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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

72h-EC50 > 0.006 mg/L (limit water solubility)
No toxic effects are to be expected up to the limit of water solubility.

Key value for chemical safety assessment

Additional information

A study determining the toxicity of SP-334 (2-(2-hexyl-decyloxy)-benzamide) to algae is available (Bogers, 1998). This test was conducted according to OECD Guideline 201 under GLP conditions. Due to the poor water solubility of the substance (≤0.006 mg/L) a homogeneous solution could not be achieved by physical means (magnetic stirring and ultrasonic treatment) after addition of the test substance. Therefore, for the final test a filtrate (5 µm) of test solution (described as slightly turbid at the beginning of the test) was prepared using acetone as solvent (1 mL/L), leading to concentrations of 0.1, 0.18, 0.32, 0.56 and 1 mg/L. Analytical measurements of test concentrations were performed with HPLC (including an additional group at 1 mg/L containing no algae). Selenastrum capricornutum was exposed to the test substance in ISO medium for 72 hours and effect parameters recorded at 24, 48 and 72 hours. Significant differences on biomass and growth rate were observed from concentrations of 0.18 and 0.32 mg/L respectively, compared to control values. However, precipitation of the test substance occurred in all tested concentrations to the extent that spectrophotometric measurements of cell densities could not be performed, and a microscope was needed instead. Furthermore, all test concentrations measured at 72 hours were below the limit of detection (0.011 mg/L) except for that in the solution containing no algae (decreasing from 1 mg/L to 0.2 mg/L at 72 hours). This indicates that most probably the observed effects are rather physical (i.e. less access to light and nutrients) due to precipitation and substance adsorption to algal surface than toxicological. Therefore, the reported EC50 values should not be considered in further quantitative risk assessment.

 

In conclusion, SP-334 is not expected to exert toxicity to algal species within the range of its water solubility ( ≤0.006 mg/L)

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