Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM Panel) was asked to deliver a scientific opinion on the risks to human health related to the presence of brominated flame retardants (BFRs) other than polybrominated diphenyl ethers (PBDEs), polybrominated biphenyls (PBBs), (hexabromocyclododecanes) HBCDDs, (tetrabromobisphenol A) TBBPA and brominated phenols and their derivatives, including emerging BFRs in food.
The less well known and less studied BFRs, subject of the current opinion, were grouped into two classes, referred to herein as ‘emerging’ and ‘novel’ BFRs. Emerging BFRs are defined as chemicals which are applied as flame retardants and that have been identified in any environmental compartment, in wildlife, in food or in humans. It should be noted that the definition for the emerging BFRs, used in this opinion, does not imply that there is evidence for an increasing trend in the concentration of these BFRs in the environment, in food or in human samples. Novel BFRs are defined as chemicals applied as flame retardants, with confirmed presence in materials and/or goods in concentrations above 0.1 %, but not identified in environmental samples, wildlife, food or humans. In total, information on 27 BFRs, of which 17 were identified as ‘emerging’ and 10 as ‘novel’, was collected by the CONTAM Panel, and it was noted that the available information varied widely for the various individual BFRs.
In general, there is a lack of experimental data on physico-chemical characteristics and stability/reactivity for all the emerging and novel BFRs. This sometimes hampered a clear identification of the compound. There is also a lack of solid information on the current use and production volume of all of the emerging and novel BFRs. Regarding the chemical identification in food or environmental samples it was noted that there are no specific analytical methods for many of the emerging and novel BFRs. However, several of them are chemically similar to established BFRs, indicating that analytical methods applied for these BFRs could be used for their detection.
A call for data on the occurrence of BFRs, including emerging BFRs, in food was issued by EFSA in December 2009. Two countries, Ireland and the UK, submitted data on 3 emerging BFRs, i.e. 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), decabromodiphenyl ethane (DBDPE) and hexabromobenzene (HBB), covering the years 2006-2008. For BTBPE, only 11 % of the analytical results were reported as >LOQ. The maximum UB concentration was observed in the food category “Animal and vegetable fats and oils” (0.8 ng/g w.w.), followed by “Milk and dairy products” (0.37 ng/g w.w.) and “Fish and other seafood” (0.34 ng/g w.w.). For DBDPE and HBB, all reported analytical values were <LOQ. The CONTAM Panel concluded that based on these data a meaningful exposure assessment was not possible.
There was a lack of published data on occurrence of the emerging and novel BFRs in food, and where there were data, these were far from sufficient to allow for a meaningful exposure assessment. Also information on the toxicity of the various BFRs considered in this opinion was in general scarce. For most of the 12 BFRs (six emerging and six novel BFRs) no toxicity data could be identified at all. For the remaining compounds the available information was not sufficient to perform a hazard characterisation. Exceptions were the emerging BFR tris(2,3-dibromopropyl) phosphate (TDBPP) and the novel BFR 2,2-Bis(bromomethyl)-1,3-propanediol (DBNPG) for which more extensive toxicity data are available. For both compounds, there is convincing evidence for genotoxicity and carcinogenicity in experimental models.
Due to the very limited available information, on occurrence, exposure and with respect to their toxicological hazards, the CONTAM Panel concluded that it was not possible to perform a risk characterisation for any of the emerging or novel BFRs considered in this opinion. Therefore, the Panel made an attempt to identify those emerging or novel BFRs that could be a potential health concern and should be considered first for future investigations. For this purpose the Panel followed a two-step approach. Firstly, it evaluated the available experimental data on occurrence in food, behaviour in the environment and toxicity. Secondly, a modelling exercise was performed focussing on the potential of the emerging and novel BFRs for persistence in the environment and for their possible bioaccumulation potential.
From the toxicological information it is evident that two BFRs, tris(2,3-dibromopropyl) phosphate (TDBPP) and dibromoneopentyl glycol (DBNPG), are genotoxic and carcinogenic, and therefore could be a potential health concern. However, due to their chemical reactivity and lack of environmental persistence, their occurrence in food is not anticipated. The limited data that are available support this assumption. Also in the modelling exercise neither of these two compounds were predicted to have a high overall persistence or the potential for bioaccumulation. Nonetheless, their evident genotoxicity and carcinogenicity warrants further surveillance of their possible occurrence in the environment and food.
Based on the limited experimental data on the environmental behaviour available, 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) and hexabromobenzene (HBB) were identified as compounds that could raise a concern due to their reported bioaccumulation factors (BAFs). The log BAFs, ranging from about 3.3 to 6.1 for BTBPE, and from 3.3 to 5.5 for HBB, for several aquatic species, indicate a very high bioaccumulation of these compounds.
For the modelling exercise, the CONTAM Panel selected two environmental characteristics, overall persistence (Pov) and the potential for bioaccumulation, as the ones most relevant to provide insight in the possibility that emerging or novel BFRs might accumulate in the food chain, and thus might appear in food intended for human consumption. The modelling exercise predicted the following BFRs to have both a high overall persistence (Pov >500 days) and a high potential for bioaccumulation: 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE), 5,6-dibromo-1,10,11,12,13,13-hexachloro-11-tricyclo[8.2.1.02,9]tridecene (DBHCTD), N,N'-ethylenebis(tetrabromophthalimide) (EBTEBPI), hexabromobenzene (HBB), hexabromocyclodecane (HBCYD), 1,2,3,4,7,7-hexachloro-5-(2,3,4,5-tetrabromophenyl)-bicyclo[2.2.1]hept-2-ene (HCTBPH), PBT, pentabromobenzyl acrylate (PBB-Acr), pentabromoethylbenzene (PBEB) and 1,2,4,5-tetrabromo-3,6-dimethylbenzene (TBX). These BFRs are thus most relevant to be addressed in further investigations. All of these compounds, with the exception of EBTEBPI and HBCYD, have been identified in the environment or in food, and hence are listed as emerging BFRs.
The CONTAM Panel noted, however, that the results of the modelling exercise should be interpreted with some caution. The modelled environmental characteristics are solely based on the chemical properties of the compounds, and the bioaccumulation screening tool that was used does not yet take biotransformation into account. On the other hand, in a model validation exercise, good agreement was found between predicted and measured concentrations of polychlorinated biphenyls for cows’ milk, beef, herring, cod, and human tissue in southern Sweden. Also several of the compounds predicted to have a high persistence have also been reported to have this property.
Assessing the outcome of the modelling exercise, a number of comments can be made. Tris(tribromoneopentyl) phosphate (TTBNPP) was predicted as likely to have a high persistence, but this compound is likely to rapidly undergo metabolic breakdown in vivo, and thus not be bioaccumulative. When it comes to bioaccumulation, the modelling exercise indicated that 11 of the BFRs with a predicted high persistence would also have a high potential for bioaccumulation. Among those with a predicted high persistence that were not indicated as bioaccumulative it should be noted that decabromodiphenyl ethane (DBDPE) and octabromotrimethylphenyl indane (OBTMPI) are likely to be bioaccumulative, because their molecular mass is not high enough to prevent bioavailability. It can also be speculated that tetradecabromo-1,4-diphenoxybenzene (4’-PeBPO-BDE208), with a molecular weight of 1 366 Dalton, is poorly bioavailable, and therefore not potentially bioaccumulative.
Although the modelling, as used in this opinion to estimate the environmental characteristics of emerging and novel BFRs, could be further improved, particularly related to inclusion of biotransformation in the bioaccumulation screening tool, the CONTAM Panel concluded that the modelling presents overall reasonable results, and that the BFRs predicted as being both persistent and bioaccumulative should be subjected to further in-depth studies.
The CONTAM Panel made a number of specific recommendations to address the substantial data gaps identified.