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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

Freshwater: EC50 0.33 µg/L, NOEC 0.22 µg/L, 5 day toxicity test with freshwater diatom, EPA 540/9-82-020, Thomas and Swiggert 1996b
Marine water: EPA FIFRA 123-2, EC50 0.11 µg/L, NOEC 0.066 µg/L, Thompson & Swigert 1997.

Key value for chemical safety assessment

EC50 for freshwater algae:
0.33 µg/L
EC50 for marine water algae:
0.11 µg/L
EC10 or NOEC for freshwater algae:
0.22 µg/L
EC10 or NOEC for marine water algae:
0.066 µg/L

Additional information

Five studies have been provided to address the toxicity to aquatic algae and cyanobacteria in freshwater and one study to address toxicity in marine water.

Five algal toxicity studies have been provided to address freshwater toxicity using three different species (Scenedesmus subspicatus, Navicula pelliculosa and Selenastrum capricornutum). The study performed with N. pelliculos (Thompson and Swiggert, 1996b) has been considered to be the key study for this endpoint on the basis that of all the studies the test organism was the most sensitive to the test material when compared to the studies performed with S. capricornutum by Thompson and Swiggert (1996a) and Grade (2000) and the study performed with S. subspicatus by Grade (1994). The study performed by Grade (1997) used test material which was a formulation containing only 10.1% CGA 276854 and so was not considered representative of the substance to be registered.

The toxicity of the test material to aquatic freshwater algae, Navicula pelliculosa was determined in a 5 day cell inhibition study performed to GLP and the standardised guideline EPA 540/9-82-020. N. pelliculosa were exposed to the test material at measured concentrations of 0.051, 0.085, 0.22, 0.42, 0.82 and 1.5 µg a.i./L. Due to a decline in test material concentration over the exposure period, the results were expressed relative to Day 0 concentrations. Negative and vehicle controls were run concurrently for comparison. Inhibition of growth was determined by measuring cell densities at 24 hour intervals. Gross cell morphological changes were determined on Day 5 by microscopic examination. Under the conditions of the test, the EC50 was determined to be 0.33 µg a.i./L with 95% confidence limit of 0.25 and 0.35 µg a.i./L, on the basis of cell density. All algal cells appeared normal in size, shape and colour through microscopic examinations of gross cell morphology. The 5 day NOAEC was determined to be 0.22 µg a.i./L. 

The toxicity of the test material to marine diatom Skeletonema costatum was determined in a 5 day cell inhibition study performed to GLP and the standardised guideline EPA 540/9-82-020. S. costatum were exposed to the test material at measured concentrations of 0.016, 0.030, 0.066, 0.14, 0.25 and 0.53 µg a.i./L. Due to a decline in test material concentration over the exposure period, the results were expressed relative to Day 0 concentrations. Negative and vehicle controls were run concurrently for comparison. Inhibition of growth was determined by measuring cell densities at 24 hour intervals. Gross cell morphological changes were determined on Day 5 by microscopic examination. Under the conditions of the test, the EC50 was determined to be 0.11 µg a.i./L with 95% confidence limit of 0.11 and 0.12 µg a.i./L, on the basis of cell density. All algal cells appeared normal in size, shape and colour through microscopic examinations of gross cell morphology. The 5 day NOAEC was determined to be 0.066 µg a.i./L.

 

All studies were performed to a high standard, according to GLP and standardised guidelines. They have thus been assigned a reliability score of 1 in line with the principles for assessing data quality set out by Klimisch (1997). The available data are deemed to be relevant, reliable and adequate for the purposes of risk assessment.

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