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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

72 hour EC50 >100 mg/L (Pseudokirchneriella subcapitata), OECD 201, EU Method C.3, OPPTS 850.5400 and JMAFF 2-7-1-1, Sipos (2015)

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
3.1 mg/L

Additional information

The effect of the test material on algal growth was assessed using the unicellular green alga Pseudokirchneriella subcapitata in accordance with the standardised guidelines OECD 201, EU Method C.3, US EPA OPPTS 850.5400 and JMAFF 2-7-1-1 under GLP conditions. The study was awarded a reliability score of 1 in accordance with the criteria for assessing data quality as set forth by Klimisch et al. (1997).

As the test material is a water soluble deep-coloured powder and the amount of light for photosynthesis is likely to be significantly affected by the shading effect of the coloured test solution, a modified test was performed in order to separate physical effect of the coloured material from its true toxic effects.

Following a preliminary test, five test concentrations in a geometric series with a separation factor of 3.2 and one untreated control were tested in the 72 hour main experiment. The test design included three replicates at each test group (light filter and treated group) and six replicates for the untreated control. The nominal concentrations of test material used in the main experiment were: 1.0, 3.1, 9.8, 31.3 and 100 mg/L. The test material concentrations were analytically determined at the start and at the end of the experiment. As the measured concentrations deviated not more than 20 per cent from the nominal in all case, biological results are based on the nominal concentrations.

The results of this experiment showed that the majority of the observed inhibition effect was related to the light absorption by the test material. However, a greater inhibition was seen at 72 hours when the test material was in contact with the algae cells for 72 hours. This indicates that there was also a toxic effect on the growth of the alga (Pseudokirchneriella subcapitata).

Under the conditions of this study, the 72 hour EC50 and NOEC values based on growth rate were >100 and 3.1 mg/L, respectively.