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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:
other: Guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Version / remarks:
Cited as Directive 87/302/EEC, part C, p. 118 (Biodegradation: Activated sludge respiration inhibition test)
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: The test substance were added directly into the test vessels.
Test organisms (species):
activated sludge
Details on inoculum:
- Laboratory culture: obtained from municipal wastewater treatment plant of Marl-Ost (Germany), which predominantely treats domestic sewage.
- Preparation of inoculum for exposure: The activated sludge were centrifuged four times for 5 min at 2000 rpm and cleaned afterwards with 600 mL tap water.
- Initial biomass concentration: 3.7 g suspended solids/L
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
18 - 20.6 °C
pH:
7.8 - 8.4
Nominal and measured concentrations:
Nominal: 100.8, 127.4, 190.8, 269.6 and 352.4 mg/L
Details on test conditions:
TEST SYSTEM
- Aeration: continuously
- No. of vessels per concentration (replicates): 1
- No. of vessels per control (replicates): 2

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: tap water
- Intervals of water quality measurement: at the end of the incubation phase (after 3h)

EFFECT PARAMETERS MEASURED: O2 consumption was measured for 8 minutes after an incubation time of 3h.
Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
> 350 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 350 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: EC50 (3h) = 5.5 mg/L

Table 1: Respiration inhibition of control, test and reference substance

 Treatment

Nominal concentration [mg/L]

Measuring time

Inhibition [%]

Test item

352.4

5

-6.6

Test item

269.6

6

-8.0

Test item

190.8

6

-6.6

Test item

127.4

6.5

-7.7

Test item

100.8

5

-9.7

Reference

5

6.5

45.9

Reference

15

7.5

77.9

Reference

30

8

86.1

Control

 

6.5

 

Control

 

7

 

Validity criteria fulfilled:
yes
Conclusions:
A 3h respiration inhibition test with domestic activated sludge revealed that DEHA is not inhibitory to aquatic microorganisms up to the saturation limit in water.
Executive summary:

A 3h activated sludge respiration inhibition test with read-across substance, bis(2-ethylhexyl) adipate (CAS 103-23-1, was performed according to EU method C.11 under GLP conditions. Different test concentrations up to ~ 350 mg/L were tested. No respiration inhibition but stimulation was observed in all treatments compared to the control. Thus, the 3h-EC50 value is determined to be above the highest concentration tested : >350 mg/L.

Description of key information

No relevant studies are available for diisodecyl adipate.

A 3h activated sludge respiration inhibition test was conducted with read-across substance, bis(2-ethylhexyl) adipate (CAS 103-23-1), according to EU method C.11 under GLP conditions. Different test concentrations up to ~ 350 mg/L were tested. No respiration inhibition but stimulation was observed in all treatments compared to the control. Thus, the 3h-EC50 value is determined to be above the highest concentration tested : >350 mg/L.

Key value for chemical safety assessment

Additional information