Bis(2-ethylhexyl) adipate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Reference 1

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 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.

Reference 2

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

05 Sep 1988

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: Only short documentation available

Qualifier:

according to guideline

Guideline:

other: DIN 38412, part 27

GLP compliance:

no

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

- stock solution: 10000 mg/L mixed with 100 mg/l Tween 80 and stired for 2 hours.
- After a short standing time the test dispersion separates back in its components.

Test organisms (species):

Pseudomonas putida

Details on inoculum:

- age of bacteria culture: 4 hours

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

30 min

Test temperature:

25 °C

Nominal and measured concentrations:

Nominal: 2500, 5000 and 10000 mg/L

Duration:

30 min

Dose descriptor:

other: EC20

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

30 min

Dose descriptor:

EC10

Effect conc.:

> 10 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

Until the highest test concentration (1000 mg/l) no effect on the bacteria measured.

Description of key information

The inhibition of the degradation activity of activated sludge is not anticipated when bis(2-ethylhexyl) adipate is introduced in appropriate low concentrations.

Additional information

Two studies investigating the toxicity of DEHA to aquatic microorganisms are available. The key study was performed according to EU method C.11 under GLP conditions (Hüls 1996). Different test concentrations up to 352.4 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 of 350 mg/L.

Similar results measured in a ROBRA test according to DIN 38412 part 27, in which the highest test concentration of 10000 mg/L caused no effect on the respiration rate of the microorganisms (BASF 1988).