There are several approaches how to test toxicity of water-insoluble compounds. However, the most often the addition of solvents is used, but it can significantly alter the toxicity of water-insoluble compounds. Furthermore, the environmental relevance of such testing is questioned. Therefore, the aim of this study was to develop the methodology for the toxicity testing of water-insoluble coating that would be easy, fast and more environmentally relevant. For this purpose toxicity of two-component waterborne epoxy coating and its components was assessed using water fleas, Daphnia magna.
Toxicity tests were carried out using a leaching method separately on coating in full composition, as well as separately on their two main components (A and B). The respective tests started with the coating of inert glass plate, drying and subsequent leaching. After leaching the medium was diluted to several concentrations and ten neonates of water fleas were added in each. In case of a good dose-response relationship the results were expressed as 48h EC50.
According to the results component B shows high toxicity, all tested concentrations caused 100% inhibition. Due to lack of data, it was not possible to determine the cause of toxicity of the compound. Component A showed lower toxicity to water fleas, where the 48h EC50 for it was 22.7 vol.% and is mainly caused by zinc oxide, which is according to its safety data sheet very toxic for water fleas. Moreover, the result showed that the tested coating in full composition is not as toxic to water fleas as their separate components. Calculated 48h EC50 for tested coating is >100 vol.%. Results of the present study demonstrated that the leaching method is a good approach to test the toxicity of water-insoluble coatings and consequently could be used to assess the impact of such compounds on the environment.
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