Is the 0.15 µG/Day Tier of the Threshold of Toxicological Concern (TTC) still Appropriate?


The TTC-based exposure limit of 0.15 µg/day is based on an evaluation of the Cancer Potency Database (CPDB) that includes information from carcinogenicity studies of over 700 chemicals. This expert group will examine whether the TTC exposure limit of 0.15 µg/day for DNA-reactive substances is still appropriate when account is taken of the mode of action (e.g. mutagenic or not) and knowledge on human relevance. This will be undertaken on a subset of carcinogenic chemicals, in the first instance.


The expert group is developing a concept for the re-evaluation of the cancer TTC dataset by providing state-of-the-art scientific background support to the derivation of the threshold for DNA-reactive carcinogens and those probably acting via different modes of action. This work might also provide support for more than one TTC limit based on considerations such as mode of action or chemical class.

  • Study inclusion and data evaluation framework definition;
  • Building and analysing a proof of concept dataset;
  • Publication of the results of the evaluation.

Expected Output

The project is applying current state-of-the-art approaches in cancer risk assessment to the existing database of carcinogens and will provide updated quantitative analyses for a representative subset of chemicals based on current approaches, including considerations of both human relevance and mode of action. This project will describe a science-based and pragmatic approach to strengthening the scientific underpinnings of the cancer-based TTC tier.

The task force presented the project in a poster session at EFSA's 2nd Scientific Conference 'Shaping the Future of Food Safety, Together’ in October 2015, in Milan, Italy.

Building upon the work of the expert group, the existing cancer database will be extended in a project funded by the European Chemical Industry Council Long-range Research Initiative (CEFIC-LRI). This project will be kicked off in April 2016.