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Only few experimental studies are available on the potassium chlorate (target substance) to assess the  aquatic toxicity. Therefore, good quality data for a related sodium chlorate (source substance) have been read-across for theses aquatic toxicity endpoints. Read-across is possible for these two substances, because the toxicity of the tests substance is expected to be related to the chlorate ion and not to the sodium or potassium ion, and both sodium and potassium chlorate were almost totally dissociate in water, producing sodium/potassium cations and chlorate anions. In water, sodium and potassium are naturally present and the amounts added with the test substance are not considered to have an impact on the total concentration and on the test result, therefore the counter ion present is not relevant for the test result. The Read-Across justification document is provided in section 13 of IUCLID.


 


Short-term as well as long-term aquatic toxicity tests show that chlorate is not very toxic to aquatic organisms.


Short-term tests with fish and invertebrates, freshwater as well as marine species, gave results greater than 1000 mg/l sodium chlorate. On a molecular weight basis this would be 1151 mg/l potassium chlorate.


For long-term tests with fish and daphnids NOEC values greater than 500 mg/l sodium chlorate were obtained. On a molecular weight basis this would be 575 mg/l potassium chlorate.


Algae species were more sensitive, but NOEC values were still greater than 100 mg/l potassium chlorate. Lemna minor was most sensitive with a NOEC of 10 mg/l sodium chlorate, which is equal to 11.5 mg/l potassium chlorate on a molecular weight basis.


Two other taxonomic groups of marine organisms were tested as well. Molluscs were not sensitive in a short-term test with a EC50 greater than 1000 mg/l sodium chlorate. On a molecular weight basis this would be 1151 mg/l potassium chlorate.


The rotifer Brachionus plicatilis was the most sensitive marine species with an EC10 of 21 mg/l sodium chlorate. On a molecular weight basis this would be 24 mg/l potassium chlorate.


Taking all aquatic data into account Lemna minor is most sensitive, with a NOEC of 10 mg/l sodium chlorate, which is equal to 11.5 mg/l potassium chlorate based on molecular weight.

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