Fenamiphos

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April - June 1986

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1986

Report date:

1986

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Version / remarks:

May 12, 1981

Deviations:

no

Principles of method if other than guideline:

The following deviations were noted from the revised OECD TG 414 (2001):
- The test substance was not administered until the day of scheduled kill, but only during the period of organogenesis.
- There are no summary data on gravid uterus weight.
- Only 16 female animals were used in the study, whereas there should be at least 20 female animals with implantation sites at necropsy. It is noted that since groups with fewer than 16 animals with implantation sites may be inappropriate.
- Sex ratio is not provided in the study report.

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:

rabbit

Strain:

Chinchilla

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: KFM, Klein tier farm Madoerin AG, CH 4414 Fuellinsdorf / Switzerland
- Age at study initiation: Between 4 and 6 months
- Weight at study initiation: 2278 - 3334 grams (post coitum)
- Fasting period before study: no
- Housing: The rabbits mere housed individually in stainless steel cages equipped ujith automatic cleaning system
- Diet (ad libitum): Pelleted standard Kliba 341, rabbit maintenance diet (Klingentalmuehle AG, CH 4303 Kaiseraugst/Switzerland)
- Water (ad libitum): Tap water
- Acclimation period: 7 days (minimum) under test conditions, after veterinary examination.

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22 +/- 3
- Humidity (%): 40 - 70
- Air changes (per hr): 10 - 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: approx. 30-04-1986 To: 23-06-1986

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

other: Distilled water with 0.5 % Cremophor EL

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
The test article mas weighed into a glass beaker on a tared precision balance (Mettler PK 300) and the vehicle added (w/v) . The mixtures were prepared using a homogenizer. During the daily administration period, homogeneity was maintained using a magnetic stirrer. The test article/vehicle mixtures were prepared daily prior to administration.

VEHICLE
- Amount of vehicle: 4 mL/kg bw

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentration and homogeneity of the test article/vehicle mixtures were determined prior the first test article administration. During the treatment period, additional samples for confirmation of concentration, homogeneity and stability were taken once. Samples were taken immediately after preparation.
The concentration of the test item in triplicate samples taken for determination of homogeneity before the study was found to vary considerably (14-140% of the nominal concentration), with mean concentrations of 71 ± 8.3, 84 ± 64, and 70 ± 16% of the nominal concentration at doses of 0.1, 0.5, and 2.5 mg/kg bw/day, respectively. At the next sampling 10 days later, the mean concentrations were all within 90% of the nominal concentration, although the variability was still high (92 ± 37, 97 ± 45, and 99 ± 41% of the nominal concentration at the three doses, respectively).

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused: After acclimation the females mere housed with males until mating has been observed.
- M/F ratio per cage: 1/1, after mating individual housing
- Proof of pregnancy: not specified, the day after mating was recorded as Day 0 post coitum

Duration of treatment / exposure:

from Day 6 - Day 18 post coitum

Frequency of treatment:

Once daily

Duration of test:

28 days

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/kg bw/day (nominal)

Remarks:

vehicle control

Doses / concentrations 2

Dose / conc.:

0.1 mg/kg bw/day (nominal)

Doses / concentrations 3

Dose / conc.:

0.5 mg/kg bw/day (nominal)

Doses / concentrations 4

Dose / conc.:

2.5 mg/kg bw/day (nominal)

No. of animals per sex per dose:

16 mated femle animals per group

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: The dosages mere based upon the results of the dose-finding embryotoxicity (including teratogenicity) study in the rabbit.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily, minimum

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Twice daily, minimum

BODY WEIGHT: Yes
- Time schedule for examinations: Daily, from day 0 until day 28 post coitum

FOOD CONSUMPTION: Yes
- Time schedule for examinations: The data were recorded on days 6, 11, 15, 19, 24 and 28 post coitum

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on day: 28 post coitum (dams were killed by cervical dislocation and fetuses removed by caesarean section)
- Organs examined:
Postmortem examinations, including gross macroscopic examination
of all internal organs, with emphasis upon the uterus, uterine contents, position of fetuses in the uterus and number of corpora lutea, were performed and the data recorded. The fetuses were removed from the uterus, weighed, examined for gross external abnormalities and prepared for internal examinations.

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes

The uteri (and uterine contents) of all pregnant females mere weighed on the scheduled day of necropsy. The weights mere used to determine the corrected body meight gain.
The uteri of the females tuhich were found at necropsy to be not pregnant were placed in an aqueous solution of ammonium sulfide to accentuate possible hemorrhagic areas of implantation sites. All tissues and organs of the females mere discarded. The stained trunks of fetuses and the sections of the heads of fetuses mere preserved .

Blood sampling:

not examined

Fetal examinations:

The following examinations were performed individually:

1) All fetuses were dissected carefully, the body cavities (thorax, abdomen, pelvis) and the organs were investigated and any abnormal findings recorded. The sex of each fetus was noted and recorded.

2) The skin was removed and the crania of all fetuses were examined for ossification.

3) The heads of all fetuses were fixed in a solution of trichloroacetic acid and formaldehyde. The heads were crosssectioned and the cephalic viscera were examined. Descriptions of any abnormalities were recorded. After evaluation, the individual sections were preserved in a solution of ethyl alcohol and glycerine (one head per container).

4) The trunks of all fetuses were placed in a solution of potassium hydroxide for clearing and stained ujith alizarin red (modified technique). The skeletons mere examined and all abnormalities and variations were recorded. The specimens mere preserved individually in plastic bags.

Statistics:

The following statistical methods mere used to analyze body weights, food consumption and reproduction data:
Univariate one-may analysis of variance uias used to assess the significance of intergroup differences if the variables could be assumed to follow a normal distribution. The Dunnett many-one t-test, based on a pooled variance estimate, urns used for intergroup comparisons (i.e. single treatment groups against the control group).
A one-may univariate analysis of variance based on Wilcoxon ranks together tuith the Kruskall-Wallis test was applied to the reproduction data parameters.
Fisher's exact test for 2x2 tables mas applied if the variables could be dichotomized without loss of information.
Individual values, means, standard deviations and t-statistics were rounded off before printing.

References:
1. C. W. Dunnett, A Multiple Comparison Procedure for Comparing several Treatments with a Control, J. Amer. Statist. Assoc. 50, 1096-121 (1955).
2. Rupert G. Miller, Simultaneous Statistical Inference, Springer Verlag, New York (1981).
3. Fisher, R.A. Statistical Methods for Research Workers, Oliver and Boyd, Edinburgh <1950).

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Group 4 (2.5 mg/kg bw): Salivation and dyspnea mere the symptoms mostly observed. Additionally, in two of the four females which died, ataxia mas noted, and in one female diarrhea mas observed. Salivation appeared for the first time on day 7 post coitum (second day of treatment) and at the last time on day 18 post coitum (last treatment-day). The signs and symptoms appeared about 30 to 60 minutes after test article administration and lasted up to 4 hours maximum.

Dermal irritation (if dermal study):

not examined

Mortality:

mortality observed, treatment-related

Description (incidence):

Group 4 (2.5 mg/kg bw): Four females died prior caesarean section on day 28 post coitum. These four females were pregnant, also. In these females, eight, five, seven and eight embryos mere noted, respectively.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

In group 4 (2.5 mg/kg bw): the mean body weight gain of dams during
the treatment period was clearly reduced in comparison to that of
group 1 (vehicle control).
Although statistically insignificant, this reduction was considered to be test article-related as the consequence of the distinct statistically significant reduction of the mean food consumption during the treatment period.

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

effects observed, treatment-related

Description (incidence and severity):

In group 4 (2.5 mg/kg bw): the mean food consumption was distinct reduced (29.4 %) during the treatment period. This reduction was statistically significant and considered to be a test article-related effect.

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

not examined

Ophthalmological findings:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Endocrine findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

The following incidental findings mere noted in groups 1 (vehicle control) and 3 (0.5 mg/kg bw): Indentations and areas mith grey-whitish discoloration on the surface of the kidneys mere noted in one female of group 1 and in one female of group 3.

Neuropathological findings:

not examined

Histopathological findings: non-neoplastic:

not examined

Histopathological findings: neoplastic:

not examined

Other effects:

not examined

Maternal developmental toxicity

Number of abortions:

no effects observed

Pre- and post-implantation loss:

effects observed, treatment-related

Description (incidence and severity):

In group 4 (2.5 mg/kg bw): increase in preimplantation loss at 2.5 mg/kg bw/day (10.9 vs. 3.3 % of corpora lutea)
In general, in a teratogenicity study, pre-implantation loss is not related to treatment, because implantation occurs before treatment starts. Since the days of gestation were counted from mating and not corrected with one day, treatment might have influenced pre-implantation loss.

Total litter losses by resorption:

no effects observed

Early or late resorptions:

no effects observed

Dead fetuses:

no effects observed

Changes in pregnancy duration:

no effects observed

Changes in number of pregnant:

no effects observed

Other effects:

no effects observed

Details on maternal toxic effects:

No test article-related or statistically significant differences in the mean number of implantations, pups or embryonic deaths mere noted in the dose groups when compared to that of the vehicle control group. The differences evident tuere considered to be incidental and within the normal range of deviations for animals of this strain and age. The mean distribution of fetuses and resorptions within the uterine horns was similar in all groups.

Effect levels (maternal animals)

Key result

Dose descriptor:

NOAEL

Effect level:

0.5 mg/kg bw/day (nominal)

Based on:

test mat.

Basis for effect level:

body weight and weight gain

clinical signs

food efficiency

mortality

pre and post implantation loss

Maternal abnormalities

Key result

Abnormalities:

no effects observed

Results (fetuses)

Fetal body weight changes:

no effects observed

Reduction in number of live offspring:

not examined

Changes in sex ratio:

no effects observed

Changes in litter size and weights:

no effects observed

Anogenital distance of all rodent fetuses:

not examined

Changes in postnatal survival:

not examined

External malformations:

no effects observed

Skeletal malformations:

effects observed, non-treatment-related

Description (incidence and severity):

A number of skeletal changes unrelated to treatment were seen in foetuses at all doses.

Visceral malformations:

effects observed, non-treatment-related

Description (incidence and severity):

One foetus at the high dose had encephalocele with reduced brain size.

Other effects:

no effects observed

Details on embryotoxic / teratogenic effects:

In foetuses, no effect that could be attributed to treatment was seen in sex ratio, body weight, external or internal malformations, skeletal abnormalities, or development.

Effect levels (fetuses)

Key result

Dose descriptor:

NOAEL

Effect level:

2.5 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no effects

Fetal abnormalities

Key result

Abnormalities:

no effects observed

Overall developmental toxicity

Key result

Developmental effects observed:

yes

Lowest effective dose / conc.:

2.5 mg/kg bw/day (nominal)

Treatment related:

yes

Relation to maternal toxicity:

developmental effects as a secondary non-specific consequence of maternal toxicity effects

Dose response relationship:

yes

Applicant's summary and conclusion

Conclusions:

The NOAEL for maternal toxicity was 0.5 mg/kg bw/day, based on mortality, clinical signs, decreased body weight and food intake at 2.5 mg/kg bw/day. The NOAEL for developmental toxicity is 0.5 mg/kg bw/day, based on the increase in pre-implantation loss at 2.5 mg/kg bw/day. The test substance was not teratogenic under the conditions of this study.

Executive summary:

The test substance was administered to groups of 16 single-mated female Chinchilla rabbits at dose levels of 0, 0.1, 0.5 and 2.5 mg/kg bw/day by gavage from day 6 to day 18 post coitum. The dose volume was 4 mL/kg bw. On day 28 all dams were sacrificed and their fetuses examined. Cholinesterase activity was not assessed.

Dams: At 2.5 mg/kg bw/day 4 dams died. Treatment-related signs of toxicity (ataxia, salivation, dyspnoea and diarrhoea) and reduced body weight gain were observed in the high dose group animals only.

Development: There were no differences between the treatment groups and the control group with regard to the mean numbers of implantations, corpora lutea, live or dead fetuses and resorptions. No effects on sex ratios of the live fetuses were seen. No changes in body weight, external or internal malformations, skeletal abnormalities, or development were noted. One fetus at 2.5 mg/kg bw/day had encephalocele with reduced brain size. This finding was not related to treatment.

NOAEL maternal: 0.5 mg/kg bw/day based on on reduced body weight gain and mortality at 2.5 mg/kg bw/day. NOAEL developmental: 2.5 mg/kg bw/day (highest dose tested). The test substance was not teratogenic in rabbits.