PARENT SESSION

2D - Mechanisms of Toxic Action
Hall 4
1:45 PM - 3:30 PM, Monday, 28 April 2003
Chair: Dietrich, D.¹, ¹
Co-chair: Haux, C.², ²

(MO4/15) Is there an environmental concentration of no toxicological concern?

Wolf, Watze^{1, 2}, Koch, Volker^{1, 3}, Geert, Boeije^{1, 4}, LeCloux, Andre^{1, 5}, Schoeters, Ilse^{1, 6}, Feijtel, Tom^{1, 4}, Holt, Martin¹, ¹ ECETOC Targetted Risk Assessment Task Force, Brussels, Belgium, Belgium² DuPont de Nemours (Belgium), Mechelen, Belgium, Belgium³ Clariant, Frankfurt, Germany, Germany⁴ Procter & Gamble, Strombeek-Bever, Belgium, Belgium⁵ Envicat Consulting, Wavre, Belgium, Belgium⁶ EuroCopper, Brussels, Belgium, Belgium

ABSTRACT- The concept of a threshold of toxicological concern used in human health assessments is based on the possibility of establishing an exposure threshold value for chemicals, below which there is no significant risk. A related concept is the Threshold of No Further Toxicological Concern, in which a dominant concern has been identified, e.g. carcinogenicity, and the evaluation of other toxicological end-point is considered not to influence the outcome of the hazard assessment. This concept will be introduced in the revised Technical Guidance Document for the risk assessment of EU Existing Chemicals. These concepts may be particularly useful for general industrial chemicals where detailed toxicity studies may not always be available. In Europe, a new chemicals policy is debated which will require all chemicals marketed or produced to be tested for human health and environmental hazards. These requirements may lead to increased animal use if all (estimated) 30.000 chemicals covered by this new policy are to be tested. There are no immediate considerations why this concept should not apply to the environmental field. However, derivation of a reasonably data based environmental threshold of toxicological concern seems currently limited to the freshwater environment due to the general lack of data for industrial chemicals for sediment, marine or soil species. Specifically for the 20.000 lower volume chemicals application of the concept may help to save animal lives. The objective of this paper is to initiate discussions on applicability of the environmental threshold of toxicological concern for freshwater systems. The assessment of existing environmental toxicological databases and substance hazard assessments for selected general chemical classes will be presented.

Key words: aquatic toxicity, threshold of concern, mode of action, risk assessment