EFSA Scientific Committee Evaluates the Threshold of Toxicological Concern Approach

The TTC opinion deals with the relevance and reliability of the science underpinning the above-mentioned approach and the possible application of the approach in EFSA’s scientific work.

7/13/2011 --- The European Food Safety Authority (EFSA) has launched for public consultation a draft opinion evaluating the relevance and reliability of the Threshold of Toxicological Concern (TTC) approach as a tool for qualitative assessment and scientific advice about human health risks from low levels of exposure to substances present in food and feed. In the opinion, EFSA’s Scientific Committee has concluded that the TTC approach is not only useful for qualitative risk assessment, but it is also suitable for setting priorities for assessing the safety of chemicals, thus enabling more efficient use of available resources and possible reductions in unnecessary animal testing. The opinion also identifies areas where the approach could be applied in EFSA’s work and the areas and substances for which it is not suitable. All stakeholders and interested parties are invited to provide their comments through the online public consultation by 15 September 2011.

Improved analytical methods allow for the detection of chemicals in food and feed at low and very low concentrations, thus resulting in an increased need for assessing the health significance of detected trace substances. The TTC approach has been developed to qualitatively assess the risk of substances present at low and very low levels and can be used for an initial assessment of a substance to determine whether a comprehensive risk assessment is required. If the chemical structure of a substance is known, its health risk can be evaluated on the basis of generic human thresholds of exposure for chemicals (TTC values). TTC values have been established for substances of similar chemical structure and likelihood of toxicity, based on extensive published toxicological data. Using a conservative approach, chemical structures have been grouped into three broad categories defined as of low, moderate or high toxicity. Substances are assessed by comparing the appropriate TTC value with reliable human exposure data. If human exposure to a substance is below the TTC value, the likelihood of adverse effects is considered to be very low.

The TTC opinion deals with the relevance and reliability of the science underpinning the above-mentioned approach and the possible application of the approach in EFSA’s scientific work. It concludes that the approach is a useful screening tool for substances with a known chemical structure, when limited or no relevant toxicity data exist, but exposure is known to be low. Reliable human exposure assessments, for which there is confidence that they are not underestimated, are critical for the use of the TTC approach. Wider use of TTC is recommended as it could contribute to reducing unnecessary animal use in toxicity testing.

The opinion identifies the TTC values which are sufficiently robust to be used in the Authority’s scientific assessments and the areas where the approach could be used. The Scientific Committee also defines categories of substances, such as high potency carcinogens, metals and proteins, for which the TTC approach is not suitable.

This opinion, which is the result of an initiative of the Scientific Committee, is part of the ongoing efforts to evaluate new risk assessment methodologies in order to ensure that risk assessment approaches used in EFSA constantly reflect the state-of-the-art in science.

In finalising its opinion, the Scientific Committee will consider all comments received during the public consultation as appropriate. A summary report will be published on the EFSA website along with the final guidance, which is expected to be completed by the end of 2011.