1-[2-(2-chloroethoxy)phenylsulfonyl]-3-(4-methoxy-6-methyl-1,3,5-triazin-2-yl)urea;triasulfuron (ISO)

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:

23 May 1989 to 20 Jun 1989

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

Version / remarks:

May 1981

Deviations:

yes

Remarks:

Filter: 0.45 µm instead of a 0.2 µm for DOC-analysis.

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

other: secondary effluent from a treatment plant

Details on inoculum:

- Source of inoculum/activated sludge: Secondary effluent from the sewage treatment plant of CH-4106 Therwil (mixture of polyvalent bacteria)

Duration of test (contact time):

28 d

Initial conc.:

>= 17 - <= 23 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral medium prepared according to the method described in the guideline.
- Test temperature: 23 ± 2 ˚C
- Lighting: Indirect daylight, dark brown glass bottles
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 2000 mL Erlenmeyer flasks
- Number of culture flasks/concentration: 2
- Sampling frequency: DOC on the days 0, 7, 14, 21, 27, 28

CONTROL AND BLANK SYSTEM
- Mineral nutrient solution without test material but with inoculum (2 replicates)
- Mineral nutrient solution with test material and with inoculum (20 mg DOC/L the test substance, 2 replicates)
- Mineral nutrient solution with reference substance and with inoculum (20 mg DOC/L reference substance aniline; 2 replicates)

Reference substance:

aniline

Remarks:

20 ± 2 mg DOC/L

Key result

Parameter:

% degradation (DOC removal)

Value:

12

Sampling time:

28 d

Details on results:

An overview of the results is provided in Table 1 in 'Any other information on results incl. tables'.

Test substance: Biodegradation measured as mg DOC/L and corrected by the blank control was calculated as 12 % (DOC/DOC) in 28 days.

Results with reference substance:

Measurements of DOC-values of biodegradation results are shown in Table 1 in 'Any other information on results incl. tables'. Biodegradation measured as mg DOC/L and corrected by the blank control was calculated as 96 % (DOC/DOC) in 28 days.

Table 1 Measurements of DOC-values of biodegradation results.

Culture medium	Flask No.	DOC concentrations after x days (mg/L)
		0	7	14	21	27	28
Mineral nutrient solution without test material but with inoculum	1 2 mean	0,81 0,81 0.81	1.71 1.30 1.51	0.50 -0.23 0,14	-0.07 0.20 0.07	0.04 0.87 0.46	0,01 0.22 0,12
Mineral nutrient solution with test material and with inoculum	1 2	17.95 17,95	16.71 16,68	15.93 15.85	14.87 15.09	15.34 15.09	15.05 15.44
Mineral nutrient solution with Reference substance and with inoculum	1 2	19.59 19.59	0.77 18,08	0 .41 0.80	0,90 0.13	0.88 1.01	0.82 0.82

 

	Flask No,	% DOC removal after x days
		0	7	14	21	27	28
Test substance	Test 1 Test 2 Test f	0 0 0	11 11 11	8 8 8	14 12 13	13 15 14	13 11 12
Reference substance	Ref. 1 Ref. 2 Ref. f	0 0 0	104 12 58	99 96 98	96 100 98	98 97 98	96 96 96

Negative degradation values are within the variation of the method.

Validity criteria fulfilled:

not specified

Interpretation of results:

not readily biodegradable

Conclusions:

In a 28-day ready biodegradability study in accordance with OECD TG 301 E, the biodegradation of the test substance was calculated as 12% (DOC/DOC). Thus, it is concluded that the test substance is not biodegradable under the test conditions.

Executive summary:

The ready biodegradability of the test item was investigated in a modified OECD screening test in accordance with OECD TG 301 E and in compliance with GLP criteria. The ready biodegradability of the test item was investigated using secondary effluent of a sewage treatment plant. The inoculum was incubated with 20 ± 3 mg DOC/L of the test substance (2 replicates) dissolved in the mineral medium at 23 ± 2 °C in the indirect daylight in dark brown glass bottles for 28 days. Mineral nutrient solution without test material but with inoculum (2 replicates), and mineral nutrient solution with reference substance and with inoculum (20 mg DOC/L reference substance aniline; 2 replicates), were incubated under the same conditions. Dissolved organic carbon (DOC) was measured at day 0, 7, 14, 21, 27 and 28. The biodegradation was calculated on the basis of the initial carbon content of the test substance and the carbon content determined on the days  of measurements. Biodegradation of the test substance and reference substance measured as mg DOC/L and corrected by the blank control was calculated as 12 and 96 % (DOC/DOC) respectively in 28 days. It is concluded that the test substance is not biodegradable under the test conditions.

Description of key information

The test substance is concluded to be "not readily biodegradable" under the test conditions, using secondary effluent from a sewage treatment plant, OECD TG 301 E, Bader 1989

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

There is one ready biodegradability study available, which followed OECD TG 301 E and was performed in compliance with GLP criteria. The ready biodegradability of the test item was investigated using aerobic activated sludge with a mixture of polyvalent bacteria and a secondary effluent of a sewage treatment plant of CH-4106 Therwil. The test sludge was incubated with 20 ± 3 mg DOC/L of the test substance (2 replicates) dissolved in the mineral medium at 23 ± 2 °C in the indirect daylight in dark brown glass bottles for 28 days. Mineral nutrient solution without test material but with inoculum (2 replicates), mineral nutrient solution with test material and with inoculum (20 mg DOC/L the test substance, 2 replicates) and mineral nutrient solution with reference substance and with inoculum (20 mg DOC/L reference substance aniline; 2 replicates), were incubated under the same conditions. Dissolved organic carbon (DOC) was measured on day 0, 7, 14, 21, 27 and 28. The biodegradation was calculated on the basis of the initial carbon content of the test substance and the carbon content determined on the days of measurements. For the calculation, the formula given in the guideline was used. Biodegradation of the test substance and reference substance measured as mg DOC/L and corrected by the blank control was calculated as 12 and 96% (DOC/DOC) respectively in 28 days. It is concluded that the test substance is not biodegradable under the test conditions.