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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

72 h EC50 = > 100 mg/L, NOEC = 100 mg/L, Scenedesmus subspicatus, OECD 201, EU Method C.3, L 'Haridon 2003

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

The toxicity of the test material to aquatic plants was investigated in the algae Scenedesmus subspicatus in accordance with standardised guidelines OECD 201 and EU Method C.3. During the study the algal culture was exposed to the test material at nominal concentrations of 0, 0.1, 1, 10 and 100 mg/L under static conditions. Since the test material was a coloured solution, a modified testing method was used whereby controls shaded by the test solution were used to compare the effects of the reduced light falling on the algae as the concentration of test material increased. Under the conditions of the study inhibition of cell growth in controls solutions with shading by the test solutions was similar to inhibition of cell growth noted in the test solutions. After 72 hours, inhibition of growth rate in each test solution (0.1, 1, 10 and 100 mg/L) minus inhibition of growth rate in the control solution with shading by this test solution was < 10 %. This was also the case for inhibition of growth in each test solution after 72 hours. It was therefore concluded that inhibition of cell growth observed in test solutions came from reduction of light intensity by the test material (shading effect) and not from a toxic effect of this test material towards algae.

As the test material was not found to be toxic at 100 mg/L nominal, chemical analysis was undertaken to measure the concentration of the test material in this solution. Measured concentrations in the limit test solution with and without algae were within ± 20 % of the nominal value (100 mg/L) throughout the test. All study results were therefore based on nominal concentrations. As no inhibition of the algal growth due to a toxic effect of the test material was observed at 100 mg/L and the measured concentrations of the test material were within ± 20 % of this nominal value throughout the test, the study was considered complete. Therefore, the 72 hour EC50 was determined to be in excess of 100 mg/L based on the specific growth rate and in excess of 100 mg/L based on biomass data. The 72 hour NOEC was determined to be 100 mg/L based on the specific growth rate and biomass data.

The study was performed in line with GLP and accepted standardised guidelines with a high standard of reporting. The study was assigned a reliability score of 1 in accordance with the criteria outlined by Klimisch (1997) and considered suitable for assessment as an accurate reflection of the test material.

The available data are considered to be complete and the result determined, 72 h EC50value > 100 mg/L, 72 h NOEC value 100 mg/L, was taken forward for risk assessment.