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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

One key study to assess the toxicity of the analogous substance manganese hydrogen phosphate to STP microorganisms exists. On this basis manganese (Mn2+) orthophosphates are not considered to be toxic to STP microorganisms. 

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
1 000 mg/L

Additional information

Results.

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50of greater than 1000 mg/l. The No

Observed Effect Concentration (NOEC) after 3 hours exposure was1000mg/l.It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/l.

Justification for read-across.

An assessment of the environmental toxicity has been made on the basis of a read-across between analogous Mn2+ containing substances.

 

All substances used as source chemicals for read-across contain Mn2+ and are very soluble in water. Due to the inorganic nature and high solubility of these materials (manganese sulphate, manganese chloride, and manganese hydrogen phosphate) the anions and cations may be considered separately. Chloride, sulphate or phosphate anions are naturally occurring components of all biological fluids and as such are not considered to have any influence on the effective toxicity of Mn2+ nor any toxicity in their own right and can be disregarded when assessing the toxicity of these materials.

Any toxicological effects will be as a result of the presence of Mn2+ and therefore an assessment of the relative toxicity of soluble inorganic manganese salts with non-toxic anions can be made on the basis of data from similar substances, such as:

 

- Manganese bis(dihydrogen phosphate)

- Manganese hydrogen phosphate

- Manganese sulphate

- Manganese chloride

 

 

When considering a testing strategy for manganese phosphates, tests have been performed on manganese hydrogen phosphate as that contributes the greater amount of Mn2+ on a %w/w basis (36.4% as compared to 22% in manganese bis(dihydrogen phosphate) these results will be directly read across to manganese bis(dihydrogen phosphate) as they are representative of a worst-case for manganese phosphates.

 

Further, where results from studies on manganese sulphate or manganese chloride are reported as units of manganese (e.g. mg Mn/L) a molecular weight calculation has been performed to translate the value into units of manganese hydrogen phosphate. This value will then be used for manganese bis(dihydrogen phosphate) as a worst-case.