Trimethylvinylsilane

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

24.01.-21.02.2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

1

Reference substance name:

Trimethylvinylsilane

EC Number:

212-042-9

EC Name:

Trimethylvinylsilane

Cas Number:

754-05-2

Molecular formula:

C5H12Si

IUPAC Name:

trimethylvinylsilane

Study design

Oxygen conditions:

anaerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): activated sludge from municipal wastewater treatment plant AZV Staufener Bucht (predominantly domestic wastewater).
- Dry solid content of the activated sludge: 3.8 g/L after drying for 4 h at 105°C.
- Preparation of the inoculum: activated sludge was washed 2x with tap water by settling the sludge,
decanting the supernatant and re-suspending the sludge.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

20 mg/L

Based on:

other: TOC/L

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: 10 mL A + 900 mL demineralised water + 1 mL B + 1 mL C + 1 mL D, and subseqently the volume is made up to 1L.
A: 8.50g KH2PO4, 21.75g K2HPO4, 33.40g Na2HPO4*2H2O, 0.50g NH4Cl are dissolved in demineralised water and made up to 1L.
B: 36.4g CaCl2*2H2O is dissolved in demineralised water and made up to 1L.
C: 22.5g MgSO4*7H2O is dissolved in deminseralised water and made up to 1L.
D: 0.25g FeCl3*6H2O is dissolved in demineralised water, stabilised with one drop of concentrated HCl and made up to 1L.
- Test temperature: 20.1-22.2°C
- pH: should be 7.4

TEST SYSTEM
- flask 120 mL volume
- Number of culture flask: 16 per test serie
- Method used to create aerobic conditions: overnight aeration with CO2-free air on the day before addition of test substance.
- Measuring equipment: inorganic carbon measurement by means of total carbon analyser TOC 5050A, Shimadzu.
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: absorber wash bottles containing 0.2M NaOH

SAMPLING
- Determination of inorganic carbon concentration of the 0.2M NaOH solution: IC between 1.7 and 2.5 mg/L
- Sampling frequency: sampling on day 7, 14, 21 and 28
- Sampling method: On each sampling date three flasks of each test series were withdrawn and 1 mL NaOH (7 M) was added. On day 28 five flasks were analysed.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Reference substance: yes: sodium benzoate, conc. 20 mg organic carbon /L
- Abiotic sterile control: no
- Toxicity control: yes: 3.9 µL of the test item (corresponding to 20.2 mg TOC/L) and 80 mL test solution containing sludge, mineral medium and reference item were added into the test vessels

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

Preliminary study:

not applicable

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

0

St. dev.:

0

Sampling time:

28 d

Details on results:

- No degradation could be observed within the test duration (28 days). The biodegradation extent of the test item at the end of the test showed a slight negative value (-0.46%, mean of five replicates).
- Toxicity control: The degradation extent in the toxicity control was 34.3% within 14 days. According to the guideline the test substance had no inhibitory effect on the inoculum.
- Reference item: The reference compound sodium benzoate reached the pass level for ready biodegradability within 7 days.
- Blank: The highest mean TIC produced in the blank flasks was 1.2 mg/L in 28 days (less TIC of NaOH produced during sampling).
- Test parameters:
-- Before adding the inoculum, the IC was determined, but no IC could be detected (-0.21 mg/L).
-- The TIC produced by the NaOH in the procedure of sampling was between 1.7 and 2.5 mg/L.
-- The temperature was 20.7 – 22.4°C throughout the whole study and therefore within the required range of 20 - 25°C (± 1°C).
- Criteria of validity:
-- The mean percentage degradation in the flasks containing the reference compound was ≥ 60% on the 7th day of incubation
-- The mean amount of TIC present in the blank controls at the end of the test was <3mg C/L
The test is valid according to OECD Test Guideline 310 (26 September 2014).

Since the test substance is highly volatile, it is not unexpected that no resp. very little biodegradation was observed in this test. According to the guideline OECD 310, substances with a Henry’s law constant of up to 50 Pa.m3.mol-1 can be tested using the recommended headspace to liquid volume ratio of 1:2 (which corresponds to the ratio in the present test: liquid volume 80 mL, total volume 120 mL). According to information from the sponsor however, the Henry’s law constant for the test item is much higher. Therefore, it can be assumed that the test item migrated to the headspace volume and was not be bioavailable to the microorganisms in the test solution.

BOD5 / COD results

Results with reference substance:

sodium benzoate reached the pass level for ready biodegradability within 7 days (78.62% ThIC)

Any other information on results incl. tables

Ultimate biodegradation in x days (% of ThIC)

Sample	Mean % degradation ± SD
	d 7	d 14	d 21	d 28
Test item	4.46 ± 5.23	6.63 ± 6.93	-0.25 ± 0.19	-0.46 ± 0.97
Reference item	78.26 ± 0.43	74.41 ± 11.15	78.62 ± 2.66	70.33 ± 2.28
Inhibition control	38.32 ± 0.39	40.13 ± 3.20	36.69 ± 1.22	34.33 ± 1.86

TIC of the NaOH during the sampling

day	d 7	d 14	d 21	d 28
IC NaOH during sampling (mg/L)	1.68	2.15	1.66	2.48

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

No degradation could be observed within the test duration (28 days).
The test item did not reach the criteria for ready biodegradability (60% of ThIC within a 10-d window).

Executive summary:

A Biodegradability, CO₂Headspace Test according to OECD 310 (September 2014) was conducted in order to investigate the ready biodegradability of the test item. The test was performed in compliance to GLP.

The CO₂Headspace Test determines the biodegradability of test items by measuring the net increase of total inorganic carbon (TIC) in sealed serum flasks with a headspace volume. The test item, as sole source of carbon corresponding to 20 mg TOC/L (standard concentration), respectively 2 - 40 mg TOC/L (accepted concentration range), is added to a mineral salts medium, and is inoculated with activated sludge (4 mg d.s. /L). The test flasks are sealed and incubated at 20 - 25°C in the dark for 28 days. Degradation is followed by determining the carbon dioxide produced via TIC-measurement (TIC = total inorganic carbon) after absorption to sodium hydroxide. The amount of carbon dioxide produced from the test item less the amount derived from the blank inoculum is expressed as a percentage of ThIC (theoretical amount of inorganic carbon) that corresponds to the TOC (total organic carbon).

The pass level for ready biodegradability is 60% of ThIC and must be reached within a 10-d window (10 days after the degree of biodegradation has reached 10%).

The degradation extent in the toxicity control was 34.3% within 14 days (tab. 3). According to the guideline the test substance had no inhibitory effect on the inoculum.

The reference compound sodium benzoate reached the pass level for ready biodegradability within 7 days.

The highest mean TIC produced in the blank flasks was 1.2 mg/L in 28 days (less TIC of NaOH produced during sampling).

The test is valid according to OECD 310 (September 2014).

No degradation could be observed within the test duration (28 days). The biodegradation extent of the test item at the end of the test showed a slight negative value (-0.46%, mean of five replicates).

In conclusion, no degradation could be observed within the test duration (28 days).

The test item did not reach the criteria for ready biodegradability (60% of ThIC within a 10-d window).