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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

To assess potential effects of methyl 2-hydroxyisobutyrate to the freshwater green alga, Pseudokirchneriella subcapitata, an Alga Growth Inhibition Test according to OECD Testing Guideline 201 was performed for 72 hours with target concentrations of 0 (AAP control), 1.00, 3.10, 9.80, 31.3 and 100 mg methyl 2-hydroxyisobutyrate/L. Cell density was determined at approximately 24, 48 and 72 hours (±1 hour from test initiation).

The acute toxicity values for Pseudokirchneriella subcapitata exposed to methyl 2-hydroxyisobutyrate over a 72-hour static exposure period and based on nominal concentrations were as follows:

Growth rate

72-hour ErC50: >100 mg/L (highest concentration tested)

72-hour ErC20: 95.6 mg/L (95% C.I. = 84.1 – 109 mg/L)

72-hour ErC10: 45.4 mg/L (95% C.I. = 36.1 – 57.1 mg/L)

72 -hour NOEC: 9.80 mg/L

Cell yield

72-hour EyC50: 54.8 mg/L (95% C.I. = 44.1 – 68.2 mg/L)

72-hour EyC20: 20.8 mg/L (95% C.I. = 13.5 – 32.1 mg/L)

72-hour EyC10: 12.5 mg/L (95% C.I. = 7.03 – 22.3 mg/L)

72-hour NOEC: 9.80 mg/L

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
9.8 mg/L

Additional information

Temperatures during the exposure period ranged from 22-23°C. The pH ranged from 7.3-7.8 and the light intensity ranged from 4680-5520 lux. Test solutions were analyzed for methyl 2-hydroxyisobutyrate concentrations at test initiation and exposure termination by gas chromatography with selected ion monitoring (GC/SIM). None of the analyses of the AAP medium control exhibited a concentration exceeding the lower limit of quantitation (LLQ) equivalent to 0.125 mg methyl 2-hydroxyisobutyrate/L. Measured concentrations of methyl 2-hydroxyisobutyrate ranged from 83.2 to 104% of nominal concentrations over the course of the exposure period. The resulting mean measured test concentrations were 0.959, 2.99, 8.92, 28.7 and 91.2 mg methyl 2-hydroxyisobutyrate/L. Because the mean measured concentration were within ± 20% of the target nominal concentrations, study endpoints were based on nominal concentrations.

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