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Experts debate way forward for TTC

Scientific experts from around the world met in Brussels to review the science underlying the Threshold of Toxicological Concern (TTC) concept. The three-day workshop, co-hosted by EFSA and the World Health Organization (WHO), is part of a broader EFSA/WHO project which aims to develop a globally harmonised tiered approach to TTC.

In a wide-ranging series of discussions the experts considered topics such as possible revisions of the Cramer classification scheme, modification of the TTC decision tree, and the general criteria that should be considered when deciding whether or not to apply the TTC method.

The scientific workshop was preceded by a one-day meeting with nearly 100 stakeholders representing NGOs, industry, government, academia and consumer organisations. The points raised by stakeholders were considered at the subsequent expert workshop.

Next steps

The conclusions and recommendations from the expert workshop will be made available for public consultation in January 2015. The comments gathered will then be published together with the final workshop report.


The TTC is a pragmatic tool that provides conservative, screening-level exposure limits in the absence of sufficient chemical-specific toxicological data. It is an important science-based approach for prioritising those chemicals with low-level exposures that require more data over those that can be presumed to present no appreciable human health risk.

Since its original development and application in the food area, further scientific developments have taken place leading to the need for a critical review and possible update of the TTC approach.


Stakeholder meeting

  1. List of participants (199.9 KB)
  2. Agenda (535.23 KB)


  1. Introduction (1 MB)
  2. Cosmetics: a special case (429.68 KB)
  3. Reliability of the TTC approach: learning from inclusion of pesticide active substances in the supporting database (525.17 KB)
  4. The most protective TTC is easily falsified – implications (167.29 KB)
  5. PAN Europe’s view (162.65 KB)
  6. A revised Cramer-Ford-Hall decision tree (411.89 KB)
  7. ILSI Europe’s view (1.65 MB)
  8. The utility of TTC in the agrochemical industry (640.78 KB)
  9. Comparison of Cramer classification between Toxtree, OECD QSAR Toolbox and Expert Judgement (821.93 KB)

Expert workshop

  1. Agenda (122.57 KB)
  2. Participants (65.42 KB)