Published studies suggest that PFBS, a substance in the same class as PFOS, persists and is mobile in the environment, according to a literature review by Norwegian authorities.
The conclusion bolsters preliminary statements about the substance made by Norway in the context of prioritisation under REACH. Norway is expected to submit a REACH substance of very high concern (SVHC) proposal for the substance by March next year.
The review, conducted by the Norwegian Geotechnical Institute on behalf of the Norwegian Environment Agency, says that degradation of PFBS has not be seen in any study conducted to date. It also describes the environmental persistence as "extreme".
Regarding mobility, the review says that PFBS contamination of the Arctic via water is expected by read-across from similar substances. For example, studies have found PFOS and PFHxS contamination of the Arctic through long-range transport.
This expectation is supported by measurement of PFBS in Arctic biota and Antarctic water, the review says. More generally, it is also supported by evidence that PFBS is "ubiquitous" in water samples. Studies have found it in marine and freshwater environments, as well as ground water and drinking water.
The bioaccumulation potential of PFBS is lower than that of similar substances, such as PFOS. However, studies have found "relatively high" concentrations of PFBS in plants grown on soil contaminated with per- and poly-fluoroalkyl substances (PFASs).
M and vM
Governments are increasingly restricting use of traditional PFASs, such as PFOS, because of their persistent, bioaccumulative and toxic (PBT) properties. Meanwhile, use of alternative, short chain PFASs, such as PFBS, is increasing.
The two substances are chemically and functionally very similar, suggesting that PFBS can be used as a substitute. However, there are growing concerns that they may also be similar in their risks to human health and the environment.
Norway outlined various concerns in February in a risk management option analysis conclusion document. The document said that, among other attributes, the substance fulfills both the persistent and very persistent criteria of REACH.
"It may even be categorised as extremely persistent, since no degradation is to be expected under environmentally relevant conditions." Additionally, PFBS is mobile and may irreversibly contaminate drinking water sources and the aqueous environment, the document said.
Overall, "PFBS exhibits properties that give rise to an equivalent level of concern to PBT/vPvB [persistent, bioaccumulative and toxic/very persistent, very bioaccumulative] substances".
Then, in August, Norway notified Echa of its intention to submit an SVHC proposal for "PFBS, its salts and related substances" in August, again citing an "equivalent level of concern" of serious effects on the environment.
Consequently, PFBS could be a test case for SVHC designation on the basis that a substance is mobile (M) or very mobile (vM) rather than B or vB.
Germany’s Federal Environment Agency, UBA, proposed the idea in 2017 as a way to improve protection of human health and the environment from certain chemicals that do not meet the B criterion but are nevertheless of concern. The chemicals are of concern because they are persistent, mobile in water and reach drinking water sources because they do not bind to solid substances, such as sand or activated carbon, and cannot be removed by filters. The agency doubled down on its position in April when it ran a two-day workshop to explore the topic.
On 14 November, the US EPA published its draft reference doses for PFBS and Gen X chemicals as part of a broad effort to address the potential risks of PFASs.