Ecological State of the Science Report on Decabromodiphenyl Ether (decaBDE): chapter 5

5. Key Uncertainties and Data Gaps

The data for bioaccumulation, biomagnification and trophic magnification of decaBDE are limited, especially for top predators in natural settings. Additional ratio-based assessments of decaBDE in top predators in natural settings, particularly in terrestrial systems, would provide better understanding of the bioaccumulation and biomagnification of decaBDE.

Overall, the relative contribution of environmental transformation of decaBDE to the total loadings of lower brominated PBDEs (i.e., having nine or fewer bromine atoms) in the environment is not known. Studies which trace and/or “fingerprint” the source of lower brominated PBDEs in the environment would help clarify the significance of in vivo and environmental debromination of decaBDE, compared to that resulting from the use of the Penta- and octaBDE formulations.

It may be beneficial to have BAF or BMF determinations for decaBDE on the total burden of parent decaBDE and the metabolites that result from accumulation and transformation of the parent chemical (e.g., lower BDEs and PBDFs). In most of the studies conducted to date, this has been difficult to accomplish because (i) the lesser debrominated products were also present in the exposure medium (i.e., food or water) and their presence in tissue could thus have resulted from both accumulation and bioformation, or (ii) full identification and quantification of most metabolites has not been conducted.

Model-estimated BCFs, BAFs and BMFs presented in this report for decaBDE and known potential transformation products vary. These relied heavily on logK_ow logK_oa E_D and k_M values, which would benefit from refinement in order to improve the precision of the model predictions.

BAFs, BMFs and other indicators of bioaccumulation or biomagnification have not been measured for some of the known metabolites and transformation products of decaBDE, especially their hydroxylated and methoxyhydroxylated forms. Further study of the behaviour of these products would be useful.