By JENNIFER McDERMOTT, Associated Press

The U.S. Air Force is changing the foam it uses to fight fires because of concerns the substance has contaminated groundwater and spread to drinking water at some military sites.

The Air Force said it awarded a $6.2 million contract on Monday to replace the firefighting foam with an “environmentally responsible foam” to reduce the risk of possible contamination of soil and groundwater.

The current foam is used where potentially catastrophic fuel fires can occur, such as in a plane crash, because it can rapidly extinguish the flames. It contains perfluorooctane sulfonate and perfluorooctanoic acid, or PFOS and PFOA, which are both considered emerging contaminants by the U.S. Environmental Protection Agency and have been linked to cancer and other illnesses.

The EPA issued stricter guidelines for human exposure to these chemicals in May, after years of pressure from public health experts and advocacy groups. The agency said the new limits were prompted by recent scientific studies linking the chemicals to testicular and kidney cancers, as well as birth defects and liver damage.

The chemicals have been detected in water at some current and former bases where the military has conducted fire or crash training. In Colorado, health officials said Wednesday that it’s highly likely that trace amounts of toxic chemicals found in three drinking water systems came from firefighting foam used at nearby Peterson Air Force Base, where firefighters used the foam in training exercises.

The new formulation does not have PFOS and contains little or no PFOA.

Mark Kinkade, spokesman for the Air Force Civil Engineer Center, said the Air Force has completed preliminary assessments at all of its sites and is now sampling groundwater and soil. He said the Air Force still has “a lot of work to do” but at the same time it’s working to protect human health and the environment by changing foams and taking other steps to ensure that foam is used safely.

Air Force fire chief James Podolske Jr. said the service must continue to use foam in its defense operations to protect people, weapon systems and infrastructure, but it will “do so in a more environmentally responsible way that also makes our operations safer for the public.”

The Air Force will no longer use the foam in training exercises, and the service plans to replace all foam in fire vehicles and at fire stations with the new formula by the end of this year. It also is retrofitting its aircraft rescue and firefighting vehicles with equipment that lets firefighters conduct vehicle operational checks and required annual foam tests without discharging the foam into the environment.

The Defense Department said earlier this year it’s examining hundreds of sites nationwide for potential contamination from the foam. It wasn’t immediately clear Thursday whether the Navy and Army are changing foams, too.

A Defense Department spokesman said the department is disposing of older foams, wherever possible, buying new foams that do not contain PFOS and investing in research to develop a foam that doesn’t contain the chemicals and can be certified to meet military standards.

PFOA has also been used in consumer products, such as nonstick pans, stain-resistant carpets and microwave popcorn bags, and has been found in the tap water of dozens of factory towns near industrial sites where it was manufactured.