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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

Based on results from Gnemi (1996), an LC50(96h) of 0.021 mg/L was determined for chlorine dioxide on the zebrafish, Danio rerio. Chlorine dioxide is highly acutely  toxic to fish, it has a short half-life in the environment following use, and there is no direct release of the active substance to aquatic systems. Chlorine dioxide in aqueous solution reacts rapidly, abiotically with organic matter and oxidisable metals, generating chlorite, chlorate and ultimately chloride as dominant species. Under the conditions of use, no chlorine dioxide is expected to be found in the environment, however the principal decomposition products, chlorite, chlorate and chloride will be. Therefore, key studies concerning these substances (except chloride) have also been included in this section such that their toxicity and ultimately risk can be characterised in the CSR.  

Key value for chemical safety assessment

Fresh water fish

Fresh water fish
Effect concentration:
0.021 mg/L

Additional information

One acute toxicity study valid was found in Chlorine dioxide for zebrafish Danio rerio (Gnemi 1996, according to C.1 EEC Guideline). Two acute toxicity studies valid were used in Sodium chlorite for sheepshead minnow Cyprinodon variegates (Ward and Boeri 1991, according to EPA OPP 72 -1; Yurk 1994, according to EPA-FIFRA 72 -3). Finally, two acute toxicity studies valid from the same authors (Ward and Boeri 1991, according to EPA OPP 72 -1 and Ward and Boeri 1991, EPA-FIFRA 72 -3 severally) were used in Sodium chlorate for rainbow trout Oncorhynchus mykiss and sheepshead minnow, respectively.

Based on results from Gnemi (1996), LC50(96h) = 0.021 mg/L of chlorine dioxide on zebrafish. Chlorine dioxide is highly acutely toxic to fish. It has a short half-life (seconds to minutes) in the environment, and there is no direct release of the active substance to aquatic systems. Chlorine dioxide in aqueous solution reacts rapidly, abiotically with organic matter and oxidisable metals, generating chlorite, chlorate and ultimately chloride as dominant species. Under the conditions of use, no chlorine dioxide is expected to be found in the environment, however the principal decomposition products, chlorite, chlorate and chloride will be.

For sodium chlorite the two lowest 96 h LC50s for fish were found at 78 mg/L of chlorite and 55.9 mg/L of chlorite (Ward 1991 and Yurk 1994 respectively). For sodium chlorate 96 h LC50s for fish > 1000 mg/L were observed.