1-(2-methyl-4-(2-methylphenylazo)phenylazo)-2-naphthol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Description of key information

Freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 1-(2-Methyl-4-(2-methylphenylazo)phenylazo)-2-naphthol (85 -86 -3) according to OECD Guideline 201 (Experimental study report, 2017). As the test substance was insoluble in water so that the stock solution 2 g/L was prepared by dissolving brown powder in acetone. Test solutions of required concentration were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture. 5x10(3) cells /ml algae culture were use in the study for total exposure period of 72hrs. Test conducted in 50 ml Glass vessel filled with 50 ml of sample volume and tested at the concentrations 0, 0, 1.2, 2.4, 5, 10, 20 mg/l. Effects on the growth rate of the organism were studied. The median effective concentration (EC50) for the test substance, 1-(2-Methyl-4-(2-methylphenylazo)phenylazo)-2-naphthol, in Desmodesmus subspicatus was determined to be 153.5 mg/L. This value indicates that the substance is likely to be non-hazardous to aquatic algae and cannot be classified as toxic as per the CLP criteria.

Key value for chemical safety assessment

EC50 for freshwater algae:

153.5 mg/L

Additional information

Freshwater algal growth inhibition test was carried out on Desmodesmus subspicatus with the substance 1-(2-Methyl-4-(2-methylphenylazo)phenylazo)-2-naphthol (85 -86 -3) according to OECD Guideline 201 (Experimental study report, 2017). As the test substance was insoluble in water so that the stock solution 2 g/L was prepared by dissolving brown powder in acetone. Test solutions of required concentration were prepared by mixing the stock solution of the test sample with OECD growth medium and inoculum culture. 5x10(3) cells /ml algae culture were use in the study for total exposure period of 72hrs. Test conducted in 50 ml Glass vessel filled with 50 ml of sample volume and tested at the concentrations 0, 0, 1.2, 2.4, 5, 10, 20 mg/l. Effects on the growth rate of the organism were studied. The median effective concentration (EC50) for the test substance, 1 -(2 -Methyl-4 -(2 -methylphenylazo)phenylazo)-2 -naphthol, in Desmodesmus subspicatus was determined to be 153.5 mg/L. This value indicates that the substance is likely to be non-hazardous to aquatic algae and cannot be classified as toxic as per the CLP criteria.

Toxicity to aquatic algae endpoint can also be considered for waiver as per ccordance with column 2 of Annex VIII of the REACH regulation, testing for this end point is considered scientifically not necessary since there are mitigating factors indicating that aquatic toxicity is unlikely to occur as the test chemical is highly insoluble (solubility: 0.023 mg/L at 25° C) in water and also having the partition coefficient value ranging from 6.66 to 6.87, respectively. Thus, test chemical can be considered to be hydrophobic in nature.