Chlorine (Cl) and bromine (Br) are elements classified as halogens. Compounds that contain organic bromine and chlorine tend to be particularly likely to bioaccumulate, be persistent and/or toxic – or to degrade in the environment into new brominated or chlorinated organic compounds with these characteristics. As they accumulate over time, these organo-halogen compounds can become widespread pollutants in air, water, soil, and sediment, where they are increasingly ingested by humans and animals. When incinerating products with chlorine or bromine dioxins are formed.*

Bromine- and chlorine-based compounds are used ubiquitously in the production of today’s modern electronic products as flame retardants, solvents, dyes, adhesives, and plastic resins. The largest uses of compounds containing bromine and chlorine are brominated flame retardants (BFRs), added to plastics to inhibit fire, and polyvinyl chloride (PVC) plastics, an inherently flame-resistant plastic resin.

It is estimated that hundreds of different chlorinated and brominated flame retardants are currently on the market. To satisfy fire safety standards, very high concentrations – generally 5% to 30% – of BFRs must be used in plastics to effectively impede fires. The most common brominated flame retardant used in components for electronic products, such as printed circuit boards (PCBs), is tetrabromobisphenol A (TBBPA). Prior to the implementation of the European Union’s Restriction of Hazardous Substances (RoHS) directive, polybromodiphenyl ethers (PBDEs), and polybrominated biphenyls (PBBs) were sometimes used to flame retard electronics.

The predominant use of chlorine in electronics has been in PVC plastics. Most internal and external cables use PVC to insulate copper wires. In order to make PVC soft and flexible additives such as phtalates are used. Many phtalates are or may be harmful to reproduction.

Smaller concentrations of bromine and chlorine are used in a wide variety of applications other than flame retardants and PVC. Components are defined as “halogen-free” when they contain no more than 900 ppm bromine, 900 ppm chlorine, and 1,500 ppm of bromine and chlorine combined. While these products are not technically “free” of bromine or chlorine, only a very small concentration is permitted to account for impurities and the limitations of testing, and these are far below concentrations where intentional addition would impart any useful properties on the material.

* Read more about dioxins