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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Read-across substance_Phosphoric acid, mono- and di-(C8-C10) ester, compds. with C12 - 14 amine_Scenedesmus subspicatus_OECD 201: ErL50(72h): 32 mg/L loading rate WSF (95 % CL: 28 - 37 mg/L loading rate WSF); EbL50(72h): 16 mg/L loading rate WSF (95 % CL: 13 - 20 mg/L loading rate WSF); NOEC(72h): 5 mg/L loading rate WSF

Key value for chemical safety assessment

EC50 for freshwater algae:
32 mg/L
EC10 or NOEC for freshwater algae:
5 mg/L

Additional information

The toxicity of the target substance (Reaction products of diphosphorus pentaoxide and alcohol C7-9-iso, C8 rich, salted with 2-ethylhexylamine) towards aquatic algae was not investigated experimentally. Taking into account the valid read-across substance (Phosphoric acid, mono- and di-(C8 -C10) ester, compds. with C12 - 14 amine), this endpoint can be fulfilled. Both substances are mixtures of mono- and (di)alkyl phosphates salted with an alkyl amine and possess therefore the same basic structure. For the detailed description and justification, please refer to the separate read-across statement by Chemservice S.A. (2013d).

The chronic toxicity of the read-across substance (Phosphoric acid, mono- and di-(C8 -C10) ester, compds. with C12 - 14 amine) towards the freshwater green algae Scenedesmus subspicatus was determined according to OECD Guideline 201 (Mead, 1999b). Based on the poor water solubility, the test solutions were prepared as Water Soluble Fractions (WSFs) by mixing the test substance with water for a prolonged period of time (24 - 48 h). The test substance phase is afterwards separated by filtration and used for testing. Based on the results of the preliminary range-finding experiment, the definitive test was conducted with nominal loading rates of 0 (control), 5.0, 10, 20, 40, and 80 mg/L WSF. Three replicate flasks per concentration were employed. Preculture conditions gave an algal suspension in log phase growth characterised by a cell density of 1.08 x 10E7 cells/mL. This suspension was diluted to a cell density of 2.28 x 10E6 cells/mL prior to use. Addition of 5 mL of this algal suspension/L of test media gave a nominal cell density of 10E4 cells/mL at initiation of the test. The test duration was 72 h under constant illumination (at approx. 7000 lux) and shaking at a temperature of 24 +/- 1 °C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group using a Coulter (R) Multisizer II Particle Counter. Total Organic Carbon (TOC) analysis was performed at the beginning and termination of the experiment. The amount of carbon in the test samples, above the background level of carbon in the control samples, was observed to increase in proportion to the nominal loading rate. Comparison of the 0 and 72 hour TOC analysis results indicate the Water Soluble Fraction of the test substance to be stable in the culture medium over the 72-hour study period. No abnormalities were detected microscopically in the test and control cultures. The test solutions were all clear colourless solutions at 0 hours. After 72 hours the 5.0 mg/L loading rate WSF replicates were bright green dispersions, the 10 mg/L loading rate WSF replicates were pale green dispersions whilst the 20, 40 and 80 mg/L loading rate WSF replicates were clear colourless solutions. The green colouration in the 5.0 and 10 mg/L loading rate WSF replicates was due to growth of the algal cells present. From the recorded data, the following results were determined: EbL50(72h): 16 mg/L loading rate WSF (95 % CL: 13 - 20 mg/L loading rate WSF); ErL50(72h): 32 mg/L loading rate WSF (95 % CL: 28 - 37 mg/L loading rate WSF); NOEL(72h): 5.0 mg/L loading rate WSF.