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Toxicity to microorganisms

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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
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
Deviations:
no
GLP compliance:
yes
Details on sampling:
After 180 minutes of aeration at 22 oC, the first sample was taken for oxygen measurement over a period of up to 10 minutes. Thereafter, in 15 minutes intervals, the rest of the samples were submitted to measurement of oxygen concentration.
Sampling was started with the control 1. Thereafter, the measurements were continued with the positive controls and the test article samples. Finally, the oxygen consumption of control 2 was determined.
Vehicle:
no
Details on test solutions:
The test article was dissolved in distilled water at a concentration of 500 mg/I.
Test organisms (species):
activated sludge, domestic
Details on inoculum:
The sludge was coarsely sieved, centrifuged, the supernatant liquid phase decanted, the solid material resuspended in tap water and again centrifuged. This procedure was repeated a further two times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge (ml) to its dry weight (g) determined. Based on this ratio, a volume of washed sludge suspension corresponding to 4.0 g dry material were made up with Soerensen buffer (pH = 7) to 1 litre. To that mlxture,50 ml OECD recommended synthetic sewage feed (see guidelines) were added. Thereafter, the sludge was incubated overnight at 20 - 25 oC under aeration.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
180 min
Test temperature:
22 oC
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
180 min
Dose descriptor:
IC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
see tables
Results with reference substance (positive control):
At a concentration of the standard of 10 mg/l, the respiration rate was inhibited to 56.1%. The IC 50 was found to be about 10 mg/L. Almost complete inhibition (94.7 %) was observed at 50 mg/l.

Fl ask         Chemical                                                 Conc. of                                Oxygen                                    Inhibition                      Starting     

No.                                                                           test chem.  (mg/l)                    consumption (mgO2/L min.) (%)     pH

                                           

1               control                                                           0                                                 0.57                                                                          7.6

               control                                                        0                                                     0.57                                                                         7.6

5               SANDOLAN BLAU E-HRL 180%             100                                    0.56                                                  1.8                             7.6

   

6              SANDOLAN BLAU E-HRL 180%              10                                        0.50                                                  12.3                      7.6

 

 

 

Validity criteria fulfilled:
yes
Conclusions:
The tests are regarded to be valid since the variance between the control sampl.es was 0 %. Furthermore it was shown that the inhibitory effect or 3,5-dichlorophenol was with 10 mg/L within the range of the IC-value of 5 to 30 mg/L. The test article showed under the same conditions, an IC 50-value of >100 mg/l.
In conclusion, the test item was found to be non-toxic to waste-water bacteria.
Executive summary:

The inhibitory effect of the test item on aerobic waste-water bacteria was investigated.


In a respiration test (OECD 209) the test article showed no inhibition (1.8 %) of the respiration rate up to a concentration of 100 mg/L.


The IC 50 was determined to be: IC 50: > 100 mg/I.


In conclusion, the test item was found to be non-toxic to waste-water bacteria.


 

Description of key information

OECD 209

In a respiration test (OECD 209) the test article showed no inhibition of the respiration rate up to a concentration of 100 mg/L.

In conclusion, the test item was found to be non-toxic to waste-water bacteria.

 

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information