Manganese bis(dihydrogen phosphate)

Toxicity to soil macroorganisms except arthropods

Description of key information

In accordance with Annex XI, Section 1.2 of Regulation (EC) No.1907/2006 (REACH) a weight of evidence approach is used to address the endpoint ‘long-term toxicity to soil macro-organisms’. Three studies are available to assess the toxicity of Mn2+ (in the form of manganese sulphate) on two species of worm. The value chosen for risk assessment is taken from the study that assessed the most relevant parameters.
No short-term studies are considered to be necessary. 

Key value for chemical safety assessment

Long-term EC10, LC10 or NOEC for soil macroorganisms:

431.32 mg/kg soil dw

Additional information

Calculation of an NOEC value relevant for Manganese hydrogen phosphate (see 'read-across justification for further information)

The lowest NOEC value in the studies performed with manganese sulphate was found to be 157 mg Mn/L ).This value is considered to be adequate for use to characterise the risk to the environment as it falls below the typical background concentrations in soil (330 mg/kg dw as reported in the ATSDR for Manganese¹). This value has been translated into a value relevant to manganese hydrogen phosphate by a molecular weight calculation.

¹Toxicological Profile for Manganese, 2002, US Department of Health and Human Services.

READ-ACROSS JUSTIFICATION  

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.