Manganese carbonate

Toxicity to aquatic algae and cyanobacteria

Description of key information

ErC50 > 100% v/v saturated solution (> 2.2 mg/L test substance), NOEC = 32% v/v saturated solution (0.69 mg/L test substance), OECD 201, EU Method C.3, Vryenhoef H (2014) study conducted with MnCO3
ErC50 > 100% v/v saturated solution (> 1.3 mg/L test substance), NOEC = 32% v/v saturated solution (0.41 mg/L test substance), OECD 201, EU Method C.3, Vryenhoef H & Mullee DM (2010) study conducted with MnO 

Additional information

Two studies are available to address the toxicity to aquatic algae. Both studies were conducted under GLP conditions and in accordance with the standardised guidelines OECD 201 and EU Method C.3.

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).

For the key study, reported by Vryenhoef (2014), Pseudokirchneriella subcapitata was exposed to solutions of the test substance at measured concentrations of 1.0, 3.2, 10, 32 and 100% v/v saturated solution (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C. The test substance solutions were prepared by stirring an excess (100 mg/L) of test substance in culture medium using a propeller stirrer at approximately 1500 rpm for 48 hours. After the stirring period any undissolved test item was removed by filtration (0.2 µm Gelman Acrocap filter, first approximate 500 mL discarded in order to pre-condition the filter) to produce a 100% v/v saturated solution of the test item. This saturated solution was then further diluted as necessary, to provide the remaining test groups.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter^®Multisizer Particle Counter.….

Analysis of the test preparations at 0 and 72 hours showed measured test concentrations to range from less than the limit of quantification (LOQ), determined to be 0.10 mg/L, at 1.0% v/v saturated solution through to 2.2 mg/L at 100% v/v saturated solution. Given that there was no significant change in the measured concentrations at 72 hours the results are based on 0-hour measured test concentrations only.

Under the conditions of the study the 72 hour EC50, based on inhibition of growth, was determined to be > 100% v/v saturated solution, (2.2 mg/L mean measured concentration of test substance). The No Observed Adverse Effect Concentration, based on inhibition of growth, was determined to be 32%v/v saturated solution (0.69 mg/L mean measured test concentration of test substance).

 

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

In the supporting study, Desmodesmus subspicatus was exposed to solutions of the test substance at concentrations of 1.0, 3.2, 10, 32 and 100% v/v saturated solution (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1°C. 

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

Under the conditions of the study the 72 hour EC50, based on inhibition of growth, was determined to be > 100% v/v saturated solution, (1.3 mg/L mean measured concentration of test substance). The No Observed Adverse Effect Concentration, based on inhibition of growth, was determined to be 32%v/v saturated solution (0.41 mg/L mean measured test concentration of test substance).

 

Overall, both studies provided similar ErC50 values (> 100% v/v saturated solution), and similar NOEC values (32% v/v saturated solution) 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.

 

The EC50 values indicate that 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.