N-[3-(dimethylamino)propyl]oleamide

Toxicity to microorganisms

Description of key information

3 h NOEC = 180 mg/L 
3 h EC20 = 280 mg//L (95% confid. interv.: 200 - 350 mg/L) 
3 h EC50 = 480 mg/L (95% confid. interv.: 400 - 600 mg/L) 

Key value for chemical safety assessment

EC50 for microorganisms:

480 mg/L

EC10 or NOEC for microorganisms:

180 mg/L

Additional information

In an activated sludge respiration inhibition test the influence of the test item on the activated sludge by measuring the respiration rate was evaluated according to OECD guideline 209, corresponding to EU C.11.

Four experiments were carried out. Activated sludge from a domestic sewage treatment plant was used as inoculum in all tests. 3,5-Dichlorophenole was used as reference item in the experiments.
First, a limit-test using the nominal concentration of 1000 mg/L was performed. After three hours a mean respiration inhibition of 90% of the activated sludge was determined.
Next, a pre-test was performed likewise using three concentrations ranging from 1 to 100 mg/L. The treatments showed no inhibition compared with the controls.
Then a main study was performed using five concentrations in duplicate, ranging from 1000 to 100 mg/L (nominal). The dry matter of the activated sludge was determined as 3.88 g suspended solids/L, giving a concentration of 1.54 g suspended solids/L in the test. The test item showed concentration-related inhibition of the activated sludge down to a concentration of 320 mg/L, no inhibition was found in the treatments containing 180 mg/L. In one replicate of the treatment 100 mg/L, though, an inhibition value of 21% was determined, which was believed to be an outlier.
Therefore, a verification experiment was performed, using the concentration 100 mg/L only. The dry matter of the activated sludge was determined as 4.18 g suspended solids/L, giving a concentration of 1.67 g suspended solids/L in the test. The test item showed no inhibition at the tested concentration; therefore, the measured value in the main study had been an outlier.
The following results for the test item were calculated using the inhibition values which were found in the main study (excluding the outlier):

3 h NOEC = 180 mg/L
3 h EC20 = 280 mg//L (95% confid. interv.: 200 - 350 mg/L)
3 h EC50 = 480 mg/L (95% confid. interv.: 400 - 600 mg/L)

All vadility criteria were met, except for the variation of the controls in the pre-test. As the pre-test was a range-finding experiment only, this was not regarded as critical concerning the outcome of the study. Within the four experiments, the EC50 which was determined for the reference item (3,5 -dichlorophenole) showed small variations only. All values lay within the range of 5 -30 mg/L which is recommended in the guideline. All experiments showed good correlation of the inhibitory effect of the test item. The result of the test can be considered valid.