Fenitrothion

Repeated dose toxicity: dermal

Administrative data

Endpoint:

short-term repeated dose toxicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 November 1990 - 10 December 1990

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1991

Report date:

1990

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

EPA OPP 82-2 (Repeated Dose Dermal Toxicity -21/28 Days)

Deviations:

no

GLP compliance:

yes

Limit test:

no

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.: 90617
Purity: 93.7%

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on species / strain selection:

Standard species/strain used for regulatory studies

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Kitayama Labs, Japan
- Females nulliparous and non-pregnant: yes
- Age at study initiation: 10 weeks
- Weight at study initiation: 1944-2311 g (males), 1704-2026 g (females)
- Housing: individual
- Diet: ad libitum
- Water: ad libitum
- Acclimation period: one week

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22-26
- Humidity (%): 45-65
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 15 November 1990 To: 10 December 1990

Administration / exposure

Type of coverage:

occlusive

Vehicle:

unchanged (no vehicle)

Details on exposure:

TEST SITE
- Area of exposure: 12x14 cm
- Type of wrap if used: occlusive

REMOVAL OF TEST SUBSTANCE
- Washing (if done): water and soap
- Time after start of exposure: 6 hours

VEHICLE
- Justification for use and choice of vehicle: undiluted

USE OF RESTRAINERS FOR PREVENTING INGESTION: yes

Analytical verification of doses or concentrations:

no

Duration of treatment / exposure:

6 hours/day for 21 successive days

Frequency of treatment:

Daily

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day

Remarks:

control (distilled water)

Doses / concentrations 2

Dose / conc.:

3 mg/kg bw/day

Doses / concentrations 3

Dose / conc.:

10 mg/kg bw/day

Doses / concentrations 4

Dose / conc.:

50 mg/kg bw/day

Doses / concentrations 5

Dose / conc.:

250 mg/kg bw/day

No. of animals per sex per dose:

5/sex

Control animals:

yes, concurrent no treatment

Details on study design:

Fenitrothion was administered percutaneously to groups of 5 male and 5 female New Zealand White rabbits at the dose levels of 0, 3, 10, 50 and 250 mg/kg bw/d by the topical route for a period of 21 successive days. The test material, a brown oily substance, was administered undiluted. The control group received distilled water.

Positive control:

Not required

Examinations

Observations and examinations performed and frequency:

Parameters evaluated were clinical observations (twice daily), dermal reactions (daily), body weights and food consumption (weekly), plasma and erythrocyte cholinesterase activity (one week before treatment, 2 and 24 hours after final dosing), haematology and biochemistry.

Sacrifice and pathology:

Brain cholinesterase activity, necropsy, organ weights and histopathology were assessed at study termination.

Statistics:

Parameters measured in this study were assessed and compared using appropriate statisitcal methods.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Signs observed in animals prior to death were hypoactivity, muscular hypotonia, tremor, bradypnoea, hypothermia, salivation, clonic convulsion, loose or mucous stool, diarrhea and soiled perineum. In the surviving three females at 250 mg/kg bw/d, one animal revealed loose stool and soiled perineum and the other two animals showed no abnormalities. No clinical signs were noted in animals of the control and 3, 10 and 50 mg/kg bw/d groups.

Dermal irritation:

effects observed, treatment-related

Description (incidence and severity):

Very slight or well defined erythema and very slight or slight oedema were observed at the application site in males and females of the 3, 10 and 50 mg/kg bw/d groups, and were classified as mild according to the Draize index. Males and females of the 250 mg/kg bw/d group showed slightly more severe irritation than other treated groups. The maximum mean irritation scores at 250 mg/kg bw/d were classified as moderate according to the Draize index. The other dermal reaction observed in all groups treated with fenitrothion was desquamation of the epidermis.

Mortality:

mortality observed, treatment-related

Description (incidence):

Five males and two females at 250 mg/kg bw/d showed deterioration of general condition and died during the administration period (two males and one female were killed in a moribund condition).

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Depression of body weight gain and decrease in body weights were observed in males and females at 250 mg/kg bw/d.

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Ophthalmological findings:

not examined

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

Increased WBC count and variable differential counts were observed in decedents at 250 mg/kg bw/d. No haematological effects were reported at lower dose levels.

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

Increased AST and ALT activity and blood urea nitrogen and a decrease in serum electrocytes were observed in some animals at 250 mg/kg bw/d. No effects on clinical chemistry parameters were reported at lower dose levels.

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not specified

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Description (incidence and severity):

Increased adrenal weight was seen in some rabbits at 250 mg/kg bw/d.

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

At 250 mg/kg bw/d, one male and one female revealed slight focal necrosis in the liver; histopathological changes in the digestive tract and kidney were considered to reflect a general deterioration of condition.

Histopathological findings: neoplastic:

no effects observed

Other effects:

effects observed, treatment-related

Description (incidence and severity):

Erythrocyte cholinesterase activity decreased in males and females at 10, 50 and 250 mg/kg bw/d. Plasma and brain cholinesterase activities decreased in males at 50 and 250 mg/kg bw/d and in females at 10, 50 and 250 mg/kg bw/d. No significant changes in erythrocyte, plasma or brain cholinesterase activities were observed at 3 mg/kg bw/d.

Effect levels

1

Key result

Dose descriptor:

NOAEL

Effect level:

< 3 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: Local dermal irritation

Remarks on result:

other: Local toxicity

2

Key result

Dose descriptor:

NOAEL

Effect level:

3 mg/kg bw/day

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: cholinesterase activity

Remarks on result:

other: Systemic toxicity

Target system / organ toxicity

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

10 mg/kg bw/day

System:

nervous system

Organ:

brain

neurons

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

yes

Any other information on results incl. tables

Summary of dermal reactions (males)

	3 mg/kg bw/d			10 mg/kg bw/d			50 mg/kg bw/d			250 mg/kg bw/d
	Erythema	Oedema	Total	Erythema	Oedema	Total	Erythema	Oedema	Total	Erythema	Oedema	Total
Day 0	0	0	0	0	0	0	0	0	0	0	0	0
Day 1	0	0	0	0	0	0	0	0	0	0	0	0
Day 2	0	0	0	0	0	0	0	0	0	0	0	0
Day 3	0	0	0	0	0	0	0	0	0	0	0	0
Day 4	0	0	0	0	0	0	0.20	0	0.20	0.20	0	0.20
Day 5	0	0	0	0	0	0	0.20	0	0.20	0.40	0	0.40
Day 6	0	0	0	0.20	0	0.20	0.40	0	0.40	0.60	0	0.60
Day 7	0.40	0	0.40	0.40	0	0.40	0.80	0	0.80	1.20	0.20	1.40
Day 8	0.40	0	0.40	0.40	0	0.40	1.00	0.20	1.20	1.25	1.00	2.25
Day 9	0.40	0	0.40	0.40	0	0.40	1.20	0.20	1.40	1.33	1.33	2.66
Day 10	0.60	0	0.60	0.60	0	0.60	1.20	0.20	1.40	1.33	0.67	2.00
Day 11	0.60	0	0.60	0.40	0	0.40	0.80	0.20	1.00	1.00	0.33	1.33
Day 12	0.60	0	0.60	0.40	0	0.40	0.80	0.20	1.00	1.00	0	1.00
Day 13	0.40	0	0.40	0.40	0	0.40	0.80	0	0.80	1.00	0	1.00
Day 14	0.40	0	0.40	0.40	0	0.40	1.00	0	1.00	1.00	0	1.00
Day 15	0.40	0	0.40	0.40	0	0.40	1.00	0	1.00	1.00	0	1.00
Day 16	0.40	0	0.40	0.40	0	0.40	1.00	0	1.00	1.00	0	1.00
Day 17	0.40	0	0.40	0.40	0	0.40	1.00	0	1.00	1.00	0	1.00
Day 18	0.40	0	0.40	0.40	0	0.40	1.00	0	1.00	1.00	0	1.00
Day 19	0.40	0	0.40	0.40	0	0.40	0.60	0	0.60	1.00	0	1.00
Day 20	0.60	0	0.60	0.40	0.20	0.60	0.40	0	0.40	1.00	0	1.00
Termination	0.80	0	0.80	0.40	0.40	0.80	0.60	0	0.60	-	-	-

Summary of dermal reactions (females)

	3 mg/kg bw/d			10 mg/kg bw/d			50 mg/kg bw/d			250 mg/kg bw/d
	Erythema	Oedema	Total	Erythema	Oedema	Total	Erythema	Oedema	Total	Erythema	Oedema	Total
Day 0	0	0	0	0	0	0	0	0	0	0	0	0
Day 1	0	0	0	0	0	0	0	0	0	0	0	0
Day 2	0	0	0	0	0	0	0	0	0	0	0	0
Day 3	0	0	0	0	0	0	0	0	0	0	0	0
Day 4	0	0	0	0	0	0	0	0	0	0.20	0	0.20
Day 5	0	0	0	0.20	0	0.20	0.20	0	0.20	1.00	0.20	1.20
Day 6	0	0	0	0.40	0	0.40	0.40	0.40	0.80	1.00	0.80	1.80
Day 7	0	0	0	0.40	0	0.40	0.60	0.40	1.00	1.40	1.00	2.40
Day 8	0	0	0	0.20	0	0.20	0.80	0.40	1.20	1.20	0.60	1.80
Day 9	0.20	0	0.20	0.20	0	0.20	0.60	0.40	1.00	1.00	0.40	1.40
Day 10	0.20	0	0.20	0.20	0	0.20	0.60	0.40	1.00	1.00	0.40	1.40
Day 11	0.20	0	0.20	0.40	0	0.40	0.60	0.40	1.00	1.20	0.20	1.40
Day 12	0.40	0	0.40	0.60	0	0.60	0.80	0.40	1.20	1.20	0.20	1.40
Day 13	0.80	0.20	1.00	1.00	0.60	1.60	0.80	0.40	1.20	1.20	0.20	1.40
Day 14	1.00	0.60	1.60	1.20	0.60	1.80	0.80	0.20	1.00	1.20	0.20	1.40
Day 15	0.80	0.60	1.40	1.20	0.60	1.80	0.80	0.20	1.00	1.00	0	1.00
Day 16	0.80	0	0.80	1.20	0.40	1.60	0.80	0	0.80	1.00	0	1.00
Day 17	0.60	0	0.60	1.20	0.20	1.40	0.60	0	0.60	1.00	0	1.00
Day 18	0.60	0	0.60	1.00	0.20	1.20	0.60	0	0.60	1.00	0	1.00
Day 19	0.60	0	0.60	1.00	0.20	1.20	0.60	0	0.60	1.00	0	1.00
Day 20	0.60	0	0.60	1.00	0	1.00	0.60	0	0.60	1.00	0	1.00
Termination	0.40	0	0.40	0.80	0	0.80	0.60	0	0.60	1.00	0	1.00

Bodyweights and weight gains

	0 mg/kg bw/d	3 mg/kg bw/d	10 mg/kg bw/d	50 mg/kg bw/d	250 mg/kg bw/d
Males
Day 0	(5)      2.482	(5)      2.471	(5)      2.503	(5)      2.439	(5)      2.448
Day 7	(5)      2.616	(5)      2.611	(5)      2.710	(5)      2.599	(5)      2.456
Day 14	(5)      2.783	(5)      2.744	(5)      2.810	(5)      2.695	(2)      2.493
Day 20	(5)      2.915	(5)      2.831	(5)      2.938	(5)      2.764	(2)      2.302
Body Weight Gains
Day 7	(5)      0.134	(5)      0.140	(5)      0.208	(5)      0.160	(5)      0.007
Day 14	(5)      0.301	(5)      0.273	(5)      0.307	(5)      0.256	(2)      0.176
Day20	(5)      0.433	(5)      0.360	(5)      0.436	(5)      0.325	(2)    -0.115*
Females
Day 0	(5)      2.522	(5)      2.482	(5)      2.583	(5)      2.437	(5)      2.531
Day 7	(5)      2.578	(5)      2.590	(5)      2.678	(5)      2.642	(5)      2.685
Day 14	(5)      2.773	(5)      2.744	(5)      2.787	(5)      2.808	(5)      2.623
Day 20	(5)      2.882	(5)       2.865	(5)      2.901	(5)      2.864	(3)      2.695
Body Weight Gains
Day 7	(5)      0.056	(5)      0.108	(5)      0.095	(5)      0.204	(5)      0.154
Day 14	(5)      0.251	(5)       0.262	(5)      0.203	(5)      0.370	(5)      0.093
Day 20	(5)      0.360	(5)      0.383	(5)      0.317	(5)      0.427	(3)      0.200

*significantly differerent to controls (p<0.05)

Cholinesterase activity

		0 mg/kg bw/d	3 mg/kg bw/d	10 mg/kg bw/d	50 mg/kg bw/d	250 mg/kg bw/d
Males
Erythrocyte	Before treatment	916.28	811.80	993.39	954.04	891.61
	2h after	1274.98	1020.21	687.90**	646.96**	-
	24h after	1198.76	829.02	1049.14	500.65**	-
Plasma	Before treatment	257.60	325.01	280.94	284.41	298.18
	2h after	355.72	357.27	317.66	218.58	-
	24h after	385.30	386.07	323.55	232.73*	-
Brain		11204.60	10057.80	8904.40	7127.60**	-
Females
Erythrocyte	Before treatment	917.69	874.41	741.74	780.84	896.69
	2h after	1291.47	1349.59	630.33*	377.49**	222.36**
	24h after a)	1135.52	1063.48	761.98	400.29**	237.47**
Plasma	before treatment	139.52	139.92	161.46	124.95	127.03
	2h after	360.55	309.10	259.03	95.36**	38.05**
	24h after	356.89	325.72	212.25**	143.90**	22.98**
Brain		12798.00	11736.20	10119.40*	9010.20**	2590.00**

*significantly different to controls (p<0.05); **p<0.01

Adrenal weights

Week 4	0 mg/kg bw/d	3 mg/kg bw/d	10 mg/kg bw/d	50 mg/kg bw/d	250 mg/kg bw/d
Males
Body weight (kg)	2.788	2.765	2.814	2.667	-
Adrenal absolute weight (g)	0.21	0.25	0.24	0.20	-
Adrenal relative weight (%)	0.07	0.09	0.08	0.08	-
Females
Body weight (kg)	2.808	2.681	2.817	2.768	2.641
Adrenal absolute weight (g)	0.21	0.20	0.25	0.22	0.28*
Adrenal relative weight (%)	0.07	0.08	0.09	0.08	11

*significantly different to controls (p<0.05)

Applicant's summary and conclusion

Conclusions:

A NOAEL could not be determined for this study due to local dermal reactions at the application site in rabbits of all treated groups. A NOAEL for systemic toxicity of 3 mg/kg bw/d can be determined based on the significant inhibition of cholinesterase activity at higher dose levels.

Executive summary:

The repeated dose dermal toxicity of fenitrothion was investigated in a 21 -day study in the rabbit. Fenitrothion was administered percutaneously to groups of 5 male and 5 female New Zealand White rabbits at the dose levels of 0, 3, 10, 50 and 250 mg/kg bw/d by the topical route for a period of 21 successive days. The test material, a brown oily substance, was administered undiluted. The control group received distilled water. Parameters evaluated included clinical observations (twice daily), dermal reactions (daily), body weights and food consumption (weekly), plasma and erythrocyte cholinesterase activity (one week before treatment, 2 and 24 hours after final dosing) and haematology, biochemistry, brain cholinesterase activity, necropsy, organ weights and histopathology at study termination. Five males and two females at 250 mg/kg bw/d showed deterioration of general condition and died during the administration period (two males and one female were killed in a moribund condition).  Signs observed in animals prior to death were hypoactivity, muscular hypotonia, tremor, bradypnoea, hypothermia, salivation, clonic convulsion, loose or mucous stool, diarrhoea and soiled perineum. In the surviving three females at 250 mg/kg bw/d, one animal revealed loose stool and soiled perineum and the other two animals showed no abnormalities. No clinical signs were noted in animals of the control and 3, 10 and 50 mg/kg bw/d groups. Very slight or well defined erythema and very slight or slight oedema were observed at the application site in males and females of the 3, 10 and 50 mg/kg bw/d groups, and were classified as mild according to the Draize index.  Males and females of the 250 mg/kg bw/d group showed slightly more severe irritation than other treated groups. The maximum mean irritation scores at 250 mg/kg bw/d were classified as moderate according to the Draize index. The other dermal reaction observed in all groups treated with fenitrothion was desquamation of the epidermis. Depression of body weight gain and decrease in body weights were observed in males and females at 250 mg/kg bw/d. Increased WBC count and variable differential counts were observed in decedents at 250 mg/kg bw/d.  No haematological effects were reported at lower dose levels. Increased AST and ALT activity and blood urea nitrogen and a decrease in serum electrolytes were observed in some animals at 250 mg/kg bw/d.  No effects on clinical chemistry parameters were reported at lower dose levels. Gross necropsy did not reveal any effects of treatment. Increased adrenal weight was seen in some rabbits at 250 mg/kg bw/d. At 250 mg/kg bw/d, one male and one female revealed slight focal necrosis in the liver; histopathological changes in the digestive tract and kidney were considered to reflect a general deterioration of condition. Erythrocyte cholinesterase activity decreased in males and females at 10, 50 and 250 mg/kg bw/d.  Plasma and brain cholinesterase activities decreased in males at 50 and 250 mg/kg bw/d and in females at 10, 50 and 250 mg/kg bw/d.  No significant changes in erythrocyte, plasma or brain cholinesterase activities were observed at 3 mg/kg bw/d. A NOAEL could not be determined for this study due to local dermal reactions at the application site in rabbits of all treated groups.  A NOAEL for systemic toxicity of 3 mg/kg bw/d can be determined based on the significant inhibition of cholinesterase activity at higher dose levels.