Manganese bis(dihydrogen phosphate)

Endpoint summary

Additional information

Summary of degradation

 

Manganese bis(dihydrogen phosphate) is an inorganic phosphate and therefore a ready biodegradation test is not applicable. In addition no experimental determination of the abiotic degradation, hydrolysis as a function of pH was performed using Method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004, since the phosphate anion has no potential mechanism for further hydrolysis, itself being the final common hydrolysis product of higher polyphosphates. For the purposes of environmental fate modelling, the substance was taken to be “ non-biodegradable“ on the basis that it is an inorganic substance and will not undergo mineralisation.

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. Kd was used in place of Kow to represent the likely partitioning behaviour of the substance during environmental fate modelling.Also, as no Koc value is available this substance has assigned the chemical class of “non hydrophobic“ when performing environmental fate modelling.

 

 

Data on volatilisation is not available; however, manganese bis(dihydrogen phosphate) is an inorganic solid and therefore can be considered to be non-volatile.

 

No experimental data on bioaccumulation exist. However due to the hydrophilic nature of the substance, bioaccumulation is not expected as accumulation in fats is not possible. The substance when dissolved in water (and so animal tissues/fluids) will effectively separate into/become simply the two ions "phosphate" and "manganese" and therefore the bioaccumulation study (required in Annex IX, Section 9.3.2.) does not apply to the hazard assessment of inorganic metals or metal compounds. The available data is adequate for classification and labelling purposes and PBT assessment is not required for inorganic substances so no further testing is required.

The potential for bioaccumulation is therefore considered to be minimal.

 

Eutrophication

 

Inorganic orthophosphates will dissociate to soluble orthophosphate (PO₄^3-) in sewerage systems, sewage treatment plants and in the environment. These phosphates are also formed by natural hydrolysis of human urine and faeces, animal wastes, food and organic wastes, mineral fertilisers, bacterial recycling of organic materials in ecosystems, etc. Phosphates are bio-assimilated by the bacterial populations and the aquatic plants and algae found in these different compartments and are an essential nutrient (food element) for plants, and stimulate the growth of water plants (macrophytes) and/or algae (phytoplankton) if they represent the growth-limiting factor.

Nutrient enrichment caused by excess of phosphate (when the conditions are such that P is a growth-limiting factor) can be a problem in some circumstances. The effects of eutrophication can range from ecosystem modifications, through to algal blooms and in extreme cases (through decomposition of plant biomass) oxygen depletion and collapse of the ecological community in a surface water causing considerable detrimental impacts on fish and other organisms as the increase in primary production leads to increased oxygen consumption, which may reduce the oxygen concentration to critical low levels.

To avoid such undesirable effects, phosphate emissions to surface water via industrial wastewater are regulated in the Council Directive 96/61/EC concerning integrated pollution prevention and control. It states that phosphates have to be taken into account for fixing emission limit values for industrial wastewater. In order to meet the requirements it may be necessary to add a treatment step for phosphate removal from industrial wastewaters before these waters are released to the aqueous environment. This method for limiting the concentration of phosphates in industrial wastewater emissions is supported by theUrban Waste Water Treatment Directive 1991/271 (EU) which requires the removal of phosphate (P) from municipal waste water in all but very small conurbations (> 10 000 person equivalents = around 6 000 population taking into account small industry and commerce inputs), wherever discharge occurs into waters potentially susceptible to eutrophication. The EU Water Framework Directive 2000/60 confirms this obligation, and reinforces it by requiring further treatment, e.g. of small conurbations, if this is necessary to achieve water quality status objectives.

De Madariaga BM (2007) developed a conceptual model and protocol for performing European quantitative eutrophication risk assessments of (poly)phosphates in detergents. In this model, the risk probability for eutrophication occurring in the most sensitive areas of a river basin (lakes, reservoirs, meadow zones, estuaries), is based on the TP (total phosphorous) concentration of the inflow water. The variability observed for similar TP concentrations is the consequence of variations in concentrations of N and/or other nutrients, other ecosystem factors and other natural variability. The study also covered the implementation of the model and a set of examples based on generic European scenarios as well as a pan European probabilistic estimation covering the diversity observed for the European conditions and enabled a probabilistic risk assessment of eutrophication relating to the use of sodium tripolyphosphate (pentasodium triphosphate) in detergents. The scientific validity of this methodology was confirmed by the EU scientific committee SCHER (Opinion of 29th November 2007).

 

Assessment of PBT/vPvB properties; comparison with the criteria of Annex XIII (Regulation (EC) No. 1907/2006.

 

According to the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.11: PBT Assessment; the PBT and vPvB criteria of Annex XIII of Regulation (EC) No. 1907/2006 (REACH) do not apply to inorganic substances. Therefore, manganese bis(dihydrogen phosphate) is not considered to require any further assessment of PBT properties.