Stockholm Convention on Persistent Organic Pollutants
POPs Review Committee (POPRC)
First Draft
Guidance on alternatives to perfluorooctane sulfonic acid (PFOS) and its derivatives
Table of Contents
Executive summary 3
1. Introduction, background and objectives 5
1.1 PFOS proposal history in short 5
1.2 Decision at COP4 5
1.3 Objective of the study 5
2. Characteristics of PFOS and its derivatives 5
2.1 PFOS substances covered by the COP4 decision 5
2.2 Properties of PFOS chemicals 7
2.3 Production and consumption of PFOS and derivatives 7
3. Alternatives to the use of PFOS 7
3.1 Textile impregnation and surface protection 8
3.2 Impregnation of packaging (paper/cardboard) 9
3.3 Cleaning agents, waxes and polishes for cars and floors 9
3.4 Surface coating, paint and varnish 10
3.5 Oil production and mining 10
3.6 Photo industry 11
3.7 Electric and electronic parts 11
3.8 Semiconductor industry 12
3.9 Aviation hydraulic fluids 13
3.10 Pesticides 13
3.11 Medical devices 14
3.12 Metal plating 14
3.13 Fire-fighting foams 16
3.14 Other uses 18
3.15 Summary of PFOS main uses and alternatives 18
4. Properties of alternative substances and hazard assessment 20
4.1 Overview 20
4.1 Shorter chain perfluoroalkyl sulfonates 21
4.2 Shorter chain perfluoroalkyl ketones and ethers 22
4.3 Fluorotelomers and fluorophosphates 23
4.4 Fluorinated co-polymers 25
4.5 Fluorinated polyethers 25
4.6 Siloxanes and silicone polymers 26
4.7 Propylated aromatics 28
4.8 Sulfosuccinates 29
4.9 Stearamidomethyl pyridine chloride 30
4.10 Fatty alcohol polyglycol ether sulfate 30
5. Comparative assessment of PFOS and its possible alternatives 31
6. Conclusions, recommendations and future developments 32
General reference list 34
Executive summary
1. At COP4 it was decided that the production and use of perfluorooctane sulfonic acid (PFOS), its salts and perfluorooctane sulfonyl fluoride (PFOSF) shall be eliminated by all Parties except for some acceptable purposes and specific exemptions, however the PFOS related chemicals used in practice are often PFOS precursors which may not be covered by the Convention.
2. The objective of this study is to summarize the present knowledge about alternatives to PFOS and to enhance the capacity of developing countries and countries with economics in transition to phase out PFOS, taking into account the need for longer phase-in times of alternatives for some uses and that no alternatives exist for other uses. While some countries have stopped and restricted a range of uses of PFOS and PFOS precursors, other countries are continuing these uses. Therefore, historical uses in some countries are ongoing uses in other countries.
3. In this paper the various uses of PFOS as surfactant in impregnation, coating, metal plating, fire-fighting foams etc. are discussed, and it is described, where alternative chemicals have been suggested, are available or already introduced to the market in some countries. There exist fluorinated or non-fluorinated alternatives to virtually all current PFOS uses. The available alternatives may not be quite perfect in all aspects. Every possible alternative mentioned is not necessarily economically and technically as fit for the purpose as PFOS, or without environmental and health hazards but nevertheless the alternatives are always considered less hazardous than PFOS.
4. The key to the performance of the fluorosurfactants is the extremely low surface tension, which currently cannot be matched with other surfactants. The most optimal substance with regards to that property is PFOS. However, due to environmental and health concerns other surfactants without fluorine content could be used as alternatives, if such low surface tension levels are not needed. Due to the relatively high prices of fluorosurfactants these switch can in some cases also have economic benefits.
5. The most common PFOS alternatives in use are fluorotelomers, which are precursors for perfluoroalkyl carboxylic acids (PFCA). In the beginning the choice was C8-fluorotelomers, however, it was shown that they are degraded into the hazardous perfluorooctanoic acid (PFOA). Of that reason the major producers of fluorochemicals have agreed with USEPA to phase-out C8-fluorotelomers before 2015. In stead there has been a shift to the less hazardous C6-, C4- and C3-perfluoroalkyl chemicals.
6. For some uses non-fluorinated chemicals have been introduced as alternatives, for instance, silicones, aliphatic alcohols and sulfosuccinates. It might also be that a particular use and product is obsolete and not essential any more, or maybe processes could change not to need PFOS, such as for digital techniques in photo industry or physical barriers in chrome plating.
7. A comparative assessment of PFOS and its possible alternatives with regards to technical, socioeconomic, environmental, health and safety aspects is a very complex process requiring a lot data and other information, and more than normally available. Often the information about PFOS is much more extensive than for the possible alternatives, which may be newly developed substances or formulations covered by trade secrets. The amount of information on the alternatives will also often be non-peer-reviewed information of a lower scientific quality. There is a need for a mechanism to continuously update information on the alternatives regarding their substitution properties and their toxicity.
8. Trustful economically data will probable also be scarce, and it has to taken into account that cost indication may be biased by coming mainly from industry. However, the sparse information received up to now suggests that the alternatives in general have comparable prices as the PFOS-related compounds. Specifically in the coating and paint area the non-fluorinated alternatives are cheaper.
9. PFOS and its derivatives are very hazardous substances, and when emitted to the environment, these chemicals will circulate there forever, since no degradation is foreseen; the final sink will be the water environment. There is no possibility for calling the emitted substances back again from the nature, therefore, globally all uses of PFOS should be phased out rapidly and as soon as possible. Stocks of PFOS-containing products, such as fire-fighting foams, should be collected and destroyed in stead of the use-up, which is mostly done now. As long the PFOS is in a container, it is under control and no damage will occur.
10. There is a need for incentives to develop safe and economical-technological feasible alternative substances and processes and to identify the driving forces for developing such PFOS alternatives. Such incentive could be legislation with only a few exemptions. The development of legislation may be time consuming and could impact industries in many ways, nevertheless it is an important tool to promote incentives to find and apply alternative substances and processes.
11. Further, a short phase-out time should be considered for the sake of human health and the environment, even for the cases when alternatives are more expensive than PFOS, making substitution non-economically at that time.
12. Because of the present restrictions and attention on PFOS it is also to be expected that closely related but non-regulated chemical structures could be made commercial as substitutes. Therefore, regulations should cover groups of chemicals in stead of single chemicals. A suggestion for simplicity would be to include all chemicals with a C8-perfluoralkyl moiety in any regulations/bans.
13. “Open” uses of PFOS derivatives, such as fat resist paper, waxes or stain/water proof property of textiles, should never be allowed as exemption, since their benefit of uses can not justify the impact on human health and environment by PFOS – and there are alternatives.
14. Some increasing effort will be needed to study the toxicological and environmental properties of alternatives and to make the resulting data and information public and trustful by publishing in peer-reviewed scientific journals. PFOS and its substitutes are studied and evaluated in parallel by authorities in many countries. More international cooperation will save resources and speed up processes.
1. Introduction, background and objectives
1.1 PFOS proposal history in short
15. In a letter of 14 July 2005 from the Swedish Ministry for the Environment proposed listing of perfluorooctane sulfonate (PFOS) in Annex A, a “Perfluorooctane sulfonate proposal” (UNEP/POPs/POPRC.1/9) was discussed at the 1st meeting of POPRC in November 2005. POPRC.1 concluded that the information on PFOS presented met the screening criteria specified in Annex D (decision POPRC-1/7). Further, at POPRC.2 in November 2006 the Risk profile on perfluorooctane sulfonate PFOS was adopted and published on 21 November 2006 (UNEP/POPS/POPRC.2/17/add.5). Later, in November 2007 POPRC3 adopted a Risk Management Evaluation for PFOS (UNEP/POPS/POPRC.3/20/add.5) published on 4 December 2007. Finally, at POPRC4 in October 2008 an addendum to the Risk Management Evaluation for PFOS was adopted and published on 30 October 2008 (UNEP/POPS/POPRC.4/15/add.6).
1.2 Decision at COP4
16. At COP4 it was decided that the production and use of perfluorooctane sulfonic acid (PFOS), its salts and perfluorooctane sulfonyl fluoride (PFOSF) shall be eliminated by all Parties except for some acceptable purposes and specified exemptions, and listing of PFOS in the annexes of the Convention was adopted (UNEP/POPS/COP.4/38). The many exceptions illustrate the need for available alternatives for various uses, especially in developing countries and countries with economies in transition.
1.3 Objective of the study
17. The objective of this study is to summarize the present knowledge about alternatives to PFOS and to enhance the capacity of developing countries and countries with economics in transition to phase out PFOS, taking into account the need for longer phase-in times of alternatives for some uses and that no alternatives exist for other uses.
2. Characteristics of PFOS and its derivatives
2.1 PFOS substances covered by the COP4 decision
18. The actual PFOS salts listed in the Annex of the Convention are specified as examples. Thus, there is no final number of substances, since PFOS salts in general are included. The 8 PFOS chemicals listed in the annex of the decision are also listed in Table 2.1 of this paper.
19.
Table 2.1: PFOS substances specified in the Annex of the Convention
PFOS substance / CAS no.Perfluorooctane sulfonic acid / 1763-23-1
Potassium perfluorooctane sulfonate / 2795-39-3
Lithium perfluorooctane sulfonate / 29457-72-5
Ammonium perfluorooctane sulfonate / 29081-56-9
Diethanolammonium perfluorooctane sulfonate / 70225-14-8
Perfluorooctane sulfonyl fluoride / 307-35-7
Tetraethylammonium perfluorooctane sulfonate / 56773-42-3
Di(decyl)di(methyl)ammonium perfluorooctane sulfonate / 2551099-16-8
20. However, there are many more PFOS-related chemicals which are supposed to be covered by the convention, since they are definitely PFOS precursors. Sweden did nominate 96 PFOS related substances. The UK report from 2004 (PFA 2004) contain a draft list of 98 “Compounds Potentially Degrading to PFOS in the Environment”. According to the Chinese delegation 66 PFOS related chemicals have been registered in a national inventory in China (year not mentioned). In 2007 in Denmark 92 polyfluorinated substances were registered in product use, among these 13 PFOS related substances (Jensen et al. 2008). In OECD’s “Preliminary List of PFOS, PFAS, PFOA and Related Compounds and Chemicals that may degrade to PFCA” many more PFOS related chemicals were listed (ENV/JM/MONO (2006)15). In Canada more than 60 PFOS chemicals have been listed.[1]
21. For many applications of “PFOS” it is not the PFOS substances mentioned in Table 2.1, which are used but some PFOS precursors not specified in the Annex of the Convention, and thus possibly not covered. Some of the most important PFOS precursors are listed in Table 2.2:
Table 2.2: Examples of PFOS precursors not specified in the Annex of the Stockholm Convention
Chemical name / Acronym / CAS no.Perfluorooctane sulfonamide / PFOSA / 754-91-6
N-Methyl perfluorooctane sulfonamide / MeFOSA / 31506-32-8
N-Methyl perfluorooctane sulfonamidoethanol / MeFOSE / 2448-09-7
N-Methyl perfluorooctane sulfonamidoethyl acrylate / MeFOSEA / 25268-77-3
Ammonium bis[2-N-ethyl perfluorooctane sulfonamidoethyl] phosphate[2] / 30381-98-7
N-Ethyl perfluorooctane sulfonamide (sulfluramid) / EtFOSA / 4151-50-2
N-Ethyl perfluorooctane sulfonamidoethanol / EtFOSE / 1691-99-2
N-Ethyl perfluorooctane sulfonamidoethyl acrylate / EtFOSEA / 432-82-5
Di[N-ethyl perfluorooctane sulfonamidoethyl] phosphate / EtFOSEP / 67969-69-1
3-[[(Heptadecafluorooctyl)- sulfonyl]amino]-N,N,N-trimethyl-1-propanaminium iodide/perfluorooctyl sulfonyl quaternary ammonium iodide / Fluorotenside-134 / 1652-63-7
Potassium N-ethyl-N-[(heptadecafluorooctyl) sulfonyl] glycinate / 2991-51-7
N-Ethyl-N-[3-(trimethoxysilyl)propyl] perfluorooctane sulfonamide / 61660-12-6
22. There are many other perfluorinated alkyl sulfonates (PFAS) and derivatives hereof with shorter or longer alkyl chain length, which are used for similar or related applications as PFOS; thus as PFOS substitutes. Some examples are shown in Table 2.3:
Table 2.3: Related perfluorinated alkyl sulfonates (PFAS)
PFC chemical name / Acronym / CAS no.Potassium perfluoroethyl cyclohexyl sulfonate / FC-98 / 67584-42-3
Perfluorobutane sulfonic acid / PFBS / 59933-66-3
Potassium perfluorobutane sulfonate / 29420-49-3
Perfluorohexane sulfonic acid / PFHxS / 432-50-7
Perfluorodecane sulfonic acid / PFDS / 335-77-3
Perfluorodecane sulfonate / 67906-42-7
23. Because of the restrictions on PFOS it is also to be expected that closely related but non-regulated chemical structures could be made commercial, such as the perfluorohexyl methyl ether sulfonate. The similarity is illustrated by the structure formulas:
Perfluorooctane sulfonate Perfluorohexyl methyl ether sulfonate
2.2 Properties of PFOS chemicals
24. The strong carbon-fluorine bond makes the perfluoroalkyl chain extremely stable and nonreactive. PFOS resists even strong acids and high temperatures and is not degradable in the environment. The basic PFOS structure is persistent and more complex PFOS related chemicals listed above will during use or presence in the environment degrade to the basic PFOS structure and is therefore called PFOS-precursors.
25. PFOS has surfactants properties with extremely low surface tensions, refractive index, and friction factor. The perfluorocarbon chain is both oleophobic and hydrophobic thus it is a repellent for water, oil and dirt and is electric insulating. These properties have been found to be useful in many applications.
26. It is useful to know that PFOS as salt is more hydrophilic and will be spread in the water environment, and the non-dissociated acid and the sulfonamides are less hydrophilic but more volatile than the salts, and therefore, will be able to be long-range transported by air. More details are to be found in the PFOS Risk Profile (UNEP/POPS/POPRC.2/17/Add.5).