Since 2016, advocates and community activists from Pennsylvania and other states have lobbied Congress and the Environmental Protection Agency to regulate PFAS, the potentially harmful chemicals that have contaminated drinking water for millions nationwide, including homeowners in Bucks and Montgomery Counties.

On Tuesday, they got a boost of star power. The actor and producer Mark Ruffalo appeared in Washington with environmental attorney Rob Bilott to urge lawmakers to take action to protect Americans from the chemicals and to promote a new film, Dark Waters, about a landmark legal and health investigation into contamination from the chemicals.

The movie, out Friday, may bring mainstream attention to a complex issue that has affected tens of thousands of residents in Horsham, Warrington, and Warminster Townships and surrounding areas for more than three years. The issue has spread across the country, and the debate over who is responsible for the contamination and cleanup of PFAS has landed on Capitol Hill.

The movie chronicles Bilott’s fight, beginning in the 1990s, on behalf of a West Virginia cattle farmer who believed contamination linked to the DuPont Co. was killing his cows. That case first revealed how harmful the chemical class may be.

As the issue gets the Hollywood treatment, Ruffalo and Bilott announced the launch of a website, fightforeverchemicals.com, that they said would serve as an information source, advocate, and coalition for people affected by the contamination.

PFAS were used for decades in Teflon, Scotchgard, food wrappers, nonstick products, and firefighting foam. They have been linked to cancer, fertility problems, liver damage, high cholesterol, and other health problems. Recently, dairy farmers in Maine and New Mexico have found PFAS in their cows’ milk, and it has been detected in food.

In February, the EPA unveiled a plan to research the chemicals and eventually propose regulations, but it will take years. States including Pennsylvania have begun the process to regulate PFAS on their own, and federal lawmakers have proposed legislation to force quicker action.

Ruffalo and Bilott appeared Tuesday with Pennsylvania Rep. Brian Fitzpatrick of Bucks County and Michigan Rep. Dan Kildee on Capitol Hill. Ruffalo was set to testify Tuesday afternoon at a House hearing on PFAS.

“We’ve got a chemical that’s been out there all these years … and we still can’t get it regulated at the federal level,” Bilott said at a panel moderated and livestreamed by the Washington Post. “You have communities that are being exposed to it, used as guinea pigs, being dosed over and over with this stuff for years.… Meanwhile, the regulatory process, the scientific process, the political process — all of that drags on.”

Dark Waters is based on a 2016 New York Times Magazine article that told Bilott’s story. After reading the article, Ruffalo said, he wanted to turn it into a movie. The West Virginia contamination was with PFOA, one type of PFAS, also found in Philadelphia-area suburban water systems.

Bilott said he first sent a letter 18 years ago to the EPA asking it to set a federal drinking water standard for PFOA.

“The system is extremely flawed in how we regulate chemicals,” he said. “The communities that are exposed are told it’s their burden, they are the ones who have to prove these chemicals are hurting them. And to do that is just unbelievably difficult.”

Bilott’s investigation raised alarm about the health effects of PFOA and led to more than 3,500 personal injury lawsuits filed against DuPont, most of which are pending. Bilott began lobbying the EPA to regulate PFOA, and the case became a foundation for research into the chemicals and their potential health effects on humans.

DuPont said in a statement for the panel that the movie “appears to grossly misrepresent things that happened years ago” and that the company did not hide scientific findings about the effects of PFOA.

“The formulation of these chemicals is so strong it cannot break down in nature.… We, all of us, 99% of human beings, have this in our blood. I have it, you have it,” Ruffalo said at the panel. “This is with us now forever.”