Disodium [(9,10-dihydro-9,10-dioxo-1,4-anthrylene)bis[imino(3-methylpropane-1,3-diyl)]]bis(benzenesulphonate)

Toxicity to aquatic algae and cyanobacteria

Description of key information

72 h ErC50 = 55.89 mg/L (95 % CL 46.23 to 67.56 mg/L), NOEC = 3.1 mg/L (values corrected for light absorption).

Key value for chemical safety assessment

EC50 for freshwater algae:

55.89 mg/L

EC10 or NOEC for freshwater algae:

3.1 mg/L

Additional information

A study was performed to assess the effect of the test material on the growth of unicellular green alga Pseudokirchneriella subcapitata in accordance with the standardised guidelines OECD 201, EU Method C.3, EPA OPPTS 850.5400, Guidelines for studies on the new chemical substance as required by the Chemical Substance Control Law (Japan) and JMAFF 2-7-7 under GLP conditions. The study was assigned a reliability score of 1 in accordance with the criteria for assessing data quality 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. Five test concentrations in a geometric series with a separation factor of 3.2 and one untreated control were tested in the main experiment. The test design included three replicates at each test group (light filter and treated group) and six replicates for the untreated control.

Algae were exposed to the test material for 72 hours at nominal concentrations of 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 cases, biological results are based on the nominal concentrations.

Statistical comparisons of biomass, average specific growth rates and yield in control and in test material groups (filter and treated groups) were carried out. 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.

Under the conditions of this study, the 72 h ErC50 was determined to be 55.89 mg/L (95 % CL 46.23 to 67.56 mg/L) while the NOEC was 3.1 mg/L (values corrected for light absorption).