Alternatives are available for all uses of hexabromobiphenyl, so prohibiting its use and production is feasible and inexpensive. This chemical is already subject to several national and international regulations, restricting its use and production.
Note that following information is extracted from the risk management evaluation document (UNEP-POPS-POPRC.3-20-Add.3).
The HBB risk profile describes three principal commercial products that contained HBB in the USA and Canada:
- acrylonitrile-butadiene-styrene (ABS) thermoplastics (used for business machine housings and electrical products such as radio and TV;
- fire retardant in cable coatings and lacquers, and
- fire retardant in polyurethane foam for auto upholstery.
Production and use of HBB have ceased in the USA, Canada, and probably most parts of the world. However, it is possible that HBB is still being produced and used in some developing countries or in countries with economies in transition. As most production and use have ceased, there are numerous alternatives available and in use. Since there may be some production and use still occurring, evaluation and assessment of alternatives is presented and will focus on the earlier known uses as far as information is available.
A number of reports on risk assessment of alternative substances and processes are available. The OSPAR priority substances Series (OSPAR, 2001) provides summary information on alternatives for brominated flame retardants. The Danish Environmental Protection Agency has described alternative halogen-free flame retardants for a variety of uses including epoxy, phenolic resins, rigid and soft polyurethane foam, textiles, and a variety of plastics including ABS (Danish EPA, 1999). Both drop-in chemical substitutes and alternative materials are listed. US EPA has described process alternatives and chemical substitutes for polyurethane foam (USEPA, 2005). The German Federal Ministry of Environment has reported on alternatives for flame retardants used in electronics, upholstery, and other sectors (BMU, 2000).
As brominated flame retardants only account for about 15% of the global flame retardant consumption, principally a large number of compounds may be considered as alternatives (OSPAR, 2001). Substitution can take place at three levels:
- brominated flame retardants can in some applications be replaced by another flame retardant without changing the base polymer; (major group of substitutes)
- the plastic material, i.e. the base polymer containing flame retardants and other additives, can be replaced by another plastic material; (e.g. polysulfone, polyaryletherketone and polyethersulfone)
- a different product can replace the product, e.g. the plastic material is replaced by another material (e.g. wool), or the function can be fulfilled by the use of a totally different solution.
Reported chemical substitutes (see indent 1) currently used in Europe comprise the group of (a) organophosphorus compounds, (b) inorganic fire retardants and (c) nitrogen containing compounds (Danish EPA, 1999).
- The group of organophosphorus compounds contains the following main substances divided into the groups of:
- halogenated organophosphorus (tris-dichloropropyl-phosphate, tris-chloropropyl-phosphate and tri-chloroethyl phosphate)
- non-halogenated organophosphorus (triphenyl phosphate, tricresyl phosphate, resorcinal bis(diphenylphosphate), phosphonic acid, ((hydroxymethyl)carbamyl)ethyl)- dimethyl ester, phosphorus and nitrogen constituents for thermosets)
- The group of inorganics contains aluminium trihydroxide, magnesium hydroxide, ammonium polyphosphate, red phosphorus and zinc borate
- The group of nitrogen containing compounds contains melamine and melamine derivatives, e.g., melamine cyanurate and melamine polyphosphate
In addition USEPA 2005 provides an assessment for tribromoneopentyl alcohol, chloroalkyl phosphate, other aryl phosphates, tetrabromophthalate diol diester and reactive brominated flame retardants as potential substitutes for PeBDE. Tetrabromobisphenol-A (TBBPA) and reactive phosphorus polyols have been mentioned as potential alternatives as well.
Description of alternatives (substances)
Alternatives for ABS plastics
Organic phosphorus compounds which are available as halogenated or non-halogenated substances can serve asalternatives for use in ABS plastics.
Halogenated organophosphorus compounds include tris-chloropropyl-phosphate (TCPP), tris-chloroethyl-phosphate, and tris dichloropropyl phosphate (TDCPP) (BMU, 2000). According to (USEPA, 2005) TDCPP is often used in polyurethane foam in the US and abroad. However, TDCPP, TCPP and tri-chloroethyl\ phosphate entail moderate concern for carcinogenicity, reproductive toxicity, developmental toxicity, systemic toxicity, genotoxicity, acute and chronic ecotoxicity, and persistence. (WHO, 1998), (USEPA, 2005)
Tetrabromobisphenol A (TBBPA or TBBP-A) is regarded as very poisonous to water-living organisms and very persistent. This flame retardant is mainly used in printed circuit boards. Since TBBPA is chemically bound to the resin of the printed circuit board, there is no direct exposure of the aquatic environment and therefore minimal risk to aquatic organisms. For disposal and recovery purposes circuit boards however, would be classified as hazardous under the Basel Convention if containing polybrominated biphenyls to an extend, that they possess Annex III characteristics (Annex VIII, A 1180). Consequently the European Regulation No (EC) 1013/2006 on Shipment of waste would subject such wastes to export prohibition in Article 36. TBBPA and other flame retardants are released during recycling of waste electrical and electronic equipment.
Non-halogenated organic phosphorus compounds as alternative flame retardants for High Impact Polystyrene (HIPS) and polycarbonate (PC) plastics include commonly used substances such as triphenyl phosphate (TPP), tricresyl phosphate (TCP), resorcinol bis(diphenylphosphate) (RDP), and phosphonic acid (2-((hydroxymethyl) carbamyl)ethyl)- dimethyl ester (Pyrovatex®) (Danish EPA, 1999).
(USEPA, 2005) reports moderate overall hazard for TPP while it is considered to be environmentally hazardous in Germany due to its toxicity to aquatic organisms (BMU, 2000) TCP toxicity apparently differs according to isomer. IPCS recommends the use of purified m- and p- isomers to prevent formation of the highly toxic o-isomer (Danish EPA, 1999). RDP is usually used in combination with TPP.
Pyrovatex® is not well-characterized though the Danish report notes that it is a weak inhibitor of acetyl choline esterase and the microsomal enzyme system and that high concentrations induced chromosome aberrations and reverse mutations. The German report notes that Pyrovatex easily separates formaldehyde and often is used together with ethylene carbamide to help trap released formaldehyde (BMU, 2000).
Both the German and Danish reports comment on the insufficiency of human and environmental toxicity data for RDP. Due to the absence of toxicity information and its possible transmission to humans from use of consumer products, the reports conclude that the data is insufficient to be able to make a recommendation.
Alternatives in coatings and lacquers
Halogen-free rubber cables can contain aluminium trihydroxide and zinc borate as flame retardant alternatives and incorporate the ethylene vinyl acetate polymer as well.Aluminum trihydroxide is the most frequently used flame retardant (Danish EPA, 1999). Due to an endothermic reaction when decomposing and other properties it is highly effective and also suppresses smoke. Its functional disadvantage is that large amounts are required (up to 50%) which can affect the properties of the material. It would be extremely unlikely for its use in consumer products to cause adverse effects. Accumulation of the substance in food chains is not detectable (Danish EPA, 1999). Also the German alternatives report describes the use of aluminum trihydroxide as a flame retardant as “unproblematic.”
Magnesium hydroxide has comparable effects; however the environmental effects still have to be assessed (Danish EPA, 1999).
Zinc borate is often combined with aluminum trihydroxide and used to substitute for antimony trioxide. The German report describes the teratogenicity of boron along with its ability to irritate the eyes, respiratory organs, and skin at high levels. It assumes that its use as a flame retardant will not result in significant additional concentrations for humans.However, it concludes that it would be important to measure the ability for boron to be released in dust before its wide use in consumer products in homes.
Alternatives for polyurethane foams
Ammonium polyphosphate (APP) is an additive flame retardant currently used to flame retard flexible and rigid polyurethane foams, as well as intumescent laminations, moulding resins, sealants and glues. APP formulations account for approximately 4-10% in flexible foam, and 20-45% in rigid foam (USEPA, 2005). APP is commonly used in combination with Aluminium hydroxide and Melamine. It metabolizes into ammonia and phosphate and is not thought to cause acute toxicity in humans (BMU, 2000). However, there are no analyses of long-term toxicity, teratogenicity,mutagenicity, or carcinogenicity. APP breaks down rapidly and does not accumulate in the food chain. Skin irritation is possible due to the formation of phosphoric acids.
Red phosphorus mainly used in polyamids is easily ignited and poorly characterized toxicologically. There is no data available for red phosphorus on ecotoxicity, carcinogenicity, mutagenicity, long-term toxicity, or toxicokinetics and no data exists on concentrations of red phosphorus in indoor or outdoor air (from sewage sludge) as a consequence of incorporating red phosphoThe US EPA rus into products. Eye and mucous membrane irritation can result due to the formation of phosphoric acid. Ecosystem accumulation is thought to be unlikely (BMU, 2000). US government researchers have noted that high levels of toxic phosphine were observed during long-term storage of red phosphorus (Anthony et al., 2006). Information from the Danish EPA (1999) confirms the observations made, and states that “smaller producers of plastic products avoid the use of red phosphorus”.
Melamine and its derivatives (cyanurate, polyphosphate) are currently used in flexible polyurethane foams, intumescent coatings, polyamides and thermoplastic polyurethanes (Special Chemicals, 2004). They are used effectively in Europe in high-density flexible polyurethane foams but require 30 to 40 percent melamine per weight of the polyol. Melamine and its derivates display several toxic effects in animals (USEPA, 1985; Danish EPA, 1999). In a fire, melamine cyanurate will release toxic fumes such as hydrocyanic acid and isocyanate (BMU, 2000).
However the Danish report notes that based on the results of the Swedish flame retardants project (Berglind, 1995) and a study from Stevens et al. (1999) there is no data on emission from products and that melamine appears to have low acute and chronic toxicity and concludes that, “…no adverse effects are envisaged from the level of exposure expected from the use of melamine as a flame retardant.”(Danish EPA, 1999). In contrast, the German report describes the lack of data, presence in environmental samples and moderate organ toxicity of melamine and concludes it is a “problematic substance” (BMU, 2000).
Specific reactive phosphorus polyols as potential alternative for soft polyurethane foam were not identified in the Danish report, though polyglycol esters of methyl phosphonic acid (CAS 676-97-1) have been used for flame retardants in polyurethane foam (e.g. CAS 294675-51-7) (OPCW, 2006). Researchers at the Oak Ridge National Laboratory in the US describe methyl phosphonic acid as one of degradation products of chemical weapons with “significant persistence.” (Munro et al., 1999) Other types of toxicity information are minimal but the substance reacts violently with water (USEPA, 1985). The phosphonic acid family also includes amino-methyl phosphonic acid (AMPA), a degradation product of the herbicide, glyphosate (also known as [carboxymethylamino] methyl phosphonic acid.) (Annex F responses, 2007, IPEN).
The US EPA Design for Environment (DfE) report on flame retardant alternatives (USEPA, 2005) investigated the toxicological properties of 15 chemical substitutes for PentaBDE in low density foam. 12 of these substances have a moderate or high concern for persistence or would produce persistent degradation products. An additional 6 substances have a moderate concern for the ability to bioaccumulate. All substances (including triphenyl phosphate, tribromoneopentyl alcohol and proprietary aryl phosphates) raised moderate overall concern for human health and ranged from low to high hazard for the aquatic environment.
Description of alternatives (technologies)
Three currently-available alternative technologies (barrier technologies, graphite impregnated foam and surface treatment) are shortly discussed in the US EPA DfE report (USEPA 2005). Barrier technologies have the widest immediate commercial applicability and involve layers of materials that provide fire resistance. These include boric acid-treated cotton materials used in mattresses; blends of natural and synthetic fibres used in furniture and mattresses (VISIL, Basofil, Polybenzimidazole, KEVLAR, NOMEX and fibreglass); and high performance synthetic materials used in fire-fighter uniforms and space suits. As regards barrier technologies that use cotton and boric acid potential negative effects of boron (see above; BMU 2000) should be taken into account and it would be important to measure the ability for boron to be released in dust before its wide use in consumer products in homes. More information on barrier fabrics or even eliminate the use of filling material can be found in Lowell, (2005) and in Posner, (2004) (USEPA, 2005). Graphite impregnated foam and surface treatments have limited commercial uses. Graphite impregnated foam (GIF) can be considered an “inherently flame-resistant foam” that is self-extinguishing and highly resistant to combustion. It is a relatively new technology and is largely used in niche markets such as for general aircraft seating. Surface treatments are also used in some applications and niche markets and may be appropriate for some textile and furniture manufacturing. However, surface treatments may not be viable as industry-wide replacements for use in low-density foam (USEPA 2005).
Technical feasibility
All the alternatives described above are technically feasible and have been used in commercial applications (Annex F responses, 2007, IPEN). No specific comments on this topic have been provided by other parties.
Costs, including environmental and health costs
The prices of the alternatives are in general not higher than the BFRs but higher loading is often necessary. This is in particular true with respect to the inorganic compounds aluminum trihydroxide and magnesium hydroxide. Due to the low price of aluminum trihydroxide alternative materials may not be more expensive than BFR containing materials, but magnesium containing materials will usually be significantly more expensive. (Danish EPA, 1999)As concerns alternative technologies, USEPA (2005) describes the boric acid-treated cotton as “… the least expensive flame-retardant barrier materials available.” However, also GIF modified foams can be priced competitively by minimizing the expense associated with flame-retardant fabric.According to IPEN however, there are important points to consider when evaluating the costs of alternatives for any product as specified in Ackermann et al., (2006):• Alternatives with a higher initial purchase cost may actually be more cost effective over the life of the product when durability and other factors are taken into account.• Mass-production of alternatives can significantly lower their costs.• The costs of initiatives to protect health and the environment are frequently overestimated in advance and later decline rapidly after the regulation is implemented.
Efficacy
According to IPEN none of the alternatives usually applied in the earlier known use fields of HBB are prohibited by federal or state laws for the uses described above and in this sense, they meet regulatory requirements meet US federal and state regulatory requirements. However, chemical manufacturers and foam manufacturing trade groups do not consider APP to be an alternative for brominated flame retardants on a large scale. Reasons for this are that APP is typically incorporated as a solid, it has adverse effects on foam properties and processing and it is not considered to be as effective as a fire retardant compared to other alternatives (USEPA, 2002 quoted in USEPA, 2005).Melamine and TDCPP as two of the most commonly used chemicals to flame retard high-density, flexible polyurethane foam either result in scorching of the foam (an aesthetic effect unless severe) or a negative effect on the physical properties of foam if used in low-density flexible foams. Also, many formulations of these chemicals are available only as solids; making them less desirable as drop in substitutes for some brominated flame retardants (USEPA, 2005). (for risk assessment of alternative use see section 2.1.1)
Availability
The alternatives described here are available since many are already in commercial use (Annex F responses, 2007, IPEN). However, the fact that many alternatives are in commercial use does not necessarily mean they are available globally.
Accessibility
The alternatives described here are accessible since many are already in commercial use (Annex F responses, 2007, IPEN). However, the fact that many alternatives are in commercial use does not necessarily mean they are available globally.
For further information, please refer to
- UNEP/POPS/POPRC.5/10/Add.1 – General guidance on considerations related to alternatives and substitutes for listed persistent organic pollutants and candidate chemicals
- Risk profile Ar, Ch, En, Fr, Ru, Sp (PDF)
- Risk management evaluation Ar, Ch, En, Fr, Ru, Sp (PDF)