• Open Access

Scientific Opinion on Exploring options for providing advice about possible human health risks based on the concept of Threshold of Toxicological Concern (TTC)


  • EFSA Scientific Committee

  • Scientific committee members: Boris Antunovic, Susan Barlow, Andrew Chesson, Albert Flynn, Anthony Hardy, Michael-John Jeger, Ada Knaap, Harry Kuiper, David Lovell, Birgit Nørrung, Iona Pratt, Alicja Mortensen, Josef Schlatter, Vittorio Silano, Frans Smulders and Philippe Vannier
  • Correspondence: scientific.committee@efsa.europa.eu
  • Acknowledgement: The Scientific Committee wishes to thank the members of the Working Group on Threshold of Toxicological Concern for the preparatory work for this scientific opinion: Susan Barlow, Alan Boobis, James Bridges, Astrid Bulder, Corrado Galli (member until February 2011), Ursula Gundert-Remy, John Christian Larsen, Jean-Claude Lhuguenot, David Lovell, Alberto Mantovani, Aldert Piersma, Josef Schlatter, Andrew Worth and Giovanni Zapponi (member until May 2011); hearing expert Sylvia Escher and EFSA staff members Daniela Maurici and Hans Steinkellner.
  • Adoption date: 22 May 2012
  • Published date: 2 July 2012
  • Question number: EFSA-Q-2008-747
  • On request from: EFSA


Synthetic and naturally occurring substances present in food and feed, together with their possible breakdown or reaction products, represent a large number of substances, many of which require risk assessment. EFSA's Scientific Committee was requested to evaluate the threshold of toxicological concern (TTC) approach as a tool for providing scientific advice about possible human health risks from low level exposures, its applicability to EFSA's work, and to advise on any additional data that might be needed to strengthen the underlying basis of the TTC approach. The Scientific Committee examined the published literature on the TTC approach, undertook its own analyses and commissioned an in silico investigation of the databases underpinning the TTC approach. The Scientific Committee concluded that the TTC approach can be recommended as a useful screening tool either for priority setting or for deciding whether exposure to a substance is so low that the probability of adverse health effects is low and that no further data are necessary. The following human exposure threshold values are sufficiently conservative to be used in EFSA's work; 0.15 μg/person per day for substances with a structural alert for genotoxicity, 18 μg/person per day for organophosphate and carbamate substances with anti-cholinesterase activity, 90 μg/person per day for Cramer Class III and Cramer Class II substances, and 1800 μg/person per day for Cramer Class I substances, but for application to all groups in the population, these values should be expressed in terms of body weight, i.e. 0.0025, 0.3, 1.5 and 30 μg/kg body weight per day, respectively. Use of the TTC approach for infants under the age of 6 months, with immature metabolic and excretory systems, should be considered on a case-by-case basis. The Committee defined a number of exclusion categories of substances for which the TTC approach would not be used.