Fenitrothion

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:

23 October 2000 - 22 November 2000

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2000

Report date:

2000

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Fenitrothion

EC Number:

204-524-2

EC Name:

Fenitrothion

Cas Number:

122-14-5

Molecular formula:

C9H12NO5PS

IUPAC Name:

O,O-dimethyl O-3-methyl-4-nitrophenyl phosphorothioate

Test material form:

liquid

Specific details on test material used for the study:

Test material: Fenitrothion (Batch No.: 00611G, Purity: 94.6%)
Reference material: Sodium benzoate (Batch No.: 403453/1, Purity: 99.6%)

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, adapted

Details on inoculum:

aerobic activated sludge from a wastewater treatment plant treating predominantly domestic wastewater. The diluted activated sludge was used as inoculum to give a final concentration of 30 mg dry weight material per liter

Duration of test (contact time):

28 d

Initial test substance concentration

Initial conc.:

100 mg/L

Based on:

other: guideline

Remarks:

This test design was selected according to the guidelines since the test item is not completely soluble at a concentration of 100 mg/l (information from the e-Pesticide Manual, Eleventh Edition, Version 1.1).

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

other:

Remarks:

The percentages of biodegradation of fenitrothion and sodium benzoate (the reference material) are calculated based on the biochemical oxygen demand (BOD) and the theoretical oxygen demand (ThOD)

Details on study design:

The reference material was tested simultaneously under the same conditions as the test material as a procedure control. Also the combination of the test material and the reference material was tested as a toxicity control. The test flasks were incubated under continuous stirring at 22°C for 28 days. Oxygen consumption was recorded manually by taking a daily reading at least each working day.

Reference substance

Reference substance:

benzoic acid, sodium salt

Results and discussion

% Degradation

% Degradation 1

Key result

Parameter:

other: % biodegradation based on ThOD NH4

Value:

6

Sampling time:

28 d

Remarks on result:

other: not readily biodegradable

% Degradation 2

Key result

Parameter:

other: % biodegradation based on ThOD NHO3

Value:

5

Sampling time:

28 d

Remarks on result:

other: not readily biodegradable

BOD5 / COD results

BOD5 / COD

BOD5 / COD 1

Key result

Parameter:

ThOD

Value:

133 other: mg O2/L test soln. ThOD NH4

BOD5 / COD 2

Key result

Parameter:

ThOD

Value:

156 other: mg O2/L test soln. ThOD NO3

Results with reference substance:

Percentage biodegradation of the reference material (Procedure control: Na-benzoate):
Base don ThOD: 87%

Any other information on results incl. tables

Percentage biodegradation of Fenitrothion
based on ThODNH4		based on ThODNO3
n=1	n=2	n=1	n=2
4	8	4	7
6 (mean)		5 (mean)

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

Fenitrothion is concluded to be not readily biodegradable under the conditions tested.