Reaction mass of 3,5,6,6-tetramethyl-4-methyleneheptan-2-one and (E)-3,4,5,6,6-pentamethylhept-3-en-2-one

Toxicity to aquatic algae and cyanobacteria

Description of key information

An OECD TG 201 guideline study in compliance with GLP with freshwater algae (Desmodesmus subspicatus) is available for the test substance. Algae were exposed to nominal concentrations of 0.78, 2.5, 7.8, 25 and 78 mg/L under static conditions for 72 hours. Because the test material is volatile, testing was conducted in completely filled, stoppered test vessels in order to minimise possible losses due to volatilisation. Measured test concentrations at t=0 were 0.57, 1.9, 6.2, 20.8 and 69.5 mg/L. Measured test concentrations at t=72 in periodically opened test vessels were 0.49, 1.8, 5.5, 18.6 and 59.6 mg/L (85 -92% of initial). To examine the loss of test substance during opening of test vessels, an additional test replicate was prepared at 0 hours and incubated alongside the test to provide samples for unopened vessel analysis. Analysis of these continuously closed vessels gave concentrations of 0.51, 1.9, 6.1, 20.2 and 61.9 mg/L (89 - 98% of initial). Based on these percentages, the results are based on initial measured concentrations. There were no statistically significant differences in growth rate and yield between the control and the 0.57, 1.9, and 6.2 mg/L test concentrations. At the higher concentrations however statistically significant inhibition of growth rate and yield was observed. Based on these data, the 72-h NOErC and NOEyC are determined at 6.2 mg/L. For growth rate, the ErC10 and ErC50 values were calculated to be 12 and 21 mg/L, respectively. For yield the EyC10 and EyC50 values were calculated to be 9.8 and 13 mg/L, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

21 mg/L

EC10 or NOEC for freshwater algae:

12 mg/L