Manganese carbonate

Short-term toxicity to fish

Description of key information

No toxic effects up to the limit of solubility of the test substance in the test medium, OECD 203, EU Method C.1, Priestly & Mullee (2010). Study conducted with MnO.

Additional information

A study was performed to assess the acute toxicity of the test substance to rainbow trout (Oncorhynchus mykiss). The method followed that described in the OECD Guidelines for Testing of Chemicals (1992) No 203, "Fish, Acute Toxicity Test" referenced as Method C.1 of Commission Regulation (EC) No. 440/2008.

Pre-study solubility work conducted indicated that it was not possible to obtain a testable solution of the test substance using traditional methods of preparation e.g. ultrasonication and high shear mixing. It was considered that the most appropriate method of preparation for the test substance was as a saturated solution.

Following a preliminary range-finding test fish were exposed, in two groups of seven, to an aqueous solution of the test substance, at a single concentration of 100% v/v saturated solution for a period of 96 hours at a temperature of 12 ºC to 15 °C under semi-static test conditions. The test substance solution was prepared by stirring an excess (100 mg/L) of test substance in dechlorinated tap water using a magnetic stirrer at approximately 100 rpm at a temperature of approximately 14 °C for 48 hours. After the stirring period any undissolved test substance was removed by filtration to give a saturated solution of the test substance. The number of mortalities and any sub-lethal effects of exposure in each test and control vessel were determined 3 and 6 hours after the start of exposure and then daily throughout the test until termination after 96 hours.

There were no mortalities or sub-lethal effects over the 96 hour test period. The 96-hour LC50 value was therefore considered to be greater than 100% v/v saturated solution.

Therefore, under the conditions of the study there were no toxic effects up to the limit of solubility of the test material in the test medium.

Since the study was conducted with manganese oxide, rather than with the registered substance itself, it was assigned a relibality score of 2 according to the criteria of Klimisch (1997).

Use of data on MnO to address data requirements of MnCO3 is considered to be justified on the basis that analogous results were obtained following chronic daphnia, and algae, testing with both substances, both substances display similar TDp results suggesting similar levels of metal release in environmentally relevant waters, and manganese is in the same oxidation state in both substance; furthermore, the anions are not expected to cause aquatic toxicity.

Overall, findings from the fish study with MnO, indicating there are no toxic effects elicited by Mn at the limit of solubility, support the conclusion that the substance is not hazardous to the aquatic environment.