3-[3,3,3-trimethyl-1,1-bis[(trimethylsilyl)oxy]disiloxanyl]propyl methacrylate

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

Study period:

From 24 May 2017 to 25 May 2017

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 (Carbon and Ammonium Oxidation))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Date of inspection: 05/07/2016 Date of issue of certificate: 28/10/2016

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material:
Supplied by study owner. Batch no. 440038-285
- Expiration date of the lot/batch: not supplied


STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: stored at approximately 4 ºC in the dark

TREATMENT OF TEST MATERIAL PRIOR TO TESTING
- The test item was dispersed directly in water.

FORM AS APPLIED IN THE TEST (if different from that of starting material)
Solution

Analytical monitoring:

no

Vehicle:

yes

Remarks:

deionised water

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Nominal amounts of test item (5, 50 and 500 mg (in triplicate)) were each separately dispersed in approximately 200 mL of deionised reverse osmosis water and subjected to ultrasonication for approximately 15 minutes followed by magnetic stirring for 24 hours, at temperatures of between 21 °C and 28 °C, in order to maximize the dissolved test item concentration. All test vessels were shielded from the light during mixing. Synthetic sewage (16 mL), activated sewage sludge (250 mL) and water were added to a final volume of 500 mL to give the required concentrations of 10, 100 and 1000 mg/L (3 replicates).
- Controls: The control group was maintained under identical conditions but not exposed to the test item.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

A mixed population of activated sewage sludge micro-organisms was obtained on 24 May 2017 from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK which treats predominantly domestic sewage.

A synthetic sewage of the following composition, was added to each test vessel to act as a respiratory substrate:
16 g Peptone
11 g Meat extract
3 g Urea
0.7 g NaCl
0.4 g CaCl2.2H2O
0.2 g MgSO4.7H2O
2.8 g K2HPO4
dissolved in a final volume of 1 liter of water with the aid of ultrasonication.

The pH of the synthetic sewage stock used to feed the activated sewage sludge was pH 7.3 and the pH of the synthetic sewage stock used for the range-finder test was pH 7.5. The pH values were measured using a Hach HQ40d Flexi handheld meter.

The activated sewage sludge sample was maintained on continuous aeration in the laboratory at a temperature of approximately 21 ºC overnight prior to use in the test. On the day of collection the activated sewage sludge (4.5 liters) was fed synthetic sewage (225 mL). The pH of the sample on the day of the test was 7.3 measured using a Hach HQ40d Flexi handheld meter. Determination of the suspended solids level of the activated sewage sludge was carried out by filtering a sample (100 mL) of the activated sewage sludge by suction through a pre-weighed GF/A filter paper* using a Buchner funnel which was then rinsed 3 times with 10 mL of deionized reverse osmosis water and filtration continued for 3 minutes. The filter paper was then dried in an oven at approximately 105 ºC for at least one hour and allowed to cool before weighing. This process was repeated until a constant weight was attained. The suspended solids concentration was equal to 3.0 g/L prior to use.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Hardness:

No data

Test temperature:

22 to 23 ºC.

pH:

7.6-8.0

Dissolved oxygen:

5.5-6.6 mg O2/L

Salinity:

No data

Conductivity:

No data

Nominal and measured concentrations:

Nominal - 10, 100, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 500 mL conical flask
- Type: open
- Aeration: with clean, oil-free compressed air via narrow bore glass tubes at a rate of 0.5 to 1.0 litres per minute
- No. of vessels per concentration (replicates): 1 x 10, 100 mg/L, 3 x 1000 mg/L
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: The test water used for the test was deionised reverse osmosis water containing less than 1 mg/L dissolved organic carbon (DOC)

OTHER TEST CONDITIONS
- Light intensity: Conducted under normal laboratory lighting


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Observations were made on the test preparations throughout the test period. Observations of the test item vessels at 0 hours were made prior to addition of activated sewage sludge.

The pH of test preparations was measured at the test start (i.e. after the addition of activated sludge) and at the end of the 3-Hour incubation period using a Hach HQ40d Flexi handheld meter.

The oxygen concentrations in all vessels were measured after 30 minutes contact time.

As each vessel reached 3 hours contact time an aliquot was removed from the conical flask and poured into the measuring vessel (250 mL darkened glass Biological Oxygen Demand (BOD) bottle) and the rate of respiration measured using a Yellow Springs dissolved oxygen meter fitted with a BOD probe. The contents of the measuring vessel were stirred constantly by magnetic stirrer. The rate of respiration for each flask was measured over the linear portion of the oxygen consumption trace (where possible between 7 mg O2/L and 2 mg O2/L). In the case of a rapid oxygen consumption, measurements may have been outside this range but the oxygen consumption was always within the linear portion of the respiration curve. In the case of low oxygen consumption, the rate was determined over an approximate 10 minute period.

TEST CONCENTRATIONS
- Range finding study: 10, 100, 1000 mg/L
- Test concentrations: As above
- Results used to determine the conditions for the definitive study:

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:

growth inhibition

Details on results:

The dissolved oxygen concentrations in all vessels after 30 minutes contact time are given in Table 2. Oxygen consumption rates and percentage inhibition values for the control, test and reference item after 3 hours contact time are given in Table 3. The pH values of the test preparations at the start and end of the exposure period are given in Table 4. Observations made on the test preparations throughout the range-finding test are given in Table 5.
The dissolved oxygen concentrations after 30 minutes contact time in all vessels were above 60% of the dissolved oxygen saturation level of 8.9 mg O2/L.
No statistically significant toxic effects were shown at all of the test concentrations employed. It was therefore considered justifiable not to perform a definitive test.
It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/L.

Results with reference substance (positive control):

*TO BE COMPLETED*

Reported statistics and error estimates:

All statistical analyses were performed using the SAS computer software package (SAS, 1999 - 2001).

Table 1 pH Values of the Test Item Preparations after Stirring and Prior to the Addition of Inoculum in the Range-Finding Test

Nominal concentration (mg/L)		pH
		Prior to Adjustment	After Adjustment
Test Item	10	8.0	-
	100	7.9	-
	1000 R1	7.7	-
	1000 R2	7.6	-
	1000 R3	7.6	-

 

Table 2 Dissolved Oxygen Concentrations of the Test Preparations after 30 Minutes Contact Time in the Range-Finding Test

Nominal concentration (mg/L)		Dissolved Oxygen Concentration (mg O2/L)	Expressed as a Percentage of a Dissolved Oxygen Saturation Level of 8.9 mg O2/L
Control	R1	5.6	63
	R2	5.6	63
	R3	5.6	63
	R4	5.5	62
Test Item	10	5.8	65
	100	5.8	65
	1000 R1	5.5	62
	1000 R2	5.9	67
	1000 R3	6.6	74
3,5-dichlorophenol	3.2	5.6	63
	10	6.1	68
	32	5.5	62

 

Table 3 Oxygen Consumption Rates and Percentage Inhibition Values after 3 Hours Contact Time in the Range-Finding Test

Nominal concentration (mg/L)		Initial O2 Reading (mg O2/L)	Measurement Period (minutes)	Final O2 Reading (mg O2/L)	O2 Consumption Rates (mg O2/L/hour)	% Inhibition
Control	R1	4.8	4	1.7	46.50	-
	R2	4.8	4	1.8	45.00	-
	R3	4.7	3	2.3	48.00	-
	R4	4.2	3	1.8	48.00	-
Test Item	10	6.9	2	2.2	45.00	4
	100	8.0	2	2.2	48.00	[2]
	1000 R1	3.7	2	2.1	48.00	[2]
	1000 R2	3.8	3	1.7	48.00	[2]
	1000 R3	3.7	3	1.8	44.00	6
3,5-dichlorophenol	3.2	6.2	8	1.7	33.75	28
	10	6.9	10	3.5	20.40	56
	32	8.0	10	7.1	5.40	88

Table 4 pH Values of the Test Preparations at the Start and End of the Exposure Period in the Range-Finding Test

Nominal concentration (mg/L)		pH
		0 Hours	3 Hours
Control	R1	7.3	7.3
	R2	7.2	7.3
	R3	7.4	7.4
	R4	7.4	7.4
Test Item	10	7.4	7.5
	100	7.3	7.4
	1000 R1	7.2	7.3
	1000 R2	7.6	7.5
	1000 R3	7.4	7.4
3,5-dichlorophenol	3.2	7.3	7.6
	10	7.6	7.8
	32	7.4	7.6

 

Table 5 Observations on the Test Preparations throughout the Test Period in the Range-Finding Test

Nominal concentration (mg/L)		Observations on Test Preparations
		0 hours*	30 Minutes Contact Time	3 Hours Contact Time
Control	R1	Pale yellow/brown dispersion	Dark brown dispersion	Dark brown dispersion
	R2	Pale yellow/brown dispersion	Dark brown dispersion	Dark brown dispersion
	R3	Pale yellow/brown dispersion	Dark brown dispersion	Dark brown dispersion
	R4	Pale yellow/brown dispersion	Dark brown dispersion	Dark brown dispersion
Test Item	10	Pale yellow/brown dispersion, few oily globules of test item visible on the surface	Dark brown dispersion, no undissolved test item visible	Dark brown dispersion, no undissolved test item visible
	100	Pale yellow/brown dispersion, oily globules of test item visible on the surface	Dark brown dispersion, oily film of test item visible on the surface	Dark brown dispersion, oily film of test item visible on the surface
	1000 R1	Pale yellow/brown dispersion, large oily globules of test item visible on the surface	Dark brown dispersion, oily layer of test item visible on the surface	Dark brown dispersion, oily layer of test item visible on the surface
	1000 R2	Pale yellow/brown dispersion, large oily globules of test item visible on the surface	Dark brown dispersion, oily layer of test item visible on the surface	Dark brown dispersion, oily layer of test item visible on the surface
	1000 R3	Pale yellow/brown dispersion, large oily globules of test item visible on the surface	Dark brown dispersion, oily layer of test item visible on the surface	Dark brown dispersion, oily layer of test item visible on the surface
3,5-dichlorophenol	3.2	Pale yellow/brown dispersion, no undissolved reference item visible	Dark brown dispersion, no undissolved reference item visible	Dark brown dispersion, no undissolved reference item visible
	10	Pale yellow/brown dispersion, no undissolved reference item visible	Dark brown dispersion, no undissolved reference item visible	Dark brown dispersion, no undissolved reference item visible
	32	Pale yellow/brown dispersion, no undissolved reference item visible	Dark brown dispersion, no undissolved reference item visible	Dark brown dispersion, no undissolved reference item visible

* Observations made prior to the addition of activated sewage sludge

Validity criteria fulfilled:

yes

Conclusions:

The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of greater than 1000 mg/L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L.

Executive summary:

Introduction

A study was performed to assess the effect of the test item on the respiration of activated sewage sludge. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2010) No. 209 "Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation)".

Methods

Activated sewage sludge was exposed to an aqueous dispersion of the test item at concentrations of 10, 100 and 1000 mg/L (3 replicates of the 1000 mg/L test concentration) for a period of 3 hours at measured temperatures of between 22 and 23 °C with the addition of a synthetic sewage as a respiratory substrate.

The rate of respiration was determined after 3 hours contact time and compared to data for the control and a reference item, 3,5-dichlorophenol.

Results

The effect of the test item on the respiration of activated sewage sludge gave a 3-Hour EC50 value of greater than 1000 mg/L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L.

It was considered unnecessary and unrealistic to test at concentrations in excess of 1000 mg/L.

The reference item gave a 3-Hour EC50 value of 7.6 mg/L, 95% confidence limits 5.9 to 9.8 mg/L.

Description of key information

The effect of the test item on the respiration of activated sewage sludge micro-organisms gave a 3-Hour EC50 value of greater than 1000 mg/L. The No Observed Effect Concentration (NOEC) after 3 hours exposure was 1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L