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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Cross-reference
Reason / purpose:
reference to same study

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
1980
Reference Type:
publication
Title:
Developmental toxicity of oral and inhaled vinyl acetate in the rat
Author:
Hurtt, ME et al.
Year:
1995
Bibliographic source:
Fund. Appl. Toxicol. V24 pp198-205

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Deviations:
no
GLP compliance:
yes
Limit test:
no

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Vinyl acetate
- Physical state: colourless liquid
- Analytical purity: 99.9% (w/v)
- Impurities (identity and concentrations): Acetaldehyde 0.01% w/v
- Lot/batch No.: T205R/X
- Storage condition of test material: The test article was stored in a cool area, in the stainless steel delivery drums which were electrically earthed. A
record was maintained of all occasions on which the drums were opened and of all quantities withdrawn, so that exposure to moisture and air was documented.
- Other: Use of hydroquinone as an inhibitor was not necessary in this study as the stability of the test article was satisfactory in its absence.

Test animals

Species:
rat
Strain:
other: CD Sprague Dawley derived
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River (UK) Ltd, Margate, Kent, UK
- Weight at study initiation: 215 - 279 g at mating (females)
- Sexually mature male rats of the same strain and from the same source were used for mating only
- Fasting period before study: None
- Housing: Prior to mating, male and female rats were housed in groups of 5 per sex in solid floor polypropylene cages with stainless steel lids. Autoclaved soft wood chips were provided for bedding. During the mating period, 2 female rats were housed with 1 male rat in similar cages. Mated females were housed singly in galvanised metal mesh cages suspended over cardboard-lined trays.
- Diet: Rodent Breeding diet (Spratts Patent Ltd., Barking, Essex, UK.) ad libitum.
- Water (e.g. ad libitum): Untreated tap water was available ad libitum except on days 6 to 15 of gestation when prepared drinking water solutions of vinyl acetate were provided.
- Acclimation period: 2 weeks

ENVIRONMENTAL CONDITIONS
- Temperature: 18-25°C
- Humidity: 40-60%
- Air changes: 18-20 per hr
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: April 1979 To: June 1979

Administration / exposure

Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
- Fresh formulations of each drinking water solution were prepared daily, throughout the exposure period.
- The formulations were made with an extra 10.0, 7.1 and 6.9 % for groups 2, 3 and 4, respectively to correct for loss of test article on standing.
- Five and a half litre batches of each concentration were prepared in tap water, on a constant ppm (v/v) basis.
- The measured volume of vinyl acetate; taken from the newest drum available was added to approximately 2 litres of tap water and dissolved. Dissolution was facilitated by shaking (for final concentrations of 1000 ppm and less, or by magnetic stirrer for concentrations greater than 1000 ppm). The
solutions were then made up to the final volume of 5.5 litres with tap water and then re-shaken.
- The pH of the tap water used was recorded at approximately one week intervals during the first 28 days on which test article formulations were prepared and daily for the last six days
- The prepared drinking water solutions were stored in screw cap, brown glass bottles, at room temperature.

Control animals received tap water (derived from the same source).

Drinking water solutions were dispensed from glass water bottles fitted with stainless steel spouts. After approximately 24 hours, the drinking water solutions were discarded and clean bottles were filled with fresh solutions.

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Analysis of test article formulations: Samples (200 mL) of each drinking water formulation were taken into stoppered, glass bottles immediately after preparation and the concentration of vinyl acetate determined. Analyses were carried out daily for the first 4 days on which test article formulations were prepared and on the 29th day.
Stability of test article formulations: The stability of vinyl acetate in tap water was investigated prior to the start of this study (HLE project number 51/1, report number 1932-51/1).
Details on mating procedure:
- Impregnation procedure: cohoused
- M/F ratio per cage: 1 male was housed with 2 females
- Length of cohabitation: Matings took place on 15 days during a 24 h period.
- Verification of same strain and source of both sexes: yes
- Proof of pregnancy: sperm in vaginal smear referred to as day 0 of pregnancy
Duration of treatment / exposure:
Days 6 - 15 of gestation.
Duration of test:
From day 0 to 20 of gestation
No. of animals per sex per dose:
24 mated females / dose
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Dose levels selected on the basis of a four week range finding study in the rat (oral) performed at Hazleton.
- Randomisation: On each mating day, the mated female rats were allocated to exposure groups according to body weight, so that the mean
weight and weight distribution were similar in all groups. Allocation to cage positions in the experimental room was randomised as was the necropsy order.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: No data

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All mated female animals were examined at least twice daily on weekdays and once on Saturdays and Sundays for signs of ill-health or overt signs of toxicity. A record of clinical changes was maintained for each animal .

BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were recorded on days 0, 2, 4, 6, 10, 15 and 20 of gestation.

FOOD CONSUMPTION : Yes
- The total weight of food consumed by each female was recorded from day 0, on days 3, 6, 9, 12, 15, 18 and 20 of gestation.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: The volume of drinking water solution/untreated tap water consumed by each female was determined daily during gestation (day 0 - day 20 of gestation).

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day 20
- Rats were subjected to a detailed internal and external macroscopic examination. Any abnormalities observed were recorded in detail.

Ovaries and uterine content:
The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: No data
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes
- Foetal weight and sex: Yes
- Foetal crown/rump length: Yes
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: Yes: half per litter

Half of the foetuses from each litter (selected by systematic alternate sampling) were eviscerated and the ossified skeletons stained with Alizarin Red and examined. The remaining foetuses were placed in Bouin's fluid and transverse sections were made and examined.
Abnormalities were recorded as major (rare and/or possibly lethal) or minor (common deviations from normal). Variants i.e. non ossification of sternebrae 5 and 6 and bipartite thoracic vertebrae (10-13) were included in the classification of minor skeletal defects.

Statistics:
For body weights, body weight gains, food /water consumption, crown/rump lengths, foetal weights : statistical evaluation was made using an analysis of variance technique for normally distributed errors or by non-parametric techniques for non-normally distributed errors. Analysis of variance established the significance of the variability between all groups to determine a treatment-related response and between treatment groups for a dose-related response. The standard deviation obtained from this analysis was used for 't'-tests between the control and treatment groups. Where necessary, the data was suitably transformed before analysis. Non-parametric testing was carried out using the Kruskal-Wallis test for treatment-related and dose-related responses. Significant differences between control and treatment groups were determined using the Wilcoxon rank sum test. All tests were carried out at 1% and 5% significance levels for a two-sided risk.
For pre-implantation loss, implantations , non-viable foetuses , intra-uterine deaths: Statistical analysis was carried out using Fisher's two-sum randomisation (permutation) test with a Monte Carlo simulation for computation of significance levels. The litter was the experimental unit and a square root transformation was used. for weighting the number of incidences and adjusting for different litter sizes. Each treatment group was tested against the control at 1% and 5% significance levels for a one-sided risk.

Results and discussion

Results: maternal animals

General toxicity (maternal animals)

Clinical signs:
effects observed, non-treatment-related
Description (incidence and severity):
Minor and non-specific clinical changes commonly observed in animals from the specified source became apparent during the course of the study, these were commonly ocular secretion or discharge. The intergroup distribution of these changes did not suggest an effect of exposure to vinyl acetate.
Mortality:
no mortality observed
Description (incidence):
There were no deaths during the course of the study. All experimental animals re-mained outwardly healthy throughout the study.
Body weight and weight changes:
effects observed, non-treatment-related
Description (incidence and severity):
A very slight degree of body weight retardation was evident in animals exposed to vinyl acetate at 5,000 ppm v/v, in comparison with control animals, at the start of the exposure period. For the remainder of the study, the mean body weight gain of this group was similar to that of the control group. The mean body weight gain of animals exposed to vinyl at 200 and 1,000 ppm v/v was similar to that of the control animals throughout the study.
Food consumption and compound intake (if feeding study):
effects observed, non-treatment-related
Description (incidence and severity):
The mean food intake of animals exposed at 5,000 ppm v/v vinyl acetate was mar-ginally lower than that of the control animals during the exposure period. For the remainder of the study, the mean food intake of this group was similar to that of the control group. The mean food intake of animals exposed to 200 and 1,000 ppm v/v was similar to that of the control animals throughout the study
Water consumption and compound intake (if drinking water study):
effects observed, non-treatment-related
Description (incidence and severity):
The mean water intake of animals exposed to 5,000 ppm v/v was significantly lower than that of the control animals during the exposure period (p<0.01). For the re-mainder of the study, the mean water intake of this group was generally similar to that of the control group. The mean water intake of animals exposed to 200 and 1,000 ppm v/v was generally similar to that of the control animals throughout the study.
The mean dose levels of vinyl acetate during the course of the study were calculat-ed to be:

Nominal concentration
ppm v/v Mean calculated dose levels
ml/kg/day mg/kg/day
200 0.030 28
1,000 0.133 124
5,000 0.511 477
Gross pathological findings:
no effects observed
Description (incidence and severity):
There were no macroscopic findings at necropsy which could be attributed to expo-sure to vinyl acetate.

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:yes

Details on maternal toxic effects:
There were no deaths and all animals appeared healthy throughout the study.
A very slight reduction in body weight was seen at 5000 ppm v/v, at the start of the exposure period but the mean body weight gain was similar to controls thereafter. There was no effect on bodyweight at 1000 or 200 ppm v/v.
A slight reduction in food consumption was seen initially at 5000 ppm.
At 5000 ppm, water consumption was significantly decreased for the overall dosing period (GD days 6-15).
There were no significant findings at necropsy.

Effect levels (maternal animals)

open allclose all
Key result
Dose descriptor:
LOAEL
Effect level:
5 000 ppm (nominal)
Based on:
test mat.
Basis for effect level:
food consumption and compound intake
water consumption and compound intake
Remarks on result:
other: slight effects
Key result
Dose descriptor:
NOAEL
Effect level:
1 000 ppm (nominal)
Based on:
test mat.
Basis for effect level:
other: no effects obsvered at this dose
Remarks on result:
other: no effects obsvered at this dose

Results (fetuses)

Details on embryotoxic / teratogenic effects:
Embryotoxic / teratogenic effects:no effects

Effect levels (fetuses)

Key result
Dose descriptor:
NOAEL
Effect level:
>= 5 000 ppm
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: no developmental effects
Remarks on result:
other: no developmental effects

Fetal abnormalities

Key result
Abnormalities:
no effects observed

Overall developmental toxicity

Key result
Developmental effects observed:
no
Lowest effective dose / conc.:
5 000 ppm
Treatment related:
no

Any other information on results incl. tables

TABLE 2  Summary of Reproductive Outcome: Drinking Water Study

Group

1

2

3

4

Dose (ppm);

0

200

1000

5000

No. litters

23

22

21

23

Mean per litter:

Live foetuses

14.6 (2.48)°

14.2 (2.40)

14.6 (2.68)

13.7 (2.42

Nidations

14.7 (2.48)

14.3 (2.40)

14.8 (2.73)

14.0 (1.95)

Mean corpora lutea

16.0 (2.34)

15.6 (l.26)

16.7 (2.13)

15.7 (1.42)

% preimplantation loss per litter

7.5(11.3)

8.1(14.1)

11.1 (13.4)

11.0 (10.4)

% resorptions per litter

0.58 (1.93)

0.91 (2.35)

1.49 (3.38)

2.75 (7.28)

Sex ratio (% males)

47.4 (13.8)

48.0 (15.2)

55.9* (13.9)

54.2 (14.2)

Mean foetal weight (g):

Total

3.6 (0.23)

3.7 (0.23)

3.7 (0.20)

3.7 (0.23)

Males

3.7 (0.23)

3.8 (0.25)

3.7 (0.22)

3.8 (0.23)

Females

3.5 (0.27)

3.6 (0.26)

3.7 (0.24)

3.6 (0.22)

Crown to-rump Length (mm)

39.8 (1.19)o

40.0 (1.44)

39.7 (0.76)

39.7 (0.92)

Numbers in parentheses represent the standard deviation.
* Significantly different from control values (Wilcoxon's test; p < 0.05).

TABLE 3  Summary of Major Alterations: Drinking Water Study

Group

1

2

3

4

Dose (ppm);

0

200

1000

5000

External

    No. examined #

336 (23)

312 (22)

306

(21)

    No. affected

0

(0)

0

(0)

Visceral

    No. examined

336 (23)

312 (22)

306

(21)

    No. affected

0

(0)

2 (2)

(0)

        Head, hydrocephaly

-

-

1 (1)

-

        Abdomen, diaphragmatic hernia

-

-

1 (1)

-

Skeletal

    No. examined

174 (23)

162(22)

159(21)

163(23)

    No. affected

0

(0)

0

(0)

Total number affected

0 (0)

0 (0)

2(2)

(0)

There were no significant differences from control values (Fisher's exact test; p > 0.05).

# Numbers examined and affected, including numbers affected with the listed major alterations, are expressed as foetuses (litters). For ease of reading, zeros have been replaced with dashes for the listed malformations.

Applicant's summary and conclusion

Conclusions:
Following oral exposure of pregnant rats to vinyl acetate in drinking water during major organogenesis, the no-observed effect level for developmental toxicity was 5000 ppm, equivalent to 477 mg/kg/day.
Executive summary:

Groups of pregnant female rats were exposed to vinyl acetate in the drinking water at nominal concentrations of 0, 200, 1000 and 5000 ppm v/v, from day 6 to day 15 of gestation, inclusive. At 5000 ppm, water consumption was significantly decreased for the overall dosing period possibly reflecting unpalatability of the drinking water solutions. A slight reduction in food consumption and body weight gain were seen initially in females at 5000 ppm, indicating slight maternal toxicity. There was no evidence of embryolethality, embryototoxicity or teratogenicity at a dose level that resulted in slight maternal toxicity. The no observed-effect level for effects on the conceptus was 5000 ppm vinyl acetate, when administered by the oral route, equivalent to 477 mg/kg/day.

The study was conducted at the standard practices at the time under GLP and according to the OECD Guideline 414 and all relevant parameters were addressed.