Brominated flame retardants; Toxicity and ecotoxicity

English Summary

A toxicological and ecotoxicological data screening was made on BFR used in Denmark. The data screening in relevant sources was performed in ultimo 1998. Although a thorough data search was made this is not a garantie that all relevant information was identified and retrieved, e.g. relevant unpublished data may exist, and information may have been published since 1998.

Data on 12 out of 19 initially selected BFR were retrieved from generally well recognised handbooks and reviews as well as from documents/publications and data found via well known on-line and off-line databases. The amount and quality of retrieved data was variable.

With the exception of vinyl bromide and 2,2-Bis(bromomethyl)propan-1,3-diol (DBNPG), most of the BFR have a high n-octanol-water partition coefficient, which indicates potential accumulation in living organisms. The high molecular weight of some of these BFR may preclude their bioaccumulation in living organisms as indicated by the low bioconcentration factors (BCF) determined for decabromobiphenyl (DeBB) and octabromodiphenyl ether (OBDE). However, a very high BCF of 18,100 was measured for hexabromocyclododecane, which has a molecular weight of 642. This indicates that the bioconcentration of high-molecular-weight substances is not fully understood and, hence, the data on these chemicals should be carefully evaluated.

Both vinyl bromide and DBNPG are suspected to be carcinogenic. Other data indicate that commercial products of decabromobiphenyl (DeBB) and brominated styrene homopolymer may also have a carcinogenic potential. Two of the compounds, 2,4,6-tribromophenol and octabromodiphenylether (OBDE), represent a possible risk of harm to the human foetus. OBDE has an effect on the liver, which is considered the primary target organ. Hexabromocyclododecane (HBCD) and pentabromodiphenylether (PeBDE) have an effect on the liver and thyroid gland. It is not known if it is a specific endocrine effect on the thyroid gland, and if the effect observed in rodents is relevant for human beings. Future research may come closer to the answer. Of all the BFR screened, only the PBDE has been found in humans. Congeners of the commercial PeBDE product were detected in adipose tissue, blood and breast milk. An OBDE congener has been identified in human adipose tissue and blood serum. DeBDE was detected and quantified in blood serum from 3 categories of workers. The general lack of data of the occurrence of BFR in human tissues and liquids may be because of missing investigations and/or inadequate analyses.

The substances HBCD, 2,4,6-tribromophenol, and tetrabromobisphenol A (TBBPA) are toxic to aquatic organisms and may cause long-term adverse effects in the aquatic environment. Pentabromotoluene, OBDE, PeBDE, and DeBDE are considered not readily biodegradable. Brominated styrene, vinyl bromide, DBNPG and DeBB were not assessed due to scarcity of data.

Some of the frequently used brominated flame retardants, TBBPA, HBCD and PBDEs, are present in sediment, mussels and fish. PBDEs have been found in whales and seals. Some of the PBB and the PBDE are highly hydrophobic and resistant to degradation processes. It is therefore possible that these chemicals may accumulate in aquatic sediments or bioconcentrate in living organisms. Signs of toxicity of individual PBB and PBDE to early life stages in rainbow trout were reported. The presence of some of the PBBs and PBDEs in mussels, fish, seals and dolphins as well as in sperm whales, which normally stay and feed in deep ocean water, combined with the ongoing industrial production of these compounds indicate that an environmental problem is rising.

Because of their environmental properties the continued release of HBCD, TBBPA, 2,4,6-tribromophenol, 5BT, OBDE, PeBDE and DeBDE may represent an increasing risk to aquatic organisms.