Imagine 4,700 felines frolicking in a field. A lion and a tiger tussle at one end. A pair of kittens unravel yarn at the other. And in between, there are 4,696 leopards, pumas, jaguars, lynx, panthers, ocelots and house cats.
Now imagine 4,700 PFAS—per- and polyfluoroalkyl substances—polymers and non-polymers spread across that same field. Some are large molecules. Others are small. Some are bioavailable, some are not.
All are PFAS, but just as the felines come in all shapes, sizes and ferocity, so do PFAS.
The chemists, toxicologists, regulators, and concerned communities debating PFAS appear to have decamped to opposite ends of the field. One group contends that all PFAS are bad and should be banned. The other group says PFAS are so different that each must be evaluated, classified and regulated individually.
That binary thinking presents a false, all-or-nothing choice. In truth, there is a middle ground. There is a way forward if we group PFAS by their chemical, biological, and physical properties.
Sorting Helps in Evaluating Risk
Despite 4,700 different PFAS when you drill down into their chemical, physical and biological properties, you’ll find that PFAS can be sorted into different buckets based on shared traits. Once they are sorted, they can be more easily evaluated to balance high value/low risk PFAS against low value/high risk PFAS.
Better still, that grading system already exists under current hazard assessment schemes like the UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS), the U.S. Toxic Substances Control Act (TSCA) and the EU REACH, breaks down into 24 questions that can be used to evaluate every PFAS.
If you apply those questions at every stage of the PFAS lifecycle, you can separate the lions and tigers from the kittens and house cats. The questions cover biological properties (11 questions), chemical properties (four questions) and physical properties (nine questions). The starting point is a determination of whether the molecule meets the PFAS chemical definition of having one or more fully-fluorinated carbon atom.
To place PFAS into their buckets, a four-step process should be considered. It is simple. It is logical. It is grounded squarely in science:
Step 1: Define the health and environmental hazard posed by the PFAS by applying the 24 chemical, physical and biological questions to the PFAS under evaluation. These questions can be applied at each PFAS life cycle stage, from its start as a raw ingredient, its processing into an intermediate component material, its formation into a final product, and its disposal at end of life.
Step 2: Identify the uses of the PFAS.
Step 3: Identify effective control measures for the PFAS.
Step 4: Determine if the hazards from Step 1 and the potential exposures from uses in Step 2 are adequately mitigated by control measures in Step 3.
Determination: Individual PFAS with the same hazard profile would be sorted into the same bucket so that regulatory measures would be consistent.
If the hazard is not sufficiently mitigated, then consider additional risk managements, such as a restriction of use, more robust control measures, appropriate labeling or a permitting process.
A PFAS sorted into a bucket with a higher hazard profile due to data gaps can be moved to a lower hazard profile when scientific data is developed to prove otherwise.
Applying the Steps
As an example, let’s apply the four steps to a raw material in the manufacturing process. Applying Step 1, we might find that the material poses a high hazard because it is toxic and partitions to water.
Applying Step 2, we determine that the PFAS material is an ingredient used to process a base material and is not present once the base material is created.
Applying Step 3, we determine that the hazardous ingredient is fully captured or destroyed with a best available technology and therefore never leaves a closed system.
At Step 4, we weigh the hazard and the use against the control measures. We may find that the material falls into a high value/low risk category because although it is hazardous, it is properly mitigated.
If we find that mitigation is lacking, for example the capture is incomplete and the hazardous material could find its way into effluent from the manufacturing process, the chemical would be placed in a different, higher risk management bucket.
If the science for a Step 1 question is unknown for a particular PFAS, the risk spectrum would require a conservative approach that could trigger a higher level control measure or restrictions on use to mitigate risk.
The result is a relative risk spectrum which can be used to determine a risk management scheme that can be applied at a more generalized level for PFAS that possess similar biological, physical and chemical properties.
The value of a risk spectrum over the all-or-nothing approach is the ability to continue to innovate and explore fluorinated chemistry for the benefit of humankind. Where the data is lacking, a degree of uncertainty is inevitable, but this simple sorting system will allow us to temper the risk of what is unknown with the science we do know.
This column does not necessarily reflect the opinion of The Bureau of National Affairs, Inc. or its owners.
Barbara J. Henry, PhD, has been a toxicologist at W. L. Gore & Associatessince 2008. She also has toxicology experience in the chemical, petrochemical and agricultural chemical industries (Chevron, PPG, Aventis and Bayer).