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Experimental data on aquatic toxicity of magnesium hydrogen orthophosphate (CAS 7757-86-0) are not available. In accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006, read-across to the chemical analogue substances calcium hydrogen orthophosphate (CAS 7757-93-9) and calcium bis(dihydrogenorthophosphate) (CAS 7758-23-8) was conducted to fulfil the standard information requirements. In accordance with Article 13 (1) of Regulation (EC) No 1907/2006, "information on intrinsic properties of substances may be generated by means other than tests, provided that the conditions set out in Annex XI are met.” In particular for aquatic toxicity, information shall be generated whenever possible by means other than vertebrate animal tests, which includes the use of information from structurally related substances (grouping or read-across). According to Annex XI, Item 1.5, of Regulation (EC) No 1907/2006 substances can be considered to be similar if their physicochemical, toxicological and ecotoxicological properties are likely to be similar or follow a regular pattern as a result of structural similarity. The target and the source substances are chemically similar phosphates compounds that differ in the associated cation. Both, calcium and magnesium are grouped to alkaline earth metals that are present almost exclusively in an oxidative state of +2. Thus, they are characterised by comparable physico-chemical properties. A comparable environmental fate and ecotoxicological profile is anticipated for both substances.

Studies on the acute toxicity of calcium hydrogen orthophosphate (CAS 7757-93-9) are available for three trophic levels (fish, Daphnia, algae). All studies were conducted according to the internationally accepted OECD guidelines. The determined E(L)C50 values were >100 mg/L for fish, Daphnia and algae. Toxic or other adverse effects were not observed for any of the tested species. Chronic toxicity data are not available. Long-term toxicity of the substance is not anticipated due to the absence of acute toxicity and the fact that calcium and phosphate are essential micronutrients for aquatic organisms.

The read-across study on the toxicity of calcium bis(dihydrogenorthophosphate) (CAS 7758-23-8) to aquatic microorganisms was conducted according to OECD guideline 209. Adverse effects on aquatic microorganisms were not observed. An EC50(3h)> 1000 mg/L based on the nominal test substance concentrations was determined.

Derived from the available aquatic toxicity data of the analogue magnesium hydrogen orthophosphate is considered not toxic to aquatic organisms.

Furthermore, in the aqueous environment nutrient enrichment (eutrophication) by the addition of phosphate can be a problem in some circumstances. In particular increased phosphate loads to surface waters may be a problem when the conditions are such that P is a growth-limiting factor. The effects of eutrophication can range from ecosystem modifications changes in balance between different species or communities through to algal blooms and in extreme cases (through decomposition of plant biomass leading to oxygen depletion) collapse of the ecological community.

To avoid such effects, phosphate emissions to surface water via industrial wastewater are regulated in the Council Directive 96/61/EC concerning integrated pollution prevention and control. This 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.

The limitation of phosphorus discharges to surface waters is similarly required by the Urban Waste Water Treatment Directive 1991/271 (EU) which requires the removal of phosphate (P) from municipal waste water in all but very small conurbations, 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 smaller conurbations, if this is necessary to achieve water quality status objectives.

Additionally, De Madariaga BM (INIA, 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 (flow regimes, climate, algal grazer communities...) 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 STPP (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). This model is considered relevant for all phosphates as the ultimate degradation products of polyphosphates (including STPP) in municipal sewage are orthophosphates.

 

References:

Council Directive 91/271/EEC of 21 May 1991 concerning urban waste-water treatment

De Madariaga, B.M., Ramos, M.J., and Tarazona, J.V. Model implementation and quantification of the eutrophication risk associated to the use of phosphates in detergents. Final study report. Green Planet Research Report GPR-CEEP-06-2-Final. 2006. Carried out by Green Planet Research and INIA (Spanish National Institute for Agricultural and Food Research and Technology) for CEEP. Published by the EU Commission at: http://ec.europa.eu/enterprise/chemicals/legislation/detergents/index_en.htm

Directive 2000/60/EC of the European Parliament and of the Council establishing a framework for the Community action in the field of water policy