Per- and polyfluoroalkyl substances (PFAS) are the subject of significant regulatory action in the U.S. and around the world. While new rules surrounding PFAS seem to be popping up everywhere, there is a great deal of silence when it comes to new scientific research surrounding its health hazards and safety.
What is PFAS?
PFAS are a group of man-made chemicals that includes PFOA, PFOS, GenX, and many others. These compounds have been made and used in a variety of industries around the globe since the 1940s.
There are estimated to be 9,000-12,000 types of these chemicals, which can be found in more than 4,700 products, including lifesaving tools for first responders, medical instruments, and a variety of household and consumer goods. For a summary of PFAS developments to date, you can access our PFAS Issue Primer here.
New PFAS Rules Coming from all Directions
The U.S. Environmental Protection Agency (EPA)
The EPA created a PFAS Strategic Roadmap in October 2021, in which the agency pledged to:
… invest in scientific research to fill gaps in understanding of PFAS, to identify which additional PFAS may pose human health and ecological risks at which exposure levels, and to develop methods to test, measure, remove, and destroy them.
According to the Roadmap, March of 2023 is the deadline for EPA to set the Maximum Contaminant Levels for certain PFAS chemicals. In June of 2022, the lifetime health advisory levels for two types of PFAS in water (PFOA and PFOS) were lowered by several thousand times below what they were in 2016. They are now set at 0.004 parts per trillion (ppt) for PFOA and 0.02 ppt for PFOS—levels so low that they cannot be detected with currently available laboratory techniques.
While these lifetime health advisory levels are not legally binding, they are used to require reporting by industry and will likely be used by states as they develop binding regulations for clean water, and will also affect the forthcoming Maximum Contaminant Levels.
As to be expected, there is controversy surrounding these unmeasurably low limits, with questions from industry and researchers about what science was used to warrant the reductions and whether it was reviewed by the EPA’s Science Advisory Board. This has led to two lawsuits against EPA, one filed by Chemours Company and one by Public Employees for Environmental Responsibility.
In August of 2022, the EPA Science Advisory Board released a report describing the results from its review of the materials used to inform the proposed changes that lower the levels. These are the foundation for the new Maximum Contaminant Level Goals. The following was posted on EPA’s website:
EPA has transmitted to the Science Advisory Board four draft documents with recent scientific data and new analyses that indicate that negative health effects may occur at much lower levels of exposure to PFOA and PFOS than previously understood and that PFOA is a likely carcinogen. The draft documents present EPA’s initial analysis and findings with respect to this new information.
EPA has made these draft documents available to the public to ensure a transparent and robust evaluation of the available information. This information will be used to inform health advisories and the development of Maximum Contaminant Level Goals and a National Primary Drinking Water Regulation for PFOA and PFOS.
However, the Science Advisory Board (SAB) made important comments about limitations of the EPA analyses that need to be taken into consideration before the March 2023 deadline to finalize the Maximum Contaminant Levels (MCLs):
… the SAB considers the supporting documents related to approaches for deriving the PFOA and PFOS MCLGs to have a number of methodological flaws. For instance, it is unclear whether the EPA used the processes from the 2020 Office of Research and Development (ORD) draft handbook for developing IRIS assessments for their evaluation steps, used a modified version of these processes, or used a completely different process. The SAB also found that the inclusion and exclusion of epidemiologic and animal studies was inconsistent across endpoints, leading to confusion about the criteria being used. In addition, several concerns about the study evaluation and evidence synthesis process used by the EPA and the lack of availability of mechanistic data in the draft MCLG documents were identified. The SAB urges that these problems be addressed with revisions that represent the state-of-practice for gathering, evaluating, synthesizing, and using evidence for decision-making.
Changes Under the Superfund Law
PFOA and PFOS are both set to be designated as a hazardous substances under the Superfund Law. This will allow EPA to force those it deems responsible for the PFAS contamination to clean it up or pay remediation costs. There does not seem to be any new research behind this decision.
In fact, in summer 2022, the Science Advisory Board Work Group for Review of Science Supporting EPA Decisions reviewed the issue of designating PFOA and PFOS hazardous substances and sent the following recommendation to EPA administrator Michael Regan:
This planned action does not merit further review by the chartered SAB because no new scientific work was initiated as part of the regulatory action development.
Several states are in the process of establishing or updating their own PFAS regulations, including California, Maine, Vermont, Washington, Connecticut, New York, Colorado, and Maryland. Many look to EPA research for guidance when making decisions, but they are not waiting on the feds.
According to PEW Trusts, state activities range from cleanup and remediation efforts to banning some types of PFAS and suing polluters—and these efforts are increasing.
Efforts to Bring Clarity to the PFAS Debate
When EPA published its Roadmap, research was purported to be at the forefront of the plan. It was thought by many this would include filling in considerable knowledge gaps within the area of study, in particular the number and severity of human health effects of PFAS exposure and at what levels, in which population subgroups, and more usable information on any harms that might result from varying combinations of PFAS existing in the environment. This research is slow in coming.
To help researchers clearly identify the gaps in knowledge surrounding PFAS, the Center for Truth in Science supported an independent critical review of the most often cited studies on PFOS and PFOA exposure and health that were used in the development of PFAS policies up to 2021. The findings of the review were published in Environmental Research.
It concluded that most PFAS studies to-date include insufficient data to draw accurate conclusions about the association of PFAS with any specific disease.
The researchers observed several limitations in the studies they reviewed, including co-exposure to multiple chemicals and limited measurement of primary and secondary outcomes related to specific toxicity. More longitudinal epidemiology studies will be needed using additional susceptible human endpoints.
The independent critical review concluded there is enough moderate evidence to call for additional study, while making sure the most rigorous methods are used. A central recommendation from the authors was the need for additional specific research to properly calculate human-relevant doses to further link associations with human risk assessment and help set tolerable daily intake.
An estimated 97% of Americans have PFAS in their bodies. It will be important to know what, if any, individual testing and preventive measures need to be taken, or if we can all relax knowing the PFAS we may have ingested to date is not likely to cause harm.
There is Not Enough New Research on PFAS
The National Academies of Science (NAS) issued a consensus study report at the end of 2022 after a review of the literature surrounding PFAS in order to come up with a set of PFAS health risks and to support preventive medicine recommendations.
The review reached strength of evidence conclusions of the health effects linked with PFAS that had been identified by the Agency for Toxic Substance Disease Registry (ATSDR). The NAS review found that:
- There is sufficient evidence of association between PFAS exposure and increased risk of decreased antibody response in adults and children, dyslipidemia in adults and children, decreased infant and fetal growth, and kidney cancer in adults.
- There is limited or suggestive evidence of increased risk of breast cancer in adults, liver enzyme alterations in adults and children, pregnancy-induced hypertension, increased risk of testicular cancer in adults, thyroid disease and dysfunction in adults, and increased risk of ulcerative colitis in adults.
- There is inadequate or insufficient evidence of several other health impacts.
Notably, the NAS review concluded there is sufficient evidence of an association between exposure to PFAS and a small number of health issues. This does not mean PFAS is a cause of these issues.
While strength of evidence is an important piece of causal analysis, there remain too many uncertainties to determine cause. Additionally, the NAS study had some limitations of its own. It only reviewed the literature published up until 2018. One comment in the report gave us cause for concern:
The committee did not formally critique the quality of any authoritative reviews, as each authoritative body has its own procedures for public comment and peer review to ensure that biases are limited in its reviews. Nonetheless, the committee noted several areas in which ATSDR’s Toxicological Profile for Perfluoro alkyls could be strengthened.
First, the toxicological profile does not provide a detailed description of the evidence identification methods or document its reasons for excluding specific studies. Second, the study quality assessment does not appear to follow a standard approach, and in some cases, it is difficult to identify the study designs that were included in the review. Third, the process for assessing the strength of the evidence is not well described.
It is true that other federal agencies also have a mission to do environmental health research, such as the National Institute of Environmental Health Sciences at NIH, the National Toxicology Program, the Agency for Toxic Substances and Disease Registry, and the Food and Drug Administration (FDA).
If they are not already doing it, frequent, regular meetings of staff from these agencies would be an efficient way to set the research agenda and direct funding according to identified, agreed upon priorities on PFAS research.
EPA has a summary of its first year accomplishments from the Roadmap listed on its website, and it claims that EPA researchers have published more than 30 papers on PFAS in scientific journals and have added new data on PFAS to the:
- Drinking Water Treatability Database: a tool that provides referenced information on the control of contaminants in drinking water
- CompTox Chemicals Dashboard: a tool that provides chemistry, toxicity and exposure data for over 900,000 chemicals, with over 300 chemical lists based on structure or category
- ECOTOX Knowledgebase: a tool that provides single chemical environmental toxicity data on aquatic and terrestrial species
But is this enough to address all of the important questions? How many of these tell us accurate information about human health effects?
We Need Stronger Science to Guide Rules
It is safe to say, based on the available scientific research, the full scientific community is not ready to support the idea that PFAS exposure causes the diseases it has been associated with, and at the contamination levels that were proposed last year.
While the evidence for some of the associations is strong, additional causal analysis (that hopefully uses advances in computational techniques and causal inference methods) could reduce lingering uncertainties from observational studies. The Center is currently supporting the development of these kinds of analyses.
In the meantime, perhaps EPA should slow down its rule making until more on PFAS is understood.