Hexabromobiphenyl (HBB)

Hexabromobiphenyl belongs to a wider group of polybrominated biphenyls (PBBs). According to the available data, production and use of hexabromobiphenyl has ceased in most, if not all, countries. However, it is possible that hexabromobiphenyl is still being produced in some countries.

FireMaster, a PBB product, was used as a fire retardant in three main commercial products:

  • acrylonitrile-butadienestyrene (ABS) thermoplastics for constructing machine housings such as motor housing and radio and TV parts
  • as a fire retardant in coatings and lacquers, and
  • in polyurethane foam for auto upholstery.

Persistence

PBBs have been reported to be persistent under field conditions. Soil samples from a former

PBB manufacturing site, analyzed several years after accidental release, still contained PBBs. However, the congener composition was different, indicating partial degradation of the PBB residue in the soil samples. According to the EHC Review, follow-up surveys over a three year period following the termination of PBB production showed no significant decline in PBB levels in sediments from a river. In laboratory investigations, mixtures of PBBs appear to be fairly resistant to microbial degradation.

Bioaccumulation

PBBs are lipophilic and able to bioconcentrate in the food chain. This is also supported by monitoring results from wildlife studies. For example, fathead minnows (Pimephales promelas) caged in a river, where water levels of PBB remained consistently at less than 0.1 μg/litre, concentrated these contaminants in their bodies more than 10 000 fold in two weeks of exposure.

Toxicity

The International Agency for Research on Cancer has classified hexabromobiphenyl as a possible human carcinogen (IARC group 2B). The PBBs are endocrine disrupting chemicals, and effects are seen on reproductive capacity in rats, mink and monkeys. There is epidemiological evidence of hypothyroidism in workers exposed to polybrominated biphenyls and of increased incidence of breast cancer in exposed women.

The US ATSDR (2004), considers the current human exposure to PBBs to be very low, because PBBs are no longer produced or used. Thus, the general population exposure to PBBs will only be from historical releases.

More information

 

References:

Adapted from Proposal for listing HBB in the Stockholm Convention (pdf), the Stockholm Convention Risk Profile (pdf), and the US Agency for Toxic Substances and Disease Registry Toxicological Profile (pdf)

Hatfield Consultants The World Bank funded by the Canadian POPs Trust Fund through the      
Canadian International Development Agency
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