Aluminium tris(dihydrogen phosphate)

Sediment toxicity

Additional information

Experimental data on the toxicity of aluminium tris(dihydrogen phosphate) (CAS 13530-50-2) to sediment organisms are not available. However, the chemical safety assessment does not indicate the need to investigate further the effects on sediment organisms. Based on the aquatic hazard assessment toxic effects of the substance on sediment organisms are not expected.

Aluminum (Al) is the most commonly occurring metallic element, comprising eight percent of the earth's crust (Press and Siever, 1974) and is therefore found in great abundance in both the terrestrial and sediment environments. Concentrations of 3-8% (30,000-80,000 ppm) are not uncommon. The relative contributions of anthropogenic aluminium to the existing natural pools of aluminium in soils and sediments is very small, and therefore, not relevant either in terms of added amounts or in terms of toxicity. Based on these exposure considerations, additional sediment and/or soil testing is not warranted. Under environmental conditions, aluminium does not exist as free elemental metal but in compound form.

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

Press F., Siever R. (1974). Earth. W.H. Freeman and Co. San Francisco