The EPA is proposing a ‘hazard index’ for GenX, 3 other PFAS. Here’s how it works.

Environmental Protection Agency Administrator Michael Regan visited Wilmington this week to announce the EPA’s first-ever proposed limits on forever chemicals in drinking water, including a so-called hazard limit that would evaluate four chemicals at once.

That measurement is of particular interest to North Carolinians and the utilities that provide them with drinking water because it includes GenX chemicals, the substances linked with Chemours’ plant in Bladen County that contaminated the drinking water of hundreds of thousands in Southeastern North Carolina.

In addition to the GenX chemicals, the hazard index includes PFBS, PFHxS and PFNA.

The EPA’s proposed drinking water limits — technically known as maximum contaminant levels — are four parts per trillion apiece for PFOA and PFOS. All six chemicals included in the new regulation are per- and polyfluoroalkyl substances, also known as PFAS, which are long-lasting chemicals that have been linked with a wide range of human health effects.

What is a hazard index?

Hazard indexes are used to measure risk when people are exposed to multiple chemicals at once, Regan told The News & Observer.

“Because we know that many PFAS are found together and at different levels at times, we are looking at the hazard index’s ability to take varying levels of toxicity for these four PFAS especially,” Regan said.

The hazard index approach is more commonly associated with air emissions or the EPA’s Superfund program than with water.

Checking the risk of four PFAS at once could mark an important shift for federal regulators who have often focused on PFOA and PFOS, said David Andrews, a senior scientist at the Environmental Working Group.

“These other compounds are well-studied, the health harms for exposure to them have been well-established and I think it is a move in that direction of considering exposure to this class of PFAS compounds — or at the simplest level at least a group out of this class of PFAS compounds,” Andrews told The News & Observer.

Filtration technology that keeps PFOA and PFOS out of drinking water, Andrews added, would likely help utilities meet the hazard index while removing additional forever chemicals.

How does it work?

A hazard index would require utilities to measure all four chemicals.

The index would measure what the utilities find against levels the EPA has determined will protect human health from exposure for each of the substances.

If any combination of the chemicals takes the water over the hazard limit, the utility would need to inform its customers.

“To prevent the health risks from mixtures of these PFAS in drinking water, we’re using this hazard index calculation to regulate PFHxS, GenX, PFNA and PFBS in public water systems,” Regan said.

Who opposes the proposal?

The American Chemistry Council, which represents chemical manufacturers, argues that the proposed limits are overly stringent and, in its view, based on flawed science.

“We would note that EPA has not yet evaluated two of the four chemistries included in the proposed ‘hazard index’ MCL. We will be interested to see how EPA explains its rationale for combining substances affecting different health endpoints into a single index, in violation of its own guidance,” the American Chemistry Council said in a statement.

The EPA is working on evaluating PFNA and PFHxS. The agency said its human health assessments will be released for public comment and peer review by the end of September.

“Those who manufacture these chemicals have and will continue to express concern. And we will continue to focus on doing what the science tells us and what the law allows us to do, which is our job: to protect public health,” Regan said.

The American Water Works Association, a lobbying organization that represents water suppliers, estimated that 5,000 water systems will need to find new water sources or install treatment technology to meet the new standards, while another 2,500 will need to update their existing technology.

Treating just PFOA and PFOS at the EPA’s proposed levels will cost $3.8 billion a year, according to a study the association commissioned from engineering company Black & Veatch.

“The 2021 Bipartisan Infrastructure Law provides increased federal water infrastructure investment, but the costs of meeting the proposed standards will far exceed the additional funding,” the association said in a press release.

The EPA’s rules are only a proposal for now. The agency has indicated it hopes the rules will become effective before the end of 2023.

This story was produced with financial support from 1Earth Fund, in partnership with Journalism Funding Partners, as part of an independent journalism fellowship program. The N&O maintains full editorial control of the work.