Information on brominated diphenyl ethers1 and perfluorooctane sulfonic acid (PFOS) and its salts and perfluorooctane sulfonyl fluoride (PFOSF) from the risk management evaluation and a technical paper on brominated diphenyl ethers
As requested in paragraph 3 of decision POPRC-7/7, the Secretariat extracted the information on brominated diphenyl ethers and perfluorooctane sulfonic acid (PFOS), its salts and perfluorooctane sulfonyl fluoride (PFOSF) in articles from the risk management evaluations2 and the technical paper on brominated diphenyl ethers developed in accordance with decision SC-4/193 as reference information for the format for the evaluation of brominated diphenyl ethers pursuant to paragraph 2 of parts IV and V of Annex A to the Stockholm Convention and work programme on brominated diphenyl ethers and PFOS, its salts and PFOSF.
Brominated diphenyl ethers in articles
Polybrominated diphenyl ethers in general are used as flame retardants of the additive type. They are physically combined with the material being treated rather than chemically combined (as in reactive flame retardants). This means that there is the possibility that the flame retardant may diffuse out of the treated material to some extent.
Industry indicates that octabromodiphenyl ether is always used in conjunction with antimony trioxide. In Europe, it was primarily used in acrylonitrile-butadiene-styrene (ABS) polymers at 12-18% weight loadings in the final product. Around 95% of the total octabromodiphenyl ether supplied in the EU is used in ABS. Other minor uses, accounting for the remaining 5% use, include high impact polystyrene (HIPS), polybutylene terephthalate (PBT) and polyamide polymers, at typical loadings of 12-15% weight in the final product. In some applications, the flame retardant is compounded with the polymer to produce pellets (masterbatch) with slightly higher loadings of flame retardant. These are then used in the polymer processing step to produce products with similar loadings as given above. The flame retarded polymer products are typically used for the housings of office equipment and business machines. Other uses that have been reported for octabromodiphenyl ether include nylon and low density polyethylene, polycarbonate, phenol-formaldehyde resins and unsaturated polyesters and in adhesives and coatings.
Commercial pentabromodiphenyl ether can be used or has been used in the following sectors:
Electrical and electronic appliances (EE appliances)
Computers, home electronics, office equipment, household appliances and other items containing printed circuit laminates, plastic outer casings and internal plastic parts such as small run components with rigid polyurethane elastomer instrument casings.
Traffic and transport
Cars, trains, aircraft and ships containing textile and plastic interiors and electrical components.
Building materials (construction industry)
Foam fillers, insulation boards, foam insulation, pipes, wall and floor panels, plastic sheeting, resins etc.
The most common use, accounting for 95-98% of commercial pentabromodiphenyl ether since 1999, has been in polyurethane foam. This foam may contain between 10 and 18% of the commercial pentabromodiphenyl ether formulation. Polyurethane foam is mainly used for furniture and upholstery in domestic furnishing, automotive and aviation industry. Other uses are in rigid polyurethane elastomers in instrument casings, in epoxy resins and phenolic resins in electrical and electronic appliances, and construction materials. For some years now, the more highly brominated decabromodiphenyl ether has been preferred in these applications. Commercial pentabromodiphenyl ether has also been incorporated in minor amounts in textiles, paints, lacquers, in rubber goods (conveyer belt, coating and floor panels) and in oil drilling fluids. Levels range from 5-30% by weight. Up to the early 1990s, commercial pentabromodiphenyl ether was used in printed circuit boards, usually FR2 laminates (phenolic resins) in Asia. Such FR2 laminates are used in household electronics (television, radio, and video), vehicle electronics, and white goods (washing machines, kitchen appliances, for example). In the early 1990s the amount of commercial pentabromodiphenyl ether used in textile treatment was 60 % of total use in the EU, but this application is now banned.
Commercial pentabromodiphenyl ether has been identified as an additive flame retardant in textiles (substance flow analyses in the ECE region). Manufacturers of furniture textiles have stated that the textile contained 0.45% pentabromodiphenyl ether in a Norwegian flow analysis reported in 2003. Stringent rules on flammability apply to textiles used in the public sector, the transport sector and business sector, but rules for domestic use can be less consistent. According to information obtained from the bromine industry the use of commercial pentabromodiphenyl ether as hydraulic fluid (as a component of a mixture) in petroleum borings and mining was discontinued 10-20 years ago. Australia has reported uses in manufacture of polyurethane foams for refrigerators and packaging, and in epoxy resin formulations supplied into aerospace market and for use as potting agents, laminating systems and adhesive systems. The US has reported use of commercial pentabromodiphenyl ether in the aircraft industry. There is no use of commercial pentabromodiphenyl ether in newer aircraft, and thus no exposure of the public, but commercial pentabromodiphenyl ether can still be in use in military aircraft.
UNEP/POPS/POPRC.4/15/Add.1: Risk management evaluation for commercial octabromodiphenyl ether.
UNEP/POPS/POPRC.3/20/Add.1: Risk management evaluation for commercial pentabromodiphenyl ether.
UNEP/POPS/POPRC.6/2/Rev.1: Work programmes on new persistent organic pollutants as adopted by the Conference of the Parties.
Inventory guidance for brominated dyphenyl ethers (draft of 1 December 2011).
Perfluorooctane sulfonic acid, its salts and perfluorooctane sulfonyl fluoride in articles
Perfluorinated substances with long carbon chains, including perfluorooctane sulfonic acid (PFOS), are both lipid-repellent and water-repellent. Therefore, the PFOS-related substances are used as surface-active agents in different applications. The extreme persistence of these substances makes them suitable for high temperature applications and for applications in contact with strong acids or bases. It is the very strong carbon-fluorine binding property that causes the persistence of perfluorinated substances.
Main production process of PFOS and PFOS-related substances is electro-chemical fluorination (ECF), utilized by 3M, the major global producer of PFOS and PFOS-related substances prior to 2000.
Direct fluorination, electro-chemical fluorination (ECF):
The reaction product, perfluorooctanesulfonyl fluoride (PFOSF) is the primary intermediate for synthesis of PFOS and PFOS-related substances. The ECF method results in a mixture of isomers and homologues with about 35-40% 8-carbon straight chain PFOSF. However, the commercial PFOSF products were a mixture of approximately 70% linear and 30% branched PFOSF derivate impurities. Other production methods for perfluoroalkylated substances are telomerisation and oligomerisation. However, to which extent these methods are applied for production of PFOS and PFOS-related substances is not evident.
The following applications are confirmed as historical use of PFOS-related substances: fire fighting foams, textile, carpets, leather/apparel, textiles/upholstery, paper and packaging, coatings and coating additives, industrial and household cleaning products, pesticides, photographic industry, photolithography and semiconductor, hydraulic fluids, and metal plating.
It is estimated that the majority of PFOS has been used as water, oil, soil and grease repellents (e.g. on fabric, leather, paper, packaging, rugs and carpets) and as surfactants (e.g. in fire fighting foams and coating additives).
PFOS and its precursors can be imported either as chemicals or in products for the specific uses. These comprise e.g. use as an anti-erosion additive in aviation hydraulic fluids; use as a component of a photoresist substance, including a photo acid generator or surfactant, or as a component of an anti-reflective coating, used in a photomicrolithography process to produce semiconductors or similar components of electronic or other miniaturized devices; use in coatings for surface tension, static discharge, and adhesion control for analogue and digital imaging films, papers, and printing plates, or as a surfactant in mixtures used to process imaging films; and use as an intermediate only to produce other chemical substances to be used solely for these uses. Historically, PFOS and its precursors were also used as surfactants in fire fighting foams and in industrial and household cleaning products; in carpet, textile, leather, and paper coatings; and in termite and ant bait insecticide products.
Fire fighting foams
The fire fighting foams can be grouped in two main categories:
Fluorine-containing foam types (some of them consist of PFOS-related substances)
Fluorine-free foam types
Textile/upholstery, carpet, leather/apparel
PFOS-related substances have been used to provide soil, oil and water resistance to textiles, apparels, home furnishings and upholstery, carpets, and leather products. Since 3M´s withdrawal from the market, PFOS-related substances are used to a much smaller extent for these applications.
Paper and packaging
PFOS-related substances have been used in the packaging and paper industries in both food packaging and commercial applications to impart grease, oil and water resistance to paper, paperboard and packaging substrates. According to 3M, fluorochemicals were used for both food contact applications (plates, food containers, bags and wraps) and non-food applications (folding cartons, containers and carbonless forms and masking papers). Since 3M´s withdrawal from the market, PFOS related substances are used to a much smaller extent for these applications.
Coatings and coating Additives
3M indicates that prior to its voluntary phase-out of PFOS production, the company would sell fluorochemical polymer coatings and coating additives which were used undiluted or diluted with water or butyl acetate to impart soil or water repellence to surfaces (including printing circuit boards and photographic film) (RPA and BRE, 2004).These polymers contained fluorocarbon residuals at a concentration of 4% or less. Other applications for aqueous coatings are to protect tile, marble and concrete. It is unclear which of these products were actually based on PFOS-related substances.
Industrial and household cleaning products (surfactants)
3M PFOS-based products were sold in the past to a variety of formulators to improve the wetting of water-based products marketed as alkaline cleaners, floor polishes (to improve wetting and levelling), denture cleansers and shampoos. Several of these products (alkaline cleaners, floor polishes, shampoos) were marketed to consumers; some products were also sold to janitorial and commercial services. A number of the alkaline cleaners were spray-applied. With regard to the UK cleaning products industry, the responses received do not indicate the use of PFOS-related substances in industrial and household cleaning products.
PFOS-based chemicals are used for the following purposes in mixtures, in coatings applied to photographic films, papers, and printing plates:
Semiconductor manufacturing comprises up to 500 steps, of which there are four fundamental physical processes:
Photolithography is the most important step towards the successful implementation of each of the other steps and, indeed, the overall process. It shapes and isolates the junctions and transistors; it defines the metallic interconnects; it delineates the electrical paths that form the transistors; and joins them together. Photolithography reportedly represents 150 of the total of 500 steps mentioned above. Photolithography is also integral to the miniaturization of semiconductors.
PFOS is used as a photoacid generator (PAG) in a mechanism called chemical amplification that increases the sensitivity of photoresist to allow etching images smaller than wavelength of light.
A number of resist suppliers sell antireflective coatings (ARC), subdivided into Top (TARC) and Bottom (BARC) coatings and used in combination with deep ultra violet (DUV) photoresist. The process involves placing a thin, top coating on the resist to reduce reflective light, in much the same way and for the same purposes that eyeglasses and camera lenses are coated.
Hydraulic fluids (for the aviation industry)
Hydraulic fluids were initially used in aircraft to apply brake pressure. As larger and faster aircraft were designed, greater use of hydraulic fluids became necessary. An increase in the number of hydraulic fluid fires in the 1940s necessitated work towards developing fire resistant fluids. The first of these fluids was developed in 1948, when fire resistant hydraulic fluids based on phosphate ester chemistry were developed.
Perfluorinated anions act by altering the electrical potential at the metal surface, thereby preventing the electrochemical oxidation of the metal surface under high fluid flow conditions. As a result, hydraulic fluids based on phosphate ester technology and incorporating additives based on perfluorinated anions are used in all commercial aircraft, and in many military and general aviation aircraft throughout the world, as well as by every airframe manufacturer.
The main uses of PFOS-related substances in metal plating are for chromium plating, and anodising and acid pickling. PFOS related substances lower the surface tension of the plating solution so that mist containing chromic acid from the plating activity is trapped in solution and is not released to air.
There is information on other historical or current PFOS applications such as in pesticides, medical applications, mining and oil surfactants, flame retardants and in adhesives. Based on current understanding, these applications represent a minor part of known PFOS applications and are therefore not further elaborated in this profile.
Table 1. Production and use of PFOS and its related substances according to Annex B to the Stockholm Convention
Production and use of PFOS and its related substances
PFOS-based chemicals are or have been used in the manufacturing of digital cameras, mobile phones, printers, scanners, satellite communication and radar systems, etc.
For most of these uses, alternatives are available or are under development.
PFOS is still used but in lower concentrations.
No substitutes with comparable effectiveness for some specific uses have been identified, and doing so may take up to 5 years, according to the industry. It should be possible to use perfluorobutane sulfonic acid, fluorinated polyethers or telomers.
Aviation hydraulic oils
PFOS-related compounds may still be used.
Other fluorinated substances and phosphate compounds could be used.
Sulfluramid is used in some countries as an active substance and surfactant in pesticide products for termites, cockroaches and other insects. Other fluorosurfactants may be used as “inert” surfactants in other pesticide products.
Synthetic piperonyl compounds such as S-Methoprene, Pyriproxyfen, Fipronil are alternative active substances, sometimes used in combination. Alternative surfactants may exist.
Old video endoscopes at hospitals contain a CCD colour filter that contains a small amount of PFOS. PFOS is also used as an effective dispersant for contrast agents in radio-opaque catheters.
Repairing such video endoscopes requires a CCD colour filter containing PFOS. New CCD filters are PFOS-free. For radioopaque ethylene tetrafluoroethylene, perfluorobutane sulfonic acid can replace PFOS.
PFOS-compounds are still used in hard chrome plating.
Cr-III has replaced Cr-VI in decorative chrome plating.
Some non-fluorinated alternatives are marketed but they are not considered equally effective in hard chrome plating.
A C6-fluortelomer is used as a substitute and may be effective. Perfluorobutane sulfonic acid derivatives may also be used. Physical barriers may also apply.
The use of PFOS-related substances in new products has been phased out in most OECD countries. Stocks are still being used up.
C6– fluorotelomers are used as substitutes in new products; fluorine-free alternatives are used for training exercises and possibly in other settings than offshore.
UNEP/POPS/POPRC.3/20/Add.5: Risk management evaluation on perfluorooctane sulfonate.
UNEP/POPS/POPRC.4/15/Add.6: Addendum to the risk management evaluation for perfluorooctane sulfonate.
Inventory for PFOS and related chemicals (draft of 1 December 2011).
1 In this document, the term “Brominated diphenyl ethers” refers to hexabromodiphenyl ether, heptabromodiphenyl ether, tetrabromodiphenyl ether and pentabromodiphenyl ether listed in Annex A to the Stockholm Convention.