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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
Specific details on test material used for the study:
Clear colourless liquid, purity 96.5%.
Analytical monitoring:
no
Details on sampling:
A stock solution of 0.5 g/l was prepared by adding 501.3 mg test substance to 1000 ml of Milli-RO water (tap water purified by reverese osmosis; Millipore Corp., Bedford, Mass., USA). Thoroough mixing (15 minutes) was used to accelearte dissolving and to ensure homogeneity. The pH of the clear and colourless stock solution was 8.0. A concentration of 100 mg/l, corresponding to 100 ml of the prepared stock solution in 500 ml final volume, was tested in duplicate.
Vehicle:
no
Details on test solutions:
A stock solution of 0.5 g/l was prepared, pH 8. The final conc. was 100 mg/l and was tested in duplicate. Inoculum was prepared according to protocol.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
Municipal sewarge treatment plant: 'Waterschap de Maaskant', 's-Hertogenbosch, the Netherlands. The sludge was coarsely sieved, washed and diluted with tap-water. A small amount of the sludge was weighed and dried at ca. 105oC to determine the amount of suspended solids (3.2 g/l of sludge, as used for the test). The pH was 7.5 on the day o fsampling and 7.8 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic sewage feed was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use.
Test type:
static
Water media type:
other: Tap-water purified by osmosis (Milli-RO) and subsequently passed over activated carbon and ion-exchange cartridges.
Limit test:
no
Total exposure duration:
30 min
Test temperature:
19.7-19.9 oC
pH:
8
Dissolved oxygen:
7.2-7.7
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
30 min
Dose descriptor:
EC50
Effect conc.:
>= 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth inhibition
Details on results:
No EC50 could be calculated because pentamethyl-trioxepane is non-toxic EC50 > 100 mg/l
Results with reference substance (positive control):
3,5-dichlorphenol was used as a reference substance. A stock solution of 0.5 g/l was prepared, pH 8. Three conc. were tested 3.2, 10 and 32 mg/l. The EC50 of 3,5-dichlorphenol is between 5-30 mg/l (11 mg/l).
Validity criteria fulfilled:
yes
Remarks:
The two control respiration rates are within 15% of each other: control 1 and 2, 46 mg/O2/l 4%, control 3 and 4, 43 mg/O2/l 2% and the EC50 of 3,5-dichlorphenol is between 5-30 mg/l (11 mg/l).
Conclusions:
Under the conditions of this test pentamethyl-trioxepane was not toxic to activated sludge bacteria at a concentration of 100 mg/l
Executive summary:

Under the conditions of this testpentamethyl-trioxepane was not toxic to activated sludge bacteria at a concentration of 100 mg/l

Description of key information

Under the conditions of this testpentamethyl-trioxepane was not toxic to activated sludge bacteria at a concentration of 100 mg/l

Key value for chemical safety assessment

EC50 for microorganisms:
100 mg/L
EC10 or NOEC for microorganisms:
100 mg/L

Additional information