Registration Dossier

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:
EPA OPP 82-2 (Repeated Dose Dermal Toxicity -21/28 Days)
Deviations:
no
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
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 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 / concentrationsopen allclose all
Dose / conc.:
0 mg/kg bw/day
Remarks:
control (distilled water)
Dose / conc.:
3 mg/kg bw/day
Dose / conc.:
10 mg/kg bw/day
Dose / conc.:
50 mg/kg bw/day
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

open allclose all
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
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.