Polybrominated Diphenyl Ethers (PBDE): Restriction of Hazardous Substances in Electronics

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Polybrominated Diphenyl Ethers (PBDEs) are a class of chemicals used in the manufacturing of many electronic devices. The use of PBDEs is restricted by the European Union’s RoHS directive due to their high toxicity.

Properties of Polybrominated Diphenyl Ethers

PBDEs are a manmade class of chemicals not found in nature. PDBEs are an organobromine compound, a compound that contains carbon bonded to the element bromine.

Chemical structure of PBDE
Source: UNEP

There are three types of commercial mixtures of PBDEs: pentabromodiphenyl ether (pentaBDE), octabromodiphenyl ether (octaBDE) and decabromodiphenyl ether (decaBDE). While all three mixtures have slightly different physical and chemical properties, all three are considered PBDEs due to their chemical structure. 

The uses of each commercial mixtures differ. For example, penta-BDEs are not commonly used in electronics. DecaBDE is the most commonly used PBDE worldwide. While decaBDE used to be exempt from RoHS regulations, the exemption expired in June 2008. 

When exposed to high temperatures, PBDEs release bromine radicals (a chemically reactive atom), which reduces the rate of combustion and makes it difficult for fire to occur or spread. This property makes PBDEs a popular flame retardant in a variety of consumer products, including electronics, furniture foam, wire insulation, and household textiles like curtains or rugs.

Polybrominated Diphenyl Ethers in Electronics

Most manufacturers of electronic and other consumer products no longer use polybrominated diphenyl ethers due to concerns about the chemical’s toxicity. However, prior to PBDEs’ reduction in use, the chemicals were primarily used as a flame retardant.

One of the main applications for PBDEs in electronics is in printed circuit boards and plastic casings for electronics.

pbde rohs - polybrominated diphenyl ether

The most common PBDE, deca-BDE, is used in several different types of plastic, such as high impact polystyrene, polyethylene and polypropylene. These materials are used to produce switches, plugs and connectors in electronics, as well as cables and wires.

PBDEs are also added as flame retardants to plastic used in electronics, such as plastic casings around televisions or computers. 

Toxicity of Polybrominated Diphenyl Ethers

While the average consumer may not experience high levels of PBDE exposure, workers who produce PBDEs or who work in waste-processing factories that deal with products coated in PBDEs experience unhealthy levels of exposure to these toxic chemicals.

Ingestion or inhalation of PBDEs can cause negative health effects including disruption of the endocrine system and, in pregnant women, disruption of  prenatal development. Other studies suggest that PBDEs can cause neurotoxicity, diabetes, cancer, and can harm the thyroid, immune system and liver. Research is still ongoing to confirm the health impacts of PBDEs.

RoHS: Restriction of Hazardous Substances

RoHS stands for Restriction of Hazardous Substances. The RoHS directive, issued in the European Union, restricts the use of several hazardous materials in electronic and electrical equipment (EEE). All EEE products sold in the EU must comply with RoHS.

RoHS restricts the use of ten hazardous substances in electronics, including polybrominated biphenyls. Electronic devices may only contain these substances in amounts lower than 1000 ppm. The allowable amount for cadmium is 100 ppm.

The materials include:

  • Cadmium (Cd)
  • Mercury (Hg)
  • Lead (Pb)
  • Hexavalent Chromium (Cr VI)
  • Polybrominated Biphenyls (PBB)
  • Polybrominated Diphenyl Ethers (PBDE)
  • Bis(2-Ethylhexyl) phthalate (DEHP)
  • Benzyl butyl phthalate (BBP)
  • Dibutyl phthalate (DBP)
  • Diisobutyl phthalate (DIBP)

Any manufacturer, importer, or distributor of electronic and electrical equipment (EEE) sold on the EU market must be compliant with RoHS. 

EEE regulated under RoHS includes a wide variety of electronic products separated into eleven categories, ranging from large household appliances to medical devices. The eleventh category is all-encompassing, as it includes any EEE not covered in the previous ten categories. 

Read more about how to ensure compliance with RoHS: What is ‘RoHS Compliant’?

Alternatives to Polybrominated Diphenyl Ethers

RoHS works to reduce the risk of PBDE exposure by restricting its use in electronic devices.

As a result of increasing concern about the toxicity of PBDEs, many electronics manufacturers no longer use them. The EU’s RoHS directive reduced the global use of PBDE with its passage in 2002. In 2004, octaBDE and pentaBDE stopped being produced in the U.S. after the only U.S. manufacturer voluntarily stopped production. In 2009, the main U.S. importer of decaBDE, as well as the two main producers, announced that they would stop using decaBDE by 2013. 

RoHS pushes industry to innovate substitutions for restricted hazardous materials. Some researchers argue that flame retardants are simply not worth the health risks, and should therefore not be used at all. However, many manufacturers and scientists are researching and using safer alternative flame retardants. One such alternative is simply using stronger, more naturally flame-resistant metals like silver or titanium, although this would increase the cost of electronic production.

PBDE-Limiting Legislation

EU RoHS is the main legislation that limits polybrominated biphenyls in electronics, but similar RoHS rules that limit PBDEs have been adopted by other countries including China and the UAE.

Legislation passed in other countries bans the use of PBDEs in all products, not just electronics. Several U.S. states have outlawed the use of PBDEs. In California’s bill AB 302, which went into effect January 2008, the use of penta- and octa-BDEs in all products was banned. The state of Washington passed a bill banning all PBDEs in April 2007, and in May 2007, the state of Maine passed a bill that banned the use of decaPBDE.

On an international scale, several types of PBDEs are restricted under the Stockholm Convention on Persistent Organic Pollutants treaty.

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