He said the EPA will propose new MCL standards by the end of the year, but he did not say what level the agency would use. It still could take years for those proposed standards to become final.
"We feel right now that 70 parts per trillion is the safe level for drinking water," Wheeler said. "As we go forward with the MCL, we will be looking to see whether or not lower levels are required according to where the science directs us."
But even with the differing state standards, Wheeler said the EPA still is working on cleanups with regulators in states that are setting lower levels.
"Regardless of what the national number is, we can work with the states using their numbers today," Wheeler said.
New York is one of those states. Its Drinking Water Quality Council voted last month to recommend a 10 ppt standard.
The issue came to widespread public attention there in 2016 with contamination around Saint Gobain Performance Plastics Corp. factories in Hoosick Falls.
As well, DuPont Co. and Chemours Co. paid $670 million in 2017 to settle thousands of lawsuits over drinking water contamination from their fluoropolymer manufacturing plant in West Virginia.
Beyond setting an MCL, the EPA plan also includes potentially listing PFOA and PFOS under federal Superfund law, which could open up companies to paying more to fund cleanups.
Additionally, Wheeler said the new action plan would expand research and enforcement actions and possibly add the chemicals to Toxics Release Inventory, which would put them on a list of chemical emissions that factories are required to publicly disclose.
The class of chemicals, known broadly by the acronym PFAS, are used in a wide range of products, including firefighting foams and coatings for paper packaging, because of their strong performance, but they have been increasingly linked to health problems.
Wheeler and other EPA officials described the action plan as unprecedented in scope for the agency, pulling in staff from all of its programs to work on an emerging chemical issue and, for the first time, holding simultaneous news conferences in all 10 EPA regional offices, reflecting widespread national concern.
One local official deeply involved with concerns around the Saint Gobain factories criticized the EPA announcement as repeating what the agency's already said.
"This entire announcement has demonstrated the lack of guidance and leadership at the highest levels of EPA," Hoosick Falls Mayor Rob Allen said on his twitter feed. "When the country needed clear and tangible direction and guidelines on handling PFAS, we got a regurgitation of descriptor words with no clear action."
The Natural Resources Defense Council said it could take five to 10 years under federal law to finalize the standards EPA is proposing.
The American Chemistry Council said it looked forward to reviewing the details of the plan.
"We continue to support strong national leadership in addressing PFAS and firmly believe that EPA is best positioned to provide the public with a comprehensive strategy informed by a full understanding of the safety and benefits of different PFAS chemistries," ACC said.
Wheeler, who still faces a Senate confirmation vote to become the permanent EPA head, said the agency has to move deliberately on its rulemakings "in order to make sure they stand up in court."
He said the EPA has not adopted any new MCLs since key changes were made in the Safe Drinking Water Act in 1996.
"To be honest, the agency has not set a new MCL since the Act was passed in 1996, so we're charting a little new territory," Wheeler said. "I can't give you a definite answer as far as how long it will take. We have to go through the regulatory process as outlined in the Safe Drinking Water Act and we're moving as quickly as we can."