Registration Dossier

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The 72-hour EL50 (growth rate) Desmodesmus subspicatus; > 100 mg/l (OECD 201, GLP)

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L

Additional information

The key study on toxicity to Desmodesmus subspicatus was conducted according to the OECD 201 in compliance with GLP. Aim of the study was to determine the loading rate of the test substance renewable hydrocarbons of wood origin (diesel type fraction) inhibiting the average specific growth rate and yield of the freshwater algae Desmodesmus subspicatus in 72 -hour study. Because the substance is complex mixture of hydrocarbons and slightly soluble to water, the study was performed in Water Accommodate Fractions (WAF).

The limit test and range-finding test were performed in parallel. Because the results from range-finding tests (WAF-loading rates of 3 mg/L, 9 mg/L, 27 mg/L, 81 mg/L, 300 mg/L, 900 mg/L and 2700 mg/L) showed no toxicity response and instead stimulated algae growth, an execution of a definitive test was not relevant. Thus, the definitive test was conducted as a limit test concentration of 100 mg/L. On the basis of the results it was concluded that the test substance stimulated both the average specific growth rate and the biomass yield of algae compared to the control after 72 hours of exposure. Therefore no effective - inhibition WAF loadings could be calculated.

Stimulation can be explained by the fact that algae utilizes - metabolizes the test substance as additional source of nutrients and consequently causes its faster growth and biomass yield. Based on the results it can also be concluded that the WAF loading of about 100 mg/L is probably the maximum possible solubility of the test substance in water, because beyond it neither growth rate or biomass are further changing.

In conclusion, based on the key study results no toxicity to algae up to maximum test concentration of 100 mg/l was observed.