District Judge Richard Gergel on Friday gave final approval to a US class-action settlement in which 3M agreed to pay as much as $12.5 billion to resolve litigation over polyfluoroalkyl substances (PFAS), which are often called "forever chemicals."

In his order, Gergel cited figures from a court-appointed official who said that just 7.5 percent of the class opted out of the agreement.

3M cited "overwhelming" support for the deal.

"This is yet another important step forward for 3M as we continue to deliver on our priorities," said Chief Executive Mike Roman.

"The final approval of this settlement and continued progress toward exiting all PFAS manufacturing by the end of 2025 will further our efforts to reduce risk and uncertainty as we move forward."

3M said previously it was accounting for $10.3 billion over 13 years.

Funds will go to public water suppliers for PFAS treatment technologies and nationwide testing for PFAS.

Found in everyday products such as non-stick frying pans and waterproof clothing, PFAS can linger in the environment for a long time and have been linked to serious health conditions including cancer and birth defects.

Attorneys had alleged that 3M and other manufacturers sold PFAS-containing products when they knew of potential health and environmental problems.

3M did not admit liability in the case.

Michael London, a lead attorney in the class-action suit from Douglas and London, said the settlement represented the largest ever for clean water.

"It's an enormous step and it comes after years of litigation," London told AFP. "It is a great deal and it helps get money to these water districts who need it."