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Toxicity to aquatic algae and cyanobacteria

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Description of key information

This study was conducted to evaluate the effects with water accommodated fractions (WAFs) of the test substance on growth of the alga, Pseudokirchneriella subcapitata, in a 72-hour static dose-response test. Treatment WAFs were prepared by adding the appropriate amount of test substance to dilution media in a 4.3 L glass aspirator bottle and stirring on a magnetic stir plate with a vortex of ≤ 10% of the static liquid depth for approximately 24 hours. Approximately one hour after stirring termination, the aqueous portion of the WAF solution was removed for testing. The nominal loading rates were 0 (control), 0.87, 2.3, 6.0, 16, 42 and 110 mg/L. The actual loading rates tested were 0 (control), 0.92, 2.4, 6.2, 16, 42 and 110 mg/L.

At 72 hours, statistically significant treatment-related effects were observed when the treatment groups were compared to the control group. The acute toxicity endpoint, EL50 (50% Effect Loading), is expressed as percent inhibition of growth derived from the average specific growth rate (r) and yield (y) relative to the control. Chronic toxicity endpoints, EL10 (10% Effect Loading), NOELR (No Observed Effect Loading Rate) and LOELR (Lowest Observed Effect Loading Rate) values were determined for average specific growth rate and yield

Based on growth rate, effects (mg/L) at 72 hours are as follows:

ErL10: 3.9 (3.5 - 4.4)

ErL50: 18 (17 - 19)

NOELR: 2.4

LOELR: 6.2

Key value for chemical safety assessment

EC50 for freshwater algae:
18 mg/L
EC10 or NOEC for freshwater algae:
3.9 mg/L

Additional information

The toxicities to algal growth were determined in GLP-compliant, static, freshwater tests following OECD guideline 201.

Based on growth rate, effects (mg/L) at 72 hours are as follows:

ErL10: 3.9 (3.5 - 4.4)

ErL50: 18 (17 - 19)

NOELR: 2.4

LOELR: 6.2