Teflon Replacement on Track to Test Definition of Hazardous Chemicals

CC BY-NC-ND 2.0. Mural "Deep Sea Food Chain" by Bruce Mahalski; photo by Pieter Pieterse

If a chemical does not bioaccumulate and is not highly toxic, do we need to worry about it building up in the environment?

After PFOS and PFOA manufacture was discontinued due to fears about potential health effects, companies had to find substitutes that could provide the same technical benefits of perfluorinated chemicals, or PFCs.

The "O" in PFOS and PFOA stands for "octyl," revealing the chemicals to have backbones of 8 carbon molecules. Like all perflourinated chemicals, the carbons along that backbone are mostly filled with fluorine atoms.

One main successor to the 8-carbon molecules is PFBS, or perfluorobutanesulfonic acid. PFBS has the same saturation of the carbon chain by fluorine atoms, but the smaller butane backbone, with only 4 carbon atoms, cycles through our bodies much faster (half of it is gone within a month, compared to over 5 years for PFOS). EPA recently released a draft toxicity assessment of PFBS which suggests that PFBS is 500 times less toxic than PFOA/PFOS.

We can keep our beloved stick-free, water- and stain-repellent properties without worrying about bioaccumulation and toxicity. Problem solved then?

Persistent and Mobile

"PBT," or persistent, bioaccumulating, and toxic has long been the standard for evaluating chemicals that aren't immediately harmful but have the potential to build up to levels that can cause deleterious effects. More recently, "vPvB" was added to the classes of concern, representing chemicals that are very persistent and very bioaccumulating - such that chemicals can still build up in the bodies of humans or animals to above thresholds of harmful effects not quite fitting the definition as "toxic".

PFBS is not a PBT, nor a vPvB, because it does not bioaccumulate. But it is very persistent. A newly released report of research conducted at request of the Norwegian Environment Agency by the Norwegian Geotechnical Institute states:

"PFBS is a perfluoroalkylsulfonate, which are amongst the most stable and persistent organic molecules possible. No studies have observed degradation of PFBS (or other perfluoroalkylsulfonates) under environmental conditions, including atmospheric photolysis."
-- PFBS in the Environment, NGI

Furthermore, PFBS is mobile, moving into groundwater. Because it never degrades, it does accumulate: in the water. Policy makers have started asking if accumulation in our groundwater and drinking water is not a risk tantamount to bioaccumulation. Instead of increasing exposure through the food chain, humans and animals face a growing exposure to the chemicals in our water.

PFBS a test case?

Now PFBS could serve as the first test case of a new class of hazards known as PMT or vPvM - chemicals which are persistant, mobile, and toxic or very persistent and very mobile. The German EPA has suggested that PMT and vPvM criteria could be used to identify "substances of very high concern" to the European Chemicals Agency. Once a chemical is identified as a "substances of very high concern," industry is required by existing laws to speed up finding substitutes and government agencies must consider restricting the use of the chemicals by law.

The use of PMT or vPvM criteria will depend on a phrase in the European Chemicals regulation REACH (Registration, Evaluation, and Authorization of CHemicals) which says that hazardous properties posing an "equivalent level of concern" to PBT and vPvB can also be listed as substances of very high concern.

In August of 2018, Norway notified the European Chemicals Agency of its intent to submit PFBS to the registry of substances which are candidates to be declared of very high concern. The submittal is expected before the 1st of March 2019. Just being named as a candidate will require some action by industry to take stock of its current usage of the chemical and communicate the potential concerns.

If Europe acts to add PMT and vPvM characteristics to the growing list of reasons to treat chemicals with care, it will surely spread to influence the decision of the US EPA and other global agencies tasked with protecting health and the environment. For now, PFBS is the test case to watch.