Health risk assessments should, where possible, be based on substance-specific toxicity data. Often, no such data are available, and appropriate read-across information cannot be identified. In such cases, default tolerable exposure values based on chemical structure can be assigned by applying a threshold of toxicological concern (TTC) approach, which can prove useful in screening and prioritising chemicals for further assessment. This is confirmed by EFSA in its finalised guidance on the use of TTC in food safety assessment. The guidance complements existing comprehensive reviews of the TTC methodology from EFSA and the World Health Organization, providing practical advice on its application. Circumstances where the TTC approach is or is not appropriate are defined, as are substance inclusion/ exclusion criteria (note that hydrazines are no longer excluded), and the TTC decision tree is fully explained. Guidance is also provided on the application of the approach to chemical mixtures, endocrine disruptors, and to risk assessments for infants and children. Notably, EFSA supports the existing TTC thresholds (in µg/kg bw/day) of 0.0025 (for potential non-threshold genotoxins), 0.3 (organophosphates and carbamates), 30 (Cramer I substances), 9 (Cramer II substances) and 1.5 (Cramer III substances).

European Food Safety Authority (2019). Scientific Committee. Guidance on the use of the Threshold of Toxicological Concern approach in food safety assessment.


The above items were taken from the July 2019 issue of Toxicology and Regulatory News which is sent automatically to members of bibra.

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