[2-[[4-[(2-chloro-4-nitrophenyl)azo]phenyl]ethylamino]ethyl](2-hydroxypropyl)dimethylammonium acetate

Toxicity to microorganisms

Description of key information

Three Klimisch 2 studies with structural analogues of the target substance are available in the assessment of the endpoint “Toxicity to microorganisms”. In all three studies, the inhibitory effect of the respective test substance on sewage sludge of domestic origin and/or from a laboratory scale STP was investigated after 30 min of exposure instead of a 3 h exposure period as foreseen by the current OECD Guideline 209. However, this shorter 30 min exposure period is in line with the version of OECD 209 that was applicable at the time of testing (→ OECD 209, 1984). In addition, cationic substances in particular generally adsorb strongly. This adsorption is linked to a rapid decrease of the test substance concentration in aqueous media in the presence of sewage sludge particles. Thus, a shorter exposure duration of 30 min is justified. Validity of the studies was assured by running respective positive control samples in the tests.

All three studies demonstrate significant inhibitory effects on the respiration of sewage sludge microorganisms, with 30-min EC₅₀ values of 276 mg/L, 111 mg/L and 32 mg/L, respectively (EC₅₀ values based on actual concentrations of active ingredients). The lowest EC₅₀ value of 32 mg/L is associated to an EC₁₀ of 10.2 mg/L. This EC₁₀ value is considered the key value and is carried forward in the risk characterization of the substance.

Key value for chemical safety assessment

EC50 for microorganisms:

32 mg/L

EC10 or NOEC for microorganisms:

10.2 mg/L

Additional information

The aforementioned results are used in the assessment of the target substance in a read-across approach.

For details on and justification of read-across please refer to the read-across report in section 13 of IUCLID.