2,2-dimethyl-1,4,2-oxathiasilinan-6-one

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2020-01-08 to 2020-02-05

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

17 July 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: Testing Methods for New Chemical Substances of Japanese Chemical Substances Control Law

Version / remarks:

Method for Testing the Biodegradability of Chemical Substances by Microorganisms (301F). Latest revision, 1 July 2019, Yakuseihatsu 0701 No. 1; 20190619 Seikyoku No. 2; Kampokihatsu No. 1907011)

Deviations:

no

GLP compliance:

yes

Remarks:

according to OECD Principles of Good Laboratory Practice (26 November 1997) and the "Standard Concerning Testing Facility Relating to New Chemical Substances" of Japanese Chemical Substances Control Law

Specific details on test material used for the study:

- Lot Nr: 910064

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: activated sludge was obtained from an aeration tank of a sewage treatment plant treating predominantly domestic sewage in Kurume-shi, Fukuoka, Japan; sampling date: January 7, 2020.
- Storage conditions: not specified
- Preparation of inoculum for exposure: the activated sludge was aerated at approximately 22ºC until use for the test.
- Concentration of sludge: additive amount of the activated sludge into the test vessel was 3.23 mL on the basis of the concentration of suspended solid in the activated sludge
- Concentration of suspended solid in the activated sludge: 2790 mg/L

Duration of test (contact time):

28 d

Initial conc.:

100 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: according to guideline
- Additional substrate: no
- Solubilising agent: none
- Test temperature: 21.4 - 22.3 °C
- pH: 7.4
- pH adjusted: yes
- Aeration of dilution water: no
- Suspended solids concentration: 30 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: closed system oxygen consumption measuring apparatus (No. CM-052); temperature controlled bath with measuring unit AI-0001 (Asahi Techneion)
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: each test solution was stirred with a stirrer
- Measuring equipment: data sampler OM7000A (Ohkura Electric); total organic carbon analyzer (No. TOC-013) TOC-LCPH (Shimadzu)
- Test performed in closed vessels due to significant volatility of test substance: yes
- Details of trap for CO2 and volatile organics: Soda lime No.1 (FUJIFILM Wako Pure Chemical)

SAMPLING
- Sampling frequency: measured continuously with a closed system oxygen consumption measuring apparatus
- Sampling method: total organic carbon analyzer (No. TOC-013) TOC-LCPH (Shimadzu)
- Sample storage before analysis: no


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes (n=2)
- Procedure control: test solution (sludge + sodium benzoate) (n=1)
- Toxicity control: test solution (sludge + test item + sodium benzoate) (n=1)

Reference substance:

benzoic acid, sodium salt

Preliminary study:

No

Key result

Parameter:

% degradation (O2 consumption)

Remarks:

based on BOD

Value:

2

Sampling time:

28 d

Key result

Parameter:

% degradation (DOC removal)

Value:

3

Sampling time:

28 d

Details on results:

All of the test item was hydrolyzed to 2-((hydroxydimethylsilyl)methylthio)acetic acid (X-88-390- OH) under the test conditions of this study. X-88-390-OH did not undergo biodegradation and remained in the test solution.

Results with reference substance:

87% degaradation in 28 days.

Table 1: Analytical results of the test solutions on Day 28.

		Sludge + test item		Theoretical amount
		Vessel No. 1	Vessel No. 2
BOD^*1	mg	2.2	0.2	53.1
Residual amount and percentage residue of DOC	mgC	10.8	19.8	11.1
	%	97	97	-
Residual amount and percentage residue of test item	-	The determination of the test item could not be perforemd because the test item is rapidly hydrolized in water.
Produced amount and percentage production of X-88-390-OH^*2 (by HPLC)	mg	32.9	32.9	33.3
	%	0.99	0.99	-

^*1 The average value of the test solutions (control blank) was subtracted from the values of the test solutions (sludge + test item).

^*2 2-((Hydroxydimethylsilyl)methylthio)acetic acid

Table 2: Percentage biodegradation on Day 28.

		Sludge + test item
		Vessel No.1	Vessel No. 2	Average
Percentage biodegradation by BOD	%	4	0	2
Percentage biodegradation by DOC	%	3	3	3
Percentage biodegradation of test item	-	The determination of the test item could not be performed because the test item is rapidly hydrolized in water. Therefore, the percentage biodegradation of the test item was not calculated.

Table 3: Validity of test conditions

		Value in this test	Value of criterion
Difference between extremes of replicate values of percentage biodegradation in test solutions (sludge + test item) on day 28	BOD	4%	<20%
	DOC	0%
Percentage biodegdradation by BOD in test solution (sludge + sodium benzoate) on day 14		87%	≥60%
Percentage biodegradation by BOD in test solution (sludge + test item + sodium benzoate) on day 14		45%	≥25%
BOD in test solutions (control blank) on day 28		23 and 21 mg/L*	≤60 mg/L

*Measurement values (7.0 and 6.4 mg) / [test volume (300 mL) / 1000] = 23 and 21 mg/L

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

In a Manometric Respiratory Test according to OECD Guideline 301 F the test item was determined to be not readily biodegradable (2% biodegradation based on BOD after 28 days).

Executive summary:

The ready biodegradability of the test substance was investigated according to OECD Guideline 301 F (Ready Biodegradability - Manometric Respirometry Test) and in compliance with the GLP principles. The biodegradation of the test substance was followed by exposing it to microorganisms from the aeration tank of a sewage treatment plant treating predominantly domestic sewage. As a reference compound (procedure control) Sodium benzoate was tested simultaneously. The test item concentration selected as appropriate was 100 mg/L (nominal). The flasks were incubated for 28 days under aerobic and dark conditions at 21.4–22.3 °C. The biodegradability was derived from BOD within the test period. All validity criteria of the test guideline were fulfilled. Since the test item is rapidly hydrolyzed to the ring-cleavage product (X-88-390-OH) in water, the quantitative analysis of the test item in the test solutions could not be performed. Therefore, X-88-390-OH instead of the test item was determined. As a result, the percentage production of X-88-390-OH was 99% in the test solutions (sludge + test item). In addition, the percentage residue of DOC was 97%. These results showed that the test item was hydrolyzed to X-88-390-OH, and X-88-390-OH did not undergo biodegradation and remained in the test solution under the test conditions of this study (2% and 3% biodegradation after 28 days based on BOD and DOC, respectively). In conclusion, the test item is regarded to be not readily biodegradable.

Description of key information

In a Manometric Respiratory Test according to OECD Guideline 301 F the test item was determined to be not readily biodegradable (2% biodegradation based on BOD after 28 days).

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The ready biodegradability of the test substance was investigated according to OECD Guideline 301 F (Ready Biodegradability - Manometric Respirometry Test) and in compliance with the GLP principles. The biodegradation of the test substance was followed by exposing it to microorganisms from the aeration tank of a sewage treatment plant treating predominantly domestic sewage. As a reference compound (procedure control) Sodium benzoate was tested simultaneously. The test item concentration selected as appropriate was 100 mg/L (nominal). The flasks were incubated for 28 days under aerobic and dark conditions at 21.4–22.3 °C. The biodegradability was derived from BOD within the test period. All validity criteria of the test guideline were fulfilled. Since the test item is rapidly hydrolyzed to the ring-cleavage product (X-88-390-OH) in water, the quantitative analysis of the test item in the test solutions could not be performed. Therefore, X-88-390-OH instead of the test item was determined. As a result, the percentage production of X-88-390-OH was 99% in the test solutions (sludge + test item). In addition, the percentage residue of DOC was 97%. These results showed that the test item was hydrolyzed to X-88-390-OH, and X-88-390-OH did not undergo biodegradation and remained in the test solution under the test conditions of this study (2% and 3% biodegradation after 28 days based on BOD and DOC, respectively). In conclusion, the test item is regarded to be not readily biodegradable.