Back in late 2014, an EFSA/WHO working group considered the TTC approach, with the overall goal of developing a globally-harmonised decision tree that would enable a tiered approach to be applied in the risk assessment of ingested chemicals. The working group focused on the Cramer classification scheme and on the major scientific principles behind the TTC concept. The full report of this meeting is now available, with the group concluding that TTC is fit for purpose as a screening tool for assessing the safety of chemicals with low exposures and inadequate hazard data, and for identifying chemicals that need further data before their risk to human health can be assessed. For substances with structural alerts for genotoxicity, the proposed TTC of 0.0025 µg/kg bw/day was considered to be sufficiently protective (excluding chemicals in the so-called cohort of concern, e.g. aflatoxin-like, azoxy- or N-nitroso-compounds, and benzidines), while carcinogens without such structural alerts should be adequately covered by other TTC tiers. The working group made some recommendations to improve and expand the TTC concept, including the need for a permanent repository for data supporting TTC and the Cramer scheme. It also supported treating organophosphates and carbamates as a separate class (with a TTC threshold of 0.3 μg/kg bw/day). A revised decision tree for use of the TTC concept was subsequently proposed.

European Food Safety Authority and World Health Organization (2016). Review of the threshold of toxicological concern (TTC) approach and development of new TTC decision tree. EFSA Supporting publication 2016, EN-1006, 50 pp., 10 March 2016.


The above items were taken from the April 2016 issue of Toxicology and Regulatory News which is sent automatically to members of bibra (click here)

News Home Guest Write For Us? Contact Us