1-[(4-chlorophenyl)methyl]-1-cyclopentyl-3-phenylurea

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:

1997-10-29 to 1997-11-26

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

other: IBAMA E.1.1.4 - Ready Biodegradability Test by Measuring the Dissolved Oxygen Uptake (Closed Bottle Test)

Version / remarks:

1988

Deviations:

no

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Activated sludge from effluent of a pilot domestic sewage treatment plant was used for test inoculation.
- Water filtered: yes. 1000 mL of effluent sludge from the pilot plant was collected and filtered on a qualitative filter paper.
- Concentration of sludge: The cell concentration of the culture was measured before starting the test to calculate the volume of inoculum required to provide a cell concentration in the test culture around 1E+5 cells/mL. The cell concentration of the inoculum determined by plating was 1.73E+8 cells/mL. With an inoculum volume of 12 mL in a 20-liter glass bottle, containing about 20 litres of nutrient solution, a concentration of 1E+5 cells/mL was reached.
- Preparation of inoculum for exposure: The solution was placed in aeration for 2 days and isolated from light during the cell growth period of the inoculum.

Duration of test (contact time):

28 d

Initial conc.:

60 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST SYSTEM
Dissolved oxygen determinations were made using a Digimed DMO - 02 oxymeter (membrane electrode method).
Calibrated BOD bottles of +300 mL were used as test vessels. All flasks were individually identified.

The water used to prepare the test solutions was deionized.

The test consisted of the following tests:
1. Blank: nutrient solution with inoculum.
2. Biodegradable standard: nutrient solution with inoculum plus 33.25 mL/L of the test substance solution. Final concentration of COD: 2 mg/L.
3. Test-substance assay: nutrient-solution with inoculum plus 33.25 mL/L of the test substance solution. Final concentration of COD: 2 mg/L.
4. Inhibition assay: nutrient solution with inoculum, 2 ml/L of glucose solution, 33.25 ml/L of the test substance solution. Final concentrations (in COD): 2 mg/L for glucose and 2 mg/L for the test substance. Total = 4 mg/L.

4000 mL of these test solutions were prepared in 5000 mL beakers and transferred to pre-identified BOD bottles

SAMPLING
Readings were taken at the beginning of the test, at 5 , 10, 15, 20 and 28 days of the test.


The flasks were hermetically sealed and incubated in the dark at 20° + 2 °C, except for the flasks referring to time "0" (start of the test), in which dissolved oxygen measurements were immediately performed after preparation.

Reference substance:

other: glucose

Key result

Parameter:

% degradation (O2 consumption)

Remarks:

COD

Value:

42.5

Sampling time:

28 d

Details on results:

The values of the dissolved oxygen determinations (mg O2/L) for each bottle for the different reading times are shown in Table 1.

Table 2 shows the COD values for each reading time and Table 3 shows the percentage of oxygen consumption in relation to COD.

Graph 1 shows the degradation curves for the test substance, glucose and the mixture test substance/glucose as a function of time.

Table 1. Dissolved oxygen (mg O₂/L)

Test	Flask #	0	5	10	15	20	28
Blank	1	8.7	8.2	7.8	8.1	7.9	8.1
	2	8.6	8.2	7.7	8.0	7.8	7.8
Glucose	1	8.7	7.1	6.4	6.1	6.1	6.0
	2	8.7	6.9	6.3	6.3	6.3	6.0
Test-substance	1	8.6	8.3	8.3	8.1	8.4	7.4
	2	8.7	8.3	8.1	7.5	8.0	7.0
Inhibition assay	1	8.7	7.2	6.4	6.0	6.3	5.6
	2	8.7	7.3	7.2	6.4	6.8	5.4

 

Table 2. COD values at each sampling day

Test	Flask #	5	10	15	20	28
Glucose	1	1.10	1.40	2.00	1.80	2.10
	2	1.40	1.50	1.80	1.60	1.90
Test-substance	1	0.00	0.00	0.00	0.00	0.60
	2	0.00	0.00	0.60	0.10	0.90
Inhibition assay	1	1.00	1.40	2.10	1.60	2.50
	2	1.00	0.60	1.70	1.50	2.70

 

The oxygen consumption (COt) for each flask of the various tests at time t was calculated using the following formula:

COt = St – Bt,

where :

COt = dissolved oxygen consumption (mg O₂/L) at time t (days), for each substance.

Bt = O₂ concentration (mg/L) of the blank (test 1) at time t (days).

St = concentration of O₂ (mg/L) of the test substance (test 2, 3 or 4) at time t (days).

 

Table 3. Percentage of oxygen consumption in relation to COD (% of degradation at time t)

Test	5	10	15	20	28
Glucose	62.5	72.5	95	85	100
Test-substance	25.0	25.0	47.5	39.0	65.0
Inhibition assay	0.0	0.0	15.0	2.5	37.5

 

The percentage of oxygen degradation at time t , of the tested substance was calculated based on the following formula :

% DO- CODt = (CO/DO- CODt) x 100 ,

where :

% DO- DQOt = % degradation of the tested substance, in time t (days)

CO= consumption of oxygen (mg O₂/L), in time t (days)

DO- DQOt = chemical oxygen demand (mg O₂/L) of the tested substance.

 

 

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

As shown in the data presented, the test of the biodegradable standard (glucose) reached about 60% of decay of COD, in an interval of 10 days counted from the moment in which 10% of degradation was reached; in the inhibition test more than 60% of the decay of COD was reached in relation to glucose in an interval of 10 days counted from the moment in which 10% of degradation was reached, proving that the test substance at the tested concentration does not cause inhibition of the biodegradation process.

The O2 depletions in the blank were 0.5 mg/L and 0.4 mg/L in 5 days and 0.6 mg/L and 0.6 mg/L in 28 days.

Therefore, the validation criteria for the present test were fulfilled according to the method E.1.1.4 of the IBAMA manual.

The percentage of biodegradation obtained for the test material within the conditions of this test was 42. 5%.

According to this result, the test material was classified as a NON BIODEGRADABLE substance, according to the criteria established in method E.1.1.4 of IBAMA's Manual for Ecotoxicity Evaluation Tests of Chemical Agents, of May 1988, which determines that substances/products with a percentage of degradation < 60% will be classified as such.

Executive summary:

The Ready Biodegradability of Pencycuron was assessed according to the method of measuring the dissolved oxygen consumption ("Closed Bottle Test") - method No. E. 1.1.4. of the IBAMA Manual of Tests for Evaluation of the Ecotoxicity of Chemical Agents of May 1988.

 

The percentage of degradation reached within the test conditions for the test substance  was 42.5% (after 28 days).

Description of key information

Test Type	Result	Assessment	Reference
Ready biodegradation study IBAMA/ Oxygen consumption	Not readily biodegradable (42.5% after 28 days)	Key study	Unspecified (1998)

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater