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Toxicity to aquatic algae and cyanobacteria

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Description of key information

In an algal growth inhibition test with Raphidocelis subcapitata, the 72-h EC10, EC20, EC50 for growth rate for MIKP were determined to be 0.94, 1.07 and 1.33 mg/L, respectively. The 72-h EC10, EC20, EC50 for yield were determined to be 0.65, 0.78 and 1.04 mg/L, respectively. The LOEC values based on growth rate and yield were determined to be 1.04 mg/L. The 72-h NOEC for growth rate and yield was determined to be 0.15 mg/L. The results are based on measured geometric mean test item concentrations.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.33 mg/L
EC10 or NOEC for freshwater algae:
0.94 mg/L

Additional information

In a growth inhibition test according to OCCD guideline 201 and EU method C.3, the effect of the test item Methyl-isobutyl-ketone-peroxide (MIKP) on the growth of a unicellular green algal species was evaluated. Exponentially growing cultures of Raphidocelis subcapitata were exposed to the nominal test item concentrations of 10.0, 3.70 1.37, 0.51, 0.19 mg/L under defined conditions. Corresponding calculated geometric mean measured concentrations were: 0.06, 0.15, 1.04, 2.10 and 6.03 mg/L. The algal growth in relation to a control culture was determined over a fixed test period of 72 hours and, thus, over several algal generations. Biological results are based on the measured geometric mean test item concentrations as the analytically measured test item concentrations were not within the range of ± 20 % of the nominal over the test period of 72 hours.

In this 72-h algal growth inhibition test with Raphidocelis subcapitata, the obtained results showed that the test item Methyl-isobutyl-ketone-peroxide (MIKP) had significant toxic effects on the growth of Raphidocelis subcapitata. The 72-h EC10, EC20, EC50 for growth rate were determined to be 0.94, 1.07 and 1.33 mg/L, respectively. The 72-h EC10, EC20, EC50 for yield were determined to be 0.65, 0.78 and 1.04 mg/L, respectively. The LOEC values based on growth rate and yield were determined to be 1.04 mg/L. The 72-h NOEC for growth rate and yield was determined to be 0.15 mg/L. All validity criteria were met. The results are based on measured geometric mean test item concentrations.