2,2'-[(4-methylphenyl)imino]bisethanol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

January 25th, 2013

Justification for type of information:

Refer to the analogue approach justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Validity criteria fulfilled:

yes

Conclusions:

Based on the available read-across data, it is concluded that the target substance is slightly toxic to activated sludge microorganisms below concentrations of 1000 mg/L. The retained key value for the toxicity to microorganisms is an EC50 (3 h) of > 1000 mg/L.

Executive summary:

The toxicity of the source substance Accelerator (PT 25E or PT 25E/2) to activated sludge microorganisms was assessed according to OECD guideline 209 and GLP at the nominal test concentrations of 0 (blank control), 10, 100 and 1000 mg/L.

After 3h of incubation, Accelerator (PT 25E or PT 25E/2) did not cause an inhibition of the respiration rate at 10 mg/L. At 100 and 1000 mg/L an inhibition of 21% and an average of 29% inhibition were observed, respectively. The inhibition at 1000 mg/L was statistically significant but below 50%. The EC50 was estimated to be >1000 mg/L related to the respiration rate. No NOEC could be determined since it was observed a statistically significant difference in inhibition at 1000 mg/L in relation to the control group, and only one replicate was used for the lower test concentrations (i.e. 10 and 100 mg/L). Therefore, the statistical significance could not be determined at test concentrations of 10 and 100 mg/L. There was no significant oxygen uptake from abiotic processes. The results at 1000 mg/L with a nitrification inhibitor showed no heterotrophic inhibition of the respiration rate. The reviewer calculated that at 1000 mg/L, the heterotrophic respiration was inhibited 4% and the nitrification respiration was inhibited 92%. The study is considered to be reliable without restrictions.

The target substance is expected to have a similar ecotoxicological profile as the source substance based on the high degree of structural and chemical similarity between the source and the target substances. Therefore, it is concluded that the key value for the toxicity of the target substance to microorganisms is an EC50 (3 h) of > 1000 mg/L.

Description of key information

EC50 (3 h) > 1000 mg/L (nominal, OECD 209, act. sludge); read-across

Additional information

There is no study available, in which the toxicity of the target substance N,N-Dihydroxyethyl-p-toluidine (CAS 3077-12-1) to microorganisms was assessed. Therefore, read-across to the structurally and chemically closely related source substance Reaction mass of 2,2'-[(4-methylphenyl)imino]bisethanol and Ethanol 2-[[2-(2-hydroxyethoxy)ethyl](4-methylphenyl)amino]- (EC 911-490-9) was performed in accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5 in order to meet the standard information requirements laid down in Annex VIII of REACh Regulation (EC) No 1907/2006. Based on the high degree of physico-chemical similarity between the target and source substances, the selected source substance is considered a suitable representative for the assessment of the toxicity of the target substance to microorganisms. A detailed read-across approach justification is provided in IUCLID section 13.

In the available study with the source substance, the nominal test item concentrations of 10, 100, and 1000 mg/L were inoculated with 1.7 g/L activated sludge (suspended solids) for 3 h according to OECD guideline 209.

After 3 h incubation, no inhibition of the respiration rate was observed at 10 mg/L. At 100 and 1000 mg/L, an average inhibition of 21% and 29%, respectively, was recorded. The test vessel containing a nitrification inhibitor showed no heterotrophic inhibition of the respiration rate at 1000 mg/L. The reviewer calculated that at 1000 mg/L, the inhibition of the heterotrophic respiration rate was 4% and that of the nitrification respiration 92%. The inhibition at 1000 mg/L was statistically significant but below 50%. The obtained EC50 (3 h) for respiration rate was > 1000 mg/L. No NOEC could be derived because a statistically significant difference in inhibition in relation to the control was identified at 1000 mg/L but only one replicate had been prepared for the lower test concentrations at 10 and 100 mg/L. Therefore, the statistical significance could not be determined at the test concentrations of 10 and 100 mg/L.

 

Based on the high degree of structural and chemical similarity between the target and the source substance and since the target substance is the main constituent of the source substance, the target substance is expected to exhibit a similar ecotoxicological profile as the selected source substance. It is concluded that the target substance N,N-Dihydroxyethyl-p-toluidine (CAS 3077-12-1) is of low toxicity to activated sludge microorganisms, resulting in an EC50 (3 h) of > 1000 mg/L.