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Flame retardants & PVC in electronics

Brominated flame retardants (BFRs) and polyvinyl chloride (PVC) are both in a category of chemicals called halogenated compounds.  Because this group of chemicals shares many traits and hazards, this section of our website looks at the whole category of chemicals.

Halogenated compounds

Halogenated organic compounds are nonmetallic chemicals that contain a halogen element, such as fluorine, chlorine, bromine, or iodine, bonded to carbon. Organo-halogens have been a focus of international concern for many decades because they are associated with a variety of negative environmental and human health impacts. Some well known (and very hazardous) examples of organo-halogens include PCBs, DDT, and CFCs (chlorofluorocarbon)— all of which are now globally banned by the United Nation’s Persistent Organic Pollutants (POPs) treaty.

Which halogenated compounds are used in electronics?

Brominated flame retardants (BFRs) have been used widely in consumer electronics, primarily in the plastics, like the casings, but also in circuit boards. There are many but widely used BFRs including:

  • PBBs – Polybrominated biphenyls – currently restricted by the European Union’s Restriction on Hazardous Substances Directive (RoHS).
  • PBDEs – Polybrominated biphenyl ethers – currently restricted by the European Union’s Restriction on Hazardous Substances Directive (RoHS).
  • Deca-BDE – Deca-bromodiphenyl ether – on April 1st, 2008 the European Court ruled that Deca-BDE must be banned in all electronic products sold in the EU.
  • TBBPA  -tetrabromobisphenol A (TBBPA), and
  • HBCD – hexabromocyclododecane  (HBCD)

Chlorine based compounds

  • Polyvinyl Chloride (PVC) is used largely as coatings for computer cables and wires.
  • TCE – trichloroethylene – is an industrial solvent, used widely by the semiconductor industry for many years.  Classified by the EPA as a human carcinogen, TCE was released into the groundwater in Silicon Valley in California.
  • TCA- Trichloroethane – another solvent used to clean chips in the semiconductor industry.
  • CFRs – Chlorinated flame retardants

Halogenated compounds’ hazards

Historically, the chemical stability of halogenated organic compounds made them appealing to electronics manufacturers. While there are many applications of bromine and chlorine in electronic products, bromine’s main use is in the brominated flame retardants (BFRs) added to protect plastic components that can be exposed to high temperatures. Chlorine is mainly used in polyvinyl chloride (PVC) applications, such as coatings for computer cables and wires, but it is also used in some chlorinated flame retardants (CFRs). However, the same characteristics that make BFRs, CFRs, PVC, and other halogenated organics appealing to electronics manufacturers also create problems in the environment.

Compounds that contain bromine and chlorine also tend to be particularly likely to bioaccumulate, be persistent and/or toxic[i]  —or to degrade in the environment into new halogenated organic molecules with these troubling characteristics.  As they accumulate over time, they can become widespread pollutants in air, water, soil, and sediment,  where they are increasingly ingested by humans and animals. Moreover, as the climate changes over the next century, scientists believe that warming temperatures will increase the toxicity of many persistent organic pollutants in the environment[ii].

Similarities to Dioxin

Of particular concern is the ability of halogenated organics to act as pre-cursors for generating dioxin, a known human carcinogen[iii] that is toxic in very low amounts. Linda Birnbaum, director of the National Institute of Environmental Health Sciences and a leading science expert on BFRs and dioxins, led the U.S. EPA’s 1994 dioxin assessment process, which concluded that there was no safe level of dioxin exposure for humans [iv].

Exposing halogenated organics such as the BFRs, CFRs, and PVC in electronics to high heat by incineration or the burning practices commonly used in informal recycling in the developing world have been demonstrated to generate dioxins.[v] Airborne dioxins travel the globe, and once they land, the dioxins can enter both terrestrial and aquatic food chains. The plastic casings from e-waste that unscrupulous recyclers sent to China is likely to be burned, generating dioxin, that is later carried by the wind currents back to the U.S.

Halogenated chemicals are problematic at many phases of the lifecycle

Scientists believe that substantial quantities of the halogenated compounds used in electronics products can be released into the environment at every stage of their lifecycles. This includes chemical manufacture, incorporation into products, and use of the products, as well as when they are disposed of or recycled[vi]. Organo-halogens can also produce toxic byproducts throughout their lifecycles, particularly when they are initially synthesized by chemical manufacturers. For example, synthesizing PVC involves the use of vinyl chloride, a known carcinogen[vii].

Electronics can contain relatively high concentrations of some halogenated compounds, such as BFRs.  These flame retardants are added to high impact plastics used in television and computer monitors at concentrations of 5%-30% by weight of those plastics.

Years of research document that many of the halogenated compounds used in electronics, especially “additive” flame retardants that are not chemically bound into the plastics, can slowly migrate out of the products during their lifetime. These halogenated compounds have been detected in the dust in home environments[viii], where children[ix] and pets[x] are particularly likely to be exposed to them.

Additionally, if the electronics are not recycled properly at the end of their useful lives, they can generate toxic dioxins in the environment. Currently, somewhere between 50-80% of the electronic waste (e-waste) that is collected by recyclers in the U.S. ends up in developing countries, including China, India, Pakistan, Vietnam and the Philippines, according to the United Nations Environment Programme[xi] and the Basel Action Network[xii]. Once there, the high-value metals are removed to be reclaimed, but most of the halogen-containing plastics are burned. This creates major problems in places where such informal recycling takes place.  In 2007, the highest levels of chlorinated dioxins and furans ever reported in the atmosphere were found in the air over Guiyu, China, an area infamous for its electronics recycling activities[xiii]. In Guiyu, the World Health Organization estimates that the daily intake of dioxins and furans by breast-fed infants exceeds guidelines by 11 to 25 times[xiv]. But is also a worldwide concern due to POPs’ ability to travel throughout the globe. In many cases polluted air travels towards the poles, but it is sometimes carried on the trade winds from Asia to North America[xv]. Air can travel from China to California in about a week.

Halogenated dioxins and furans

New research indicates that when significant quantities of bromine and chlorine are present in materials being combusted under certain conditions, such as via the informal practices used in Guiyu, China, and elsewhere in the developing world, they result in mixed halogenated dioxins and furans[xvi]. Although relatively few scientists have looked for these mixed halogenated dioxins and furans, the compounds have been reported in the Japanese atmosphere,[xvii] as well as in Japanese rain, soil, and river sediments,[xviii] and marine sediments in Hong Kong and Korea[xix]. In an unpublished study presented at the 2008 Dioxin meeting, scientists reported that the concentrations of mixed halogenated dioxins and furans in the soil in Guiyu exceeded the total amounts of both chlorinated and brominated dioxins and furans, taken together[xx].

Some tests suggest that some of the thousands of different compounds of mixed halogenated dioxins and furans that could be generated when electronics are burned may be even more toxic[xxi] than 2,3,7,8 TCDD, the most toxic chlorinated dioxin known[xxii]. Also of concern is the fact that more than a thousand different mixed halogenated dioxins and furans can be formed that have the halogenated atoms in the same positions known to be involved with the high degree of binding to the aryl hydrocarbon (AH) receptor that is associated with 2,3,7,8 TCDD’s toxicity[xxiii].

 



[i] Thornton, J. Pandora’s Poison. Cambridge, Mass: MIT Press, 2000

[ii]  Noyes, P. B., et al. The Toxicology of Climate Change: Environmental Contaminants in a Warming World. Environment International (2009): DOI 10.1016/j.envint. 2009.02.006

[iv] U.S. Environmental Protection Agency, HEALTH ASSESSMENT DOCUMENT FOR 2,3,7,8-TETRACHLORODIBENZO-p-DIOXIN (TCDD) AND RELATED COMPOUNDS. VOL. III OF III. [EPA/600/BP-92/001c] (Cincinnati, Ohio: U.S. Environmental Protection Agency, August, 1994.)

[v] Costner, P. 1998. Correlation of chlorine input and PCDD/PCDF at a full-scale hazardous waste incinerator. Organohalogen Compounds vol 36: 147-152

[vi] Santillo, D.; Johnston, P. (2003): Playing with fire: the global threat presented by brominated flame retardants justifies urgent substitution. Environment International 29, 725-734.

[viii] Blake, Ann; McPherson, Alexandra; Thorpe, Beverly.  2004. Brominted Flame Retardants in Dust on Computers: The Case for Safer Chemicals and Better Computer Design, Clean Production Action and the Electronic Take Back Coalition.

[ix] Heather M. Stapleton, Joseph G. Allen et al (2008): Alternate and New Brominated Flame Retardants Detected in U.S. House Dust. Environ. Sci. Technol., 2008, 42 (18), pp 6910–6916 http://pubs.acs.org/doi/full/10.1021/es801070p

[xi] UNEP. Environment Alert Bulletin 5, January 2005. http:/www.grid.unep.ch/product/publication/download/ew_ewaste.en.pdf

[xii] Basel Action Network. Exporting Harm—The High-Tech Trashing of Asia (http://www.ban.org).

[xiii] Huiru Li, Liping Yu, Guoying Sheng,Jiamo Fu,and Ping’an Peng (2007):Severe PCDD/F and PBDD/F Pollution in Air around an Electronic Waste Dismantling Area in China. Environ. Sci. Technol., 2007, 41 (16), pp 5641–5646. http://pubs.acs.org/doi/abs/10.1021/es0702925

[xiv] Janet, K, Y, Chan; Xing, G, H; Xu, Y; Liang, Y; Chen, L, X; Wu, S, C; Wong, Chirs, K, C; Leung, Cliement, K, M and Wong, M, H, (2007): Body Loadings and Health Risk Assessment of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans at an Intensive Electronic Waste Recycling Site in China, Environmental Science & Technology / Vol. 41, NO, 22, 2007

[xv] Yienger, J.J. (2000): The episodic nature of air pollution transport from Asia to North America. Journal of Geophysical Research, Volume 105, Issue D22, p. 26931-26946.

[xvi] Söderström, G. and Marklund, S. (2002). PBCDD and PBCDF from incineration of waste-containing brominated flame retardants. Environmental Science & Technology 36 (9): 1959-1964

[xvii] Hayakawa, K., Takatsuki, H., Watanabe, I., Sakai, S. (2002) Polybrominated diphenyl ethers (PBDEs), polybrominated dioxins/furans (PBDDs/DFs) and monobromo-polychlorinated dioxins/furans (MoBPXDDs/DFs) in atmosphere and bulk deposition in Kyoto, Japan. Organohalogen Compounds 59: 299– 302

[xviii] Ohta, S., Nakao, T., Nishimura, H., Okumura, T., Aozasa, O., Miyata, H. (2002) Contamination levels of PBDEs, TBBPA, PCDDs/DFs, PBDDs/DFs and PXDDs/DFs in the environment of Japan. Organohalogen Compounds 57: 57–60

[xix] Terauchi, H., Takahashi, S., Lam, P.K.S., Min, B-Y., Tanabe, S. (2009) Polybrominated, polychlorinated and monobromo-polychlorinated dibenzo-p-dioxins/dibenzofurans and dioxin-like polychlorinated biphenyls in marine surface sediments from Hong Kong and Korea. Environmental Pollution 157: 724–730

[xx] Organohalogen Compounds, Volume 70 (2008), page 000813-816. http://www.ban.org/Library/Scientific/ewaste_contaminates_chinese_city_with_dioxins.pdf

[xxi] Samara, F.; Gullett, B. K.; Harrison, R.O.; Chu, A.; Clark, G.C. (2009) Determination of relative assay response factors for Toxic Chlorinated and Brominated dioxins/furans using an enzyme immunoassay (EIA) and a chemically activated luciferace cell bioassay. Environment International, vol 35, 588-593.

[xxii] http://www.who.int/mediacentre/factsheets/fs225/en/index.html

[xxiii] Korach, K. Reproductive and Developmental Toxicology. CRC Press, Boca Raton, FL: 1998.