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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The substance was not inhibiting to microbial activity at a nominal test concentration of 100 mg/L in the ready biodegradability test.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

The valid study on the ready biodegradability included a toxicity control with the positive reference substance aniline (at 100 mg/L) and the test substance allyl hexanoate (at 100 mg/L). The microbial activity in this toxicity control was not significantly inhibited. According to ECHA guideline R.7b, the non-inhibiting test concentration in the toxicity can be regarded as NOEC for microbial toxicity in the hazard assessment. In contrast, a study on the acute toxicity of allyl hexanoate on the ciliate Tetrahymena pyriformis produced an EC50 value (based on growth inhibition) of 1.63 mg/L. ECHA guidance R.7b says that "preference is given to tests with a mixed inoculum that assess the functioning of the entire microbial community in an STP, rather than tests based on single species or even microbial sub-systems" (page 149). Therefore, the study on Tetrahymena is not considered in the derivation of a threshold value for toxicity to micro-organism and the PNEC STP will be based on the non-inhibitory concentration applied in the toxicity control of the study on ready biodegradability conducted with non-adapted activated sludge.