Fenitrothion

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

18 September 2001 - 18 September 2001

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2002

Report date:

2002

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Principles of method if other than guideline:

The effect of fenitrothion on the respiration of activated sewage sludge (from a water treatment works containing effluent of predominantly domestic origin) was examined according to OECD Guideline 209. Test solutions were prepared as follows:
Control solutions: two solutions of activated sludge at a concentration of 1.6 g/l in dechlorinated water.
Test solutions: five solutions of activated sludge as the control, but with the addition of fenitrothion at 10, 31.6, 100, 316 and 1000 mg/l
Reference solutions: three solutions of activated sludge as the control, but with the addition of the reference item, 3,5-dichlorophenol,at concentrations of 4, 12 and 36 mg/l.
The above solutions were incubated for three hours at 21°C, and then the oxygen consumption was monitored for a period of approximately 10 minutes using a chart recorder. The oxygen consumption of the test and reference item solutions were then compared with the controls and the EC50 (concentration causing 50% inhibition of the respiration rate) was then estimated.

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

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

DO2 measured for 10 minutes

Test solutions

Vehicle:

no

Details on test solutions:

Each concentration was prepared separately by adding 16 mL of sewage feed to each of the flasks which were made up to 300 mL
with water only in the case of the controls or a nominal mixture of water and test item in the case of the test solutions.
Each mixture was then made up to 500 mL by adding 200 mL of inoculum. As 200 mL of inoculum were added in a final volume of 500 mL,
the organic material concentration from inoculum was 1.6 g/L (± 10%).
The solutions were aerated at between 0.5 to 1 liter of air per minute using a Pasteur-pipette connected with a flexible tube to an air pump as an aeration device.
Solutions were prepared approximately every 15 minutes for test times of 3 hours.
In order to verify the quality of the inoculum, the controls were prepared at the beginning (first control) and the end (second control) of the test.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

activated sludge collected from a water treatment works containing effluent from a predominantly domestic origin

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Remarks on exposure duration:

Solutions were prepared approximately every 15 minutes for test times of 3 hours.

Post exposure observation period:

After 3 hours of aeration/contact time, the content of the test flask was poured into the measuring apparatus and the oxygen concentration was determined for a period of approximately 10 minutes.

Test conditions

Hardness:

280 ± 20 mg/L

Test temperature:

21°C

pH:

6.0 - 8.0

Dissolved oxygen:

Initial DO conc TBC (supposedly saturated)

Nominal and measured concentrations:

Nominal: 10, 31.6, 100, 316 and 1000 mg/L

Details on test conditions:

2.2.3 Environmental conditions during the test Temperature: 21°C.

Illumination: Dilution water:

Duration of test: Aeration:

no special precautions were taken.
dechlorinated tap water was used, with a hardness of 280 ± 20 mg/L as CaC03.
3 hours.
air was bubbled through each solution at the rate of 0.5 to 1 Umin
until the start of oxygen concentration measurements.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Results and discussion

Effect concentrations

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

Respiration rates of the test and reference solutions.
The respiration rate of the test solution of highest concentration (1000 mg/L) was equivalent to the respiration rate of the first control (i.e. these rates were within 15% of each other).
Therefore, the oxygen consumption rate of the four other test solutions (10 to 316 mg/L) was not determined.
EC50s, based on nominal concentrations, were as follows:
Item 3-hour EC50 (mg/L) 95% confidence limits (mg/L)
Test item > 1000
Reference item16.0 16.0 13.8- 18.7


The difference between the two controls was <15% and the EC50 of the reference compound was between 5 and 30 mg/l (16 mg/l), therefore the test was
considered valid.

Any other information on results incl. tables

Effects on biological methods for sewage treatment - summary and conclusions

 

Type of study	Test species & Time scale	Dose range tested	Result	Reference
Effects on biological methods for sewage treatment	Activated sewage sludge (3 hours)	10, 31.6, 100, 316 and 1000 mg/l	EC50(3hour) : >1000 mg/l	L’Haridon J., 2002 (HW-0484)

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Remarks:

As the difference between the two controls was below 15% and the EC50 of 3,5-dichlorophenol was between 5 and 30 mg/L, the test was therefore considered valid.

Conclusions:

Due to the nature of use of the compound, i.e. agricultural and horticultural, sewage treatment plants are unlikely to be exposed to fenitrothion.
However, when the effect of the compound on the organisms involved in the treatment of wastewater was investigated, it had no effect on
the oxygen consumption of the sewage sludge inoculum at the highest dose tested with an EC50 of >1000 mg/l. Therefore fenitrothion has a
very low toxicity to the micro-organisms involved in the treatment of domestic waste water and will not adversely affect the sewage treatment processes.

Executive summary:

At the request of Sumitomo Chemical Agro Europe SA, Saint-Didier-au-Mont-d'Or, France, the effect of the test item, FENITROTHION, on the respiration of activated sewage sludge was evaluated using a 3-hour static test according to OECD guideline (No. 209, 4th April 1984).

Methods:

The concentrations of FENITROTHION tested were chosen according to EEC criteria for classification of dangerous substances towards aquatic organisms and also to determine suitable non-inhibitory concentrations to be used in biodegradability tests.

The EC50 (concentration expected to cause 50% inhibition of the respiration rate)

of the test item and the reference item was determined considering the oxygen consumption of the controls as 100%.

The validity criteria were met (the difference between the two controls was below 15% and the EC50 of 3,5-dichlorophenol was between 5 and 30 mg/L), the test was considered valid.

The respiration rate of the test solution of highest concentration (1000 mg/L) was equivalent to the respiration rate of the first control (i.e. these rates were within 15% of each other). Therefore, the oxygen consumption rate of the four other test solutions (10 to 316 mg/L) was not determined.

EC50s, based on nominal concentrations, were as follows:

  3-hour EC50 (mg/L)       95% confidence limits (mg/L)

                                                              

Test item:             > 1000

Reference item:       16.0                                13.8 - 18.7

The test item should be considered as non-toxic for the microorganisms of a the sewage treatment plant.