2,4-dichlorophenol

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Modern guideline study conducted to GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Report date:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

2,4-dichlorophenol

EC Number:

204-429-6

EC Name:

2,4-dichlorophenol

Cas Number:

120-83-2

Molecular formula:

C6H4Cl2O

IUPAC Name:

2,4-dichlorophenol

Details on test material:

The purity of the test substance was reported to be 100%. The appearance was is observed to be a white monoclinic crystals with a phenolic odour.The substance is stored in the dark in a cool, well ventilated area at room temperature.

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
None

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

Activated sludge was obtained from Cambridge Sewage Treatment Works on 6th April 2010. The sludge was sieved to 850 µm, settled, decanted and resuspended using mineral media. It was centrifuged at 4000 rpm for 10 minutes and the supernatant discarded. The sludge was resuspended again, centrifuged at 4000 rpm for a further 10 minutes and the supernatant again discarded. Dry sludge solids determination was conducted on the pellets produced. This was 8.6%. The volume of the mineral medium was 1.5 l per bioreactor and the dry sludge solids in the test was 0.03g/l.

Initial test substance concentration

Initial conc.:

ca. 20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

Conical flasks of nominal volume 2000 ml were filled with 1500 ml of inoculated mineral medium.The blank, references and test bottles were set up in duplicate with a single replicate for a toxicity control. Test and reference materials were added to the appropriate bottles to a final concentration of 20 mg Carbon/litre. Atmopsheric air was pumped into the test system and scrubbed clean of carbon dioxide by passing over soda lime. The air then continues into the test vessel where it collects any evolved carbon dioxide before moving into the carbon dioxide traps, each containing 200 ml of 0.05 M sodium hydroxide solution. The test solutions were stirred for the duration of the study.

Reference substance

Reference substance:

acetic acid, sodium salt

Results and discussion

Preliminary study:

Not applicable

% Degradation

Parameter:

% degradation (CO2 evolution)

Value:

4

Sampling time:

28 d

Details on results:

2,4-Dichlorophenol failed to meet the requirement for a pass in this test (> or = 60% degradation relative to the theoretical carbon dioxide value) with a maximum of 5% recorded on day 2 of the test. However, owing to the stringency of the test it does not necessarily mean that the test substance is not biodegradable under environmental conditions, only that it indicates that more work would be necessary to establish biodegradability. The inoculum blank should not normally produce more than 40 mg/l CO2 (10.9 mg C/l) for the test to be valid. A value of 29.6 mg/l CO2 (8.1 mg C/l) was recorded. The guideline requires that the reference material degrades by at least 60% of its theoretical CO2 value, a maximum value of 88% degradation of sodium acetate was achieved on day 29. The test protocol requires that a 10 day window is applied to the degradation results (60% degradation to be reached within 10 days of 10% of the theoretical CO2 produced). 2,4-Dichlorophenol did not acheive 60% degradation, therefore the 10 day window does not apply.Inspection of the toxicity control data indicates that 2,4-dichlorophenol was not inhibitory to the micro-organism population. All the test and validity criteria were successfully achieved during the study. The final conclusion of this study is therefore that 2,4-dichlorophenol is not biodegradable in an aerobic aqueous environment.

Any other information on results incl. tables

The biodegradation rate of the test material in comparison to the reference material over the period of the test is tabulated below:-

Time (days)	Biodegradation (%)		Biodegradation (%)
	Reference Material, Sodium Acetate		Test Material, 2,4 -Dichlorophenol
0	0		0
2	35		5
5	56		3
7	63		2
10	66		0
14	76		-2
19	80		-2
23	82		-2
28	84		-2
29	87		-1
29	88		4

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The final conclusion of this study is therefore that 2,4-dichlorophenol is not biodegradable in an aerobic aqueous environment.

Executive summary:

2,4 -Dichlorophenol has been subjected to a biodegradation study according to OECD guideline 301B - CO2 evolution test. The reference substance was sodium acetate. The study was conducted to GLP. 2,4 -Dichlorophenol failed to meet the requirement for a pass in this test (> or = 60% degradation relative to the theoretical carbon dioxide value). Therefore, the final conclusion of this study is that 2,4-dichlorophenol is not biodegradable in an aerobic aqueous environment.