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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:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Qualifier:
according to
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
adopted April 4th, 1984
GLP compliance:
yes
Test organisms (species):
activated sludge
Details on inoculum:
- Test organism: mixture culture of bacteria )sludge of a Husman apparatus).
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
19.5 °C
Nominal and measured concentrations:
Nominal: 1, 3.2, 10, 32 and 100 mg/l
Details on test conditions:
TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2

EFFECT PARAMETERS MEASURED: oxygen consumption, measured with an oxygen-sensitive electrode system: OXI DIGI 530.
The respiration rate of each test concentration was calculated as a percentage of the mean of the two control respiration rate. The results were plotted on a log (concentration) / normal (% inhibition) graph and the IC50 value was derived.
Reference substance (positive control):
yes
Remarks:
3,5 - Dichlorophenol
Duration:
3 h
Dose descriptor:
IC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Duration:
3 h
Dose descriptor:
IC0
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Details on results:
No inhibition was recorded up to the highest concentration tested.
Results with reference substance (positive control):
IC50 of 3,5 - Dichlorophenol: 16 mg/l.

Bacteria inhibition (IC50) at 3 hours - Oxygen consumption tests

Test substance
(mg/l)
3 h
Oxygen consumption
(mg/l/min)
Inhibition
(%)
100 1.80 0
32 1.70 0
10 1.74 0
3.2 2.80 0
1 2.00 0
Control (K1) 1.72 mean: 1.68
Control (K2) 1.63
3,5- Dichlorophenol (mg/l)
100 0.13 92.3
32 0.19 88.7
10 1.27 24.4
Validity criteria fulfilled:
yes
Remarks:
The two control respiration rates do not differ more than 15 % and the EC50 of the reference item is in the range of 54 -146 mg/l.
Conclusions:
IC50 (3h) > 100 mg/l (nominal)
Executive summary:

The inhibitory effect of the substance to the microorganisms was assessed according to OECD guideline 209. The substance, tested in five different concentrations, was in contact with a mixed culture of a Husman apparatus. In parallel, two controls non containing the substance and a positive control, containing the reference substance run in parallel. After 3 hours, the oxygen consumption was measured in all the tested solutions, control and positive control. The log concentration-inhibition percentage was presented in a graph and the IC50 was interpolated from the graph.

No inhibition was recorded up to the highest concentration tested.

Conclusion

IC50 (3h) > 100 mg/l (nominal)

Description of key information

Non toxic to microorganisms

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:
100 mg/L

Additional information

The inhibitory effect of the substance to the microorganisms was assessed according to OECD guideline 209. The substance, tested in five different concentrations, was in contact with a mixed culture of a Husman apparatus. In parallel, two controls non containing the substance and a positive control, containing the reference substance run in parallel. After 3 hours, the oxygen consumption was measured in all the tested solutions, control and positive control. The log concentration-inhibition percentage was presented in a graph and the IC50 was interpolated from the graph. No inhibition was recorded up to the highest concentration tested.