Climbazole

Toxicity to soil microorganisms

Description of key information

A test with the soil bacteria Arthrobacter globiformis resulted in an EC50 of 456 mg/kg dw.

A nitrogen transformation test resulted in a NOEC of 1000 mg/kg dw.

Key value for chemical safety assessment

Short-term EC50 for soil microorganisms:

456 mg/kg soil dw

Long-term EC10 or NOEC for soil microorganisms:

1 000 mg/kg soil dw

Additional information

The toxicity to soil microorganisms was investigated with two different tests.

In a soil nitrogen transformation test according to OECD 216 and GLP (key, RL1, 2014), the inhibition of five different test concentrations (62.5, 125, 250, 500 and 1000 mg/kg dw) was tested. After 28 days of exposure no significant inhibition or stimulation of the microbial nitrate transformation was found at all test item concentrations compared to the untreated control (NOEC = 1000 mg/kg soil dw). However, after 7 and 14 days a stimulation of the microbial nitrate transformation rate was observed. The test substance concentrations that induced stimulated microbial nitrate transformation in this study are relatively high. It is possible that the temporary and reversible dose-dependent effect observed at these concentrations was due to the contribution of the degradation of the test item to overall microbial activity, rather than due to the comparable low nitrogen content of the test item or a disturbance of microbial activity. Due to the constraints of the study design it is not possible to discriminate between these possible causes of the observed stimulation.

Additionally, a test with the soil bacteria Arthrobacter globiformis was recently published in a paper by Richter et al. 2013 (RL4). The short-term toxicity of the test item to the soil bacterium Arthrobacter globiformis was studied according to the draft ISO guideline 10871. The bacteria were incubated for 2 h in well plates with quartz sand at 30°C. The determined EC50 was 456 mg/kg dw.