Relevance of bioaccumulating substances in the TTC concept

Recently, the European Food Safety Authority (EFSA) stated that the Threshold of Toxicological Concern (TTC) thresholds should not be used for substances that are known or predicted to accumulate. Bioaccumulation of substances is usually considered unfavourable but so far a relation with toxicity at low dose exposure is insufficiently investigated to draw conclusions on the relevance of bioaccumulation at low dose exposure. In this manuscript it is investigated which physical chemical properties are related to bioaccumulation in order to predict accumulating properties of a substance, and is evaluated if the toxicity of known bioaccumulating substances is higher than for non-accumulating substances. Based on the evaluation it is concluded that the current TTC thresholds are derived with a dataset in which bioaccumulating substances are present, whereas the toxicity of the bioaccumulating substances is already taken into account in the TTC thresholds. The authors demonstrated that there is no need to exclude potential bioaccumulating substances from the TTC concept.