3,4-dichlorobenzonitrile

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:

January - March 1997

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)

Qualifier:

equivalent or similar to guideline

Guideline:

other: EEC directive 92/69, C.4-C

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): activated sludge freshly obtained from a municipal sewage treatment plant (Waterschap de Maaskat, `s-Hertogenbosch, The Netherlands)
- Treatment: The sludge was kept under continuous aeration until furher treatment. Before use, the sludge was allowed to settle for at least 30 minutes and the liquid decanted for use as inoculum at the amount of 10 mL/L of mineral medium.
- Concentration of suspended solids: 4.3 g/L in the concentrated sludge.

Duration of test (contact time):

29 d

Initial conc.:

12 mg/L

Based on:

TOC

Parameter followed for biodegradation estimation:

CO2 evolution

Key result

Parameter:

% degradation (CO2 evolution)

Value:

2.6

Sampling time:

29 d

Remarks on result:

other: Theoretical CO2production of test substance: 1.79 mg CO2/mg

Results with reference substance:

The positive control contained 80.1 mg sodium acetate (ThCO2 = 1.073 mg CO2/mg) resulting in a theoretical CO2 production following complete degradation of 85.9 mg per 2 litres.

Theoretical CO2 production:

The Theoretical CO2 production (ThCO2) of 3,4 -Dichlorobenzonitrile was calculated to be 1.791 mg CO2/mg.

The concentration was 49.1 (A) and 48.9 mg (B) 3,4 -Dichlorobenzonitrile in 2 litres test medium. Hence, the theoretical CO2 production following complete degradation was 87.9 mg for A and 87.6 mg per 2 litres for B.

The toxicity control contained 80.1 mg sodium acetate and 49.0 mg 3,4 -Dichlorobenzonitrile in 2 litres of test medium. Hence, the theoretical CO2 production following complete degradation of 3,4 -Dichlorobenzonitrile plus sodium acetate was 173.7 mg per 2 litres.

Biodegradation:

The results are summarized in Tables 1 -3.

The relative degradation values calculated from the mesurements performed during the test period revealed no significant degradation of 3,4 -Dichlorobenzonitrile (significant: >10%).

In the toxicity control more than 25 % degradation occurred in 14 days (based on ThCO2). Therefore, the test substance was assumed to be not inhibitory.

Table 1: CO2 evolution and percentage of biodegradation of the test substance (bottle A).

day	mL titrant blank (mean)	mL titrant CO2 trap	produced CO2 mL HCl	Normality N	produced mg CO2	cumulative mg CO2	degradation %
2	48.85	47.58	1.27	0.050	1.40	1.40	1.6
5	47.79	47.64	0.15	0.050	0.17	1.57	1.8
7	47.52	47.61	0.00	0.050	0.00	1.57	1.8
9	47.75	48.13	0.00	0.050	0.00	1.57	1.8
14	47.83	48.10	0.00	0.050	0.00	1.57	1.8
19	47.22	46.93	0.29	0.050	0.32	1.89	2.2
23	46.88	47.04	0.00	0.050	0.00	1.89	2.2
27	47.16	47.11	0.05	0.050	0.06	1.95	2.2
29	47.23	47.02	0.21	0.050	0.23	2.18	2.5
29	47.40	47.37	0.03	0.050	0.03	2.21	2.5
29	48.63	48.47	0.16	0.050	0.18	2.39	2.7

Table 2: CO2 evolution and percentage of biodegradation of the test substance (bottle B).

day	mL titrant blank (mean)	mL titrant CO2 trap	produced CO2 mL HCl	Normality N	produced mg CO2	cumulative mg CO2	degradation %
2	48.85	48.03	0.82	0.050	1.40	0.90	1.0
5	47.79	47.50	0.29	0.050	0.17	1.22	1.4
7	47.52	47.35	0.17	0.050	0.00	1.41	1.6
9	47.75	47.84	0.00	0.050	0.00	1.41	1.6
14	47.83	47.94	0.00	0.050	0.00	1.41	1.6
19	47.22	47.25	0.00	0.050	0.32	1.41	1.6
23	46.88	47.10	0.00	0.050	0.00	1.41	1.6
27	47.16	47.11	0.05	0.050	0.06	1.47	1.7
29	47.23	46.68	0.55	0.050	0.23	2.08	2.4
29	47.40	47.47	0.00	0.050	0.03	2.08	2.4
29	48.63	48.46	0.17	0.050	0.18	2.27	2.6

 

Table 3: CO2 evolution and percentage of biodegradation of the toxicity control.

day	mL titrant blank (mean)	mL titrant CO2 trap	produced CO2 mL HCl	Normality N	produced mg CO2	cumulative mg CO2
2	48.85	36.99	0.35	0.050	0.39	0.39
5	47.79	31.74	1.11	0.050	1.22	1.61
7	47.52	33.51	1.73	0.050	1.90	3.51
9	47.75	38.10	1.45	0.050	1.60	5.11
14	47.83	40.13	1.22	0.050	1.34	6.45
19	47.22	40.79	1.68	0.050	1.85	8.30
23	46.88	44.22	1.92	0.050	2.11	10.41
27	47.16	46.12	1.29	0.050	1.42	11.83
29	47.23	45.59	1.27	0.050	1.40	13.23
29	47.40	46.81	1.10	0.050	1.21	14.44
29	48.63	48.38	0.00	0.050	0.00	14.44

Monitory of temperature and pH:

The temperature in a vessel with water in the same room varied between 20 and 23 °C.

The pH values of the different test media collected in table 4.

Table 4: pH values of the different test media.

	just before the start of the test	on day 28
blank control (A)	7.3	7.8
blank control (B)	7.4	7.8
positive control	7.3	8.0
3,4-Dichlorobenzonitrile (A)	7.4	7.7
3,4-Dichlorobenzonitrile (B)	7.5	7.7
toxicity control	7.5	8.0

Acceptability of the test:

The positive control substance was degraded 73 % in 14 days and 83 % degradation was reached at the test period.

The total CO2 release in the blank reached a total value of 14 mg CO2 per 2 litres of medium.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

3,4-Dichlorobenzonitrile was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Executive summary:

3,4-Dichlorobenzonitrile was tested for its ready biodegradability in the carbon dioxide (CO₂) evolution test (modified Sturm test, OECD 301 B) at ca. 49 mg per 2 liters corresponding to ca. 12 mg TOC/L. The theoretical CO₂production (ThCO₂) of 3,4-Dichlorobenzonitrile was calculated to be 1.791 mg CO₂/mg.

The relative degradation values calculated from the measurements performed during the test period (29 d), revealed no significant degradation of 3,4-Dichlorobenzonitrile (significant: >10%).

In the toxicity control 3,4 -Dichlorobenzonitrile was found to be not inhibitory.

3,4-Dichlorobenzonitrile was not readily biodegradable under the conditions of the modified Sturm test presently performed.

Description of key information

3,4-Dichlorobenzonitrile was not readily biodegradable under the conditions of the modified Sturm test presently performed (2.7 % degradation in 28 days).

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

3,4-Dichlorobenzonitrile was tested for its ready biodegradability in the carbon dioxide (CO₂) evolution test (modified Sturm test, OECD 301 B) at ca. 49 mg per 2 liters corresponding to ca. 12 mg TOC/L. The theoretical CO₂production (ThCO₂) of 3,4-Dichlorobenzonitrile was calculated to be 1.791 mg CO₂/mg.

The relative degradation values calculated from the measurements performed during the test period (28 d), revealed no significant degradation of 3,4-Dichlorobenzonitrile (significant: >10%).

3,4-Dichlorobenzonitrile was not readily biodegradable under the conditions of the modified Sturm test presently performed.