Problems faced when evaluating the bioaccumulation potential of substances under REACH

Abstract

The identification and regulation of substances that combine persistence, bioaccumulation potential, and toxicity ("PBT" substances) is one central aspect of the European chemical legislation REACH (Registration, Evaluation, Authorisation, and Restriction of Chemicals), because these substances may elicit adverse long-term effects after release to the environment. The determination of a substance that has persistence, bioaccumulation potential, and toxicity is based on a set of distinct cutoff criteria identified in Annex XIII of the REACH regulation. Regarding the bioaccumulation potential, the evaluation is focused on the substance's bioconcentration factor as single decisive criterion. In addition, the REACH guidelines provide a selection of standardized test procedures for measuring bioconcentration factor and guidance in appraising test results. However, alternative test results like bioaccumulation factors and biomagnification as well as additional indications for a bioaccumulation potential such as trophic magnification are only allowed for supporting evidence. The currently used test systems with aquatic exposure have been demonstrated to generate reliable results for the majority of neutral, lipophilic organic substances, which facilitate clear decision-making by means of the crucial bioconcentration factor cutoff criteria of Annex XIII. However, certain substance groups such as highly hydrophobic organic substances and amphiphilic and nonlipophilic compounds are difficult to evaluate with common test strategies due to inappropriate test systems or accumulation mechanisms not based on lipophilicity. Recent scientific progress has already been made to establish alternative test systems and to refine the bioaccumulation assessment by consideration of additive accumulation mechanisms and indications. This article gives an overview on actual shortcomings in the current bioaccumulation assessment under REACH and also provides suggestions for a refinement of evaluation.