Brominated flame retardants; Toxicity and ecotoxicity

3. Conclusion

The amount and quality of data on the selected BFR varied considerably.

It is difficult to make a general conclusion on the health effects of BFR. With the exception of vinyl bromide and 2,2-Bis(bromomethyl)propane-1,3-diol (DBNPG), most of the BFR have a high n-octanol-water partition coefficient, which indicates potential accumulation in living organisms.

Both vinyl bromide and DBNPG are suspected to be carcinogenic and 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. 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. PeBDE was detected in adipose tissue, blood and breast milk of human beings. OBDE has been identified in human adipose tissue (up to 8 mg/kg fat) and blood serum (not quantified). DeBDE was detected and quantified in blood serum from all of 3 categories of workers: Hospital cleaners, clerks working full-time at computer screens and personnel at an electronics dismantling plant. The highest blood serum concentrations were in workers at the electronics dismantling plant (median 4.8 mg/kg fat). The serum conc. decreased during summer vacation in the electronics dismantling workers, and results indicated a shorter half-life with increasing degree of bromination. The exposure to PBDE may occur via contaminated food as well as via inhalation of airborne particulate matter.

The substances 2,4,6-tribromophenol, HBCD and tetrabromobisphenol A (TBBPA) were considered to be toxic to aquatic organisms and they may cause long-term adverse effects in the aquatic environment. The substances pentabromotoluene (5BT), OBDE, PeBDE and DeBDE are not readily biodegradable in screening tests. Brominated styrene, vinyl bromide, DBNPG and DeBB were not assessed due to scarcity of data.

Some of the brominated flame retardants included in this investigation are potentially toxic to aquatic organisms and may cause long-term adverse effects in the aquatic environment. The brominated flame retardants, most frequently used (TBBPA, HBCD, PBB and PBDE) are present in sediment, mussels and fish. PBB and PBDE are further present in dolphins, sperm whales and seals. Similar to the polychlorinated biphenyls (PCB) and polychlorinated diphenyl ethers (PCDE) some of the PBB and the PBDE are highly hydrophobic and resistant to degradation processes (de Boer, J., Wester, P. G., Klamer, H. J., Lewis, W. E., and Boon, J. P., 1998). 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 (Hornung, M. W., Zabel, E. W., and Peterson, R. E., 1996). Both PBB and PBDEs are slowly degraded in the environment (Pijnenburg, A. M., Everts, J. W., de Boer, J., and Boon, J. P., 1995). The presence of 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 (de Boer, J., Wester, P. G., Klamer, H. J., Lewis, W. E., and Boon, J. P., 1998).

The scientific basis for a risk evaluation of the BFR, included in this investigation, in the aquatic environment is very small and more knowledge is required to improve this. 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.