PFOS has been used in firefighting foam, while PFOA is used in consumer products such as nonstick pans and stain-resistant carpets.

The city’s water supply has since been relying on the Kilmer Springs filtration plant, which was found to be free of the chemicals in most recent testing, city officials said.

The U.S. Environmental Protection Agency said last week that long-term exposure to either chemical at concentrations above 70 parts per trillion could have adverse health impacts. That is substantially lower than the agency’s prior advisory level of 400 parts per trillion.

Two of the six test results from water sampled at the Big Springs filtration plant in late March exceeded the new limits, the highest being 124 parts per trillion, city officials said last week.

Prior to the new limits, the city said it had been in full compliance with all EPA standards.

Test results from water sampling that was done on May 2 at the Big Springs plant are anticipated next week, Steve Knipe, director of the Martinsburg Utilities Department, said Friday.

Knipe also said he is awaiting the outcome of an analysis of springs that have been eyed as a possible water source alternative to the Big Springs well.

Meanwhile, a joint team from the state Department of Environmental Protection and the state Bureau for Public Health is due to be in area by the middle of next week to conduct their the water-contamination investigative work, DEP spokesman Jake Glance said Friday.

Air Force probe

The states probe joins an ongoing investigation by the U.S. Air Force, which had used firefighting foam at the 167th Air Lift Wing Air National Guard base at Eastern West Virginia Regional Airport.

The airport is within the Big Springs wellhead-protection area.

In a statement Friday, 167th Airlift Wing officials said that it began working with the Air Force Civil Engineer Center in August 2015 to determine if the PFOS/PFOA compounds found in a foam suppressant used in fire emergencies were still present where the substance was used during training or emergencies.

“At this time, there is no conclusive evidence that these compounds are present as a result of their use by the 167th,” Air Force officials said.

They also noted Friday that the last incident, which required use of the foam, was at the 2011 Thunder Over the Blue Ridge Open House and Air Show, when a civilian aircraft crashed during an aerial performance.

A replacement for aqueous film-forming foam has been identified that doesn’t include the chemicals in question, the Air Force has said.

The airlift wing said it stopped training with the foam in 2008 and reserved it for fire emergency use only at that time.

“We work with local, state and federal environmental agencies to ensure we remain in compliance with all environmental standards,” wing commander Col. Shaun Perkowski said in the statement.

“As members of the community who live and work in Martinsburg, we are committed to protecting our environment as an engaged community partner,” he said.

The Air Force said last week that it expects to award a contract in July to conduct a site investigation at the military base at Eastern West Virginia Regional Airport to determine if the compounds are present in the environment, and if they migrated in groundwater off the installation.

The airlift wing was among the first group of Air National Guard bases in the nation that have been investigated for possible release of the compounds as part of a firefighting effort or training, the Air Force has said.