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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

EC50 (72 h, growth rate) = 5.3 mg/L (mean measured) for Pseudokirchneriella subcapitata (OECD 201)

NOECr (72, growth rate) = 1.6 mg/L (mean measured) for Pseudokirchneriella subcapitata (OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:
5.3 mg/L
EC10 or NOEC for freshwater algae:
1 mg/L

Additional information

One key study is available for 2-{2-chloro-4-mesyl-3-[(tetrahydrofuran-2-ylmethoxy)methyl]benzoyl}cyclohexane-1,3-dione, in which the toxicity to algae was investigated. The study (M-116272-01-1; 2003) was conducted according to GLP and OECD guideline 201. In a static test system in freshwater, the test organism Pseudokirchneriella subcapitata was exposed to five nominal concentration of 0.32, 0.56, 1.0, 1.8, 3.2, and 5.6 mg/L. Triplicate algal cultures with an initial cell density of 10000 algal cells/mL were incubated in a synthetic medium at 25 ± 1 °C for 96 hours. Chemical analysis of the freshly prepared and aged (96 h) test solutions was performed for all tested concentrations. Analyses of freshly prepared medium resulted in test item concentrations ranging from 84.6% to 106.6% of nominal values. Analyses of aged medium at experimental termination (96 h) resulted in test item concentrations ranging from 75.9% to 102.3% of nominal values. Mean measured concentrations of the whole exposure period varied between 80.2 and 100.3%. Based on chemical analysis, all mean measured concentrations were above 80% of the nominal concentrations. The results of this study were initially reported on nominal but analytically confirmed concentrations following OECD guideline 201 (1984). However, for regulatory purposes results were re-calculated based upon the newer OECD guideline 201 adopted in 2006 (M-287714-01-1; 2007). Re-calculations are reported as mean measured values and given here. The mean measured concentration of test item inhibiting the growth and the resulting ECr50 in comparison with the solvent control after 72 hours test duration was 5.3 mg test item/L. Significant inhibition of specific growth rate based on a comparison of slopes of the growth curves was observed in the three highest treatment levels of 1.8, 3.2 and 5.6 mg/L after 72 hours test duration. The no observed effect concentration (NOEC) was considered to be 1.0 mg test item/L.