Reaction products of diazotised 4,4-diaminodiphenylamine-2-sulfonic acid, subsequently coupled with 6-amino-4-hydroxynaphthalene-2-sulfonic acid, further diazotised and coupled with metaphenylendiamine, sodium salts

Toxicity to aquatic algae and cyanobacteria

Description of key information

NR

Additional information

Direct Black 22 (DBk22) was tested for short term toxicity to algae and cyanobacteria on Selenastrum capricornutum. The IC50 recorded at 72 hours was 38.5 mg/L of active material (Riva, 2000). The read across test substance showed an EC value for growing rate of 14 mg/L (Dolezavola, 1994).

Nevertheless coloured substances are often assumed to behave differently in the algal growth inhibition test due to shading of the algae.

Several studies on algae conducted on dark dyes, including those with a modified test system for dye-stuffs, showed that the growth inhibition is mainly correlated to the reduced light absorption, caused by the stained water and not due to an effective toxicity of the dye.

A modified test design has been proposed by the cooperation of the Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers (ETAD), Memmert et al^[1], in order to eliminate the effect of shading. Nevertheless this method has some limitations, as it focuses on the shadow effect, giving no information on the real potential toxicity for algae of the tested substance.

In order to clarify the (eco)toxicological properties related to toxicity for aquatic plants, it was considered a read across test with the analogue Similar Substance 01 using Lemna gibba as a test organism (Caduff, 2012), as the test substance is a dyestuff which could influence the photosynthesis capacity of algae cells in the test solution.

Reference

^[1] Memmert U, Motschi H, Inauen J, W. uthrich V. Inhibition of algal growth caused by coloured test substances. ETAD Project E 3023. Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers, Basel, Switzerland, 1994.