Table of Contents
- Properties of Polybrominated Biphenyls
- Polybrominated Biphenyls in Electronics
- Toxicity of Polybrominated Biphenyls
- RoHS: Restriction of Hazardous Substances
- Alternatives to Polybrominated Biphenyls
- PBB-Limiting Legislation
Polybrominated Biphenyls (PBBs) are a class of chemicals used in the manufacturing of many electronic devices. The use of PBBs is restricted by the European Union’s RoHS directive due to their high toxicity.
Properties of Polybrominated Biphenyls
PBBs, sometimes referred to as brominated biphenyls or polybromobiphenyls, are a manmade class of chemicals not found in nature.
There are three types of commercial mixtures of PBB: hexabromobiphenyl (hexaBB), octabromobiphenyl (octaBB) and decabromobiphenyl (decaBB). While all three mixtures have slightly different physical and chemical properties, all three are considered PBBs due to their chemical structure.
PBBs are very stable substances that are resistant to heat, acids, bases, and oxidation. PBBs are soluble in fat but are insoluble in water. PBBs are also quite effective as a flame retardant. These properties made PBBs popular in a variety of consumer products, including electronics.
Polybrominated Biphenyls in Electronics
Most manufacturers of electronic and other consumer products no longer use polybrominated biphenyls due to concerns about the chemical’s toxicity. However, prior to PBBs’ reduction in use, PBBs were primarily used as a flame retardant.
One of the main applications for PBBs in electronics is the infusion of PBBs into circuit boards. Because circuit boards work to pass electric currents, flame retardants are necessary to reduce the risk of electricity-caused fires.
PBBs are also added as flame retardants to plastic used in electronics, such as plastic casings around televisions or computers. PBBs are added to these plastic shells late in the manufacturing process without bonding to the plastic, making it easier for PBBs to leach off the plastic later in a product’s life cycle.
Toxicity of Polybrominated Biphenyls
It is currently unclear whether the average consumer experiences exposure to PBBs in electronics, as there is very little data on how these chemicals leach out of electronics. However, it is abundantly clear that workers who produce PBBs or who work in waste-processing factories that deal with products coated in PBBs experience unhealthy levels of exposure to PBBs.
Exposure to high levels of PBBs has been shown to cause hypothyroidism, disruption of the endocrine system, immune system abnormalities, and skin problems. While research is ongoing, multiple governmental agencies have stated that PBB is a likely carcinogen.
The most famous case of health impacts due to PBB exposure is an incident in Michigan in 1973, in which cattle feed supplements were accidentally switched with PBB fire retardants. As a result, PBBs contaminated hundreds of farms and entered the food system, including milk, other dairy products, eggs, and beef.
Research on the affected Michigan population found increased levels of PBBs in people’s blood, and many people reported negative health impacts (although it is unclear whether those impacts were caused by PBB exposure). Although the health impacts of PBBs have been studied extensively in mice, most research on the human health impacts of PBBs comes from this incident.
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 Biphenyls
RoHS works to reduce the risk of PBB exposure by restricting its use in electronic devices.
As a result of RoHS legislation, many electronics manufacturers no longer use PBBs. In fact, some U.S. companies stopped using PBBs in the 1970s after the incident in Michigan, and many major electronics manufacturers such as Apple, Dell and Motorola voluntarily stopped using PBBs in the early-mid 2010s.
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.
RoHS is the main legislation that limits polybrominated biphenyls in electronics. However, the production and use of PBBs in the United States has decreased significantly since 1976.
Many U.S. states have created programs or rules to regulate the cleanup of historical PBBs in water and soil. For example, states including California, Indiana, Michigan, Mississippi, Nebraska, New York, Texas and West Virginia have adopted screening values for PBB in drinking water, groundwater, and soil. Action must be taken when PBBs are found in water or soil above a certain level established by the state.
Additionally, RoHS rules that limit PBBs have been adopted by other countries including China and the UAE.