New data suggests that the safety threshold for PFOA in drinking water should be as low as .1 parts per trillion, according to the nation’s top toxicologist. Linda Birnbaum, director of the National Institute for Environmental Health Sciences, cited the figure, which is 700 times lower than the safety level set by the Environmental Protection Agency, at a conference on PFAS at Northeastern University last week.

While PFOA has already been tied to kidney and testicular cancer, among other diseases, recent research linking PFOA exposure to pancreatic cancer is the basis for the lower number cited by Birnbaum. The research was done by the National Toxicology Program, which is a division of the NIEHS.

“If you look at the data, pancreatic tumors are present at very, very low concentrations from PFOA,” Birnbaum told the audience at the conference. “If you use the pancreatic tumors in the rats in the NTP study to calculate what would really be a virtually safe dose, you’re getting down at about .1 ppt. Well, that’s really low. And that’s only for one PFAS.” Birnbaum suggested that regulators might ultimately issue one drinking water standard for the entire class, which contains thousands of compounds.

About the EPA’s current water standard, Birnbaum said, “Many of us would think that is not health protective.”

According to a summary of the experiment, male rats exposed to PFOA developed both cancerous and noncancerous tumors of the pancreas. At the lowest of three doses given in the experiment, 20 out of 50 rats developed the tumors. At the higher doses, more than half of the exposed rats developed the tumors.

The summary also shows that PFOA increased the numbers of cancerous and noncancerous liver tumors in the two-year rat study. At the conference, Birnbaum mentioned that the recent experiments also showed that PFAS exposure affected breast development. “There were clearly impacts on the growth of the mammary gland and problems with lactation,” she said.

Both the NIEHS, which conducts scientific research on the effects of the environment on health, and the EPA, which is responsible for environmental regulation, have said they are prioritizing PFAS, industrial compounds used in firefighting foam, nonstick coatings, and other products that persist indefinitely in the environment and accumulate in people. But the new information about their health effects has been emerging very slowly.

The Japan National Institute of Health Sciences first asked the NTP to study the perfluorinated compounds in 1990, noting that in rats the chemicals induced the presence of a biomarker of DNA damage thought to be related to cancer. In 2003, the EPA also nominated the compounds for further study, citing their “presumed widespread human exposure” and the known toxicity of certain compounds in the class.

The rats in this two-year study were given their first dose of PFOA almost 10 years ago, in July 2009. And the NTP released a statistical analysis of the tumor study in June 2018. Yet more than a year later, the NIEHS has not published reports of the studies, which regulators typically need to fully understand the science when setting safety levels.

Asked in March about the delay in releasing the reports, Robin Arnette, of the NIEHS’s office of communications and public liaison, wrote in an email to The Intercept that “NTP routinely releases data tables for completed studies while formal reports are in preparation” and that reports that go along with the toxicology research on PFAS “are currently undergoing external peer review. We anticipate their publication on the NTP website later in 2019.”

A technical report based on the research “is in preparation and external peer review will take place later in 2019; the date is not yet set,” according to Arnette’s email, which also said, “Timelines and prioritization are dynamic. We are actively managing our usual processes to enable efficient delivery of information for those agents of growing public concern.”

Although the reports have yet to be released, some state regulators are already considering the NTP data as they set safety thresholds for PFAS. The Minnesota Department of Health cited the NTP tables in its April health-based guideline for PFHxS. And in March, California regulators set interim safety levels of 14 and 13 ppt for PFOA and PFOS, while citing “new cancer data recently released by the National Toxicology Program” and noting that safety levels “and the health effects on which they are based may change.”

The amount of these chemicals deemed safe to ingest in drinking water has been dropping quickly over the past several years, as is often the case as scientists learn more about how chemicals affect health. Between 2009 and 2016, the EPA’s official safety threshold for PFOA was 400 ppt. In 2016, the agency lowered the number to 70 ppt. Several states have since calculated lower limits. Vermont set drinking water health advisory limits of 20 ppt for PFOA. And, in April, New Jersey proposed drinking water standards of 14 ppt for PFOA and 13 ppt for the closely related chemical PFOS.

Update: June 20, 2019

After publication, the National Institute of Environmental Health Sciences provided the following statement from Linda Birnbaum:

The NIEHS has undertaken an extensive PFAS research program, which involves many studies, hundreds of chemicals, and partnerships across federal government. There are almost 5,000 PFAS chemicals in use today. Right now, we don’t know enough about the uses and potential hazards of exposure to PFAS, but if our research results for PFAS are similar to what we’ve seen with other biologically active chemicals such as lead, arsenic, and asbestos, I would not be surprised if the safe level of PFAS for humans is as low as 1.0-0.1 PPT. That’s why this research is so important, and necessary for protecting public health.