N'-(ethylcarbonimidoyl)-N,N-dimethylpropane-1,3-diamine monohydrochloride

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August to October 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

White Crystalline powder

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage.

Test type:

semi-static

Water media type:

other: Tap water purified by reverse osmosis

Limit test:

yes

Total exposure duration:

3 h

Remarks on exposure duration:

3 hours, during which aeration and stirring took place.

Post exposure observation period:

After the 3-hour contact time the oxygen consumption was recorded for a period of approximately 10 minutes.

Test temperature:

20-22 C

pH:

7.7

Nominal and measured concentrations:

Five concentrations: 3.2, 10, 32, 100, 320 and 1000 mg/L. 5 replicates per test group and 6 replicates for the control.

Details on test conditions:

Contact time: 3 hours, during which aeration and stirring took place.
Vessels: All glass open bottles/vessels.
Milli-RO / Milli-RO water: Tap water purified by reverse osmosis (Millipore Corp., Bedford, Mass., USA).
Synthetic medium (=sewage feed): 16 g peptone, 11 g meat extract, 3 g urea, 0.7 g NaCl, 0.4 g CaCl2.2H2O, 0.2 g MgSO4.7H2O, 2.8 g K2HPO4. Dissolved in Milli-RO water, made up to 1 litre
and filtered. The pH was within 7.5 ± 0.5.
Air supply: Clean, oil-free air.
Aeration: The aeration was adjusted in such a way that the dissolved oxygen concentration at the start was above 60-70% saturation (60% of air saturation is > 5 mg/L at 20°C) and to maintain the sludge flocs in suspension.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

ca. 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

>= 69 - <= 132 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

>= 123 - <= 199 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

>= 347 - <= 470 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

inhibition of total respiration

Details on results:

A combined limit/ Range-finding test was carried out. It showed 11%, 26% and 90% inhibition of the respiration rate at a concentration of 10,100 and 1000mg/l respectively. Therefore, the expected EC50 was between a concentration of 100 and 1000mg/l. There was no oxygen uptake from abiotic processes. All test conditions prescribed by the study plan were met. Although the validity criterion of the mean control oxygen uptake was less than 30 mg O2/L.h (29.28 mg O2/L.h) the study was considered to be valid, since the validity criterion stated in the OECD Guideline (20 mg O2/g.h) was met.

For the final test, The effects observed were in agreement with what was expected based on the results of the combined limit/range-finding test. The results of this test allowed for reliable determination of a NOEC and ECx values. No statistically significant inhibition of the respiration rate of the sludge was recorded at 100 mg 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride per liter (for more information on statistics see Appendix 4). At higher concentrations the inhibitory effect of 1- (3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride on aerobic waste water
(activated sludge) bacteria increased with increasing concentration, with 42% and 80% inhibition of the respiration rate at 320 and 1000 mg/L, respectively.

Validity criteria fulfilled:

yes

Conclusions:

In conclusion, under the conditions of this present test 1-(3-Dimethylaminopropyl)- 3- ethylcarbodiimide hydrochloride was not toxic to waste water bacteria (activated sludge) at or below a concentration of 100 mg/L (NOEC). The EC10 was 101 mg/L (95% confidence interval: 69 - 132 mg/L). The EC20 was 163 mg/L (95% confidence interval: 123 - 199 mg/L). The EC50 was 403 mg/L (95% confidence interval: 347 - 470 mg/L).

Executive summary:

The objective of the study was to evaluate 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride for its ability to adversely affect aerobic microbial treatment plants and, if possible, to determine the EC50 and/or the no-observed effect concentration (NOEC). The influence of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride on the respiration rate of activated sludge was investigated after a contact time of 3 hours. The study procedures described in this report were based on the OECD guideline No. 209, 2010. The batch of 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride tested was a white crystalline powder with a purity of 99.9% (titrimetric assay). No correction was made for the purity/composition of the test item. The test started with the preparation of a stock solution of 10 g/L. Magnetic stirring was applied to accelerate dissolution and to ensure homogeneity. Volumes of the clear and colourless stock solution corresponding to the test concentration were then added to the test media. Optimal contact between the test item and test medium was ensured by applying continuous aeration and stirring during the 3-hour exposure period. Thereafter, oxygen consumption was recorded for approximately 10 minutes. The final test was performed based on the result of a preceding combined limit/range-finding test. Six concentrations were tested, ranging from 3.2 to 1000 mg/L and increasing with a factor 3.2. Five replicates per concentration and six replicates for an untreated control group were tested. No statistically significant inhibition of the respiration rate of the sludge was recorded at 100 mg 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride per L. At higher concentrations the inhibitory effect on aerobic waste water (activated sludge) bacteria increased with increasing concentration, with 42% and 80% inhibition of the respiration rate at 320 and 1000 mg/L, respectively. The batch of activated sludge was tested for sensitivity with the reference item 3,5-dichlorophenol, and showed normal sensitivity. The study met the acceptability criteria prescribed by the study plan and was considered valid. 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride was not toxic to waste water (activated sludge) bacteria at a concentration of 100 mg/L (NOEC). The effect parameters for the inhibition of the respiration rate are presented below.

Parameter	1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride Concentration (mg/L)
NOEC	100
EC10	101 (69 -132mg/L)
EC20	163 (123 -199 mg/L)
EC50	403 (347 -470 mg/L)

Description of key information

A combined limit/ Range-finding test was carried out. It showed 11%, 26% and 90% inhibition of the respiration rate at a concentration of 10,100 and 1000mg/l respectively. Therefore, the expected EC50 was between a concentration of 100 and 1000mg/l. There was no oxygen uptake from abiotic processes. All test conditions prescribed by the study plan were met. Although the validity criterion of the mean control oxygen uptake was less than 30 mg O2/L.h (29.28 mg O2/L.h) the study was considered to be valid, since the validity criterion stated in the OECD Guideline (20 mg O2/g.h) was met.

For the final test, The effects observed were in agreement with what was expected based on the results of the combined limit/range-finding test. The results of this test allowed for reliable determination of a NOEC and ECx values. No statistically significant inhibition of the respiration rate of the sludge was recorded at 100 mg 1-(3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride per liter. At higher concentrations the inhibitory effect of 1- (3-Dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride on aerobic waste water (activated sludge) bacteria increased with increasing concentration, with 42% and 80% inhibition of the respiration rate at 320 and 1000 mg/L, respectively.

EC50 values are >=347 <=470mg/L

NOEC ca 100 mg/L

EC10 >=69 <=132 mg/L

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L