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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Description of key information

EC50 (72 h) >100 mg/L (nominal), read across
NOEC (72 h) ≥100 mg/L (nominal), read across

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information

One study report for aluminium dihydrogen triphosphate is available from MOE (2003).

The test substance is poorly soluble in water, therefore, a suspension of the test substance in the dilution water was prepared to the equivalent of 100 mg/L, and agitated for 48 hours, after which any test substance that had not dissolved was removed by filtration; the resulting filtrate was used as the test solution. The test concentration was confirmed by analysis. The inhibitory concentration was calculated using the measurements obtained at the start. The EC50 is > 0.911 mg/L (the highest tested concentration).

Lower Concentrations show an increase in growth rate compared to the control. The phosphate anion (PO43-) is ubiquitous in natural waters and an essential micronutrient for many organisms. Orthophosphates are not anticipated to induce direct acute or long-term adverse effects on aqueous or terrestrial organisms. Because phosphates are a key nutrient for plants,elevated phosphate concentrations in water can lead to excessive growth of algae and other water plants.

Furthermore, the test solution analyses revealed concentrations at 19-100% of the theoretical value for the measurement value at the start of exposure, with the percentage decreasing with test concentration. This suggests that the test substance dissociated (dissolved) in aqueous solution at high concentrations, but precipitated out at low concentrations; this is thought to be the main reason for the decrease in concentration.

On the basis of the discussion presented above the results of acute toxicity studies on aluminium metaphosphate (CAS 13776-88-0)  have been used for read across and are justified on the basis that Al3+ion is of concern with regards to potential toxicity and both substances are inorganic orthophosphates containing a phosphate anion and an aluminium cation. Therefore the results on aluminium metaphosphate (CAS 13776-88-0) can be used for assessment.


The acute toxicity of aluminium metaphosphate (CAS 13776-88-0) to algae was investigated in a study by Wenzel (2015). This test was conducted according to OECD 201 under GLP conditions.Since the test item is of low water solubility, the nominal test concentrations were individually prepared using the Water Accommodated Fraction (WAF) approach according to the OECD guidance documents No. 23 and 29 to obtain the maximal solubility of the test item under the test conditions.

72 h EC50 value of >100 mg/L (nominal) and NOEC of ≥100 mg/L (nominal) have been determined for the effects of the structural related aluminium metaphosphate (CAS 13776-88-0) on the growth of Pseudokirchneriella subcapitata(Wenzel, 2014).