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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Key value for chemical safety assessment

EC50 for freshwater algae:
98.2 mg/L
EC10 or NOEC for freshwater algae:
42.7 mg/L

Additional information

The inhibiton of growth of the alga, Selenastrum capricomutum, from exposure to Methyl n-Amyl Ketone was determined in a 72-hour OECD 201 study conducted under GLP conditions. The algae were exposed to 5 concentrations (nominally 12.5, 25, 50, 100, and 200 mg/L) of the test substance prepared in algal growth media. Geometric means of 6.2, 11.9, 22.1, 42.7, and 86.3 mg/L were calculated from analyzed values of the exposure solutions sampled throughout the test. The test substance was observed to be unstable under the test conditions as 80.7% loss was observed in the light-exposed chemical control flasks and 77.1% loss was observed in the control flasks which were maintained under light-shielded conditions. The observed loss was attributed to volatilization of the test substance during the test. Two measures of growth (biomass and growth rate) were used to detennine the effects of the test substance on the algae in comparison to controls. Cell counts were made at 24-hour intervals and growth curves and graphs of concentration versus percent inhibition were plotted. Based upon mean measured concentrations the EbC50(0-72hr) value was estimated to be 75.5 mg/L. The ErC50 (0-72hr) value was estimated to be 98.2 mg/L. The 72-hour NOEC value was estimated to be 42.7 mg/L. The EC50 and NOEC for growth rate are being used as the key value for the chemcial safety assessment.