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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:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
comparable to guideline study with acceptable restrictions
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
yes
Remarks:
test was adapted to minimize volatile losses e.g. closed system
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
activated sludge, domestic
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
30 min
Duration:
30 min
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

After 30 min incubation the test substance showed less then 50 % inhibition on the oxygen consumption at the maximum test concentration of 1000 mg/l.


 

Executive summary:

The toxicity to microorganisms of cyclohexanone was assessed in an experimental study according to the OECD guideline 209. The test set up was adapted to minimize volatile losses. An inoculum consisting of domestic activated sludge was exposed to different concentrations with a maximum concentration of 1000 mg/l (nominal) for 30 min. As effect the inhibition of total respiration rate was defined. After 30 min incubation the test substance showed less than 50 % inhibition on the oxygen consumption at the maximum test concentration of 1000 mg/l. Therefore, the EC50 after 30 min was > 1000 mg/l.

Description of key information

In both studies with the single components of the mixture no relevant inhibition of the respiration rate was measured therefore an EC50 > 1000 mg/l can be assumed also for the mixture.

Key value for chemical safety assessment

EC50 for microorganisms:
1 000 mg/L

Additional information

No experimental study with the mixture was conducted. Since there are reliable experimental studies for the single components of the mixture available, the most sensitive value of both can be used to derive the value for the mixture assuming a worst-case scenario.


The toxicity to microorganisms of cyclohexanol was assessed in an experimental study according to the OECD guideline 209. An inoculum consisting of industrial activated sludge with an initial biomass of 1000 mg/l was exposed to the nominal test concentrations 15, 75, 150, 375, 750, 1995 mg/l cyclohexanol and a control for 30 min. As effect the inhibition of total respiration rate was defined. No effect was determined within the test period. Therefore, the EC20 after 30 min was  > 1995 mg/l (BASF. 1981).


The toxicity to microorganisms of cyclohexanone was assessed in an experimental study according to the OECD guideline 209. The test set up was adapted to minimize volatile losses. An inoculum consisting of domestic activated sludge was exposed to different concentrations with a maximum concentration of 1000 mg/l (nominal) for 30 min. As effect the inhibition of total respiration rate was defined. After 30 min incubation the test substance showed less than 50 % inhibition on the oxygen consumption at the maximum test concentration of 1000 mg/l. Therefore, the EC50 after 30 min was > 1000 mg/l (Volskay, 1988).


In both studies with the single components of the mixture no relevant inhibition of the respiration rate was measured therefore an EC50 > 1000 mg/l can be assumed also for the mixture.

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