Fenitrothion

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

03 March 1987 to 07 March 1987

Reliability:

1 (reliable without restriction)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Report date:

1987

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

EPA OPP 122-2 (Algal Toxicity, Tiers I and II)

Version / remarks:

US.EPA-FIFRA, 40 CFR, Section 158.150
Guideline 122-2
(1982)

Deviations:

no

Test guideline 2

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

GLP compliance:

yes

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:

The Fenitrothion (Lot: 60553,) test material was received on February 18, 1987, in good condition. The sample upon receipt was observed to be a brown liquid and was stored at room temperature in the dark. The compound contained 94.6% active ingredient, Test concentrations were based on active ingredient. The compound purity 94.5%. All standard weights and dilutions used in the preparation of test concentrations were recorded.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Analysis of algae nutrient medium samples for Fenitrothion were taken at 0- and 96-hours o ." During the conduct of the study , aliquots of the test medium wer e collected below the sur f ace using a glass pipet .

Test solutions

Vehicle:

yes

Remarks:

acetone

Details on test solutions:

The 4.0 mg/l nominal working standard was prepared by injecting an appropriate ·aliquot of a stock solution (prepared in acetone) into the sterile medium. The standard was agitated for 10-15 minutes using a magnetic stirring apparatus before preparing the test concentrations. The solvent control received an aliquot of acetone equivalent to the solvent concentration of the 4.0 mg/l nominal concentra­ tion. Each treatment level and the controls were prepared in triplicate using 100 ml of the appropriate concentration for each test vessel. Each test flask received 1.0 ml of algal inoculum containing approx\mately 1.0 X 10^6 cells/ml resulting in approximately 1.0 X 10^4 cells/ml for each flask. Actual initial cell count of control flasks resulted in a mean cell count of 1.0 X 10^4 cells/ml.

Test organisms

Test organisms (species):

Selenastrum sp.

Details on test organisms:

Selenastrum capricornutum (same as Peudokirchneriella subcapitata)

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Test conditions

Test temperature:

23-24°C

pH:

initial 7.5

Nominal and measured concentrations:

Nominal concentrations for the definitive study were a geometric series of 0.25, 0.50, 1.0, 2.0 and 4.0 mg/l. The mean measured concentrations were:0.24, 0.61, 0.92, 1.9 and 4.8 mg/L.

Details on test conditions:

Following preparation, the test vessels were positioned in a random fashion and incubated for 96 hours at 24 ±1 °C under continuous "cool-white" fluorescent light and constant shaking. Light intensity was maintained at 400 ±10% ft-c and shaker speed was 100 rpm. Temperature and light intensity were monitored throughout the study

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

1.3 mg/L

Nominal / measured:

meas. (arithm. mean)

Effect concentrations 2

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

1.2 mg/L

Nominal / measured:

meas. (arithm. mean)

Effect concentrations 3

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

0.61 mg/L

Nominal / measured:

meas. (arithm. mean)

Effect concentrations 4

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.61 mg/L

Nominal / measured:

meas. (arithm. mean)

Details on results:

A significant inhibition effect (a•0.05)on growth for the 0.92, 1.9 and 4.8 mg/l mean measured test concentrations of Fenitrothion to Selenastrum capricornu­tum, as compared to the control after 96 hours. In addition it was observed that all of the significantly affected concentrations had algae populations exhibiting cell deformation after 96 hours . This effect was manifested by the cells having a "bloated" appearance as compared to the normal cell morphology. This adverse effect was first noted at 48 hours in the 1.9 and 4.8 mean measured concentrations. Cell deformation increased with increasing concentration over time in the affected levels .
The calculated EC50 96-hour EC 1.3 mg/L and 72 hrs EC50 1.2 mg/L. The NOEC value determined to be 0.61 mg/L for 72 and 96 hrs

Any other information on results incl. tables

Mean measured concentrations (Nominal concentrations)  (mg/l)	Mean Cell Counts (cells/mL/10^4)
	0-hour	24-hours	48-hours	72-hours	96-hours
Control	1.0	2.9	5.5	30	100
Solvent control		2.7	6.0	32	100
0.24 (0.25)		2.6	5.3	34	99
0.61 (0.50)		2.7	5.2	24	110
0.92 (1.0)		2.6	5.1	20*	68*
1.9   (2.0)		2.5	4.0*	5.2*	23*
4.8   (4.0)		1.0*	1.1*	2.6*	3.6*

*: Denotes a significant (a=0.05) inhibition effect from control

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

72hr-EC50 1.2mg/l, 72hr-NOEC 0.61mg/l ( OECD)
96hr-EC50 1.3mg/l, 96hr-NOEC 0.61mg/l ( US EPA OPP)

Executive summary:

96-hour static acute algae study with Fenitrothion was success­ fully completed on March 7, 1987. The five nominal concentrations of Fenitrothion which ranged from 0.25 to 4.0 mg/l were selected from the results of range-finding tests. Selenastrum capricornutum was exposed to the test material at mean concentrations of 0,0.24, 0.61, 0.92, 1.9, and 4.8 mg/L for 96 hours. Cell counts were conducted at 24, 48, 72, and 96 hours for each concentration. Initial cell counts were performed only on control replicates. All EC50 calculations used the mean measured concentrations of Fenitrothion.

The growth data were subjected to a one-way analysis of variance (ANOVA ) and multiple means test (Dunnett's Test), which indicated a significant inhibition effect (α = 0.05) on growth for the 0.92, 1.9 and 4.8 mg/l mean measured test concentrations of Fenitrothion to Selenastrum capricornutum, as compared to the control after 72 and 96 hours. In addition it was observed that all of the significantly affected concentrations had algae populations exhibiting cell deformation after 96 hours . This effect was manifested by the cells having a "bloated" appearance as compared to the normal cell morphology. This adverse effect was first noted at 48 hours in the 1.9 and 4.8 mean measured concentrations. Cell deformation increased with increasing concentration over time in the affected levels.

Validity: Log phase growth was confirmed at 72-hours with a mean count of 3.0 X 10^5 cells/mL- in the control, which was a 30X increase from the initial 1.0 X 10^4 cells/ml. At 96-hours with a mean count of 1.0 X 10^6 cells/mL- in the control, which was a 100X increase from the initial 1.0 X 10^4 cells/ml. The growth data were subjected to a one-way analysis of variance (ANOVA ) and multiple means test (Dunnett's Test), which indicated a significant inhibition effect (α = 0.05) on growth for the 0.92, 1.9 and 4.8 mg/l mean measured test concentrations of Fenitrothion to Selenastrum capricornutum, as compared to the control after 72 and 96 hours. In addition it was observed that all of the significantly affected concentrations had algae populations exhibiting cell deformation after 96 hours. The calculated EC50 values at 72 hr for Fenitrothion was (based on cell counts), was 1.2 mg/L.