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Toxicity to aquatic algae and cyanobacteria

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Experimental results on the toxicity of Triiron bis(orthophosphate) (CAS 14940-41-1) to algae are not available. The assessment is therefore based on an expert statement regarding the feasibility of a short-term toxicity study and on read-across data. In accordance with Annex XI, 1.5, of Regulation (EC) No 1907/2006, read-across to the structurally related Iron II Sulfate Heptahydrate (CAS 7782-63-0) 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. For further details please see chapter 6.1 of the IUCLID file.

One study is available for the read across substance Iron (II) Sulfate Heptahydrate (CAS 7782-63-0). The static study (MOE, 2002) on the toxicity of Iron II Sulfate Heptahydrate to Pseudokirchneriella subcapitata was conducted according to OECD 201. The test concentrations (3.2, 5.6, 10, 18, 32, 56, 100, 180 and 320 mg/L nominal) were prepared separately by diluting the stock solution. Analytical determinations were performed at the start and after 72 hours of exposure to ensure a proper maintenance of the test concentration throughout the experiment. The concentration of iron was measured and the test substance concentration was found by conversion. The test substance concentration in the test water was 3.5 – 329 mg/L at the start of exposure, and 2.5 – 280 mg/L after 72 hours. The time-weighted mean of the measured concentration with respect to the nominal concentration was 3.0, 5.2, 9.5, 16.6, 27.8, 51.1, 83.3, 157 and 304 mg/L. The growth rate of Pseudokirchneriella subcapitata was observed for an exposure period of 72 hours. At test termination after 72 hours an EC50 = 150 mg/L (nominal) and a NOEC = 100 mg/L (nominal) were determined.

Therefore, based on the available read across data Triiron bis(orthophosphate) (CAS 14940-41-1) is considered not toxic to freshwater algae at levels up to the limit of water solubility of 1.5 mg/L.