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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

The biological results are expressed on the basis of loading rates, since the test item is characterised as an UVCB, and, also on measured time-weighted average concentrations.

Based on Loading Rates :

Growth Rate -

ErL50 (72 hour) > 100 mg/L

NOErL (72 hour) = 32 mg/L

Based on Yield -

EyL50 (72 hour) > 100 mg/L

NOEyL (72 hour) = 32 mg/L

Based on measured Time-Weighted Average Concentrations :

Growth Rate -

ErC50 (72 hour) > 0.38 mg/L (> saturation concentration)

NOErC (72 hour) = 0.32 mg/L

Based on Yield -

EyC50 (72 hour) > 0.38 mg/L (> saturation concentration)

NOEyC (72 hour) = 0.32 mg/L

Key value for chemical safety assessment

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

Additional information

One study investigating the short-term toxicity of the test substance to freshwater algae is available. The test was performed according to GLP and OECD guideline 201 using Pseudokirchneriella subcapitata as test organism. An EC50 test was performed based on the results of two preceding tests, i.e. a combined limit/range-finder and an EC50 test with a narrower range of concentrations. Exponentially growing algal cultures were exposed to a control and WAFs prepared at loading rates of 1.0, 3.2, 10, 32 and 100 mg/L. Samples for analytical confirmation of actual exposure concentrations were taken at the start and after 24 and 72 hours of exposure.

Samples taken from the 32 and 100 mg/L loading rates were analyzed and showed initial concentrations of 9.3 and 14 mg/L, respectively. These concentrations decreased below the area of the lowest calibration solution, i.e. below 0.14 mg/L within 24 hours of exposure. Note that some undissolved test substance particles were observed at the loading rates of 32 and 100 mg/L from 24 hours of exposure onwards indicating that it was likely that the start concentrations exceeded the actual solubility limit. The Time Weight Average (TWA) exposure concentrations at the 32 and 100 mg/L loading rates were calculated to be 0.32 and 0.38 mg/L, respectively.

Both the EC50 for growth rate reduction and yield inhibition exceeded a glass-wool filtered WAF that was obtained from a loading rate of 100 mg/L, i.e. exceeded a TWA concentration of 0.38 mg/L. The NOEC for both growth rate reduction and yield Inhibition equaled the concentration present in a glass-wool filtered WAF prepared at a loading rate of 32 mg/L. The corresponding TWA concentration is 0.32 mg/L. Based on this result, the substance is not considered to be acutely harmful to freshwater algae.