Tens of thousands of Australians are suing the government over chemical contamination of land, with the support of US advocate Erin Brockovich, lawyers behind the class action said Tuesday.

A chemical substance known as PFAS, found in firefighting foam and with suspected links to some cancers, was used on army bases and at fire stations across the country between the 1970s and 2000s.

Shine Lawyers said it would file a class action on behalf of people living near eight major defense department sites.

National broadcaster ABC said the case represents the largest class-action suit ever filed in Australia.

Lead counsel Joshua Aylward said PFAS had “leached into the environment” in communities across Australia.

“I’ve spent a lot of time with people who are crying because they’ve found out that their water is contaminated, and they’ve been drinking it for years,” he said.

“Residents are learning that their kids have exceptionally high levels in their blood and they are really concerned for their family.”

Up to 40,000 people who live or work on PFAS-contaminated land could be eligible for compensation from the government if the class action succeeds, the law firm said.

Brockovich — famous for her legal fight over a gas pipeline that contaminated drinking water in California — is backing the move and met with affected residents in Western Australia state last week.

“The science is in on these chemicals. It can cause cancer,” she told the ABC.

“It’s fearful and it should be concerning for all of us,” said Brockovich, whose own anti-pollution fight became the subject of a Hollywood film starring Julia Roberts.

PFAS, or perfluoroalkyl and polyfluoroalkyl substances, are a group of chemical substances found in a wide range of products such as fire-retardant.

The health impacts of the substances are debated. The US Environmental Protection Agency has called them “possibly carcinogenic” but Australia’s health department says there is “no conclusive evidence” to support a cancer link.

Shine Lawyers argues that Australian residents have been unable to move away from PFAS-leeching army bases, as their properties are now deeply unattractive to prospective buyers.

Three other class actions against the defense department are already underway in relation to PFAS contamination, officials said.