When actor Mark Ruffalo first became involved in the environmental movement, he said he “didn’t even want people to call me an activist, because activist was a bad word back then”.

“I’ve done a lot to make it sexy since then,” he joked.

Now Ruffalo has come full circle – he will be portraying activist and environmental lawyer Rob Bilott in the upcoming film Dark Waters.

The movie chronicles Bilott’s decision, back in 1998, to take on the case of a West Virginia farmer whose cattle were dying off after drinking water contaminated by a nearby DuPont chemical plant.

Since then he has obtained favorable settlements, thousands of Americans in class-action lawsuits against Dupont, and brought national attention to the prevalence of PFAS, a class of toxic chemicals that have contaminated water supplies around the US.

Speaking alongside Ruffalo at a charity event earlier this week with the non-profit Center for Environmental Health, Bilott said, “It’s just awesome” that the Avengers star will be playing him in the film, out 22 November.

Ruffalo, who first became interested in Bilott’s story after reading a New York Times Magazine profile that chronicles the lawyer’s decades-long battle against DuPont and other chemical companies, is both producing and starring in the movie.

“I had just started to get into thinking about doing more production, getting into that side of the business more and more and so I had reached out to Rob,” Ruffalo said later, in an email to the Guardian.

He wanted to know more about what it was like for Bilott, who was working as a corporate defense attorney at a law firm that primarily defended chemical companies, to take on DuPont.

“Rob said ‘Listen, if you option this story I will tell you everything’.”

Directed by Todd Haynes, Dark Waters also features Anne Hathaway as Bilott’s wife Sarah, and Tim Robbins as Thomas Terp, Bilott’s supervisor when he first took on DuPont. William Jackson Harper plays James, a junior associate at Bilott’s firm.

Dart Waters, official trailer

It took nearly 20 years since he first took on that case in West Virginia, but Bilott’s work eventually began to pay off. In 2005, DuPont reached a $16.5m settlement with the Environmental Protection Agency, which had accused the company of withholding information about the chemical PFOA, a type of PFAS, which was toxic and had been leeching out into the environment.

In 2017, DuPont and its spinoff company Chemours agreed to pay more than $671m to about 3,550 people who had been affected by PFOA leaking from a chemical plant in Parkersburg, West Virginia.

Both firms denied any wrongdoing.

Forever chemicals

The Environmental Protection Agency has yet to ban PFOA, although some companies have phased out its use, they continue to use other types of PFAS chemicals, that “are just as bad” Bilott said. Some of these chemicals are still used in some common products such as non-stick pans, waterproof makeup, plastic food packaging despite scientific evidence linking PFAS exposure with cancer, thyroid problems, and developmental issues in children. Because they don’t break down in the environment, PFAS have been nicknamed “forever chemicals”. Some varieties can persist in the human body for years, if not decades.

By promoting the upcoming movie, and Bilott’s book Exposure – which was released Tuesday – the actor and the lawyer said they hope to increase public awareness of just how ubiquitous the chemicals are, and mobilize people into action.

“PFOA is pervasive. It is everywhere and it is forever,” Ruffalo told the Guardian over email.

“We have been poisoned and the corporation that has been doing it has known for years it has been doing it. And it has been covering it up,” he said, referring to the legal actions. “And I want people to know and to be outraged by that. And to protect themselves and their families.”

One concern, he said, was that some schools serve children their lunches in plates and trays containing PFAS, Ruffalo said at the CEH event. “It would take 10 parents calling to any school to stop that tomorrow,” he said.

Bilott added that he’s heartened to see governments moving toward legislation to phase the chemicals out of everyday products. In the US, Congress is seeking to address PFAS as part of a 2020 defense bill, after reports found high levels of the chemicals in groundwater near military installations and airports that use firefighting foam containing PFAS. Companies like DuPont and 3M have maintained that the chemicals pose no health risk at current levels.

Last year, a United Nations added PFAS chemicals PFOA and PFOS, to a list of toxic substances that should be globally banned.

“We’re talking about something here that’s in water all over the country, all over the world. It’s in everybody’s blood,” Bilott said. “The more attention we can bring to this, the better.”