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Toxicity to aquatic algae and cyanobacteria

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Description of key information

72 h ErC50 >0.45 mg/L; 72 h NOEC <0.26 mg/L, Pseudokirchneriella subcapitata, OECD 201, Muddiman 2013c

Key value for chemical safety assessment

Additional information

The acute toxicity of the test material to the freshwater green alga Pseudokirchneriella subcapitata was investigated in a study conducted in accordance with the standardised guideline OECD 201 under GLP conditions.

The algae were exposed to the test material for 72 hours under static conditions at nominal concentrations of 18, 32, 56, 100, 180 and 320 mg/L. A control group was exposed to the Algal Assay Procedure (AAP) medium under the same conditions. The 0 to 72 hour biomass was expressed as yield and average growth rate relative to the performance of the control data.

This was a limit of solubility test as the test material was not soluble in water. The nominal solutions were prepared and stirred overnight and allowed to stand for approximately 4 hours. The solution used in the test was transferred using a syphon to avoid the transference of any settled test material.

At 0 hours the measured concentrations ranged from less than the limit of detection (LOD), assessed as 0.04 mg/L, to 5.09 mg/L. At 72 hours the measured concentrations ranged from less than the LOD to 0.04 mg/L. Following this, all results are based on geometric mean measured concentrations. The geometric mean concentrations were <0.04, <0.04, <0.07, <0.18, <0.26 and 0.45 mg/L for the nominal dose levels of 18, 32, 56, 100, 180 and 320 mg/L, respectively.

The 72 hour cell density in the control averaged 90.4 x 10⁴ cells/mL. Cell density in the 18, 32, 56, 100, 180 and 320 mg/L treatment levels averaged 88.8, 87.3, 96.7, 70.8, 82.1 and 17.8 x 10⁴ cells/mL, respectively.

At 72 hours, no significant reduction in yield was detected in the <0.07, <0.18 and <0.26 mg/L treatment levels compared to the control data. Therefore, the 72-hour NOEC for yield was determined to be <0.26 mg/L. The 72-hour EyC50 was calculated as <0.3511 mg/L with 95 % confidence intervals of 0.3045 and 0.3854.

At 72 hours, no significant reduction in growth rate was detected in the <0.07, <0.18 and <0.26 mg/L treatment levels compared to the control data. Therefore, the 72 hour NOEC for growth rate was determined to be <0.26 mg/L. The 72 hour ErC50 was calculated as >0.45 mg/L.

Under the conditions of this study, the 72-hour ErC50 value of the test material was calculated to be >0.45 mg/L (geometric mean concentration). The NOEC for growth rate was calculated as <0.26 mg/L (geometric mean concentration).

The study was conducted to GLP and a standardised guideline. It was therefore assigned a reliability score of 1 and considered suitable for assessment as an accurate reflection of the test substance.

The available data are considered to be complete; the results determined, 72 h ErC50 >0.45 mg/L; 72 h NOEC <0.26 mg/L, were taken forward for risk assessment.