In an effort to determine how tens of thousands of people nationwide have been affected by tainted water near military bases, residents in some of those areas would receive health screenings under an amendment proposed by Pennsylvania's U.S. senators.

Contamination from military use of firefighting foam, which contains chemicals known as PFOS and PFOA, has sparked fear and frustration among communities near bases from Pennsylvania to Washington state, along with a flurry of attempts from state and federal lawmakers to compel the Pentagon to step up its response.

Residents near the Willow Grove and Warminster bases in Bucks and Montgomery Counties found out in 2014 that their tap or well waters were contaminated. The military is now testing nearly 400 bases for the chemicals, known as PFOA and PFOS, and as of April had confirmed water contamination at or near more than 35 of them. Contamination from industrial sites has also cropped up in sampling.

The amendment, proposed by Sens. Pat Toomey (R, Pa.) and Bob Casey (D., Pa.) would require the Centers for Disease Control and Prevention to choose eight areas affected by the contamination for "biomonitoring," which looks at the chemicals to which people have been exposed and what remains in their bodies. Testing would begin within six months and be done within two years.

Casey said on a conference call Wednesday that he and Toomey would urge the CDC to include the vicinity of Warrington, Warminster, and Horsham, near the suburban Pennsylvania former air bases, in the set of communities to be monitored.

It would provide some more immediate data as the CDC also embarks on a five-year health analysis, for which Congress has already authorized $7 million.

"It is time for the CDC to ensure that appropriate exposure assessments related to any possible contamination in drinking water are completed," Toomey said in a statement Wednesday, noting that federal efforts to tackle the problem have so far fallen short.

A separate measure sponsored by Casey and Sens. Maria Cantwell (D., Wash.) and Shelley Moore Capito (R., W.Va.) would increase Pentagon funding for cleanup of contaminated military sites nationwide. It would provide more than $72 million in new funds for remediation — $30 million for the Air Force and $42 million for the Navy — bolstering a budget that is already more than $575 million.

In July, the House passed amendments separately authorizing $60 million for remediation and $10 million for health screenings. That bill is in a Senate subcommittee, and all the amendments have yet to be passed into law.

"The fact is that this is a bigger problem than the Department of Defense planned for," Casey said. "We'd like to authorize as much funding as possible for the cleanup, but this is what we think we can get done this year. More funding will be needed for future years."