4H-Pyrazino[2,1-a]isoquinolin-4-one, 2-acetyl-1,2,3,6,7,11b-hexahydro-

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:

2004-12-13 to 2005-02-07

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

Version / remarks:

1984

Deviations:

no

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Due to the low solubility of the test item in test water, adequate amounts of the test item were directly weighed into each test flask.

Test organisms (species):

anaerobic bacteria from a domestic water treatment plant

Details on inoculum:

The sludge was washed by centrifugation and the supernatant liquid phase was decanted. The solid material was resuspended in tap water and again centrifuged. The latter procedure was repeated twice. An aliquot of washed sludge suspension was made up with tap water. To this mixture, 50 mL synthetic sewage feed per litre was added daily, starting one day prior to use, and the sludge was kept at room temperature under continuous aeration until use. Immediately before use, an aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (g) to its dry weight (g) determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 2.5 g dry material per litre, were made up with tap water.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

19-20 °C

pH:

7.4

Dissolved oxygen:

8.7 - 2.3 mg/L

Nominal and measured concentrations:

nominal 10, 32, 100, 320 and 1000 mg/L

Details on test conditions:

The test was performed in 500 mL glass flasks.

For the measurement of the respiration rate a well-mixed sample of each test medium was poured into a Karlsruher flask after exactly 3 hours incubation time, and was not further aerated. The oxygen concentration was measured with an oxygen electrode, and was recorded for about ten minutes. During measurement, the samples were continuously stirred on a magnetic stirrer. The oxygen consumption (in mg oxygen / L / minute) was determined from the most linear part of the respiration curve, and were determined in the range between approximately 8.7 - 2.3 mg oxygen / L.

The pH and the oxygen concentrations were determined at the start and at the end of the incubation period in all treatments. The water temperature was measured in one control medium at the start and the end of the incubation period.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

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

Results with reference substance (positive control):

The 3-hour EC50 of 3,5-Dichlorophenol was calculated to be 7.1 mg/L.
Based on the results of the reference substance the test is considered valid.

Validity criteria fulfilled:

yes

Conclusions:

The test item is not toxic to activated sludge under the conditions of this test.

Executive summary:

The purpose of the 3-hour toxicity test was to evaluate the influence of the test item on the activity of activated sludge by measuring the respiration rate under defined conditions and according to OECD TG 209. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test item after an incubation period of 3 hours. The inhibitory effect of the test item at the particular concentrations was expressed as percentage of the mean respiration rate of two controls. The respiration rates of the test item treated activated sludge was in the range of control and slightly inhibited. For the test concentrations of 10 mg/L, 32 mg/L and 100 mg/L, the maximum difference from control was 12.6 %. For the test concentrations of 320 mg/L and 1000 mg/L the differences were 1.1 % and 21.8 %, respectively. Test item concentrations exceeding 1000 mg/L were not tested. The 3-hour EC50 was determined to be greater than 1000 mg/L by Probit analysis using the inhibition rates of the 1000, 320, 100, 32 and 10 mg/L test concentrations.

In conclusion, the test item is not toxic to activated sludge under the conditions of this test.

Description of key information

Toxicity to microorganisms was assessed in an OECD TG 209 compliant study and EC50 was greater than 1000 mg/L (reference 6.1.7-1).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

Toxicity to microorganisms

The purpose of the 3-hour toxicity test was to evaluate the influence of the test item on the activity of activated sludge by measuring the respiration rate under defined conditions and according to OECD TG 209. The respiration rate (oxygen consumption) of an aerobic activated sludge fed with a standard amount of synthetic sewage was measured in the presence of various concentrations of the test item after an incubation period of 3 hours. The inhibitory effect of the test item at the particular concentrations was expressed as percentage of the mean respiration rate of two controls. The respiration rates of the test item treated activated sludge was in the range of control and slightly inhibited. For the test concentrations of 10 mg/L, 32 mg/L and 100 mg/L, the maximum difference from control was 12.6 %. For the test concentrations of 320 mg/L and 1000 mg/L the differences were 1.1 % and 21.8 %, respectively. Test item concentrations exceeding 1000 mg/L were not tested. The 3-hour EC50 was determined to be greater than 1000 mg/L by Probit analysis using the inhibition rates of the 1000, 320, 100, 32 and 10 mg/L test concentrations.

In conclusion, the test item is not toxic to activated sludge under the conditions of this test.