Captan

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:

2014-11-12 to 2014-12-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- Name of test material: Captan, N-(trichloromethylthio)cyclohex-4-ene-1,2-dicarboximide
- Molecular formula: C9H8Cl3NO2S- Cass No.: 133-06-2
- Molecular mass: 300.59
- Physical state: white solid
- Date of arrival: 29 January and 4 Feburary 2002
RADIOLABELLED TEST SUBSTANCE
- Test Item: CAPTAN, [carboximide-14C]
- Chemical name: 2-[(Trichloromethyl)sulfanyl]-3a,4,7,7a-tetrahydro-1H-isoindole-1,3(2H)-dione
- Molecular formula: C9H8Cl3NO2S
- Specific activity: 5.11 MBq/mg corresponding to 41.68 mCi/mmol
- Source: ADAMA MAKHTESHIM LTD.
- Batch number: XXI/58/A/2
- Radiochemical purity: 93.46 %
- Chemical purity 92.13 %
- Storage: Below -18 °C

NON RADIOLABELLED TEST SUBSTANCE
- Test item: Captan
- Sum formula (A.I.): C9H8Cl3NO2S
- Appearance: Solid, Off-white powder
- Source: ADAMA MAKHTESHIM LTD.
- Batch number: 93138112
- Purity: 94.3 %
- Storage: Keep locked up and keep the container tightly closed, protected from light in a dry, cool and well-ventilated place in the original container.
- Expiry date: 2015-02-16
- Test system: Inoculum of the aqueous phase of non-adapted activated sludge
- Source: Municipal sewage treatment plant. 31137 Hildesheim. Germany- Receipt: 2014-11-07

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Duration of test (contact time):

28 d

Initial conc.:

738 g/L

Based on:

test mat.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

13

St. dev.:

5

Sampling time:

28 d

Details on results:

In the toxicity control containing both test and reference item a biodegradation of 46 % (related to Aniline) was determined within 14 days and it came to 72 % after 28 days. The biodegradation of the reference item was not inhibited by the test item in the toxicity control. Furthermore the solvent acetonitrile didn’t impact the degradation of Aniline sulphate, [14C(U)]-.The biodegradation of the test item (look at attached graphic, Figure 1) in comparison to the readily degradable functional control and the toxicity control. The mean 10 % level (beginning of biodegradation) was reached after a long-lasting adaptation phase on day 19. The biodegradation increased only slowly within the further course of the study and the 60 % pass level was not reached until test end. The mean biodegradation after 28 days was 13 %.Under the test conditions the test item is classified as not readily biodegradable in the 10-day-window and within 28 days.

Table 5.2.1-1: CO2-Production (as total radioactivity) and Biodegradation in the test item vessels

Study day	Date	Test item
		Replicate 1			Replicate 2
		[kBq/1.8 L]		Degradation [%]	[kBq/1.8 L]		Degradation [%]
		Gross Sum	Net Sum		Gross Sum	Net Sum
1	2014-11-13	0.3	0.3	0	0.3	0.3	0
2	2014-11-14	1.1	1.0	0	1.0	1.0	0
5	2014-11-17	5.4	5.4	1	5.6	5.5	1
7	2014-11-19	10.2	10.2	1	13.6	13.5	1
9	2014-11-21	16.4	16.4	2	17.7	17.6	2
12	2014-11-24	22.6	22.5	2	21.7	21.6	2
14	2014-11-26	25.4	25.3	2	23.9	23.8	2
16	2014-11-28	27.9	27.9	3	25.9	25.8	2
19	2014-12-01	32.1	32.0	3	33.4	33.3	3
22	2014-12-04	39.4	39.3	4	40.3	40.2	4
26	2014-12-08	62.6	62.5	6	52.8	52.7	5
28	2014-12-10	87.5	87.4	8	60.6	60.5	6
29	2014-12-11	159.4	159.3	15	116.1	116.0	11

Validity criteria fulfilled:

yes

Remarks:

Degradation of the functional control reached the pass level of ≥ 60 % after 12 days. Differences of extremes of replicate values of removal of the test item at the end of the test was less than 20 %.

Interpretation of results:

not readily biodegradable

Conclusions:

Substance is not readily biodegradable

Executive summary:

The ready biodegradability of captan, [carboximide-14C] was determined with a non-adapted activated sludge over a test period of 28 days in the Modified Sturm Test. The mean biodegradation after 28 days was 13 %.

Substance is not readily biodegradable

Description of key information

Not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

Biodegradation for captan was determined by a CO2 evolution test according to OECD 301 B. Degradation of captan was very slow. The mean 10 % level was reached after a long-lasting adaptation phase on day 19. The biodegradation increased only slowly within the further course of the study and the 60 % pass level was not reached until test end. The mean biodegradation after 28 days was 13 %.

Captan is known to hydrolyse rapidly with half-life time DT50 (pH7) of 4.9 hours (Lee, K.S. 1989). Captan / its degradation products are assessed not to be ready biodegradable.