As negotiations continue in Congress over a defense spending bill that could provide for some federal cleanup and regulation of PFAS, executives from the companies that manufactured and used the chemicals faced tough questions from a congressional committee Tuesday.

At the core of the hearing was the question of how and whether Congress should act to hold polluters accountable and ensure faster cleanup of sites across the country, including in Bucks and Montgomery Counties, where PFAS have seeped into drinking-water supplies from military bases or former manufacturing sites. That question is also part of negotiations over the defense spending bill.

A 3M executive told the committee that there is no evidence the chemicals have an adverse effect on human health; Democratic lawmakers pushed back, citing studies that have linked PFAS to health issues including cancers, thyroid problems, hypertension, high cholesterol, and fertility problems. Meanwhile, a DuPont executive said that his company supports regulating two types of PFAS as hazardous substances, and an executive from Chemours — a DuPont spinoff — said DuPont did not leave it with enough money for the remediation and cleanup it inherited.

Court documents and other records have indicated that 3M and DuPont were aware of the potential health risks of the substances they used for decades. Scientific research has linked PFAS to health problems, though researchers have said they are still studying causation.

“These companies here with us today have screwed up, and we need to hold them accountable for doing so,” Rep. Harley Rouda (D., Calif.) said as the hearing began before the House Committee on Oversight and Reform.

Politicians and activists have demanded that the federal government regulate the substances and that the military and manufacturers clean up contamination.

The companies phased out two types of the chemicals from 2000 to 2010 in a voluntary program with the Environmental Protection Agency, but PFAS are still in use in the United States. The substances remain unregulated by the federal government. Testifying Tuesday, the companies touted actions they’ve taken that they say reduce the impact of the chemicals.

But Denise Rutherford, 3M’s senior vice president of corporate affairs, contended that PFAS do not cause human health problems based on available research. She told lawmakers that the amount of the chemicals in the blood of 3M workers has dropped since 2000, and that the company voluntarily phased out the use of two types of PFAS.

“The data available today show no conclusive evidence of adverse health effects,” Rutherford told the committee.

Between 1989 and 1997, however, 3M and DuPont studies found elevated rates of cancer among people who worked with perfluorinated chemicals. One study, part of a collection made public in Minnesota court proceedings, found that working in production of one PFAS chemical for 10 years was associated with increasing the risk of prostate cancer by three times.

Democratic lawmakers called for broad accountability from the manufacturers.

“You want to get credit for the decision to no longer produce these dangerous chemicals voluntarily, but in the same breath want us to believe that there’s no science that says that these chemicals are dangerous at all,” said Rep. Dan Kildee (D., Mich.), addressing 3M. “There’s plenty of science out there that demonstrates that these are harmful chemicals and dangerous for human consumption. Otherwise, you wouldn’t have taken them off the market in the first place.”

Republican lawmakers questioned the purpose of the hearing and, like 3M, said any federal action should be based on scientific research.

“We need to make sure that we let the science do it and not, as Congress, tell the scientists how to do their job,” said Rep. Fred Keller (R., Pa.), suggesting that Democrats were asking for stricter regulations of the chemicals for political reasons.

The White House threatened in July to veto the House version of the defense spending bill and listed PFAS-related items among dozens of concerns. The House and Senate versions passed during the summer each contained provisions that, among other things, would phase out military use of PFAS in firefighting foam and food packaging; require water quality monitoring for PFAS; designate the chemicals as hazardous substances under federal law; and provide funding for more studies and cleanup.

One provision would require the EPA to set a safe drinking-water standard, which the EPA says is in progress, but will take years longer than activists say is acceptable.

A group of lawmakers, including Pennsylvania representatives, wrote a letter last week urging the committees working on the bills to keep the PFAS provisions, saying the measures can “help chart a new course” in dealing with contamination.

In testimony, DuPont endorsed legislative proposals already in the spending bill or introduced in Congress, including requiring the EPA to set drinking-water regulations within two years and listing PFAS as hazardous substances.

“We’re not here standing in the way of regulation,” said Daryl Roberts, DuPont chief operations and engineering officer.

Chemours and 3M executives testified that the decision to regulate the chemicals should be left to the EPA. Chemours pointed to a commitment to reduce air and wastewater emissions by at least 99% by the end of the year.

3M said Monday it would continue remediating manufacturing sites where it has a cleanup partnership with authorities and would establish a clearinghouse to share best practices and analytical technology for PFAS with other researchers. The company supports federal “science-based regulation” and PFAS research, Rutherford said.