Reaction mass of 2-[[4-[[3,5-dimethyl-4-(oxiran-2-ylmethoxy)phenyl]methyl]-2,6-dimethyl-phenoxy]methyl]oxirane and 1,3-bis[4-[[3,5-dimethyl-4-(oxiran-2-ylmethoxy)phenyl]methyl]-2,6-dimethyl-phenoxy]propan-2-ol and 1-[4-[[3,5-dimethyl-4-(oxiran-2-ylmethoxy)phenyl]methyl]-2,6-dimethyl-phenoxy]-3-[4-[[4-[3-[4-[[3,5-dimethyl-4-(oxiran-2-ylmethoxy)phenyl]methyl]-2,6-dimethyl-phenoxy]-2-hydroxy-propoxy]-3,5-dimethyl-phenyl]methyl]-2,6-dimethyl-phenoxy]propan-2-ol

Toxicity to microorganisms

Link to relevant study record(s)

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

Analytical monitoring:

not required

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- The test substance was weighed directly into the appropriate 1000 mL erlenmeyer flasks.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

The sludge was sourced from a sewage treatment plant receiving predominantly domestic sewage.

The sludge was sieved using a 2 mm screen and allowed to settle for 30 minutes. The supernatant above the settled solids was removed and the total suspended solids concentration of the settled sludge was determined. Total suspended solids in the settled sludge was adjusted to a nominal concentration of approximately 3000 mg/L by dilution with municipal water. Fifty mL of synthetic sewage was added to each litre of adjusted sludge. The sludge was maintained at 20 +/- 2°C overnight and continuously aerated. The pH and total suspended solids concentration of the activated sludge were determined on the day of use in the study.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

Temperatures measured throughout the period of sludge maintenance and during the test ranged from 20.5 - 21.1°C.

pH:

The measured pH of the sludge on the day of testing was 7.9.

Dissolved oxygen:

Dissolved oxygen concentrations at the start of the study were above 60-70% air saturation value. This ensured to maintain the sludge flocs in suspension.

Nominal and measured concentrations:

0 (control), 10, 100 and 1000 mg/L.
A vessel was also included to assess the abiotic potential of the test substance (test substance, no inocula at 1000 mg/L).

Details on test conditions:

TEST SYSTEM
- Test vessel: 1000 mL glass erlenmyer flasks
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: Filled to 500 mL (control contained 16 mL of synthetic sewage, 234 mL of municipal water and 250 mL inoculum). Subsequent reference and test substance dosed biotic mixtures were prepared by combining 16 mL of synthetic sewage, the appropriate volume of reference substance stock solution, or amount of test substance and an appropriate volume of municipal water, followed by 250 mL of inoculum.
- No. of vessels per concentration (replicates): Triplicate test vessels at 1000 mg/L, single test vessels at 10 or 100 mg/L.
- No. of vessels per control (replicates): Duplicate test vessels
- Biomass loading rate: 2827 mg/L suspended solids (inoculum).

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Municipal water

OTHER TEST CONDITIONS
- Photoperiod: continous


EFFECT PARAMETERS MEASURED: Respiration rates used to calculate oxygen uptake rates and percentage of inhibition.

TEST CONCENTRATIONS
- 10, 100 and 1000 mg/L.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

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

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

1 000 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):

The EC50 of the reference substance (3,5-Dichlorophenol) was in the accepted range of 2 to 25 mg/L (23 mg/L) for total respiration

Respiration rates and percentage inhibitions:

Treatment	Nominal Conc. (mg/L)	Respiration rate (mgO2/L/hr)	Percent respiration inhibition (%)
Control (1)	0	28.7	NA
Control (2)	0	32.0	NA
Reference	3	27.2	10.4
Reference	15	21.4	29.6
Reference	50	4.9	83.9
Test substance	10	29.4	3.1
Test substance	100	29.4	3.1
Test substance	1000	30.1	0.7
Test substance	1000	29.4	3.1
Test substance	1000	34.8	-14.7
Test substance (abiotic)	1000	-0.6	NA

Validity criteria fulfilled:

yes

Conclusions:

The effect of the test item on the respiration of activated sludge micro-organisms gave a 3 hour EC50 value of >1000 mg/L, with a NOEC value of 1000 mg/L.

Description of key information

An Activated Respiration Inhibition Test (ASRIT) according to the OECD 209 guidelines was conducted to determine the effect of the test material to sewage treatment plant microbes. 

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The effect of the test item on the respiration of activated sludge micro-organisms gave a 3 hour EC50 value of >1000 mg/L, with a NOEC value of 1000 mg/L.