Registration Dossier

Data platform availability banner - registered substances factsheets

Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Ecotoxicological information

Toxicity to microorganisms

Currently viewing:

Administrative data

Link to relevant study record(s)

Referenceopen allclose all

Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Version / remarks:
Cited as Directive 88/302/EEC, C.11
GLP compliance:
yes
Analytical monitoring:
no
Test organisms (species):
activated sludge, domestic
Details on inoculum:
Activated sludge was from the sewage treatment plant Marl-West (Lippeverband), treating predominantly domestic sewage.
Content of suspended solids: 3.01 g/l (activated sludge). This gives a concentration of 1203 mg/l in the test medium.
Test type:
static
Total exposure duration:
3 h
Test temperature:
Temperature: 18-22 deg C.
At the beginning of the incubation: 18.0 - 18.5 deg C;
during the determination of oxygen content: 18.5 - 19.5 deg C.
Dissolved oxygen:
Oxygen consumption:
Control 1: 29.92 mg O2/l*h
Control 2: 31.60 mg O2/l*h
The difference between control 1 and 2 does not exceed 15% (5.3%).
Nominal and measured concentrations:
Nominal: 125, 250, 55, 1000, and 2000 mg a.i./L
Measured: 124.8; 250; 499.8; 1000.4 and 2000.2 mg a.i./L
Details on test conditions:
Type: aquatic
Reference substance (positive control):
yes
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 2 000 mg/L
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
In the tested concentration range of 124.8; 250; 499.8; 1000.4 and 2000.2 mg/l there was no inhibition of
respiration of activated sludge.  EC50 > 2000 mg/l rounded up two significant places and calculated as active
substance. 
Results with reference substance (positive control):
Reference substance: 3,5 Dichlorophenol, 5, 15, 30 mg/l. 
EC50 - limit: 5-30 mg/l; EC50-determined: 6.5 mg/l.

Table 1: Controls, reference substance (3, 5-dichlorophenol) and test substance (D5): oxygen consumption and percentage inhibition of the respiration rate.

Flask

Nominal concentration (mg/l)

Oxygen consumption

(mg O2/l/hour)

% Inhibition

respiration rate

Control (average of two)

0

30.76

-

 

Test substance

2000.2

30.71

0.2

Test substance

1000.4

31.97

-3.9

Test substance

499.8

32.88

-6.9

Test substance

250

32.29

-5.0

Test substance

124.8

31.54

-2.5

 

Reference substance

5

17.60

42.8

Reference substance

15

8.84

71.3

Reference substance

30

5.83

81.0

 

Conclusions:
An ASRI 3hr EC50 of >2000 mg/l was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2009-11-12
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
GLP compliance:
yes
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)

- Method: 50 mg of the test substance was added to 250ml of purified tap water and stirred.
Test organisms (species):
activated sludge
Details on inoculum:
- Source: Municipal sewage treatment plant: ‘Waterschap de Maaskant', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage

- Preparation of inoculum for exposure: coarsely sieved then washed.

Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Post exposure observation period:
Oxygen consumption was measured and recorded for approximately 10 minutes.
Test temperature:
19.8-20.0°C
pH:
7.4
Nominal and measured concentrations:
100 mg/L
Details on test conditions:
TEST SYSTEM

- Test vessel:

- Material, size, headspace, fill volume: 1L test bottle

- Aeration: continuous vigorous aeration during contact time

- No. of vessels per concentration (replicates): Two

- No. of vessels per control (replicates): One at the initial, one at the final test points.

- Biomass loading rate: activated sludge: 4.0 g/l

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Tap-water purified by reverse osmosis (Milli-RO) and subsequently passed over activated carbon and ion-exchange cartridges (Milli-Q) (Millipore Corp.).


Reference substance (positive control):
yes
Remarks:
3,5-Dichlorophenol
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Details on results:
The two control had a difference in respiration rate of 8%, which is the limit for a valid study.
Results with reference substance (positive control):
A positive control test with 3,5-dichlorophenol yielded an EC50 of 7.7 mg/L. The validity criteria of the Guideline were fulfilled.

Test sample

Nominal concentration of test substance (mg/l)

Oxygen conc. At start (mg O2/l)

Oxygen consumption (mg O2/l/h)

% Inhibition

respiration rate

pH

 

 

Initial control

0

6.4

68

-

7.4

Final control

0

7.3

63

-

7.4

Dodecamethylcyclohexasiloxane (1)

100

6.1

72

-10

7.4

Dodecamethylcyclohexasiloxane (2)

100

7.1

68

-4

7.4

 

 

3,5-dichlorophenol

5

-

-

32

-

12

-

-

73

-

30

-

-

86

-

Validity criteria fulfilled:
yes
Conclusions:
An EC50 >100 mg/l for toxicity to microorganisms was determined in a reliable study conducted according to an appropriate test protocol, and in compliance with GLP.
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
09 February 2012 - 09 February 2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This study has been performed according to OECD and/or EC guidelines and according to GLP principles
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Deviations:
no
Qualifier:
according to guideline
Guideline:
EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
ISO 8192 (Water quality - Test for inhibition of oxygen consumption by activated sludge for carbonaceous and ammonium oxidation)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
no
Vehicle:
no
Details on test solutions:
The batch of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane tested was a clear colourless liquid with a purity of 97.41% ±0.01. Since 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane may have the potential to be volatile (information obtained by the sponsor), the test substance was pipetted below the surface of Milli-RO-water (200 ml, tap water purified by reverse osmosis) and stirred briefly to mix (5 minutes) in closed dark brown bottles. The initial loading rates were 2.5 times the final loading rate. Subsequently, 16 ml synthetic medium, 250 ml sludge and Milli-RO water up to 500 ml were added resulting in the required loading rates. Optimal contact between the test substance and test organisms was ensured applying continuous aeration and stirring.
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
The sludge was coarsely sieved, washed and diluted with ISO-medium. A small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids (3.0 g/l of sludge, as used for the test). The pH was 7.4 on the day of testing. The batch of sludge was used one day after collection; therefore 50 ml of synthetic medium 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:
freshwater
Limit test:
yes
Total exposure duration:
3 h
Post exposure observation period:
After the 3-hour contact time, the oxygen consumption was recorded for a period of approximately 10 minutes. During measurement, the sample was not aerated but continuously stirred on a magnetic stirrer. The pH and temperature were determined in the remaining part of the reaction mixture.
Test temperature:
Between 18.0 and 19.6°C.
pH:
Before addition of sludge: 7.6 - 7.7
After the 3 hour exposure period: 7.5 - 8.3
Dissolved oxygen:
The oxygen concentration at the start of measurements was at least 7.5 mg O2/l

Controls: 48 mg O2/l h
2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane 10 mg/l: 50 mg O2/l h
2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane 100 mg/l: 52 mg O2/l h
2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane 1000 mg/l: 50 mg O2/l h
Nominal and measured concentrations:
Nominal loading rates: 10, 100 and 1000 mg/l
Details on test conditions:
TEST SYSTEM
- Type: open
- Material, size, headspace, fill volume: All glass
- Aeration:During exposure with clean, oil-free air
- No. of vessels per concentration (replicates): 1 for 10 and 100 mg/l and 3 for 1000 mg/l
- No. of vessels per control (replicates): 2
- Biomass loading rate: 1.5 g/l suspended solids in final test mixture

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap-water purified by reverse osmosis (Milli-RO
EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : The respiration rate from each vessel, in mg O2/l/hr, was calculated from the linear part of the respiration curve, which was generally between 2 and 7 mg O2/l.

TEST CONCENTRATIONS
- Test concentrations: combined limit/range-finding test at 10, 100 and 1000 mg/l (loading rates)
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
(loading rate)
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
> 1 000 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
(loading rate)
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:

In the combined limit/range-finding test no statistically significant inhibition of the respiration rate of the sludge was recorded at a loading rate of 1000 mg 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane per litre (Two Sample t-Test : α=0.05 Toxstat).

There was no oxygen uptake from abiotic processes and the results at 1000 mg/l with a nitrification inhibitor showed no heterotrophic inhibition of the respiration rate.
Results with reference substance (positive control):
The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/l for total respiration (4.0 mg/l).
Reported statistics and error estimates:
ECx
For the reference substance the percentage inhibition was plotted against the logarithm of the concentrations and the EC50 was determined using linear regression analysis.

For 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane no EC50 could be calculated because the test substance proved to be non-toxic (EC50 > a loading rate of 1000 mg/l).

NOEC estimation
The NOEC was based on statistical analysis of the data. Data obtained for the test concentrations were compared with those obtained for the control using TOXSTAT Release 3.5, 1996, D.D. Gulley, A.M. Boelter, H.L. Bergman.
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of this present test 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane was not toxic to waste water (activated sludge) bacteria up to and including a loading rate of 1000 mg/l (NOEC).

The EC50 exceeded a loading rate of 1000 mg/l.

Description of key information

Toxicity to microorganisms: 3 hour EC50 >1000 mg/l; NOEC >=1000 mg/l (OECD 209)

Key value for chemical safety assessment

Additional information

Under the conditions of the OECD TG 209 test, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane was not toxic to waste water (activated sludge) bacteria up to and including a loading rate of 1000 mg/l (NOEC). The EC50 exceeded a loading rate of 1000 mg/l.

The registration substance has a purity of >70% Vi4-D4, with <20% 2,4,6,8,10-pentamethyl-2,4,6,8,10-pentavinylcyclopentasiloxane (Vi5-D5; CAS 17704-22-2; Impurity 1) and <10% 2,4,6-trimethyl-2,4,6-trivinylcyclotrisiloxane (Vi3-D3; CAS 3901-77-7; Impurity 2) present as impurities. After due consideration of the properties, the presence of these impurities is not expected to affect the overall hazard profile of the substance. Vi5-D5 and D5 are within the Reconsile Siloxane Category of substances within which, in general, the substances exhibit no evidence of significant toxicity to microorganisms. Table 7.1.7 presents microorganism toxicity data available for substances within the Siloxane Category. Vi3-D3 and D3 do not fall within the Category definition, however the substances are structurally similar, and a study with D3 concludes that no evidence of significant toxicity to STP organisms. It is therefore considered valid to read-across the results for D5 and D3. Additional information is given in a supporting report (Peter Fisk Associates, 2017) attached in Section 13 of the IUCLID 6 dossier.

Read-across studies are in place as supporting studies, to consider the properties of the impurities. Data for Vi5-D5 are read-across from decamethylcyclopentasiloxane D5 (CAS 541-02-6), data for Vi3-D3 are read-across from hexamethyltrisiloxane D3 (CAS 541-05-9). An ASRI 3 hour EC50 of >2000 mg/l was determined for D5. An ASRI EC50 >100 mg/l was determined for D3.

Table: Microorganism toxicity data available for substances within the Siloxane Category

CAS

Name

Result: E(I)C50(mg/l)

Result: NOEC (or EC10/ EC20) (mg/l)

Guideline Number

Test method

Duration (h)

Reliability

540-97-6

Dodecamethylcyclohexasiloxane

>100 mg/l

 

OECD 209

ASRI

3

1

541-05-9

Hexamethylcyclotrisiloxane

>100 mg/l

>100 mg/l

OECD 209

ASRI

3

1

541-02-6

Decamethylcyclopentasiloxane

>2000 mg/l

 

C11

ASRI

3

1

107-46-0

Hexamethyldisiloxane

>>100

≥100

OECD 209

ASRI

3

1

141-62-8

Decamethyltetrasiloxane

>100 mg/l

 

OECD 209

ASRI

3

1

352230-22-9

Siloxanes and Silicones, di-Ph, Ph (trimethylsilyl)oxy

>1000 mg/l

≥1000 mg/l

OECD 209

ASRI

3

1

2627-95-4

1,1,3,3-tetramethyl-1,3-divinyldisiloxane

>1000 mg/l

≥1000 mg/l

OECD 209

ASRI

3

1

2554-06-5

2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane

>1000 mg/l

≥1000 mg/l

OECD 209

ASRI

3

1

N/A (EC 939-487-8)

Phenyl silsesquioxanes

>1000

≥1000

OECD 209

ASRI

3

1

99363-37-8

dimethyl, methyl(3-aminopropyl) siloxane, trimethylsiloxy-terminated

> water soluble fraction

≥ water soluble fraction

OECD 209

ASRI

3

1

71750-79-3

dimethyl, (aminoethylaminopropyl)methyl siloxane, trimethylsiloxy-terminated

> water soluble fraction

≥ water soluble fraction

OECD 209

ASRI

3

1