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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

Link to relevant study record(s)

Description of key information

Acute toxicity to  fresh water algae (Pseudokirchneriella subcapitata): The 96h-EC50 (growth rate), 0.24 mg/l (95% CI%,  0.085 to 0.70 mg/l) and the NOEC value, 0.0079 mg/l.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.24 mg/L
EC10 or NOEC for freshwater algae:
0.008 mg/L

Additional information

Toxicity of the test substance to aquatic algae was determined by conducting growth inhibition test in compliance with principles of GLP and OECD guideline No. 201. This study was considered as reliable with no restrictions and hence used as a key value for hazard assessment and classification and labeling of the substance.

Two other tests were also performed in compliance with GLP using the standardised method similar to EPA 40 CFR 797.1050.One of these studies was performed with modification of addition of humic acid (10 mg/l and 20 mg/l) into the AAP medium. These test results were regarded as supporting studies because of growth medium modification, no analysis of test solution concentrations and lack of specific growth rate recorded as a result of the study.

Under the conditions of the key study, test substance reduced growth rate and inhibited the yield of this fresh water algae species significantly at 0.025 mg/l and higher. Effects appeared to be algistatic rather than algicidal up to and including a concentration of 0.84 mg/l.

Under the conditions of the supporting study, a 96-hour EC50 value of 0.01 mg/l based on biomass yield was established where no humic acid was added to the dilution water.A comparison of this value with the EC50 values (biomass yield) generated during humic acid addition (0.053 and 0.06 mg/l) demonstrated that the addition of humic acid at concentrations of 10 to 20 mg/l, decreased the toxicity of the substance by approximately 6-fold.

Since no reported values were presented for specific growth rate in this study report, the 96-hour ErC50 was recalculated to be > 0.11 mg/L and NOEC 0.0030 mg/L. Recalculated 96-hr ErC50 was 0.954 mg/L and NOEC 0.008 mg/L (as compared to control without humic acid) for 20 mg/L humic acid solution. Based on the results of both studies, the effects appeared to be algistatic rather than algicidal.


Based on the results of the key and supporting studies, the test substance can be concluded as very toxic to aquatic life (aquatic acute cat. 1). All the studies indicated that the effects of the substance on algal growth are algistatic rather than algicidal.