Registration Dossier

Administrative data

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2001
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2001
Report date:
2001

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
GLP compliance:
yes (incl. QA statement)

Test material

Constituent 1
Chemical structure
Reference substance name:
Ammonium 2-amino-4-(hydroxymethylphosphinyl)butyrate
EC Number:
278-636-5
EC Name:
Ammonium 2-amino-4-(hydroxymethylphosphinyl)butyrate
Cas Number:
77182-82-2
Molecular formula:
C5H12NO4P.H3N
IUPAC Name:
ammonium 2-amino-4-(hydroxymethylphosphinyl)butyrate

Sampling and analysis

Analytical monitoring:
no

Test solutions

Vehicle:
yes
Details on test solutions:
2000 mg test item (content of: glufosinate-ammonium 50.8 %
w/w) were filled up to 200 mL with deionized water to achieve
a concentration of nominal 5 g/L of the active ingredient glufosinate-
ammonium.

Test organisms

Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Species: activated sludge, micro organisms from a domestic waste water
treatment plant.

Origin: supplied by the sewage plant Grofi-Zimmern, Germany

Conditioning:
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 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 3 g dry material
per litre, were made up with tap water. The pH of the activated
sludge was determined to be pH 7.8. The activated sludge was
used directly for the test without storage.

Study design

Test type:
static
Water media type:
freshwater
Remarks:
tab water
Limit test:
no
Total exposure duration:
3 h

Test conditions

Test temperature:
18 - 19 °C
pH:
7.8 (sludge)
7.3 - 8.3 (test)
Dissolved oxygen:
6.9 - 9.1 mg/L O2 / L
Nominal and measured concentrations:
10, 32, 100, 320, 1000 mg/L nominal
Details on test conditions:
Surrounding Type:
controlled environment room

Aeration:
with compressed air (approximately 0.6 litre per minute)

Stock Solution of 3,5-Dichlorophenol:
2000 mg test item (content of: glufosinate-ammonium 50.8 % w/w) were filled up to 200 mL with deionized water to achieve a concentration of nominal 5 g/L of the active ingredient glufosinate- ammonium. 3,5-Dichlorophenol was used as a reference item (positive control): 0.5 g of 3,5-Dichlorophenol was dissolved according to the OECD Guideline No. 209 in 10 mL 1 mol/L NaOH and diluted to about 30 mL with deionized water. Excess of NaOH was neutralized with 0.5 mol/L H2SO4 to the point of incipient precipitation. Thereafter, the mixture was made up to one litre with deionized water. The final pH was measured to be 7.8 and the final concentration amounted to 500 mg/L.

Preparation of Test Flasks:
One test solution with a final volume of 500 mL was tested per treatment in a glass flask (>500 mL). Samples were prepared in about 15-minute intervals.

Measurement of Respiration Rate:
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 O2 / L minute) was determined from the most linear part of the respiration curve.

Measurement of pH, Dissolved Oxygen and water temperature:
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

Results and discussion

Effect concentrations
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
Details on results:
Based on measured inhibition rates, the 3-hour EC 20 was determined to be 359 mg glufosinate-ammonium/L with 95 % confidence limits from 210 to 731 mg/L. The EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg glufosinate-ammonium/L less than 50 % inhibition was noted after three hours incubation. Nevertheless, the 3-hour EC 50 is clearly higher than 1000 mg glufosinate-ammonium/L under the present test conditions.
Results with reference substance (positive control):
The 3-hour EC 50 for the positive control 3,5-Dichlorophenol, which was tested in the same way as the test item, was found to be 5.4 mg/L and is within the range of 5 - 30 mg/L.

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Conclusions:
The EC 50 could not be quantified because up to the highest nominal test concentration of 1000 mg glufosinate-ammonium/L less than 50 % inhibition was noted after three hours incubation. Nevertheless, the 3-hour EC 50 is clearly higher than 1000 mg glufosinate-ammonium/L under the present test conditions.
Executive summary:

3h-EC50 > 1000 mg/L