Manganese carbonate

Short-term toxicity to aquatic invertebrates

Description of key information

No toxic effects at the limit of solubility of the test substance in the test medium, OECD 202, EU Method C.2, Priestly & Mullee (2010). Studies conducted with MnCO3 & MnO

Additional information

Two studies are available to address the acute toxicity to daphnia. Both studies were conducted under GLP conditions and in accordance with the standardised guidelines OECD 202 and EU Method C.2.

The key study was conducted with the registered substance, manganese carbonate, and was assigned a reliability score of 1 in line with the criteria of Klimisch (1997).

Pre-study solubility work conducted indicated that it was not possible to obtain a testable solution of manganese carbonate using traditional methods of preparation e.g. ultrasonication and high shear mixing. It was therefore considered that the most appropriate method of preparation for the test substance was as a saturated solution. Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of manganese carbonate at a concentration of 100% v/v saturated solution for 48 hours at a temperature of approximately 20°C under static test conditions. Immobilisation and any adverse reactions to exposure were recorded after 24 and 48 hours.

Under the conditions of the study the 48-hour EC50 was determined to be greater than 100% v/v saturated solution. Correspondingly the No Observed Effect Concentration was 100% v/v saturated solution. Based on the mean measured test concentration as manganese carbonate the 48-hour EC50 was estimated to be greater than 3.6 mg/L. Correspondingly the No Observed Effect Concentration was 3.6 mg/L. This study showed that there were no toxic effects at saturation.

Supporting information is available in the form of a study conducted with manganese oxide. 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.

Since this study was conducted with manganese oxide, rather than with the registered substance itself, it was assigned a relibaility score of 2 in line with the criteria of Klimisch (1997).

Pre-study solubility work conducted with manganese oxide indicated that it was not possible to obtain a testable solution using traditional methods of preparation. It was therefore considered that the most appropriate method of preparation of manganese oxide was as a saturated solution.

Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to an aqueous solution of manganese oxide at a concentration of 100% v/v saturated solution for 48 hours at a temperature of approximately 20 °C under static test conditions. Immobilisation and any adverse reactions to exposure were recorded after 24 and 48 hours.

Under the conditions of the study the 48 hour EC50 was determined to be greater than 100% v/v saturated solution. Correspondingly the No Observed Effect Concentration was 100% v/v saturated solution. Based on the mean measured test concentration as manganese oxide the 48-hour EC50 was estimated to be greater than 4.0 mg/L. Correspondingly the No Observed Effect Concentration was 4.0 mg/L. This study showed that there were no toxic effects at saturation.

Overall, both studies provided similar EC50 values indicating that MnO and MnCO3 are likely to exhibit a similar level of release to the environment and exert a similar toxic effect to aquatic organisms. Both substances elicited no toxic effects at the limit of solubility supporting the conclusion that the substance, manganese carbonate, is not hazardous to the aquatic environment.