Manganese bis(dihydrogen phosphate)

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.99 mg/L

Assessment factor:

10

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.099 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.198 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

insufficient hazard data available (further information necessary)

Sediment (marine water)

Hazard assessment conclusion:

insufficient hazard data available (further information necessary)

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

4.31 mg/kg soil dw

Assessment factor:

100

Extrapolation method:

assessment factor

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

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 phosphates) 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.

For the derivation of PNECs it was decided to use the worst-case data performed on a manganese phosphate (algal growth study, manganese hydrogen phosphate) as the starting point due to the fact that the bulk of the data for the environment is literature data and whilst for the Mn ion this could be considered to be reliable data it was not performed to current guidelines or under the conditions of GLP and as such it is considered that calculating a PNEC based on the most recent data on the most relevant substance would give the most reliable value to be taken forward into risk assessment. In addition, a consideration of the worst-case scenario for the calculation of PNECs would result in freshwater and marine PNECs that are below the natural background concentrations of Mn as reported in FOREGS Geochemical atlas of Europe Part 1 (Mean natural background concentration reported to be 0.056 mg Mn/l) and as such this is not considered to be an appropriate calculation.

Classification has been based on an assessment of all data; including data for the Mn ion and represents a worst-case for the environment.

Conclusion on classification

Environmental classification justification

The classification and labelling of soluble manganese phosphates has been determined by taking into account the 2^ndATP to Regulation (EC) No. 1272/2008 (EU CLP) as outlined by the strategy detailed in ECHA’s ‘Guidance on the Application of the CLP Criteria:ANNEX IV: METALS AND INORGANIC METAL COMPOUNDS’. This strategy relies on an assessment of the solubility of the metal compounds and evidence of rapid removal of the metal ion from the water column.

In order to determine the classification of a ‘soluble’ manganese compound using the available guidance, both the acute and chronic ERVs and solubility data are required. The ecotoxicity reference values for a metal compound can be calculated by:

• AcuteERV_compound= acute ERV of Mn ion x (Mwt of Mn compound /Awt of Mn)

• ChronicERV_compound= chronic ERV of Mn ion x (Mwt of Mn compound /Awt of Mn)

Reference values for Mn2+ have derived by using the lowest relevant value for each taxonomic group from the data available .In the case of the Long-term data, the value used is based on the most relevant in terms of study methodology/reliability and/or most appropriate test species. These values have been used to derive a reference value for manganese hydrogen phosphate on the basis of a molecular weight calculation (see ‘read-across justification) and as a worst-case scenario the lowest available value is used for classification. These are as follows:

 

AcuteERV_compound: 8.71 mg MnHPO₄/L

 

ChronicERV_compound: 0.17 mg MnHPO₄/L

 

The data on the adsorption /desorption for manganese has been taken from the publically available literature and is considered to be limited. The most relevant value for use in risk assessment is K_d= ca. 1200. This is the lowest available value and therefore is considered to be indicative of metal that is known to partition to organic matter (soils/sediments) as opposed to remaining in the water column and as manganese hydrogen phosphate and manganese bis(dihydrogen phosphate) are both soluble they can be considered to be ‘readily transformed’ in the environment for the purpose of determining an appropriate classification. 

On the basis of the above manganese bis(dihydrogen phosphate) is not considered to be acutely toxic to the aquatic environment (acute reference value: >1 mg/L) but is considered to be classified as chronic category 3 as the substance is considered to meet the following criteria:

‘If there is evidence of rapid environmental transformation:

Classify the metal compound as Category Chronic 3 if the chronic ERVcompound > 0.1mg/l and ≤ 1 mg/l.’