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Report on the seminar "Performing aquatic toxicity tests with poorly soluble substances"

Verslag van de workshop "Het uitvoeren van aquatische toxiciteitstesten met slecht in water oplosbare stoffen"


This document contains the papers, discussions and recommendations of a one-day seminar "Performing aquatic toxicity tests with poorly soluble substances" held in Bilthoven, the Netherlands on March 17, 1995. The great interest and participation in the workshop demonstrated the urgent need for more guidelines and harmonization among regulatory authorities and contract laboratories. This is necessary to solve the problems that occur when poorly soluble substances have to be tested and results have to be interpreted for classification and risk assessment procedures. The seminar was aimed at the exchange of information on performance and technical aspects, as well as on problems of policy interpretation relating to the ecotoxicological testing of organic compounds particularly difficult to dissolve in water. Subjects of the presentations held by government representatives, contract laboratories and universities were: risk assessment, substance classification, theory of solubility, bioavailability and practical aspects in ecotoxicity testing. Concluded was that tests performed with test concentrations above the solubility level or with a large amount of solvent probably result in an underestimation of true toxicity levels due to bioavailability and the solubility process. In risk assessment, tests with effect levels above the solubility level are not valid and further testing may be requested. Rejection of data for classification in these cases would mean no classification, which is undesirable. Therefore it was suggested to classify the effects at the water solubility level of the compound. Due to the large number of poorly soluble compounds submitted for registration it was concluded that additional guidelines are needed for performing toxicity tests (like the preparation and analysis of test concentrations) and for interpreting test results like effect levels above solubility limits.

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