hoosick Falls water system has been declared safe to drink — Saint-Gobain paid to install a carbon filtration system on the village water treatment plant and has said it will pay to install and maintain a larger system by the fall.

The feds call PFOA an “emerging contaminant.” Municipalities don’t have to test for it. States have no records of whether it was used at certain facilities.

Alyssa Schuren, commissioner for Vermont’s Department of Environmental Conservation, and Gov. Peter Shumlin have publicly called for changes at the federal level. They both called the Federal Hazardous Substances Act “broken.”

“We should be testing chemicals before they get onto the market,” Schuren said at a meeting at Bennington College on March 9. “The federal law has fallen very short on this point. The states are just left to look around and ask themselves what different industries they had and whether it was used there.”

Vermont, New York and federal environmental agencies are investigating the contamination to determine how far it has spread in the groundwater and what remediation would be required.

PFOA, also called C8, is the subject of more than 3,000 lawsuits against the DuPont Corporation. Residents in the Ohio Valley allege the dumping of PFOA led to them becoming sick.

A panel of scientists spent seven years researching PFOA. Their research published in peer-reviewed journals linked C8 exposure to six diseases: ulcerative colitis, pregnancy-induced hypertension, high cholesterol, thyroid disease, testicular cancer and kidney cancer.

Bennington College recently received a grant from the National Science Foundation that will allow students and faculty to conduct cutting-edge research on the chemical.

“This is a relatively new pollutant and there is a lot of confusing information out there,” Janet Foley, of the college’s chemistry department, said when the grant was awarded. “This project enables us not only to teach at the frontier of what is known about PFOA, but also to conduct original research with students that will produce better information for our community.”

The college aims to involve students in research questions that have community-wide implications. Does PFOA end up in produce from working farms or home gardens? How much, if any, is absorbed by maple trees and ends up in sap and then maple syrup?

Among other unknowns include how much is a safe amount.

The EPA’s “advisory level” is 400 parts per trillion (ppt). But scientists argue that’s too high. For Hoosick Falls, the level was reduced to 100 ppt out of an abundance of caution. But Vermont has one of the lowest in the country at 20 ppt.

The crisis in Hoosick Falls prompted other municipalities to test for it, as well. Among them was Williamstown — officials announced last week that lab test results show a presence of less than 2 parts per trillion.