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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

72-hour EC50 > 24 mg/L  (no effects at limit of solubility), OECD 201, EU Method C.3, ISO 8692 and OECD 23, Migchielsen (2007)

Key value for chemical safety assessment

EC50 for freshwater algae:
24 mg/L

Additional information

The toxicity of the test material to the aquatic algae, Selenastrum capricornutum, was investigated in a study which was conducted under GLP conditions and in accordance with the standardised guidelines OECD 201, EU Method C.3, ISO 8692 and OECD 23.

During the study exponentially growing algal cultures were exposed to a blank control and a 0.45 µm filtered solution prepared at a loading rate of 100 mg/L. In addition, dilutions containing 1.0 and 10% of the filtrate were tested. The total test period was 72 hours and the initial algal cell density was 10^4 cell/mL. Samples for analyses of actual exposure concentrations were taken at the start, after 24 and 72 hours of exposure.

Analysis of the samples taken from the filtrate prepared at a loading rate of 100 mg/L showed that measured concentrations remained stable at 24 mg/L throughout the 72- hour test period. The low lithium background measured in samples from the blank-control originated from lithium traces present in the purified water used for preparation of the test medium and this did not affect the exposure of algae or the study integrity.

Under the conditions of the present study with Selenastrum capricornutum, no significant inhibition of cell growth or
reduction of growth rate was recorded at or below an exposure concentration of 24 mg/L, being the concentration
measured in a 0.45 µm filtered solution prepared at a loading rate of 100 mg/L (NOEC). Instead, Lithium iron
phosphate stimulated algal cell growth, which was most likely related to the presence of phosphate in the test
substance that served as an extra nutrient source for the algae.

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