American anti-pollution campaigner Erin Brockovich has announced that at least two American law firms are prepared to pursue Alcoa in the United States on behalf of residents who live near its alumina refineries south of Perth, at Wagerup, Pinjarra and Kwinana.

The residents say their health has been adversely affected by emissions from the refineries. Simon Morrison from Shine Lawyers says the residents will not have to pay any money initially to join the claim.

"The US law firms involved in this claim do operate claims on what we call a contingent basis, which means no fee is payable to them unless the claim succeeds," he said.

"The next step for them is to obviously conduct some investigations of their own on the core issues surrounding the litigation.

"That would then follow what we call a forum application, in other words, bringing the matter in front of a judge in America, to test that issue of whether this is a case that can actually be brought in the United States."

Alcoa says any legal action will be vigorously defended.