Climbazole

Toxicity to aquatic algae and cyanobacteria

Description of key information

Based on the available results, the most sensitive ErC50 value of 0.034 mg/L from the test with Lemna minor and the most sensitive ErC10 value of 0.026 mg/L from the test with Desmodesmus subspicatus (2011) were taken into account for the hazard assessment and classification.

Key value for chemical safety assessment

EC50 for freshwater algae:

0.034 mg/L

EC10 or NOEC for freshwater algae:

0.026 mg/L

Additional information

Several tests with green algae and diatoms are available. Three results are based on a recently published paper (Richter et al., 2013). Even though their reliability could not be assigned due to limited details mentioned in the publication (RL4), the results were considered in the hazard assessment and classification on the basis of a weight of evidence approach.

Two studies with Desmodesmus subspicatus are available. One study (2011, RL1) was done according to OECD 201 and GLP over 72 hours. Seven concentrations of 0.001, 0.0032, 0.01, 0.032, 0.1, 0.32 and 1 mg/L were tested in a static test. The concentrations were measured at the beginning and the end of the test. The results were based on the geometric mean of the measured concentrations. The ErC50 was determined to be 0.3 mg/L and the ErC10 to be 0.026 mg/L. The concentration not causing growth inhibition (NOEC (growth rate)) was determined to be 0.013 mg/L.

The second study with Desmodesmus subspicatus (1993, RL4) was done according to DIN EN 28692 by a laboratory of the German Federal Health Office. As only a handwritten protocol is available, a reliability could not be assigned (RL4). The protocol contains two experiments: In the first one, 8 concentrations in the range of 0.32 – 41.2 mg/L (spaced by a factor of two) and in the second experiment, 10 concentrations in the range of 0.0008 – 0.432 mg/L (spaced by a factor of two) were used.The concentration of the test substance causing 50% reduction in growth of biomass (EbC50) was determined at 0.087 mg/L. In addition, the ErC50 was determined from the raw data to be >= 0.216 mg/L (50% reduction at concentration of 0.216 mg/L and 54% reduction at concentration of 0.432 mg/L). The concentration causing 10% reduction in growth of biomass after 72h was determined to be 0.032 mg/L. The ErC10 determined from raw data was > 0.027 mg/L (3% inhibition) and < 0.054 mg/L (12.9% inhibition) after 72 hours.

Additionally to the tests with Desmodesmus subspicatus, two results based on tests with Pseudokirchneriella subcapitata and Navicula pelliculosa are available from the paper from Richter et al. (2013):

The acute toxicity of the test substance to Pseudokirchneriella subcapitata and the diatom Navicula pelliculosa was tested according to OECD 201 over 72 hours in a static system. Concentrations from 0.15 – 2.4 mg/L (P. subcapitata) and from 0.008 – 0.2 mg/L (N. pelliculosa.) were tested. The ErC50 for Pseudokirchnerialla subcapitata was determined to be 1.19 mg/L and the ErC10 to be 0.315 mg/L based on nominal concentrations. The ErC50 for Navicula pelliculosa was determined to be 0.291 mg/L and the ErC10 to be 0.108 mg/L based on nominal concentrations.