Carbamic acid, N-[(butylthio)thioxomethyl]-, butyl ester

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:

10 July - 8 August 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2013

Report date:

2013

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

(1992)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

(2008)

Deviations:

no

Test guideline 3

Qualifier:

according to guideline

Guideline:

ISO DIS 9439 (Ultimate Aerobic Biodegradability - Method by Analysis of Released Carbon Dioxide)

Version / remarks:

(1999)

Deviations:

no

Test guideline 4

Qualifier:

according to guideline

Guideline:

other: ISO International Standard 10634 "Water Quality - Guidance for the preparation and treatment of poorly water-soluble organic compounds for the subsequent evaluation of their biodegradability in an aqueous medium" (1995)

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

butyl N-[(butylsulfanyl)methanethioyl]carbamate

EC Number:

691-061-8

Cas Number:

1001320-38-2

Molecular formula:

C10H19NO2S2

IUPAC Name:

butyl N-[(butylsulfanyl)methanethioyl]carbamate

Test material form:

solid

Remarks:

yellow grease-like solid

Specific details on test material used for the study:

Molecular formula: C10H19NO2S2
Name: n-butoxycarbonyl n-butyl dithiocarbamate (active ingredient)
CAS Number: 1001320-38-2

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', Heeswijk-Dinther, The Netherlands, receiving predominantly domestic sewage.

- Treatment: The freshly obtained sludge was used immediately. The concentration of suspended solids was determined to be 3.2 g/L in the concentrated sludge. Before use, the sludge was allowed to settle (35 minutes) and the supernatant liquid was used as inoculum at the amount of 10 mL/L of mineral medium.

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

12 mg/L

Based on:

other: Total organic carbon (TOC). No correction made for purity/composition of test substance

Initial test substance concentration 2

Initial conc.:

25 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

TEST CONDITIONS
- Composition of medium: 1 litre mineral medium contains: 10 mL of solution (A), 1 mL of solutions (B) to (D) and tap-water purified by reverse osmosis and subsequently passed over activated carbon and ion-exchange cartridges.
Stock solutions of mineral components
A) 8.50 g KH2PO4; 21.75 g K2HPO4; 67.20 g Na2HPO4.12H2O; 0.50 g NH4Cl; dissolved in Milli-Q water and made up to 1 litre, pH 7.4 ± 0.2
B) 22.50 g MgSO4.7H2O dissolved in Milli-Q water and made up to 1 litre.
C) 36.40 g CaCl2.2H2O dissolved in Milli-Q water and made up to 1 litre.
D) 0.25 g FeCl3.6H2O dissolved in Milli-Q water and made up to 1 litre.

- Test temperature: varied between 21.9 and 22.3°C
- pH:
At t=0 d: 7.5-7.6
At t=28 d: 7.5 – 7.8
- pH adjusted: No
- Aeration of test medium: Overnight prior to the start of the test. During the test the medium was aerated and stirred continously.
- Suspended solids concentration: The concentration of suspended solids was 3.2 g/L in the concentrated sludge.

- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 2 litre all-glass brown coloured bottles
- Number of culture flasks/concentration:
Test suspension: containing test substance and inoculum (2 bottles).
Inoculum blank: containing only inoculum (2 bottles)
Positive control: containing reference substance and inoculum (1 bottle).
Toxicity control: containing test substance, reference substance and inoculum (1 bottle).
- Method used to create aerobic conditions:
A mixture of oxygen (ca. 20%) and nitrogen (ca. 80%) was passed through a bottle, containing 0.5 - 1 litre 0.0125 M Ba(OH)2 solution to trap CO2 which might be present in small amounts. The synthetic air was sparged through the scrubbing solutions at a rate of approximately 1-2 bubbles per second (ca. 30-100 mL/min).
- Details of trap for CO2:
The CO2 produced in each test bottle reacted with the barium hydroxide in the gas scrubbing bottle and precipitated out as barium carbonate. The amount of CO2 produced was determined by titrating the remaining Ba(OH)2 with 0.05 M standardized HCl (1:20 dilution from 1 M HCl (Titrisol® ampul). Titrations were made every second or third day during the first 10 days, and thereafter at least every fifth day until the 28th day, for the inoculum blank and test suspension. Titrations for the positive and toxicity control were made at least 14 days.

- Pre-incubation medium: The day before the start of the test (day -1) mineral components, Milli-RO water (ca. 80% total volume) and inoculum (1% final volume) were added to each bottle. This mixture was aerated with synthetic air overnight to purge the system of CO2.

- Preparation of test bottles: At the start of the test (day 0) test and reference substance were added to the bottles containing the microbial organisms and mineral components. The volumes of suspensions were made up to 2 litres with Milli-RO water, resulting in the mineral medium described before. Three CO2-absorbers (bottles filled with 100 mL 0.0125 M Ba(OH)2) were connected in series to the exit air line of each test bottle.


SAMPLING
- Sampling frequency: Titration were made on day: 2, 5, 7, 9, 14, 19, 23, 27 and 29
- Sampling method: Titration of the whole volume of CO2-absorber

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Positive control: yes
- Toxicity control: yes

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

% Degradation

% Degradation 1

Parameter:

% degradation (CO2 evolution)

Value:

23

Sampling time:

28 d

Remarks on result:

other: Bottle A

% Degradation 2

Parameter:

% degradation (CO2 evolution)

Value:

25

Sampling time:

28 d

Remarks on result:

other: Bottle B

Details on results:

- In the toxicity control more than 25% biodegradation occurred within 14 days (42%, based on ThCO2). Therefore, the test substance was assumed not to inhibit microbial activity.

BOD5 / COD results

Results with reference substance:

- The ThCO2 of sodium acetate was calculated to be 1.07 mg CO2/mg. At day 14 the biodegradation of sodium acetate was 76%.

Any other information on results incl. tables

 Acceptability of the test:

1.    The positive control substance was biodegraded by at least 60% (76%) within 14 days (pass level was reached within a 10 -day window).

2.    The difference of duplicate values for %-degradation of the test substance was always less than 20.

3.    The total CO₂ release in the blank at the end of the test did not exceed 40 mg/L (46 mg CO₂ per 2 litres of medium, corresponding to 23 mg CO₂/L).

4.    The Inorganic Carbon content (IC) of the test substance (suspension) in the mineral medium at the beginning of the test was less than 5% of the Total Carbon content (TC). Since the test medium was prepared in tap-water purified by reverse osmosis (carbon levels < 500 ppb), IC was less than 5% of TC (mainly coming from the test substance, 12 mg TOC/L).

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

S-10903 was not readily biodegradable under the conditions of the modified Sturm test

Executive summary:

The readily biodegradation of S-10903 under the conditions of the carbon dioxide (CO2) evolution test (modified Sturm test) was investigated according to OECD guideline 301 B and GLP principles. A single test concentration of 12 mg TOC/L was tested during 28 days. Based on the obtained results, S-10903 was not readily biodegradable (ca. 24% biodegradation in 28 days). The study is considered to be reliable without restrictions.