EPA Scientifically-Challenged PFAS Numbers

With much fanfare, the EPA announced the proposed drinking water regulations for two “forever chemicals,” PFOA and PFOS. EPA Administrator Michael Regan said, “Communities across the country have suffered far too long from the ever-present threat of PFAS pollution. That is why President Biden launched a whole-of-government approach to aggressively confront these harmful chemicals, and EPA is leading the way forward.”

This statement and others indicate that the Biden Administration has decided to use the PFAS issue for political purposes with the environmental community.  

What is an MCL?

The Maximum Contaminant Level (MCL) is the enforceable drinking water standard. Drinking water utilities must ensure that their water does not contain levels of chemicals that exceed the MCL. EPA proposed an MCL of 4 parts per trillion (4 ppt) for PFOA and PFOS. This is the lowest level detectable in drinking water – analytical methods cannot find these chemicals below 4 ppt.  

For comparison purposes, the MCL for cyanide, which everybody recognizes is an extremely toxic chemical, is 0.2 parts per million (ppm) – equivalent to 200,000 ppt. Since the MCLs are based on health, this translates to PFOA/PFOS being 50,000 times more toxic than cyanide, which should strike any scientist as somewhat absurd.      

The Safe Drinking Water Act sets forth a two-step process for setting drinking water regulations. Before setting the MCL, the EPA must first develop a maximum contaminant level goal (MCLG):

  • This is a non-enforceable health goal at which “no known or anticipated health effects occur and which allows an adequate margin of safety.” 
  • Then MCL is then set as close to the MCLG as technically feasible, “with the use of the best technology, treatment techniques, or other means which the Administrator finds available (taking cost into consideration).” -  Safe Drinking Water Act

The MCLG is set at the level of a chemical determined not to cause health problems after a lifetime of exposure to drinking water. You can think of this as a safe level goal; drinking water utilities do not need to remove chemicals to this level. It is the benchmark for setting the MCL – which must be set as close to it as technically feasible.    

The EPA faced a big problem when setting the MCLG for PFOA and PFOS. EPA had already determined safe levels for these chemicals in their Health Advisories, levels normally adapted as the MCLGs for chemicals that do not cause cancer. Health Advisories are calculated using the same methods as MCLGs to determine identical outcomes - safe levels for chemicals in drinking water. 

In July 2022, EPA surprised much of the scientific community by proposing Health Advisories of 0.004 ppt for PFOA and 0.020 ppt for PFOS. These levels are so low that current methods can not measure them. As I have written for ACSH and the National Groundwater Association, the problem with the health advisories is not simply how low the numbers are; the problem is that the numbers are based on non-credible science. For PFOA/PFOS, the EPA selected effects on the immune system, measured by changes in antibody levels, as the critical adverse health effect, a controversial decision.  

Most countries and agencies have used other health endpoints to calculate safe levels for PFOA/PFOS. The EPA’s Health Advisory numbers are significantly lower than most - more than 100,000-fold differences between the safe levels from different countries. This is unprecedented; typically, there are only minor disagreements between countries on safe levels. [1]

In my opinion, EPA could not risk setting the MCLGs at the Health Advisory levels because of the extremely thin scientific basis for their Health Advisories. EPA did not want their drinking water regulation mired in controversy over these numbers.   Instead, the EPA ignored the dilemma of the Health Advisory by changing the subject.

Instead of basing the MCLGs on noncancer effects, they based them on cancer effects and proposed they be set at zero. The EPA’s policy is there is no known safe threshold for genotoxic carcinogens. But, this is problematic for the following reasons:

  • There is no clear evidence that PFOA/PFOS causes cancer. Most human studies have NOT shown cancer from exposure to PFOA or PFOS. According to EPA’s Regulatory Impact Analysis, “Data on the association between PFOA exposure and kidney cancer are limited but suggest a positive association between exposure and increased risk of kidney cancer.”

This suggestive evidence determined that PFOA/PFOS were “Likely to be Carcinogenic to Humans,” and the MCLG was set at zero, as per EPA’s policy.

  • EPA ignored the critical difference between genotoxic and nongenotoxic carcinogens. Genotoxic chemicals damage genetic information in a cell (mutations). The MCLG is set to zero -  a non-threshold approach. The non-threshold approach assumes that any concentration will cause an increased risk of cancer. Other chemicals cause cancer without damaging genetic information. Their MCLG is set by a Health Advisory or Reference Dose [2] – there is a threshold at which the chemical causes damage.

Mutagenicity testing determines whether a chemical acts by a genotoxic mechanism. As discussed previously, various mutagenicity tests are readily available for testing chemicals. If most tests are positive, the chemical is mutagenic; if most are negative, the chemical is not mutagenic. All the evidence says that PFOA and PFOS are not mutagenic and act by a non-genotoxic mechanism. The MCLG should have been set at the Health Advisory level.

The EPA chose to set the MCLGs at zero, only saying that “There is no evidence demonstrating a threshold level of exposure below which there is no appreciable cancer risk, and therefore, it is assumed that there is no known threshold for carcinogenicity.” 

EPA did not follow the science or their regulations; instead, defining a number that suggests that these chemicals are more toxic than cyanide. This makes little sense. The EPA’s own analysis considers that 20% of total PFAS exposure comes from drinking water sources, with 80% from food and other sources. Proposing such a low drinking water number will do little to reduce human exposure to PFAS. This confirms my belief that EPA backed into a drinking water number to achieve a policy result.       

One of the most important consequences of allowing this regulatory agenda to overrule the scientific evidence is that billions of dollars will be spent by water utilities and passed on to the consumers on an issue that poses far less risk than the proposal indicates. This is my next topic; the EPA’s economic analysis – the huge costs and the purported thousands of lives saved due to this rule. 

[1] To address this issue, a coalition was formed to try to bring order from chaos; a collaboration between interested scientists worldwide to develop one safe dose range for all, the “Advisory Committee for International Collaboration on the PFOA/PFOS Safe Dose.” Results are expected later this year.  

[2] A reference dose (RfD) estimates daily exposure to the human population (including sensitive subpopulations) likely to have no appreciable risk of deleterious effects during a lifetime.