Trisodium trimetaphosphate

Endpoint summary

Additional information

Summary of degradation

Trisodium trimetaphosphate is an inorganic phosphate and therefore a ready biodegradation test is not applicable.

 

One key study (Walker J, 2010) exists for the endpoint 'hydrolysis as a function of pH'. The study, conducted in fresh water, shows that trisodium trimetaphosphate was hydrolytically stable over the course of the study. However this data should be viewed in parallel with the supporting data provided as this information gives a more accurate picture of the behaviour and stability of the substance in natural waters and therefore is more relevant for the purposes of exposure estimations and risk assessment. Trisodium trimetaphosphate will not persist in natural waters as the trimetaphosphate will undergo undergoes hydrolysis (this occurs at a rate much slower than that of only condensed phosphates) and biotic degradation and assimilation by algae and/or micro-organisms. The ultimate degradation of trimetaphosphate is orthophosphate.

 

Soil and sediment degradation studies are not considered to be scientifically feasible as there is no available analytical method that could differentiate between the contributions to the analysable solution originating from the test material and that originating from the required soil / sediment matrix / solution matrix due to the ubiquitous nature of the Na⁺ and PO₄^3-ions.

 

Data on volatilisation is not available. Trisodium trimetaphosphate 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 "sodium" which are natural ionic components of blood, cell fluids, etc and therefore no further testing is considered to be necessary. In addition, no risk of secondary poisoning is anticipated for the same reasons.

 

Eutrophication

 

Trisodium trimetaphosphate is hydrolysed or biotically degraded (by the action of phosphatases) to soluble inorganic orthophosphate (PO₄^3-) in wastewater, sewerage systems and natural waters. Sources of inorganic phosphate are human urine and faeces, animal waste, food and organic waste, mineral fertilisers, bacterial recycling of organic materials in ecosystems, etc. Soluble phosphates are then bio-assimilated by the bacterial populations and the aquatic plants and algae found in these different compartments. Phosphates 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 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 (> 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 to the regulation do not apply to inorganic substances. Therefore trisodium trimetaphosphate is not considered to require any further assessment of PBT properties.