Thiophanate-methyl

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:

2012-11-12 to 2013-03-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I))

Version / remarks:

1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated: Chemicals Evaluation and Research Institute, Japan
- Concentration of sludge: 30 mg/L
- Type and size of filter used: ADVANTEC 5C, 185 mm

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: Milli-Q water
- Test temperature: 25.3 - 25.8 °C (for the ready biodegradability)
25.2 - 25.5 °C (for the confirmation of nitrification)
- pH: At the start of incubation, the pH values of the [Sludge + Test substance] system, the [Sludge blank] system, the [Sludge + Aniline] system and the [Water + Test substance] system were 7.5, 7.5, 7.4 and 7.3, respectively. At the end of incubation, the pH values of the [Sludge + Test substance] system, the [Sludge blank] system, the [Sludge + Aniline] system and the [Water + Test substance] system were 7.5 (mean value), 7.3,8.9 and 6.1, respectively.
- pH adjusted: no
- Suspended solids concentration: 4040 mg/L
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: A combination of culture glass tanks, pumps and a timer (handmade instrument)
- Number of culture flasks/concentration: 6
- Method used to create aerobic conditions: stirring
- Test performed in closed vessels due to significant volatility of test substance: substance not volatile, still closed vessel used
- Test performed in open system: no

SAMPLING
- Sampling frequency: Biological oxygen demand (BOD) measured daily with enclosed respirometer
- Sampling method: manual

CONTROL AND BLANK SYSTEM
- Inoculum blank: activated sludge
- Activity control: Activated sludge + aniline
- Test suspensions: activated sludge + Test substance
- Abiotic control: Water + Test substance

Reference substance:

aniline

Test performance:

Biological oxygen demand (BOD) which occurred by the degradation of the test substance in the presence of the standard activated sludge was measured periodically (28 days) with the enclosed respirometer. After the measurement of BOD, the concentration of the test substance was determined with a HPLC. And then the biodegradability of the test substance was evaluated from the results of the BOD and HPLC measurements. Since the test substance was not completely soluble in water, the concentration of the dissolved organic carbon was not measured.
After finishing the BOD measurement for 28 days, the contents of each bottle (Bottle No. 1 - 6) were filtered with a filter paper, and the concentration of ammonium ion in the solution was determined by the ionic electrometry.

Key result

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

28 d

Remarks on result:

other: The percentage biodegradation obtained from the BOD measurement (n = 3, mean value)

Details on results:

The amounts of oxygen uptake of the [Sludge + Test substance] systems after 28 days were 4.134, 4.777 and 4.667 mg for Bottle No. 2, 3 and 4, respectively. The amount of oxygen uptake of the [Sludge blank] system after 28 days was 2.359 mg. The amount of oxygen uptake of the [Water + Test substance] system after 28 days was 0.000 mg. The percentage biodegradations from the BOD measurement were 3.4 and 4 % for Bottle No. 2, 3 and 4, respectively, and the average value was 4 %. The difference of the percentage biodegradation between the maximum and the minimum was less than 20 % and the amount of oxygen uptake of the [Sludge blank] system was not greater than 60 mg O2/L after 28 days. So the validity criteria of the biodegradation test were fulfilled.

Results with reference substance:

The percentage biodegradation of aniline was 87 % after 7 days and 99 % after 14 days. Since these values exceeded the criteria (40 % after 7 days and 65 % after 14 days according to the OECD test guideline), the activity of the activated sludge was considered as good.

Table 1: Biodegradability from the BOD Measurement

Bottle No.	Test system	Weight (mg)	ThOD		7 days		14 days			21 days		28 days
					O2 uptake (mg)	B* (%)	O2 uptake (mg)		B* (%)	O2 uptake (mg)	B* (%)	O2 uptake (mg)	B*
													(%)	Average (%)
1	Water + Test substance	30.02	2.009		0.000	-	0.000		-	0.000	-	0.000	-	-
2	Sludge + Test substance	30.01	2.009		0.000	0	1.439		2	2.954	2	4.134	3	4
3		30.03	2.009		0.000	0	1.607		2	3.014	3	4.777	4
4		30.02	2.009		0.000	0	1.241		1	2.743	2	4.667	4
5	Sludge + Aniline	30.00		2.405	62.94	87		72.17	99	73.53	100	74.23	100	-
6	Sludge blank	—		—	0.000	—		0.450	—	1.485	—	2.359	—	-

*: Percentage biodegradation

 

Table 2: Biodegradability from the H PLC Measurement

Bottle No.	Test system	TM
		Weight (mg)	Peak area	Dilution factor	Concentration in the methanol extract*	Residual amount**	% biodegradation		Disappearance rate
					(µg/mL)	(mg)	(%)	Average (%)	(%)	Average (%)
1	Water + Test substance		30.02	32274	20	20.53	20.53	—	32	—
2	Sludge + Test substance	30.01	35688	20	22.68	22.68	-11	5	24	35
3		30.03	30683	20	19.52	19.52	5		35
4		30.02	25737	20	16.40	16.40	20		45
6	Sludge blank	—	0	1	0.007	—	—	—	—	—

*: Concentration in the methanol extract (µg/mL) = Detected concentration (µg/mL) * Dilution factor

**: Residual amount (mg) = Concentration in the methanol extract (µg/mL) x 1000 (mL) * 1E-3

 

Table 3: Quantitation Results

Bottle No.	test system	Initial weight (mg)	TM (mg)	MBC*(mg)	AV-1951*(mg)	2-AB*(mg)	Total weight (mg)
1	Water + Test substance	30.02	20.53	1.94	1.01	0.01	23.49
2	Sludge + Test substance	30.01	22.68	5.04	1.99	0.07	29.78
3		30.03	19.52	5.54	2.14	0.10	27.30
4		30.02	16.40	5.52	2.11	0.09	24.12

*: Converted values into the weight of TM

 

Table 4: Production Rate of Ammonia

Bottle	Test system	Production rate (%)
No.		Measurement 1	Measurement 2	Measurement 3	Average
1 (for Nitrification)	Water + Test substance	< 5	< 5	< 5	< 5
2 (for Nitrification)		0	0.3	0	0.1
3 (for Nitrification)	Sludge + Test substance	0	0	0	0
4 (for Nitrification)		0	0	0	0
5 (for Nitrification)	Sludge + Aniline	98.3	93.1	95.8	95.7

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The ready biodegradability test of the test item was conducted according to OECD 301 C and the percentage biodegradation obtained from the BOD measurement was 4 % (n = 3, mean value).

Executive summary:

The ready biodegradability test of the test item was conducted according to OECD Guideline for Testing Chemicals 301 C (1992). Biological oxygen demand (BOD) which occurred by the degradation of the test item in the presence of the standard activated sludge was measured periodically (28 days) with an enclosed respirometer. After the measurement of BOD, the concentration of the test item was determined with high performance liquid chromatograph (HPLC). And then the biodegradability of the test item was evaluated from the results of the BOD measurement. The percentage biodegradation obtained from the BOD measurement was 4 % (n = 3, mean value). On the other hand, the percentage biodegradation obtained from the HPLC measurement was not evaluated because the residual amount of the test item in the [Water + Test substance] system at the end of incubation was less than 90 % of the initially applied amount. The disappearance rates of the test item were 35 % (n = 3, mean value) in the [Sludge + Test substance] system and 32 % in the [Water + Test substance] system. Since Carbendazim, AV-1951 and 2-AB were confirmed to be the degradation products in these systems, the recovery as the test item was calculated by summing up the amounts of these products and the residual amount of the test item. As a result, the test item in each system was recovered almost quantitatively. Since the test item was known to be hydrolysed in aqueous solutions, it was judged that the influence of hydrolysis is bigger than that of biodegradation in the degradation of the test item in the [Sludge + Test substance] system. Therefore, it was concluded that the test item is not ready biodegradable.

Description of key information

The ready biodegradability test of the test item was conducted according to OECD 301 C and the percentage biodegradation obtained from the BOD measurement was 4 % (n = 3, mean value).

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

The ready biodegradability test of the test item was conducted according to OECD Guideline for Testing Chemicals 301 C (1992). Biological oxygen demand (BOD) which occurred by the degradation of the test item in the presence of the standard activated sludge was measured periodically (28 days) with an enclosed respirometer. After the measurement of BOD, the concentration of the test item was determined with high performance liquid chromatograph (HPLC). And then the biodegradability of the test item was evaluated from the results of the BOD and HPLC measurements. The percentage biodegradation obtained from the BOD measurement was 4 % (n = 3, mean value).

On the other hand, the percentage biodegradation obtained from the HPLC measurement was not evaluated because the residual amount of the test item in the [Water + Test substance] system at the end of incubation was less than 90 % of the initially applied amount. The disappearance rates of the test item were 35 % (n = 3, mean value) in the [Sludge + Test substance] system and 32 % in the [Water + Test substance] system. Since Carbendazim, AV-1951 and 2-AB were confirmed to be the degradation products in these systems, the recovery of the test item was calculated by summing up the amounts of these products and the residual amount of the test item. As a result, the test item in each system was recovered almost quantitatively. Since the test item was known to be hydrolysed in aqueous solutions, it was judged that the influence of hydrolysis is bigger than that of biodegradation in the degradation of the test item in the [Sludge + Test substance] system. Therefore, it was concluded that the test item is not ready biodegradable.