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Ecotoxicological information

Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
July 2012
Reliability:
1 (reliable without restriction)
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
GLP compliance:
yes
Vehicle:
yes
Details on test solutions:
Test item in aqueous solution.

The test water used for the range-finding and definitive tests was deionized reverse osmosis water containing less than 1 mg/L Dissolved Organic Carbon (DOC).
Test organisms (species):
activated sludge, domestic
Details on inoculum:
A mixed population of activated sewage sludge micro-organisms was obtained on 25 April 2012 for the range-finding test and on 17 July 2012 for the definitive test from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK which treats predominantly domestic sewage.
Limit test:
yes
Total exposure duration:
3 h
Test temperature:
20 ± 2 °C
pH:
pH 7.0 and 8.0
Nominal and measured concentrations:
18, 32, 56, 100 and 180 mg active ingredient(ai)/L (5 replicates per concentration)
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
80 mg/L
Conc. based on:
act. ingr.
Basis for effect:
growth inhibition
Remarks on result:
other: 95% confidence limits 72 - 89 mg mg/L
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
32 mg/L
Conc. based on:
act. ingr.
Basis for effect:
growth inhibition
Details on results:
No statistically significantly toxic effects were shown at the test concentrations of 18 and 32 mg ai/L, however statistically significantly toxic effects were shown at the test concentration of 56, 100 and 180 mg ai/L. Based on these results the No Observed Effect Concentration (NOEC) after 3 hours exposure was 32 mg ai/L.

The coefficient of variation of oxygen uptake in the control vessels was 4.6% and the specific respiration rate of the controls was 23.82 mg oxygen per gram dry weight of sludge per hour. The validation criteria have therefore been satisfied.
The validation criterion for the reference item EC50 value was also satisfied.

In some instances, the initial and final dissolved oxygen concentrations were outside those recommended in the test guidelines (7.0 mg O2/L and 2.0 mg O2/L respectively). This was considered to have had no adverse effect on the results of the study given that in all cases the oxygen consumption rate was determined over the linear portion of the oxygen consumption trace.

The dissolved oxygen concentrations after 30 minutes contact time in all vessels were above 60 to 70% of the dissolved oxygen saturation level of 8.9 mg O2/L.
Results with reference substance (positive control):
The reference item gave a 3-Hour EC50 value of 7.3 mg/L, 95% confidence limits 5.6 – 9.5 mg/L.
Validity criteria fulfilled:
yes
Conclusions:
The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of 80 mg ai/L, 95% confidence limits 72 - 89 mg/L active ingredient. The NOEC after 3 hours exposure was 32 mg/L active ingedient.
Executive summary:

A mixed population of activated sewage sludge micro-organisms was obtained from a sewage treatment plant. Organisms were exposed concentrations of 18, 32, 56, 100 and 180 mg/L in a static test for 3 hours. The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of 80 mg/L, 95% confidence limits 72 - 89 mg/L, based on oxygen consumption. The NOEC after 3 hours exposure was 32 mg/L.

Description of key information

Elementis Specialities (2012) reports a 3-hr EC50 for toxicity to microorganisms of 80 mg/L and a 3-hr NOEC of 32 mg/L for the read-across substance methyl trimethyl-3-[(1-oxododecyl)amino]propylammonium sulphate.

A reliable toxicity study with microorganisms is not available for the substance. However, a study for the structural analogue methyl trimethyl-3-[(1-oxododecyl)amino]propylammonium sulphate is available and is included in this dossier for read-across purposes. Elementis Specialities (2012) conducted a reliable (Klimisch 1) GLP compliant study following OECD 209 methods with methyl trimethyl-3-[(1-oxododecyl)amino]propylammonium sulphate. A mixed population of activated sewage sludge micro-organisms was obtained from a sewage treatment plant. Organisms were exposed concentrations of 18, 32, 56, 100 and 180 mg/L in a static test for 3 hours. The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of 80 mg/L, 95% confidence limits 72 - 89 mg/L, based on oxygen consumption. The NOEC after 3 hours exposure was 32 mg/L.

Consequently these values will be taken as the toxicity in microorganisms endpoint in read-across for the substance.

Key value for chemical safety assessment

EC50 for microorganisms:
80 mg/L
EC10 or NOEC for microorganisms:
32 mg/L

Additional information