Fenamiphos

Repeated dose toxicity: oral

Administrative data

Endpoint:

chronic toxicity: oral

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1991-10-29 to 1992-04-28

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:

1991

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 452 (Chronic Toxicity Studies)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Fenamiphos

EC Number:

244-848-1

EC Name:

Fenamiphos

Cas Number:

22224-92-6

Molecular formula:

C13H22NO3PS

IUPAC Name:

{ethoxy[3-methyl-4-(methylsulfanyl)phenoxy]phosphoryl}(propan-2-yl)amine

Test material form:

solid: crystalline

Test animals

Species:

dog

Strain:

Beagle

Details on species / strain selection:

The Beagle dog was selected as the test animal due to its suitability and acceptance as a non-rodent species for toxicological testing as well as the availability of a large historical database on the strain.

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: White Eagle Laboratories, Doylestown, Pennsylvania
- Females nulliparous and nonpregnant: yes
- Age at study initiation: not be greater than nine months of age
- Weight at study initiation: 7.62 - 9.11kg
- Housing: stainless steel cages
- Diet (ad libitum): Purina Mills Lab Canine Diet 5006-3
- Water (ad libitum): tap water via automatic waterers
- Acclimation period: at least seven days

DETAILS OF FOOD AND WATER QUALITY:
A sample from each batch of feed and corn oil used in this study was analyzed for selected contaminants by Hazleton Laboratories America, Inc., Madison, Wisconsin. Tap water (Kansas City Municipal Water) was analyzed for impurities quarterly by NUS Laboratories in Houston, Texas. Contaminant concentrations specified in the Certification Profile for Purina Mills Certified Lab Chows (see Appendix VI, page 640) were used as the standard by which to gauge acceptable levels of contaminants in feed, corn oil and water.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 18 - 25
- Humidity (%): 40 - 70
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

oral: feed

Vehicle:

corn oil

Details on oral exposure:

DIET PREPARATION
Corn oil will be used as a vehicle for the test article at one percent by weight of the diet; acetone will serve as a solvent In the diet preparation process. The control diet will be prepared the same way except without the test article. Administration of treated and control feed to all test groups will be Initiated on the same day and continued on a dally basis thereafter. The feed with designated amounts of the test article for four test groups (three treated and one control) will be mixed weekly and stored In the freezer at -23 °C until used (refer to Diet Prep Protocol concerning the mixing procedures for this study). Moreover, a sample of each batch of control and treated feed will be stored in the freezer for archiving.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentration of active ingredient will be verified prior to study initiation and at approximately six-month intervals. The homogeneity and stability (following both room temperature and freezer exposure) of the test substance in the feed also will be determined prior to study initiation on both the low (1 ppm) and high (12 ppm) dietary levels. During the in-life phase of the study, the stability of the test article in the ration will be determined quarterly, utilizing uneaten feed left at room temperature over a normal feeding period.

Duration of treatment / exposure:

12 months

Frequency of treatment:

not applicable, diet ad libitum

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg diet

Doses / concentrations 2

Dose / conc.:

1 mg/kg diet

Remarks:

equivalent to 0.03 mg/kg bw/day in males and females

Doses / concentrations 3

Dose / conc.:

3 mg/kg diet

Remarks:

equivalent to 0.089 mg/kg bw/day in males and 0.083 mg/kg bw/day in females

Doses / concentrations 4

Dose / conc.:

12 mg/kg diet

Remarks:

equivalent to 0.308 mg/kg bw/day in males and 0.349 mg/kg bw/day in females

No. of animals per sex per dose:

2 animals per sex and dose

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Doses for this study were chosen based principally on the results of a 2-year study and a 90-day study of the test item in dogs. The 2-year study utilized dose levesls of 0.5, 1, 2, 5 and 10 ppm, while the 90-day study utilized levels of 0, 0.6, 1.0 and 1.7 ppm in the diet. With the exception of a reduction of cholinesterase activity, the animals appeared

Examinations

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes, twice daily

BODY WEIGHT: Yes, weekly

FOOD CONSUMPTION AND COMPOUND INTAKE: Yes, daily
The amount of fenamiphos administered to the test was calculated on a mg/kg/day basis from these data.

OPHTHALMOSCOPIC EXAMINATION: Yes, on all animals prior to administration of the test substance and on all survivors at termination of the study. The pupil reflex, conjunctiva, cornea and iris were initially examined prior to dilation with a mydriatic (Tropicacyl 1%); following mydriasis, the lens, vitreous humor and retina were examined. An ophthalmoscope will be used in the examination which will include retinal photographs of both eyes taken with a fundus camera.

HAEMATOLOGY: Yes, at three months, six months, nine months and at termination

CLINICAL CHEMISTRY: Yes
Cholinesterase activity (plasma and erythrocyte), clinical chemistry and complete blood counts including differentials will be determined three separate times prior to administration of the test article.

HORMONES: Yes, thyroid hormone will be assessed in control animals only, as they are serving as a common control for a concurrent dog study

URINALYSIS: Yes, at three months, six months, nine months and at termination. In addition, a single urinalysis will be done prior to initiation of dosing.

OTHER: Yes, palpation for abnormal growths or masses and visual observations
for pharmacotoxic effects will be assessed on a weekly basis

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
A complete gross examination will be conducted on all animals that are found dead during the study or that are sacrificed (by IV injection of euthanasia solution) due to moribundity or study termination. In addition, the following tissues will be examined and preserved in ten percent buffered formalin with the exception of the eyes, optic nerves and lacrimal gland of the third eyelid which will be collected in Bouin's:

All gross lesions with a border
of normal tissues
Adrenals
Bone
Femur
Ribs, costochondral junction
Sternum
Bone marrow
Brain (The left half of the brain will be taken for determination of cholinesterase activity)
Cerebral cortex
Cerebellar cortex
Medulla/pons
Cecum
Cervix
Colon
Dorsal aorta
Epididymis (longitudial section)
Esophagus
Eyes
Gall bladder
Heart
Joint, femorotibial
Kidneys
Lacrimal gland, 3rd eyelid
Larynx
Liver
Lungs
Lymph node
Cervical
Meserteric
Mammary gland
Muscle, gastrocnemius
Optic nerves
Ovaries
Pancreas
Parathyroids
Peripheral nerve, Sciatic
Pituitary
Prostrate gland
Rectum
Salivary glands
Skin, inguinal
Skull (examined only - not collected)
Small intestine
Duodenum
Jejunum
Ileum
Spinal Cord
Cervical
Thoracic
Lumbar
Spleen
Stomach
Testes
Thymus
Thyroid
Trachea
Urinary bladder
Uterus

Weights on the following organs will be recorded:
Heart
Lung
Liver
Spleen
Adrenals
Kidneys
Gonads
Thyroid
Pituitary
Brain, including brainstem

HISTOPATHOLOGY: Yes
All of the above mentioned tissues will be trimmed, processed, embedded in paraffin, sectioned and mounted, stained with H & E (Hematoxylin and Eosin) and examined microscopically for all animals, including those found dead or sacrificed in extremis.

Statistics:

Continuous data examined statistically were analyzed by Analysis of Variance (ANOVA) followed by a Student's t-test for between-group comparisons if a significant F value was obtained in the ANOVA.

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

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

not examined

Ophthalmological findings:

no effects observed

Haematological findings:

effects observed, treatment-related

Description (incidence and severity):

12 mg/kg feed: mild anemia characterized by lower erythrocyte counts and lower haemoglobin and haematocrit values was observed in males (refer to Table 1 in "Any other information on results incl. tables").

Clinical biochemistry findings:

effects observed, treatment-related

Description (incidence and severity):

> 1 mg/kg feed: There was a dose-dependent inhibition of plasma ChE activity in both sexes. Toxicologically relevant inhibition of erythrocyte ChE activity was established for male and female dogs at 12 mg/kg feed. At this dose level also brain ChE activity was slightly lower in treated dogs in comparison to the control animals.

Endocrine findings:

not examined

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Immunological findings:

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Other effects:

no effects observed

Effect levels

1

Key result

Dose descriptor:

LOAEL

Effect level:

0.35 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

clinical biochemistry

2

Key result

Dose descriptor:

NOAEL

Effect level:

0.083 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

clinical biochemistry

Target system / organ toxicity

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

0.35 mg/kg bw/day (actual dose received)

System:

nervous system

Organ:

other: no target organ

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

yes

Any other information on results incl. tables

Table 1: Chronic study on dogs – hematology

Dose level	Hgb [g/dl]	HCt [%]	RBC [10*6/mm³]		Dose level	Hgb [g/dl]	HCt [%]	RBC [10*6/mm³]
males					females
day -3					day -3
0 ppm	13.5	40.1	6.05		0 ppm	14.6	42.7	6.35
1 ppm	15.1	44.1	6.58		1 ppm	15.3	44.9	6.80
3 ppm	14.1	41.1	6.25		3 ppm	15.6	45.2	6.73
12 ppm	13.6	40.1	5.78		12 ppm	15.4	44.3	6.83
day 98					day 98
0 ppm	16.5	47.4	7.13		0 ppm	15.9	45.7	6.80
1 ppm	15.7	45.3	6.63		1 ppm	16.5	47.3	7.13
3 ppm	15.7	45.2	6.78		3 ppm	17.1	48.9	7.25
12 ppm	14.1+	40.7	5.80+		12 ppm	15.0	43.0	6.30
day 189					day 189
0 ppm	17.0	49.7	7.35		0 ppm	17.2	50.5	7.35
1 ppm	16.3	47.4	6.90+		1 ppm	16.2	47.2	7.03
3 ppm	15.9	46.0	6.85		3 ppm	15.9	46.2	6.80
12 ppm	14.5	42.0+	5.98+		12 ppm	15.0	43.9	6.38

day 280					day 280
0 ppm	16.2	45.5	6.90		0 ppm	15.0	42.3	6.38
1 ppm	16.4	45.7	6.83		1 ppm	15.6	43.6	6.62
3 ppm	15.8	44.4	6.68		3 ppm	16.2	45.3	6.81
12 ppm	14.8	41.9	6.09+		12 ppm	16.6	46.6	6.79
day 361					day 361
0 ppm	16.7	48.4	7.28		0 ppm	16.7	47.7	7.13
1 ppm	16.7	47.2	7.00		1 ppm	16.1	45.9	7.03
3 ppm	16.5	47.0	7.08		3 ppm	16.8	47.9	7.15
12 ppm	15.6	44.9	6.45+		12 ppm	16.8	48.2	7.05

Applicant's summary and conclusion

Conclusions:

The NOAEL was concluded to be 3 mg/kg feed, equivalent to 0.083 mg/kg bw/day, based on lower brain and erythrocyte ChE activities and on haematological findings at 12 mg/kg feed.

Executive summary:

The test substance was administered to groups of 4 male and 4 female Beagle dogs in the diet. 

Dose levels: 0, 1, 3 and 12 mg/kg feed (equivalent to 0.03, 0.089, 0.308 mg/kg bw/day in males and 0.03, 0.083, 0.349 mg/kg bw/day in females). Study duration: 12 months.

General observations: No treatment related effects on feed consumption or body weight gain were observed. All animals survived until the scheduled end of the study. Clinical observations and ophthalmic examinations provided no indication for any treatment-related effects.

Hematology, clinical chemistry, urinalysis: Mild anemia characterized by lower erythrocyte counts and lower haemoglobin and haematocrit values was observed in males at 12 mg/kg feed.

The measurements of ChE activities provided the following findings: There was a dose-dependent inhibition of plasma ChE activity in both sexes at > 1 ppm. Toxicologically relevant inhibition of ery ChE activity was established for male and female dogs at 12 mg/kg feed. At this dose level also brain ChE activity was slightly lower in treated dogs in comparison to the control animals.

Gross pathology, organ weights, histopathology: Absolute and relative organ weights were unaffected in all dose group animals. No treatment- related gross- or histopathological changes were observed.

In summary, brain ChE activity significantly reduced (<20%) in females at 0.35 mg/kg bw/day. Mild, transient anaemia in males at 0.35 mg/kg bw/day (decreased erythrocyte counts: 11-19%, haemoglobin: 7-15%, haematocrit: 7-15%, increased MCV: 4-5%) Inhibition erythrocyte ChE activity (>20%) at males 0.35 mg/kg bw/day. Erythrocyte ChE activity compared to pre-treatment values: significant decrease males and females (>20%) at ≥ 0.083 mg/kg bw/day.

A LOAEL and NOAEL based on brain cholinesterase inhibition of 0.35 and 0.083 mg/kg bw/day were derived.