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Toxicity to microorganisms

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Reference
Endpoint:
toxicity to microorganisms
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Range study on 16 July 1999 and definatibe study on 22 July 1999
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
other: "Activated Sludge Respiration Inhibition test" Commission Directive 87/302/EEC.
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
(1984)
Deviations:
no
Qualifier:
according to
Guideline:
EPA OPPTS 850.6800 (Modified Activated Sludge, Respiration Inhibition Test for Sparingly Soluble Chemicals)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
Test material was prepared by direct solution in water.
2000 mg of test material were dissolved in water and the volume adjusted to 500 ml to give a 4000 mg/l stock solution. Aliquots (12.5, 22.5, 40, 70 and 125 ml) of this stock solution were each separately dispersed with activated sewage sludge (200 ml), synthetic sewage (16 ml) and water. to a final volume of 500 ml, to give the test concentrations of 100, 180, 320, 560 and 1000 mg/l.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The activated sewage sludge sample from the aeration stage of the Severn Trent Water Plc STP at Belper, Derbyshire, UK, was maintained on continuous aeration in the laboratory at a temperature of 21 C and was used on the day of collection. The pH of the sample was 7.5 and the suspended solids equal to 3.9 g/l prior to use
Test type:
other: aerobic
Water media type:
other: laboratory tap water dechlorinated by passage through activated carbon filter
Limit test:
no
Total exposure duration:
3 h
Remarks on exposure duration:
As required by Guidance documents
Post exposure observation period:
None
Hardness:
100 mg/l as CaCO3
Test temperature:
21 C
pH:
Not mentioned
Dissolved oxygen:
1.8 - 8.9 mg O2/l (see results table)
Salinity:
Not mentioned
Conductivity:
Not mentioned
Nominal and measured concentrations:
Nominal concentrations
100, 180, 320, 560 and 1000 mg/l
Details on test conditions:
Study was conducted under normal laboratory lighting
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol at 3.2, 10 and 32 mg/l
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
740 mg/L
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
180 mg/L
Results with reference substance (positive control):
See table of results below
Reported statistics and error estimates:
Not mentioned

Oxygen consumption rates and percentage inhibition values in definitive study after 30 minutes contact time

Nominal concentration (mg/l) Initial O2 reading (mg O2/l) Measurement period (minutes) Final O2 reading (mg O2/l) O2 consumption rates (mg O2/l.min) % Inhibition
Control R1 7.2 10 1.8 0.5 -
R2 7.5 10 2.2 0.5 -
BMS 214702-01 100 7.2 9 2.0 0.6 [8]
180 7.0 9 2.0 0.6 [5]
320 7.2 10 2.2 0.5 7
560 7.4 10 3.0 0.4 18
1000 8.8 10 8.5 0.0 94
3,5-dichlorophenol 3.2 7.1 10 2.2 0.5 8
10 7.5 10 4.5 0.3 44
32 8.3 10 7.2 0.1 79

Values in [] indicate an increase in respiration rate as compared to controls

Validity criteria fulfilled:
not specified
Conclusions:
At high concentrations the substance was inhibitory to sludge micro-organisms. A 3-hour EC50 of 740 mg/l and a NOEC of 180 mg/l were determined.
Executive summary:

Methods

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge Respiration Inhibition Test". EEC Commission Directive 87/302/EEC and US EPA Ecological Effects Test Guidelines OPPTS 850.6800.

Procedure

Following a preliminary range-finding study, activated sewage sludge was exposed to an aqueous solution of the test material at concentrations of 100, 180, 320, 560 and 1000 mg/l for a period of 3 hours at 21 C with the addition of a synthetic sewage as a respiratoru substrate. The rate of respirtion was determined after 30 minutes and 3 hours contact time and compared to data for the control and a reference material, 3,5 -dichlorophenol.

Results

The effect of the test material on the respiration of activated sewage sludge gave a 3-hour EC50 of 740 mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 180 mg/l.

Description of key information

A study was performed to assess the effect of the test material on the respiration of activated sewage sludge. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 209 "Activated Sludge Respiration Inhibition Test". EEC Commission Directive 87/302/EEC and US EPA Ecological Effects Test Guidelines OPPTS 850.6800.

The effect of the test material on the respiration of activated sewage sludge gave a 3-hour EC50 of 740 mg/l. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 180 mg/l.

Key value for chemical safety assessment

EC50 for microorganisms:
740 mg/L
EC10 or NOEC for microorganisms:
180 mg/L

Additional information