Fenitrothion

Long-term toxicity to fish

Administrative data

Endpoint:

fish early-life stage toxicity

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

June 23, 1988 - September 27, 1988

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 72-4 (Fish Early Life-Stage and Aquatic Invertebrate Life-Cycle Studies)

Version / remarks:

U. S. EPA-FIFRA, 40 CFR, Section 158.145, Guideline 72-4

Deviations:

no

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:

Fenitrothion (Batch No.: 60553, Purity: 94.5%,)

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

The concentrations were determined on days 0, 1, 7,14 and every 7 days thereafter during the study as well as on day 96, which was study termination.

Test solutions

Vehicle:

yes

Details on test solutions:

The mean measured concentrations for the five test levels were 0.025, 0.046, 0.088, 0.17 and 0.35 mg/L. These values ranged from 85 to 100% of the nominal test concentrations. The analytical results indicated that the test compound was stable under test conditions.

Test organisms

Test organisms (species):

Oncorhynchus mykiss (previous name: Salmo gairdneri)

Details on test organisms:

Groups of 120 rainbow trout eggs were exposed to the control, solvent control and test material at mean measured concentrations of 0.025, 0.046, 0.088, 0.17 and 0.35 mg/L.

Study design

Test type:

flow-through

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 d

Remarks on exposure duration:

96 days (60 days post-hatch)

Post exposure observation period:

N/A

Test conditions

Nominal and measured concentrations:

Mean measured concentrations :0.025, 0.046, 0.088, 0.17 and 0.35 mg/L (85 to 100% of the nominal test concentrations)

Results and discussion

Effect concentrations

Key result

Duration:

96 d

Dose descriptor:

NOEC

Remarks:

Based on mean standard length and blotted wet weight

Effect conc.:

0.088 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Remarks on result:

other: 96 d (60 d post-hatch)

Details on results:

Egg viability: Newly fertilised embryos (fertilised <8 hours before test initiation) were used for the initiation of this study. After 13-days the viability of the additional 200 eggs (50 per replicate) placed in the control chambers at initiation was determined. Viability of these additional eggs ranged from 63 to 69% in the 4 replicates and was averaged to 66%. This was somewhat lower than was normally expected for rainbow trout egg fertilisation at ABC Laboratories' testing facility. This was attributed to the temperature of the eggs and sperm upon arrival (~14.5 °C). Normally, eggs arrive at a temperature range of 5-10 °C. Michael Rexrode, one of the U.S.-EPA's authors of the Standard Evaluation Procedure (July, 1986) for FIFRA fish early life stage studies, was contacted regarding this matter and gave his assurance that if the remaining phase of the study proceeded normally, that 66% viability would not be a problem.

Time to hatching: Hatching began on day 31 and continued until day 37. Compared to the controls and other test levels, hatching was accelerated in the highest test level of 0.35 mg/l during the first few days of the hatching period. The control was the last test group in which hatching was initiated. 95% of hatching was completed by day 36.

Egg hatchability: As discussed above, average egg viability was determined to be 66%. Therefore, calculations of hatchability were based on 20 viable eggs out of 30 total eggs per replicate at initiation (30 x 0.66 = 20).
Mean hatchability ranged from 90% in the solvent control to 98% in the control. The 2 x 2 contingency table comparison for the control and solvent control indicated that a significant difference existed in hatchability between the two groups (Pearson chi-square probability of 0.05). Therefore, the control presented the most rigorous hatch comparison for the five exposure levels. No statistically significant reduction (p <0.05) in hatching was found in any test levels by using 2 x 2 contingency tables.

Fry survival (35-Day and 60-Day post-hatch): No statistically significant solvent effect was detected for the parameter of fry survival by using 2 x 2 contingency table comparison.
Analysis of both the 35 and 60-day post-hatch data indicated that fry survival was significantly reduced in the highest test level of 0.35 mg/l when compared to the control.

Growth (standard length and wet weight): Bartlett's test for homogeneity of variances showed no significant differences (P >0.01) between treatment group variances. Therefore, no data transformations were necessary in either the day 35 or the day 60 data analyses.
35-day post hatch - standard length: Tukey's HSD test identified fish in the levels of 0.046, 0.088, 0.17 and 0.35 mg/l as having significantly reduced lengths compared to the control fish.
61-day post hatch - standard length and wet weight: Analysis of the 60-day post hatch pooled replicate data revealed a statistically significant reduction in both weight and length for the fish of the two highest dose levels of 0.17 and 0.35 mg/l when compared to the control.
Therefore, it appears that the reduction of length noted in the levels of 0.046, 0.088 mg/l on day 35 was transient in nature and will not be considered as an effect for MATC determination.

Morphological and behavioural observation:Sublethal physical and behavioural effects noted during this study were as follows: 1) fish on the bottom of the test chamber (some on their side), 2) quiescence, 3) dark or light discoloration, 4) fin(s) discoloured white, 5) aggressive behaviour, 6) exophthalmia, 7) spinal curvature, 8) distended abdomen, 9) swimming either vertically, inverted or with head down, 10) erratic swimming, 11) remaining at the top of the water column, 12) surfacing, 13) caudal fin either eroded or missing and 14) gulping air at the surface.
Once past the swim-up stage, a few of the fish in the control, solvent control, 0.025, 0.046 and 0.088mg/l were intermittently observed to have the listed effects. These gradually diminished as the study progressed.
A minority of fish in the 0.17 mg/l dose level and a majority in the 0.35 mg/l dose level exhibited sublethal effects throughout the study. In the latter days of the study, the most notable effects in these two levels were "fish on the bottom" and "fish with missing or eroded caudal fins". Therefore, sublethal effects were most notable in the two highest dose levels, particularly at the 0.35 mg/l dose level. But in the lower test levels sublethal effects did not occur in enough of the fish for a sufficient duration to be judged as an effect.

Any other information on results incl. tables

Egg hatchability and fry survival

 

Mean Measured Test Concentration (mg/l)	Mean Egg Hatch & (SD) (%)	35-Day Post-Hatch Survival (%)	60-Day Post-Hatch Survival (%)
Control	98 (± 5.0)	93	93
Solvent control	90 (±10.8)	88	86
0.025	95 (± 7.1)	97	97
0.046	93 (± 9.6)	97	97
0.088	94 (±12.5)	98	98
0.17	93 (± 5.0)	95	93
0.35	94 (± 9.5)	54*	47*

* Denotes statistically significant reduction (P<0.05) when compared to control group by using 2 x 2 contingency tables.

Mean standard length and blotted wet weight

 

Mean Measured Test Concentration (mg/l)	35-Day Post -Hatch	60-Day Post-Hatch
	Mean Standard Length (mm)	Mean Standard Length (mm)	Mean Wet Weight (g)
Control	30+2.7	37+3.8	0.761+0.219
Solvent control	29+2.9	38+3.3	0.800+0.221
0.025	30+2.2	37+2.5	0.763+0.185
0.046	28*+2.7^1)	36+3.3	0.717+0.197
0.088	27*+2.8^1)	36+3.5	0.694+0.194
0.17	25*+2.3	33*+3.3	0.536*+0.176
0.35	20*+2.1	23*+2.3	0.166*+0.056

* Denotes statistically significant reduction (P<0.05) when compared to control group by using one-way ANOVA with Tukey's HSD multiple.

1) Since no statistically significant effects were detected in the 60-day data, it appears that the day 35 length reduction noted in the levels of 0.046 and 0.088 mg/l was transient in nature and was not considered to be an effect

Applicant's summary and conclusion

Conclusions:

The lowest No Observed Effect Concentration (NOEC) for fenitrothion technical was estimated to be 0.088 mg/l and the lowest observed effect concentration (LOEC) was estimated to be 0.17 mg/l, based on standard length and wet weight.

Executive summary:

Groups of 120 rainbow trout eggs were exposed to the test material at mean measured concentrations of 0.025, 0.046, 0.088, 0.17 and 0.35 mg/l for 96 days (60 days post-hatch) in a flow-through system. The concentrations were determined on days 0, 1, 7,14 and every 7 days thereafter during the study as well as at test termination, and ranged from 85 to 100% of the nominal test concentrations. The analytical results indicated that the test compound was stable under test conditions. No statistically significant reduction (p <0.05) in egg hatching was found in any test levels. Analysis of both the 35 and 60-day post-hatch data indicated that fry survival was significantly reduced in the highest test level of 0.35 mg/l when compared to the control. Sublethal effects in morphology and behaviour were most notable in the two highest dose levels, particularly at the 0.35 mg/l dose level. But in the lower test levels sublethal effects did not occur in enough of the fish for a sufficient duration to be judged as an effect. Analysis of the 60-day post hatch pooled replicate data revealed a statistically significant reduction in wet weight and length for the fish of the two highest dose levels of 0.17 and 0.35 mg/l when compared to the control. Consequently, the lowest No Observed Effect Concentration (NOEC) for fenitrothion technical was estimated to be 0.088 mg/l and the lowest observed effect concentration (LOEC) was estimated to be 0.17 mg/l, based on standard length and wet weight.