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Short-term toxicity to aquatic invertebrates

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Description of key information

Daphnia magna were exposed to chlorine dioxide for 48 hours in an acute immobilization test, under GLP and following C.2 EEC Guideline. No animals were immobilized in the control group. EC50(48h) = 0.063 mg/L of 100% ClO2, i.e. 0.032 g/L of 0.2% ClO2 solution being 1 g/L its density.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.063 mg/L

Additional information

One valid study with Daphnia magna was found on chlorine dioxide. This study was performed under GLP conditions and according to a standard protocol. The results obtained revealed an EC50(48h) = 0.063 mg/L.

The short half-life of chlorine dioxide in the environment following use and the fact that there is no direct release of the active substance to aquatic systems, means that no exposure is expected for the aquatic compartment. Chlorine dioxide reacts rapidly in environmental compartments degrading to chlorite and chlorate as dominant species. In the absence of oxidisable substances, and in the presence of pH > 9, chlorine dioxide dissolves in water and decomposes with the slow formation of chlorite and chlorate ions.

Five valid studies on chlorite were found with Daphnia magna, eastern oyster (Crassostrea virginica), and mysid shrimp (Mysidopsis bahia). These studies were performed under GLP and according to standard protocols. Depending on the species, EC50(48h) = 0.064 mg/L (for Daphnia, as chlorine dioxide), 16 mg/L (for eastern oyster), and 0.49 mg/L (for Mysisdopsis bahia); i.e. from 1 to 254 times higher than the EC50 of chlorine dioxide. LC50(96h) = 0.43 mg/L (for mysid shrimp).

Chlorine dioxide and chlorite both degrade rapidly to chlorate under environmental conditions. For this reason, toxicity data on chlorate have been provided.

Two valid studies on chlorate with Daphnia, and mysid shrimp were included. EC50(48h) > 1000 mg/L for both species; i.e. 15873 times higher than the EC50 for chlorine dioxide concentration.