A PROPOSAL FOR THE DEFINITION OF “PFOS” IN THE DIRECTIVE 2013/39/EU
(presented by Italy)
TheDirective 2013/39/EUintroduced a new priority substance n°35 which is defined as:
Perfluorooctane sulfonic acid and its derivatives (PFOS) with the CAS number: 1763-23-1
The CAS number refers to the Perfluorooctane sulfonic acid (C8HF17O3S), but it is not clear to which compounds the definition “its derivatives” applies.
In fact the definition of “its derivatives” has led to some discussion during the implementation in some Member States.
The simplest interpretation is that it refers to the salts, as PFOS is not sold as acid but rather as its salts.The most commonly used salts are tetraethylammoniumperfluorooctanesulfonate (CAS No. 56773-42-3, with trade names such as Fluorotenside-248, SurTec 960, FC-248 and FT-248m) and potassium perfluorooctanesulfonate (CAS No. 2795-39-3, with trade name FC-80).
Lithium (CAS No. 29457-72-5), diethanolamine(CAS No. 70225-14-8), and ammonium(CAS No. 29081-56-9) salts of PFOS may also be used.
The EFSA report on PFOS [Perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and their salts: Scientific Opinion of the Panel on Contaminants in the Food chain, The EFSA Journal (2008) 653, 1-131] cites the CAS No 2795-39-3 of the potassium salt.
The EQS template, developed in the CIS-WG E group,refers to anion perfluorooctanesulfonate,. The sheet explains that “PFOS is the perfluorooctanesulphonate anion and is not a substance as such and therefore does not have a specific CAS number. It is commercially available in the form of salts, derivatives (PFOS-substances) and polymers (PFOS-polymers). The term PFOS related substances is used to refer to any or all of the substances which contain the PFOS moiety and may break down in the environment to give PFOS (EA, 2004)”. But it refers to the following CAS numbers:
1763-23-1 (acid)
2795-39-3 (potassium salt)
29081-56-9 (ammonium salt)
29457-72-5 (lithium salt)
70225-39-5 (diethanolamine salt)
56773-42-3 (tetraethyl-ammonium salt)
251099-16-8 (didecyldimethyl-ammonium salt)
If we check the Directive 2006/122/EC, PFOS is defined as:
Perfluorooctanesulfonates (PFOS) C8F17SO2X (X = OH, Metal salt (O-M+), halide, amide, and other derivatives including polymers)
This definition includes the perfluorooctanesulfonyl fluoride (CAS No. 307-35-7) and polymers which can release or form PFOS.
A wide definition is also in the Stockholm Convention on POPs:
“PFOS is a fully fluorinated anion, which is commonly used as a salt or incorporated into larger polymers. PFOS and its closely related compounds, which may contain PFOS impurities or substances that can result in PFOS, are members of the large family of perfluoroalkylsulfonate substances.”
But the regulated compounds under Stockholm Conventionare only:
perfluorooctane sulfonic acid (CAS No: 1763-23-1) and its salts
and perfluorooctanesulfonyl fluoride (CAS No: 307-35-7)
In USA, US EPA defines “PFOS equivalent” as “all products that could completely degrade to PFOS”, while OEHHA (Chemical for CIC Consultation: PFOS and Its Salts and Transformation and Degradation Precursors, Office of Environmental Health Hazard Assessment; California Environmental Protection Agency, July 2010) states that: “Perfluorooctanesulfonate (PFOS) and its salts are perfluorinated organic compounds with surfactant properties. Common salts of PFOS include the ammonium, diethanolamine, potassium , and lithium forms. PFOS can be released from several fluorochemicals, such as perfluorooctane sulfonamide (PFOSA), N-ethyl perfluorooctanesulfonamidoethanol (N-EtFOSE), and N-ethylperfluorooctane sulfonamide (N-EtFOSA) by transformation or degradation processes”.
In conclusion, after this short review on PFOS definition, we think that it is necessary to amend the definition in Directive 2013/39/EU in order to specify the substances that should be monitored. In fact it is not clear if the PFOS derivatives include also non-ionic compounds such as perfluorooctanesulfonyl fluoride or perfluoroalkylsulphonamides.
From an operational point of view, in aqueous environments PFOS is present only as its anion perfluorooctanesulfonate (C8F17O3S-), because the salts dissolve in water at pH of natural waters. Anion is also the species analysed in laboratories by liquid chromatography mass spectrometric methods, and therefore is usually reported in the analytical reports.
As conclusion, our suggestion is that the word “derivatives” is substituted by “salts” or, alternatively, a footnote is added in the Table to explicit the list of “derivative” compounds.
In addition, it is necessary to establish which is the correct compound to be reported by MS: the anion perfluorooctanesulfonate (C8F17O3S-) or the corresponding acid (C8HF17O3S).