The TTCshort forThreshold of Toxicological Concern is a tool of the risk management for the prioritisation of substances as part of the risk assessment. For substances (with a known chemical structure) for which no adequate toxicological data are available, the estimated exposureExposureTo glossary for this chemical substance is compared instead to the TTCshort forThreshold of Toxicological Concern value derived for chemical substances of a similar structure (i. e. a similar structural class). The TTCshort forThreshold of Toxicological Concern concept is exclusively a prioritisation tool. The TTCshort forThreshold of Toxicological Concern value is based on toxicity data for substances that have similar structural properties.