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Toxicological information

Carcinogenicity

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Description of key information

The information considered to be key to the evaluation of the carcinogenicity of vinyl acetate are Hazleton (1988b), subsequently published by Bogdanffy et al. (1994b) for inhalation exposure and Hazleton (1988a), subsequently published as Bogdanffy et al., 1994a, for oral exposure. The drinking water study by Umeda et al. (2004) is also considered a key study although there are uncertainties regarding the test substance solutions and Maximum Tolerated Dose exceedance on tumour outcomes.

While some non-guideline bioassays also reported tumours in rats and mice following drinking water administration, (i.e. Maltoni et al., 1997; Minardi, 2002) these studies had methodological issues and exhibited relatively high spontaneous occurrence of tumours in study control groups, rendering interpretation of these results difficult. A detailed review of these and other studies related to the mode of action of vinyl acetate has been reported in the EU RAR, 2008.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Referenceopen allclose all

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, guideline study, published in peer reviewed literature, minor restrictions in design and/or reporting but otherwise adequate for assessment.
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
yes
Remarks:
urine & blood analysed at 2 yrs only (no interim assessment or interim sacrifice).
GLP compliance:
yes
Species:
rat
Strain:
other: F344/DuCrj
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Japan Inc., Kanagawa, Japan
- Age at study initiation: 6 weeks
- Weight at study initiation: no data
- Housing: Individually in stainless steel wire-mesh hanging cages
- Diet (ad libitum): CRF-1, Oriental Yeast Co. Ltd., Tokyo, Japan
- Water (ad libitum): Assigned by dose level
- Acclimation period: 2 weeks
- Randomisation: By stratified randomization into 4 weight-matched groups

ENVIRONMENTAL CONDITIONS
- Temperature: 24±2°C
- Humidity: 55±10%
- Air changes (per hr): 15-17
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: No data
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
- Vinyl acetate dissolved in deionised water to give target concentrations of 400, 2000 or 10000 ppm (g/g).
- A drinking bottle filled with a full volume (200 mL) of the vinyl acetate-formulated drinking water was used, in order to prevent a decrease in the vinyl acetate concentration due to evaporation from the bottle.
- The drinking water formulations prepared twice a week.
- Stability of vinyl acetate in the drinking water examined 4 days after preparation. The concentrations of vinyl acetate and acetic acid in the drinking water were determined with a gas chromatograph and a liquid chromatograph-mass spectrometer, respectively.
- The pH of the drinking water was measured
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The vinyl acetate concentrations in the drinking water 4 days after preparation decreased to 72-80% (attributed mainly to the loss due to evaporation).
Four days after preparation acetic acid concentration and the pH were 9.2 ppm and pH 4.0 for the 400 ppm formulation, 47 ppm and pH 4.2 for the 2000 ppm formulation and 263 ppm and pH 3.6 for the 10000 ppm formulation.
Duration of treatment / exposure:
104 weeks
Frequency of treatment:
Continuous
Post exposure period:
None
Remarks:
Doses / Concentrations:
0, 400, 2000 or 10000 ppm (g/g)
Basis:
nominal in water
Remarks:
Doses / Concentrations:
0, 21, 98 or 442 mg/kg/day (males)
Basis:
actual ingested
Remarks:
Doses / Concentrations:
0, 31, 146 or 575 mg/kg/day (females)
Basis:
actual ingested
No. of animals per sex per dose:
50
Control animals:
yes, concurrent vehicle
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly for the first 13 wks and every 4 wks thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes: Weekly for the first 13 wks and every 4 wks thereafter.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: Weekly for the first 13 wks and every 4 wks thereafter.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At termination
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes
- How many animals: All surviving animals
- Parameters examined: According to the authors, the haematological parameters specified in OECD test guideline 453 were measured

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At termination
- Animals fasted: Yes
- How many animals: All surviving animals
- Parameters examined: According to the authors, the blood biochemical parameters specified in OECD test guideline453 were measured

URINALYSIS: Yes
- Time schedule for collection of urine: During the last week of treatment (week 104)
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes
- Parameters examined: pH, protein, glucose, ketone bodies, bilirubin, occult blood, and urobilinogen

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- Organs were examined macroscopically, and according to the authors, the tissues specified in OECD test guideline 453 were examined for histopathology.

HISTOPATHOLOGY: Yes
- Tissues were fixed in 10% neutral buffered formalin, and embedded in paraffin by the routine procedures. Tissue sections 5 µm thick were prepared and stained with haematoxylin and eosin.
- The oral cavity was examined histopathologically at six different levels. The maxilla and mandible were decalcified with a 5% formic acid-formalin solution. Then the maxilla was trimmed with the nasal cavity in three cross sections at the levels of the posterior edge of the upper incisor teeth (Level I), the incisive papilla (Level II) and the anterior edge of the upper molar teeth (Level III). The mandible was trimmed in three cross sections at the levels of the posterior edge of the lower incisor teeth (Level IV), the anterior edge of the lower molar teeth (Level VI) and the middle point between Levels IV and VI (Level V).
Statistics:
Non-neoplastic lesions and urinary data: analysed by chi-square test.
Neoplastic lesions: analysed by Peto's test and Fisher's exact test.
Body weight, food and water consumption, haematological and blood biochemical parameters: analysed by Dunnett's Test.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
-- No significant difference in the survival rate of males or females was found between any treated group and the respective control.
- As a clinical sign, an oral cavity nodule appeared in a 400 ppm female after the 87th wk.

BODY WEIGHT AND WEIGHT GAIN
- Body weights of the 10000 ppm males and females at the end of the 2-yr administration period were significantly lower by 8 and 10%, respectively, than those of the respective controls.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
- Water consumption of the 10000 ppm males and females decreased by 15% and 18%, respectively, compared to the corresponding controls throughout the experimental period.
- Daily vinyl acetate intake per body weight, estimated by water consumed, showed a dose-related increase except at 10000 ppm. The estimated daily vinyl acetate intake per body weight was 0, 21, 98 and 442 mg/kg/day for males and 0, 31, 146 and 575 mg/kg/day for females, in the 0, 400, 2000 and 10,000 ppm groups, respectively.

HAEMATOLOGY/CLINICAL CHEMISTRY/URINALYSIS
- No treatment-related effects, however statistically significant changes occurred sporadically in several parameters.

ORGAN WEIGHTS
- Statistically significant changes in organ weights were observed in several organs of the 10000 ppm exposed males and females, but those changes were not associated with histopathological changes.

GROSS PATHOLOGY
- Mandibular nodules occurred in 3 males in the 10000 ppm group, and a female in the 400 ppm group. A maxillary nodule appeared only in a female in the 10000 ppm group.

HISTOPATHOLOGY:
- Squamous cell carcinomas and squamous cell papillomas were observed in the oral cavity and the oesophagus. The incidence of oral cavity squamous cell carcinomas and papillomas was increased in the 10000 ppm group of both sexes and an oesophagus squamous cell carcinomas was observed in a 10000 ppm female.
- The majority of the squamous cell carcinomas showed proliferative invasion into the subepithelial tissue (indicative of severe malignancy).
-Pre-neoplastic hyperplasias were observed in the upper digestive tract of males and females at 10000 ppm, except for a forestomach squamous cell hyperplasia in both a control and a 2000 ppm male.
- One oral cavity squamous cell carcinoma was also seen in the 2000 ppm group and one in the 400 ppm female group.
- Mapping of the neoplastic and pre-neoplastic lesions in the rat oral cavity of the 10000 ppm group revelaed that 4 squamous cell carcinomas out of 8 tumours tended to occur at Level VI, although neoplastic and pre-neoplastic lesions were distributed throughout the oral cavity. Focal basal cell hyperplasia was observed at two different sites in the oral cavity of a single animal.
Dose descriptor:
BMDL10
Effect level:
477 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: Combined incidence of squamous cell carcinomas and papillomas in the oral cavity and the estimated daily vinyl acetate intake per body weight.
Remarks on result:
other: Effect type: carcinogenicity (migrated information)

Number of rats with neoplastic and pre-neoplastic lesions in the upper digestive tract

 

(Table based on Umeda Y 2004, J Occup Health: 46: 87-99, Tables 5 and 6)

Tissue

male (50/group)

female (50/group)

male (1199)

female (1147)

Dose level (ppm)

0

400

2000

10000

0

400

2000

10000

 

 

Oral cavity

Squamous cell papilloma

0

0

0

2

0

0

0

0

3

1

Squamous cell carcinoma

0

0

0

5**

0

1

1

3*

0

1

Basal cell hyperplasia

0

0

0

2

0

0

0

1

-

-

Epithelial dysplasia

0

0

0

0

0

0

0

2

-

-

Oesophagus

Squamous cell carcinoma

0

0

0

0

0

0

0

1

0

0

Basal cell hyperplasia

0

0

0

0

0

0

0

4*

-

-

Squamous cell hyperplasia

0

0

0

1

0

0

0

1

-

-

Stomach

Basal cell hyperplasia

0

0

0

2

0

0

0

5*

-

-

Squamous cell hyperplasia

2

0

1

0

0

0

0

0

-

-

50 rats/sex/group

* - Statistically significant: p<0.05 (Fisher’s exact test or Peto’s test or Chi-square test)

** -Statistically significant: p<0.01 (Fisher’s exact test or Peto’s test or Chi-square test)

Conclusions:
Oral administration of vinyl acetate to rats in drinking water at nominal concentrations of 0, 400, 2000 or 10000 ppm (g/g) for 2 years induced squamous cell carcinomas and papillomas and pre-neoplastic lesions in the upper digestive tract in both sexes.  A lower confidence limit of a benchmark dose (BMDL10) of 477 mg/kg/d was obtained from a dose-response relationship between combined incidence of squamous cell carcinomas and papillomas in the oral cavity of rats and the estimated daily vinyl acetate intakes per body weight, and compared with literature values.
Executive summary:

Oral administration of vinyl acetate to rats in drinking water at nominal concentrations of 0, 400, 2000 or 10000 ppm (g/g) for 2 years induced squamous cell carcinomas and papillomas and pre-neoplastic lesions in the upper digestive tract in both sexes. The incidence of these lesions was dose-related. Incidences of squamous cell carcinomas and papillomas were increased in the oral cavity of the 10000 ppm group in both sexes, and an oesophagus squamous cell carcinoma was observed in a 10000 ppm female. Mapping of the neoplastic and pre-neoplastic lesions in the oral cavity of the 10000 ppm group revealed that both the lesions occurred predominantly at Level VI, in the region of the mandible. A lower confidence limit of a benchmark dose (BMDL10) of 477 mg/kg/d was obtained from a dose-response relationship between combined incidence of squamous cell carcinomas and papillomas in the oral cavity of rats and the estimated daily vinyl acetate intakes per body weight, and compared with literature values.

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, guideline study, published in peer reviewed literature, minor restrictions in design and/or reporting but otherwise adequate for assessment.
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
yes
Remarks:
Urine & blood analysed at 2 yrs only (no interim assessment or interim sacrifice).
GLP compliance:
yes
Species:
mouse
Strain:
other: Crj:BDF1
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Japan Inc., Shiga, Japan
- Age at study initiation: 6 weeks
- Weight at study initiation: no data
- Housing: Individually in stainless steel wire-mesh hanging cages
- Diet (ad libitum): CRF-1, Oriental Yeast Co. Ltd., Tokyo, Japan
- Water (ad libitum): Assigned by dose level
- Acclimation period: 2 weeks
- Randomisation: By stratified randomization into 4 weight-matched groups

ENVIRONMENTAL CONDITIONS
- Temperature: 24±2°C
- Humidity: 55±10%
- Air changes (per hr): 15-17
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: No data
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
- Vinyl acetate dissolved in deionised water to give target concentrations of 400, 2000 or 10000 ppm (g/g).
- A drinking bottle filled with a full volume (200 mL) of the vinyl acetate-formulated drinking water was used, in order to prevent a decrease in the vinyl acetate concentration due to evaporation from the bottle.
- The drinking water formulations prepared twice a week.
- Stability of vinyl acetate in the drinking water examined 4 days after preparation. The concentrations of vinyl acetate and acetic acid in the drinking water were determined with a gas chromatograph and a liquid chromatograph-mass spectrometer, respectively.
- The pH of the drinking water was measured.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The vinyl acetate concentrations in the drinking water 4 days after preparation decreased to 86-96% (attributed mainly to the loss due to evaporation).
Four days after preparation acetic acid concentration and the pH were 9.2 ppm and pH 4.0 for the 400 ppm formulation, 47 ppm and pH 4.2 for the 2000 ppm formulation and 263 ppm and pH 3.6 for the 10000 ppm formulation.
Duration of treatment / exposure:
104 weeks
Frequency of treatment:
Continuous
Post exposure period:
None
Remarks:
Doses / Concentrations:
0, 400, 2000 or 10000 ppm (g/g)
Basis:
nominal in water
Remarks:
Doses / Concentrations:
0, 42, 202 or 989 mg/kg bw/day (males)
Basis:
actual ingested
Remarks:
Doses / Concentrations:
0, 63, 301 or 1418 mg/kg bw/day (females)
Basis:
actual ingested
No. of animals per sex per dose:
50
Control animals:
yes, concurrent vehicle
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly for the first 13 wks and every 4 wks thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study):
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes: Weekly for the first 13 wks and every 4 wks thereafter.

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: Weekly for the first 13 wks and every 4 wks thereafter.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: At termination
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes
- How many animals: All surviving animals
- Parameters examined: According to the authors, the haematological parameters specified in OECD test guideline 453 were measured

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: At termination
- Animals fasted: Yes
- How many animals: All surviving animals
- Parameters examined: According to the authors, the blood biochemical parameters specified in OECD test guideline 453 were measured

URINALYSIS: Yes
- Time schedule for collection of urine: During the last week of treatment (week 104)
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes
- Parameters examined: pH, protein, glucose, ketone bodies, occult blood, and urobilinogen

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- Organs were examined macroscopically, and according to the authors, the tissues specified in OECD test guideline 453 were examined for histopathology.

HISTOPATHOLOGY: Yes
- Tissues were fixed in 10% neutral buffered formalin, and embedded in paraffin by the routine procedures. Tissue sections 5 µm thick were prepared and stained with haematoxylin and eosin.
- The oral cavity was examined histopathologically at six different levels. The maxilla and mandible were decalcified with a 5% formic acid-formalin solution. Then the maxilla was trimmed with the nasal cavity in three cross sections at the levels of the posterior edge of the upper incisor teeth (Level I), the incisive papilla (Level II) and the anterior edge of the upper molar teeth (Level III). The mandible was trimmed in three cross sections at the levels of the posterior edge of the lower incisor teeth (Level IV), the anterior edge of the lower molar teeth (Level VI) and the middle point between Levels IV and VI (Level V).
Statistics:
Non-neoplastic lesions and urinary data: analysed by chi-square test.
Neoplastic lesions: analysed by Peto's test and Fisher's exact test.
Body weight, food and water consumption, haematological and blood biochemical parameters: analysed by Dunnett's Test.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
no effects observed
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
effects observed, treatment-related
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
- No significant difference in the survival rate of males or females was found between any treated group and the respective control.
- The incidence of oral cavity nodules, noted clinically, was significantly increased in both sexes at 10000 ppm; in 3 males after the 57th week and in 5 females after the 95th week.

BODY WEIGHT AND WEIGHT GAIN
- Body weights of the 10000 ppm males and females at the end of the 2-yr administration period were significantly lower by 30 and 18%, respectively, than those of controls.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
- Water consumption was lower in males and females dosed at 10000 ppm group than in the control, especially in the later period of the study.
- Mean daily vinyl acetate intake per body weight, estimated by water consumed, was 0, 42, 202 or 989 mg/kg/day for males and 0, 63, 301 or 1418 mg/kg/day for females, for the 0, 400, 2000 or 10000 ppm groups, respectively.

HAEMATOLOGY/CLINICAL CHEMISTRY/ URINALYSIS
- There were no treatment-related effects, although there were occasional statistically significant changes in several parameters. No further details reported.

ORGAN WEIGHTS
- Statistically significant changes in organ weights were observed in several organs in males and females dosed at 10000 ppm, but those changes were not associated with histopathological changes. No further details reported.

GROSS PATHOLOGY
- Mandiblar nodules occurred in 3 males and 5 females in the 10000 ppm group. Maxillary nodules were seen in 3 males and 1 female in the 10000 ppm group.

HISTOPATHOLOGY:
Incidences of squamous cell tumours in the oral cavity, forestomach of male and female mice and in the oesophagus of male mice significantly increased in a dose related manner (Peto's test).
-At 10000 ppm vinyl acetate there was a significant increase in the incidence of squamous cell carcinomas and papillomas in the oral cavity, oesophagus, forestomach and larynx (males), together with basal cell hyperplasia, squamous cell hyperplasia and epithelial dysplasia.
- Squamous cell carcinomas in the larynx and papillomas in the oesophagus were also seen in some 2000 ppm females.
- At 10000 ppm, mapping of the neoplastic and pre-neoplastic lesions in the oral cavity revealed that the incidence of those lesions was higher at Level V of the mandibular region than at any other Levels. More than 60% of male mice and 35% of female mice had two or more pre-neoplastic lesions at different sites, whereas there was only one male mouse bearing a carcinoma and basal cell hyperplasia at different sites.
- Isolated incidences of a tongue squamous cell papilloma and a carcinoma were seen in females at 10000ppm, were within the range of the concurrent and of the historical control data.
-Five and two animals with squamous cell tumours in the 10000 ppm group had atrophy of the salivary gland at Level V and Level II, respectively. Two and one animals bearing pre-neoplastic lesions also had salivary gland atrophy in the mandible at Levels IV and V, respectively.
- Other types of tumours were observed in the spleen, lungs, uterus and nasal cavity of the treated groups, but the incidences of those tumours were not statistically different from those in the controls.
Dose descriptor:
BMDL10
Effect level:
477 mg/kg bw/day (nominal)
Sex:
male/female
Basis for effect level:
other: Combined incidence of squamous cell carcinomas and papillomas in the oral cavity and the estimated daily vinyl acetate intakes per body weight.
Remarks on result:
other: Effect type: carcinogenicity (migrated information)

Number of mice with neoplastic and pre-neoplastic lesions in the upper digestive tract

 

(Table based on Umeda Y 2004, J Occup Health: 46: 87-99, Tables 2 and 3)

Tissue

male (50/group)

female (50/group)

male (996)

female (998)

Dose level (ppm)

0

400

2000

10000

0

400

2000

10000

 

 

Oral cavity

Squamous cell papilloma

0

0

0

4

0

0

0

3

0

1

Squamous cell carcinoma

0

0

0

13**

0

0

0

15**

0

0

Basal cell hyperplasia

0

0

1

18**

0

0

1

17**

-

-

Squamous cell hyperplasia

0

0

2

13**

0

0

1

6*

 

 

Epithelial dysplasia

0

0

0

24**

0

0

0

17**

-

-

Oesophagus

Squamous cell carcinoma

0

0

0

7**

0

0

0

1

0

0

Basal cell hyperplasia

0

0

0

9**

0

0

0

15**

-

-

Squamous cell hyperplasia

0

0

0

2

0

0

0

2

-

-

Epithelial dysplasia

0

0

0

2

0

0

0

7**

 

 

Forestomach

Squamous cell papilloma

0

0

0

2

0

0

0

1

2

4

Squamous cell carcinoma

1

0

0

7*

0

0

0

3

0

2

Basal cell hyperplasia

0

0

0

1

0

0

0

1

 

 

Squamous cell hyperplasia

0

0

0

3

0

2

0

4*

 

 

Epithelial dysplasia

0

0

0

1

0

0

0

0

 

 

Larynx

Squamous cell carcinoma

0

0

0

2

0

0

1

1

0

0

Basal cell hyperplasia

0

0

0

3

0

0

0

6*

 

 

Squamous cell hyperplasia

0

0

0

1

0

0

0

0

 

 

Epithelial dysplasia

0

0

0

2

0

0

0

3

 

 

Tongue

Squamous cell papilloma

0

0

0

0

0

0

0

1

0

1

Squamous cell carcinoma

0

0

0

0

2

0

0

1

0

2

50 rats/sex/group

* - Statistically significant: p<0.05 (Fisher’s exact test or Peto’s test or Chi-square test)

** -Statistically significant: p<0.01 (Fisher’s exact test or Peto’s test or Chi-square test)

Conclusions:
Oral administration of vinyl acetate to mice in drinking water at nominal concentrations of 0, 400, 2000 or 10000 ppm (g/g) for 2 years induced squamous cell carcinomas and papillomas and pre-neoplastic lesions in the upper digestive tract in both sexes. A lower confidence limit of a benchmark dose (BMDL10) of 477 mg/kg/d was obtained from a dose-response relationship between combined incidence of squamous cell carcinomas and papillomas in the oral cavity of mice and the estimated daily vinyl acetate intakes per body weight, and compared with literature values.
Executive summary:

Oral administration of vinyl acetate to mice in drinking water at nominal concentrations of 0, 400, 2000 or 10000 ppm (g/g) for 2 years induced squamous cell carcinomas and papillomas and pre-neoplastic lesions in the upper digestive tract in both sexes. The incidence of these lesions was dose-related. Squamous cell carcinomas and papillomas were observed in the oral cavity, oesophagus, forestomach and larynx of the 10000 ppm group, together with basal cell hyperplasia, squamous cell hyperplasia and epithelial dysplasia. Mapping of the neoplastic and pre-neoplastic lesions in the oral cavity of the 10000 ppm group revealed that both the lesions occurred predominantly at Level V. A lower confidence limit of a benchmark dose (BMDL10) of 477 mg/kg/d was obtained from a dose-response relationship between combined incidence of squamous cell carcinomas and papillomas in the oral cavity of mice and the estimated daily vinyl acetate intakes per body weight, and compared with literature values.

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, near guideline study, available as unpublished report and as a publication in peer reviewed literature , no restrictions, fully adequate for assessment
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
yes
Remarks:
blood samples only at weeks 52 & 78 (satellite animals).
Principles of method if other than guideline:
Groups or 90 males and 90 females, previously exposed to vinyl acetate in utero, during lactation and through weaning, were dosed with solutions of vinyl acetate in drinking water for up to 104 weeks. Sixty animals per sex were main study animals and 30 per sex were satellite animals used for laboratory investigations and interim kills at 52 or 78 weeks.
GLP compliance:
yes
Species:
rat
Strain:
other: Sprague-Dawley derived [Crl:CD(SD)BR]
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: The animals were selected from pups obtained in a reproduction study (HUK 4661-51/17a), and were the offspring of dams treated with vinyl acetate for 10 weeks prior to mating and throughout gestation and lactation until the pups were weaned.
- Sixty and 30 male and 60 and 30 female pups and 5 male and 5 female replacement pups in each group were selected for this chronic study. These animals, with the exception of the replacement pups which were killed at week 12, were treated for up to 104 weeks with interim kills after 52 and 78 weeks.
- Age at study initiation: approximately 28 days
- Weight at study initiation: 98.4-199.4 g (males), 84.5-161.8 g (females)
- Housing: Groups of 5 per sex in stainless steel mesh cages suspended over cardboard-lined trays
- Diet: SQC Rat and Mouse Maintenance Diet No. 1, expanded, ground fine (Special Diets Services Ltd., Witham UK.) ad libitum except overnight (approximately 17-20 hrs) prior to blood and urine collection from the satellite animals, and all animals before termination.
- Water: Drinking water solutions were available ad libitum except overnight (approximately 17-20 hrs) prior urine collection from the satellite animals. Drinking water solutions were dispensed from glass bottles fitted with stainless steel spouts, water solutions and untreated drinking water was replaced with fresh solution every 24 hours.
- Acclimation period: Not applicable

ENVIRONMENTAL CONDITIONS
- Temperature: 19-25°C
- Humidity: 40-70%
- Air changes (per hr): Minimum of 15
- Photoperiod (hrs dark / hrs light): 12/12 (0600-1800)

IN-LIFE DATES: From: 9 July 1984 9 To: 18 July 1986
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
- Solutions of vinyl acetate in drinking water were prepared daily. Batches of each concentration were prepared in the drinking water on a constant ppm (v/v) basis.
- The test article formulations were formulated by an extra 5% for each dose level, to correct for hydrolysis over the 24 hour period.
- The pH of each formulation was recorded.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Drinking water formulations were analysed to verify the concentration of the vinyl acetate at intervals of 4 weeks throughout the study from week 2. Achieved concentrations were considered acceptable (±20% of nominal). There was one exception to this at week 30 where duplicate analyses gave results of 76% and 80% of target.
Duration of treatment / exposure:
104 weeks
Frequency of treatment:
Continuous
Post exposure period:
None
Remarks:
Doses / Concentrations:
0, 200, 1000 or 5000 ppm (v/v)
Basis:
nominal in water
Remarks:
Doses / Concentrations:
0, 30, 150 or 670 mg/kg approx at week 1
Basis:
other: calculated body weight equivalent dose
Remarks:
Doses / Concentrations:
0, 10, 60 or 235 mg/kg approx at week 104
Basis:
other: calculated body weight equivalent dose
No. of animals per sex per dose:
90
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The results of a range of earlier studies (HUK report numbers 1840-51/2, 2146-51/4, 2195-51/6, 3866-51/18 and Lijinsky, W. and Reuber, M.D., 1983) were used to assist in the selection of dose levels for this study.
- Sixty animals of each sex were assigned as main study animals and 30 animals of each sex were assigned as satellite animals in each group. The satellite animals were used for laboratory investigations and interim kills of 10 males and 10 females from each group after 52 and 78 weeks. Since there were only a few survivors of the remaining satellite animals at week 104, and in the absence of any effects on laboratory investigations, no laboratory investigations were performed at termination.
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Twice daily for signs of ill health or overt toxicity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Once weekly (the examination included palpation for tissue masses).

BODY WEIGHT: Yes
- Time schedule for examinations: Individual body weights were recorded on the first day of the 104 week study, at weekly intervals for the first 28 weeks, and once every 4 weeks thereafter.

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption per cage of animals, with the exception of the satellite animals, was determined weekly for the first 28 weeks, and then for one week in every 4 weeks thereafter.

FOOD EFFICIENCY: No

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: Water consumed per cage of animals, with the exception of the satellite animals, was determined weekly for the first 28 weeks, and then for one week in every 4 weeks thereafter.

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Time schedule for collection of blood: Blood samples were obtained from the satellite animals only at weeks 52 and 78.
- Blood samples were collected by orbital sinus puncture.
- Anaesthetic used for blood collection: Yes (ether)
- Animals fasted: Yes, overnight (about 20 hours)
- How many animals: 10/sex/group
- Parameters checked: Blood (0.3 mL) was collected into EDTA anticoagulant: haemoglobin, mean cell volume, red blood cell count, total and differential white blood cell count.
- The following indices were calculated: packed cell volume, mean cell haemoglobin, mean cell haemoglobin concentration.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: Blood samples were obtained from the satellite animals only at weeks 52 and 78.
- Animals fasted: Yes, overnight (about 20 hours)
- How many animals: 10/sex/group
- Parameters checked: Blood (0.4 mL) was collected into lithium heparin anticoagulant: glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, alkaline phosphatise, creatinine phosphokinase, sodium, potassium, chloride, calcium, glucose, blood urea nitrogen, total protein, albumin, albumin/globulin ratio.

URINALYSIS: Yes
- Time schedule for collection of urine: Urine samples were obtained from the satellite animals only at weeks 52 and 78.
- Metabolism cages used for collection of urine: No data
- Animals fasted: Yes, overnight (about 17 hours)
- Parameters checked: volume, pH, specific gravity, glucose, protein, bilirubin, ketones, urobilinogen, blood, microscopy of spun deposits, reducing substances.

NEUROBEHAVIOURAL EXAMINATION: No

OTHER:
- Two blood smears were prepared from the sample collected into EDTA anticoagulant. One smear was stained with Romanowsky stain and examined microscopically for the differential white blood counts. The other smear was stained with brilliant cresyl blue (but was not examined for reticulocytes as no signs of anaemia were detected).
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- The following procedures were applied to all animals killed at the end of the study, those killed in extremis, and where possible to those found dead:
- A full external and internal examination was made, including all body cavities (thoracic, abdominal and cranial) and all lesions were recorded.
- All unusual macroscopic abnormalities were photographed.

ORGAN WEIGHTS: Yes
- The following organs from all animals surviving to the terminal kill and from all satellite animals killed at the interim kills were weighed before fixation: adrenals, brain, heart, kidneys, liver, pituitary, ovaries, testes, spleen, thyroid.

HISTOPATHOLOGY: Yes
- Samples of the following tissues were fixed in 10% neutral buffered formalin (with the exception of the eyes which were fixed in Davidson's fluid, the testes which were fixed in Bouin's solution, and the bone marrow smear which was fixed in methanol): adipose tissue, aorta, adrenals, brain (medullary, cerebellar and cortical sections), bone marrow smear+, caecum, colon, duodenum, eyes (and optic nerves), ear canal+, fallopian tubes, femur, ganglia (lumbar, sacral and dorsal), hindlimbs (post-distal portions for tibial and plantar nerves)+, Harderian glands, heart, ileum, jejunum, kidneys, liver, larynx, lungs, lymph nodes (mandibular, mediastinal, mesenteric and bronchial), mammary gland, muscle (quadriceps), nasal turbinates (4 levels), ovaries, oesophagus, pituitary, pancreas, prostate, rectum, sciatic nerves, skin, spleen, salivary gland (submaxillary), seminal vesicles, spinal cord (high cervical), stomach (forestomach and glandular), testes with epididymides, thymus (where present), tongue, trachea, thyroids (with parathyroids where identified), uterus (including cervix) urinary bladder gross lesions and tissue masses.
- All tissues listed above (except those indicated +) from all animals in the control and high dose groups and from animals that died or were killed in extremis were embedded in wax B.P. (mp 56°C), sectioned at a nominal thickness of 5 µm and stained with haematoxylin and eosin.
Statistics:
Data were processed, where appropriate, to give group mean values and standard deviations. The following parameters were analysed statistically: survival, body weight and body weight gain, food consumption, water consumption, haematology parameters, clinical chemistry parameters, organ weights and selected tumours.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
no effects observed
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
no effects observed
Details on results:
BODY WEIGHT AND WEIGHT GAIN
- At the start of treatment in this chronic study the mean body weight of high dose animals was about 5% lower than controls. This difference was considered to be associated with the preceding in utero exposure to vinyl acetate (HUK report number 4661-51/17a).
- There was a significant reduction in body weight gain of high dose main study animals compared to controls. In males this was apparent during both the first and second years (p<.001), however in females it was apparent only in the second year (p<.05). The group mean body weights were about 11% and 6% less than controls for high dose males and females at week 52, and about 17% and 11% less than controls, respectively, at week 104.
- The satellite animals were generally comparable to the main study animals allowing for the different group sizes and interim kills.
- There were no treatment-related differences in mean body weights of low and intermediate dose animals, compared to controls. However, there was an apparent reduction in body weight gain of low dose main study males. The comparison in body weight gain between low dose and control males was significant in weeks 13 (p<.05), 52 and 104 (p<.01). Since this difference was not apparent in low dose females or low dose male satellite animals it is considered not to be biologically significant.

FOOD CONSUMPTION
- The group mean food consumption of high dose males was generally lower than that of the controls throughout the study. The difference in this fluctuating measurement was slight (range about 3% to 15% less than controls) but it was significant on the occasions analysed (between p<.05 and p<.001). The effect was not apparent as early in high dose females and remained marginal (range about 3% to 10% less than controls) and did not achieve statistical significance.

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study)
- There was a dose-related reduction in water consumption during the first year of the study, with only high dose animals clearly affected in the second year.
- At week 13 the group mean water consumptions were 6%, 11%, 33% and 4%, 15%, 33% less than controls, for males and females in low, intermediate and high dose groups respectively.
- During the second year of the study the only clear effect that remained was the marked significant (p<.001) reduction in water consumption of high dose animals compared to controls. Generally, the group mean water consumption of low and intermediate dose males was less than controls and no consistent difference was apparent in the females.

ORGAN WEIGHTS
- The relative kidney weights of high dose males were significantly greater than controls, but there was no treatment-related histopathological indication for this change. There were no other effects on organ weights.

Relevance of carcinogenic effects / potential:
Vinyl acetate in drinking water at concentrations up to 5000 ppm (v/v) showed no evidence of any treatment-related oncogenic response.
Dose descriptor:
NOAEL
Effect level:
1 000 ppm
Sex:
male/female
Basis for effect level:
other: No toxicologically significant effects. Body weight gain reduced at 5000 ppm.
Remarks on result:
other: Effect type: toxicity (migrated information)
Dose descriptor:
NOEL
Effect level:
5 000 ppm
Sex:
male/female
Basis for effect level:
other: No evidence of any treatment-related oncogenic response.
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Conclusions:
Treatment of rats for 104 weeks with vinyl acetate in drinking water at 200, 1000 or 5000 ppm (v/v) resulted in a dose-related reduction in water consumption, particularly at 5000 ppm(v/v) where there were effects on body weight gain and food consumption. There were no treatment related clinical effects and no evidence for any treatment related carcinogenic effects. The no observed effect level for toxicity was considered to be 1000 ppm and the no observed effect level for carcinogenicity was 5000 ppm vinyl acetate.
Executive summary:

Groups of 90 male and 90 female Sprague Dawley-derived rats, previously exposed in utero to vinyl acetate, were given 0, 200, 1000 or 5000 ppm vinyl acetate (v/v) in drinking water for up to 104 weeks. 60 animals/sex were assigned as main study animals and 30 animals/sex were assigned as satellite animals in each group. The satellite animals were used for laboratory investigations and interim kills of 10 males and 10 females from each group after 52 and 78 weeks. A dose-related reduction in water consumption, particularly at 5000 ppm (v/v), was observed during the first year and remained present at 5000 ppm throughout the second year. At 5000 ppm there was also a reduction in body weight gain throughout both years in males and in females only during the second year. A slight reduction in food consumption was also seen in males at 5000 ppm. There were no treatment related clinical effects or histopathology findings at the 52, 78 or 104 week examinations. There was no evidence for any treatment related carcinogenic effects. The no observed effect level for toxicity was considered to be 1000 ppm and the no observed effect level for carcinogenicity was 5000 ppm vinyl acetate.

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
4 (not assignable)
Qualifier:
no guideline followed
Principles of method if other than guideline:
Exposure of male and female breeding mice from the 12th day of pregnancy
GLP compliance:
not specified
Species:
mouse
Strain:
Swiss Webster
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: No details reported
- Age at study initiation: 17 weeks
- Housing:No details reported
- Diet (e.g. ad libitum): No details reported
- Water : water containing 0, 1000 or 5000 ppm vinyl acetate monomer ad libitum

ENVIRONMENTAL CONDITIONS- No details reported
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS:
Solutions of vinyl acetate monomer were prepared in drinking water on a daily basis, just before the daily water supply was provided to the mice.

Analytical verification of doses or concentrations:
not specified
Duration of treatment / exposure:
78 weeks
Frequency of treatment:
continuous exposure
Post exposure period:
until death (up to 168 weeks of age)
Remarks:
Doses / Concentrations:
0, 1000, 5000 ppm
Basis:
nominal in water
No. of animals per sex per dose:
13 or 14 males and 37 females
Control animals:
yes, sham-exposed
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Weekly for first 13 weeks, every 2 weeks until the end of the experiment

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly for first 13 weeks, every 2 weeks during exposure and every 8 weeks until the end of the experiment.

FOOD CONSUMPTION :
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: No data

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No data

OPHTHALMOSCOPIC EXAMINATION: No data

HAEMATOLOGY: No data
- Time schedule for collection of blood:

CLINICAL CHEMISTRY: No data

URINALYSIS: No data

NEUROBEHAVIOURAL EXAMINATION: No data

OTHER:
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes
- the following tissues were submitted : brain, pituitary gland, Zymbal glands, salivary glands, Harderian glands, head (5 sections) (only in animals that survived more than 100 weeks), tongue, thyroid, thymus and mediastinal lymph nodes, lung, heart, diaphragm, liver, spleen, pancreas, kidneys and adrenal glands, oesophagus, stomach, intestine (4 levels), bladder, prostate, uterus, gonads, interscapular fat pad, subcutaneous and mesenteric lymph nodes, and any other organs and tissues with pathological lesions.
- The tissues were trimmed and processed as paraffin blocks. 3-5-micron sections were were routinely stained with haematoxylin-eosin. Specific stainings were performed when needed.
- The same group of pathologists examined all slides microscopically; a senior pathologist reviewed all the tumours and any other lesion of ontological interest. All pathologists followed the same criteria of histopathological evaluation and classification.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
no effects observed
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
Survival - there was a decrease in survival of males, at both 1000 and 5000 ppm, up to 72 weeks of age. Then from 72 to 120 weeks an increase of survival was observed among the males at 5000 ppm. The females at 1000 ppm had a slight decrease in survival but there was no difference from controls at 5000 ppm.

Neoplastic findings - At 5000 ppm, there was an increased incidence of total benign tumours in females and an increase in total malignant tumours in males and females.
Zymbal gland carcinomas were more numerous among females at 5000 ppm and squamous cell dysplasia of the zymbal gland was increased in males and females at 5000 ppm and females at 1000 ppm.
There was a higher incidence of squamous cell carcinomas of the oral cavity in males and females at 5000 ppm, including tongue carcinomas and squamous cell dysplasia, squamous carcinomas and squamous cell dysplasia of the oesophagus, squamous cell carcinomas and acanthomas of the forestomach.
The number of lung tumours per 100 animals was increase in males and females at 5000 ppm and in females at 1000 ppm.
There was a dose related increased incidence of malignant tumours of the uterus (leiomyosarcomas and adenocarcinomas).
Dose descriptor:
NOAEL
Effect level:
5 000 ppm (nominal)
Sex:
male/female
Basis for effect level:
other: 780 mg/kg/d. Squamous cell tumours in oral cavity, tongue, oesophagus and forestomach. Also tumours in Zymbal gland, lung and uterus.
Remarks on result:
not determinable
Remarks:
no NOAEL identified. Effect type:carcinogenicity (migrated information)
Conclusions:
In a life time study, mice were exposed to vinyl acetate, at 0, 1000 or 5000 ppm in the drinking water, from 17 weeks of age for 78 weeks and were then monitored until death. There was a dose related increase in total malignant tumours; carcinomas of the Zymbal glands; oral cavity, tongue, oesophagus, and forestomach; lung tumours and uterine tumours.
Executive summary:

Vinyl acetate monomer was administered in drinking water at doses of 0, 1000 or5000ppm (v/v), to Swiss mice, 17 weeks old at the start of the experiment. The treatment lasted 78 weeks and the animals were monitored until spontaneous death. There were no signs of systemic toxicity. There was a dose related increase in total malignant tumours; carcinomas of the Zymbal glands; oral cavity, tongue, oesophagus, and forestomach; lung tumours and uterine tumours. On the basis of these data the authors conclude that vinyl acetate monomer must be considered a multipotential carcinogen.

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP, non-guideline study, available as unpublished report and as a publication in the peer reviewed literature, no restrictions, fully adequate for assessment.
Reason / purpose:
reference to same study
Qualifier:
no guideline available
Principles of method if other than guideline:
To determine whether repeated exposure to vinyl acetate correlated with tissue toxicity assessed primarily by cell proliferation.
GLP compliance:
yes (incl. certificate)
Species:
mouse
Strain:
other: B6D2F1/CrlBr mice (BDF1)
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc, Raleigh, North Carolina, USA
- Age at study initiation: approx 46 days
- Weight at study initiation: 21.4-25.7 g
- Housing: Individually in suspended, stainless steel, wire-mesh cages
- Diet: PMI Nutrition International, Inc. Certified Rodent LabDiet® 5002 ad libitum
- Water: test water solutions, prepared with either distilled water or tap water ad libitum
- Acclimation period: 7 days quarantine + 3 days pre-test

ENVIRONMENTAL CONDITIONS
- Temperature: 22±3°C)
- Humidity: 50±10
- Air changes (per hr): Not reported
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 27 September 1999 To: 28 December 1999
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Vinyl acetate was added to either tap water or distilled water and thoroughly mixed for a period of time that was adequate to ensure a homogeneous mixture. Control water was similarly mixed. Test solutions were prepared fresh at approximately 3 or 4day intervals.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Test solutions were stable when stored for 4 days at room temperature. The analytically determined concentrations of vinyl acetate in the drinking bottles of animals were considered acceptable for evaluating the toxicity of vinyl acetate at the selected targeted concentrations.
Duration of treatment / exposure:
92 days
Frequency of treatment:
continuous
Post exposure period:
none
Remarks:
Doses / Concentrations:
0, 1000, 5000, 10000 or 24000 ppm
Basis:
nominal in water
Remarks:
Doses / Concentrations:
0, 250, 1200, 2300 or 5300 mg/kg body weight,
Basis:
actual ingested
No. of animals per sex per dose:
20
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Based on the results of chronic drinking water studies and a range-finding experiment conducted prior to this study.
- Study purpose: To determine whether repeated exposure to vinyl acetate correlated with tissue toxicity, as assessed primarily by cell proliferation in and histopathology of upper digestive tract tissues.

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at least once/day

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice during 1st week and once/week thereafter.

BODY WEIGHT: Yes
- Time schedule for examinations: twice during 1st week and once/week thereafter.

FOOD CONSUMPTION: yes
- Time schedule for examinations: once/week

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: twice/week

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (oral cavity, oesophagus, forestomach, duodenum) high dose and controls only
Other examinations:
CELL PROLIFERATION: On test days 1, 8, 29, and 92, 5 mice per group were prepared for evaluation of oral cavity cell proliferation using pulsed 5-bromodeoxyuridine (BrdU) uptake techniques and histopathology.
Statistics:
Body weight and gain, food consumption and efficiency and water consumption: Test for lack of trend followed by additional statistical tests based on significance: Jonckheere-Terpstra trend test, preliminary tests for pairwise comparison or Levene’s test for homogeneity, Shapiro-Wilk test for normality, one-way repeated measure analysis of variance followed with Dunnett's test or Kruskall-Wallis test followed with Dunn's test.

Labelling Index: Levene’s test for homogeneity and Shapiro-Wilk test for normality. If not sig. Three-way repeated measure analysis of variance followed, with Dunnett's test. If sig. Mann-Whitney U test.

Incidence of Clinical Observations: Cochran-Armitage test for trend.
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):
effects observed, treatment-related
Food efficiency:
no effects observed
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY: No mortalities and no clinical signs of toxicity.

BODY WEIGHT AND WEIGHT GAIN: No effects

FOOD CONSUMPTION: At various intervals during the study, mice from all test groups had statistically significantly lower mean daily food consumption compared to controls. However, for the interval day 0 – 92, no statistical differences were observed. Mice from all test groups did exhibit lower mean daily food consumption during the study compared to controls.

FOOD EFFICIENCY: No effects

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): The mean daily water consumption was statistically significantly lower in mice from all test groups at various intervals during the study and for the period day 0 – 92. The lower consumption was attributed to the fact the water solutions were most likely not palatable to the animals. The mean daily intake of vinyl acetate (based on nominal vinyl acetate concentrations) from the 1000, 5000, 10,000, and 24,000 ppm groups was 250, 1200, 2300, and 5300 mg/kg body weight, respectively

GROSS PATHOLOGY: No effects

HISTOPATHOLOGY: No effects

ORAL CAVITY CELL PROLIFERATION: Statistically significant and dose-related increases in mean basal cell proliferation occurred only in the lower jaw (corresponding to JBRC level V) in the 10000 and 24000 ppm groups at 92 days. The increases were approximately 2.4- and 3.4-fold above the control group mean for the 10000 and 24000 ppm groups, respectively. Based on the magnitude of the increases and the dose-related nature of the response, these increases were considered to be compound-related. There were no other statistically significant increases in cell proliferation in 24000 ppm mice compared to controls at any of the time points evaluated. Cell proliferation was not evaluated in the oesophagus or forestomach.
Dose descriptor:
NOAEL
Effect level:
24 000 ppm (nominal)
Sex:
male
Basis for effect level:
other: 5300 mg/kg/d. Highest dose tested.
Remarks on result:
other: Effect type: toxicity (migrated information)
Dose descriptor:
NOAEL
Effect level:
5 000 ppm (nominal)
Sex:
male
Basis for effect level:
other: 1200 mg/kg/d. Increases in mean cell proliferation in the lower jaw at 10000 and 24000 ppm (2300 and 5300 mg/kg/d.)
Remarks on result:
other:
Remarks:
Effect type: other: cell proliferation (migrated information)
Conclusions:
In a 90 day drinking water study, vinyl acetate produced a toxicologically-significant increase in cell proliferation in the lower jaw of mice following 92 days of exposure at concentrations of 10,000 ppm or greater. The no observed effect level for toxicity was considered to be 24000 ppm, equivalent to 5300 mg/kg/day, but the no observed effect level for cell proliferation was considered to be 5000 ppm, equivalent to 1200 mg/kg/day.
Executive summary:

Five groups of 20 male B6D2F1/CrlBr mice (BDF1) received vinyl acetate in their drinking water at nominal concentrations of 0, 1000, 5000, 10000 or 24000 ppm for 92 days. On test days 1, 8, 29, and 92, 5 mice per group were prepared for evaluation of oral cavity cell proliferation using pulsed 5-bromodeoxyuridine (BrdU) uptake techniques and histopathology. All mice survived to their scheduled termination and there were no toxicologically significant clinical signs and no effects on body weight. Water consumption was consistently lower in all groups than in the controls, reflecting palatability. The mean daily intake of vinyl acetate (based on nominal vinyl acetate concentrations) from the 1000, 5000, 10,000, and 24,000 ppm groups was 250, 1200, 2300, and 5300 mg/kg body weight, respectively. There were no treatment related gross lesions in the oral cavity, oesophagus, forestomach or duodenum in any of the mice and there were no microscopic lesions in the oral cavity of mice in the 24000 ppm group. There was a dose-related and statistically significant increase in cell proliferation in the lower jaw, seen in mice at 10000 and 24000 ppm, and the increases in labelling indices were approximately 2.4 – 3.4 fold above the controls, respectively. In the mouse, the no observed effect level for toxicity is considered to be 24000 ppm, equivalent to 5300 mg/kg/day, but the no observed effect level for cell proliferation is considered to be 5000 ppm, equivalent to 1200 mg/kg/day.

Endpoint:
carcinogenicity: oral
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP compliant non-guideline study, available as unpublished report and as a publication in the peer reviewed literature, no restrictions, fully adequate for assessment
Reason / purpose:
reference to same study
Qualifier:
no guideline available
Principles of method if other than guideline:
To determine whether repeated exposure to vinyl acetate correlated with tissue toxicity assessed primarily by cell proliferation.
GLP compliance:
yes (incl. certificate)
Species:
rat
Strain:
other: CDF®(F-344)/CrlBr
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Inc, Raleigh, North Carolina, USA
- Age at study initiation: approx 46 days
- Weight at study initiation: 106.2-143.2 g
- Housing: Individually in suspended, stainless steel, wire-mesh cages
- Diet: PMI Nutrition International, Inc. Certified Rodent LabDiet® 5002 ad libitum
- Water: test water solutions, prepared with either distilled water or tap water ad libitum
- Acclimation period: 7 days quarantine + 3 days pre-test

ENVIRONMENTAL CONDITIONS
- Temperature: 22±3°C
- Humidity: 50±10%
- Air changes (per hr): Not reported
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 27 September 1999 To: 28 December 1999
Route of administration:
oral: drinking water
Vehicle:
water
Details on exposure:
PREPARATION OF DOSING SOLUTIONS: Vinyl acetate was added to either tap water or distilled water and thoroughly mixed for a period of time that was adequate to ensure a homogeneous mixture. Control water was similarly mixed. Test solutions were prepared fresh at approximately 3 or 4 day intervals.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Test solutions were stable when stored for 4 days at room temperature. The analytically determined concentrations of vinyl acetate in the drinking bottles of animals were considered acceptable for evaluating the toxicity of vinyl acetate at the selected targeted concentrations.
Duration of treatment / exposure:
92 days
Frequency of treatment:
continuous
Post exposure period:
none
Remarks:
Doses / Concentrations:
0, 1000, 5000, 10000 or 24000 ppm
Basis:
nominal in water
Remarks:
Doses / Concentrations:
0, 81, 350, 360 or 1400 mg/kg body weight
Basis:
actual ingested
No. of animals per sex per dose:
20
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: Based on the results of chronic drinking water studies and a range-finding experiment conducted prior to this study.
- Study purpose: To determine whether repeated exposure to vinyl acetate correlated with tissue toxicity, as assessed primarily by cell proliferation in and histopathology of upper digestive tract tissues.

Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: at least once/day

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: twice during 1st week and once/week thereafter.

BODY WEIGHT: Yes
- Time schedule for examinations: twice during 1st week and once/week thereafter.

FOOD CONSUMPTION: yes
- Time schedule for examinations: once/week

FOOD EFFICIENCY:
- Body weight gain in kg/food consumption in kg per unit time X 100 calculated as time-weighted averages from the consumption and body weight gain data: Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Yes
- Time schedule for examinations: twice/week

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No
Sacrifice and pathology:
GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (oral cavity, oesophagus, forestomach, duodenum) high dose and controls only
Other examinations:
CELL PROLIFERATION: On test days 1, 8, 29, and 92, 5 rats per group were prepared for evaluation of oral cavity cell proliferation using pulsed 5-bromodeoxyuridine (BrdU) uptake techniques and histopathology.
Statistics:
Body weight and gain, food consumption and efficiency and water consumption: Test for lack of trend followed by additional statistical tests based on significance: Jonckheere-Terpstra trend test, preliminary tests for pairwise comparison or Levene’s test for homogeneity, Shapiro-Wilk test for normality, one-way repeated measure analysis of variance followed with Dunnett's test or Kruskall-Wallis test followed with Dunn's test.

Labelling Index: Levene’s test for homogeneity and Shapiro-Wilk test for normality. If not sig. Three-way repeated measure analysis of variance followed, with Dunnett's test. If sig. Mann-Whitney U test.

Incidence of Clinical Observations: Cochran-Armitage test for trend.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
effects observed, treatment-related
Food efficiency:
no effects observed
Water consumption and compound intake (if drinking water study):
effects observed, treatment-related
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
no effects observed
Details on results:
BODY WEIGHT AND WEIGHT GAIN: Rats in the 5000, 10,000, and 24,000 ppm groups had statistically significantly lower mean body
weights and mean body weight gains during the study relative to controls.

FOOD CONSUMPTION: Rats in the 10,000 and 24,000 ppm groups had statistically significantly lower mean daily food consumption compared to controls. Food consumption was lower in the 5000 ppm group during the study although statistical significance was not observed.

FOOD EFFICIENCY: No effects

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): Mean daily water consumption was consistently and significantly lower during the study in rats administered water solutions containing 5000, 10,000, or 24,000 ppm. Based on overall mean water consumption data, the mean daily intake of vinyl acetate (based on nominal concentrations) from the 1000, 5000, 10,000, and 24,000 ppm groups was 81, 350, 660, and 1400 mg/kg body weight, respectively.

GROSS PATHOLOGY: No effects

HISTOPATHOLOGY: No effects

ORAL CAVITY CELL PROLIFERATION: In rats administered 24,000 ppm, statistically significant increases in mean basal cell cell proliferation, relative to controls, occurred in the upper jaw (corresponding to JBRC level III) on days 29 and 92 and in the lower jaw (JBRC level VI) on days 1 and 29. These increases were small (less than 2-fold) and although statistically significant, were considered to be of equivocal biological significance. Cell proliferation was not evaluated in the oesophagus or forestomach.
Dose descriptor:
NOAEL
Effect level:
1 000 ppm (nominal)
Sex:
male
Basis for effect level:
other: 81 mg/kg/d. Reduced body weight and water consumption at =5000 ppm. Reduced food consumption at =10000 ppm.
Remarks on result:
other: Effect type: toxicity (migrated information)
Dose descriptor:
NOAEL
Effect level:
24 000 ppm (nominal)
Sex:
male
Basis for effect level:
other: 1400 mg/kg/d. Small increases in mean cell proliferation in the jaws were considered to be of equivocal biological significance.
Remarks on result:
other:
Remarks:
Effect type: other: cell proliferation (migrated information)
Conclusions:
In a 3 month study in male rats, administration of vinyl acetate in drinking water at concentrations of up to 24,000 ppm resulted in no mortalities or adverse clinical signs. There were no treatment related histopathological findings in oral cavity, oesophagus, forestomach or duodenum in the high dose group animals. Cell proliferation in the upper and lower jaw was seen in rats at 24000 ppm but the increases in labelling indices were considered to be of equivocal biological significance. The no observed effect level for toxicity is considered to be 1000 ppm, equivalent to 81 mg/kg/day, and the no observed effect level for cell proliferation is considered to be 24000 ppm, equivalent to 1400 mg/kg/day.
Executive summary:

Five groups of 20 male rats were administered vinyl acetate in the drinking water for 92 days at concentrations of 0, 1000, 5000, 10,000 or 24,000 ppm. On test days 1, 8, 29, and 92, 5 rats per group were prepared for evaluation of oral cavity cell proliferation using pulsed 5-bromodeoxyuridine (BrdU) uptake techniques and histopathology. There were no mortalities and no adverse clinical signs. Water consumption was consistently lower than controls at dose levels of 5000 ppm or higher and the achieved doses of vinyl acetate were therefore calculated to be 81, 350, 660, and 1400 mg/kg body weight for the 1000, 5000, 10000 and 24000 ppm groups, respectively. Body weights were statistically significantly lower during the study compared to controls at 5000 ppm or higher and food consumption was reduced at 1000 and 24000 ppm. There were no treatment related histopathological findings in oral cavity, oesophagus, forestomach or duodenum in the high dose group animals. Cell proliferation in the upper and lower jaw was seen in rats at 24000 ppm but the increases in labelling indices, whilst statistically significant, were less than 2-fold above the controls and were considered to be of equivocal biological significance. The no observed effect level for toxicity is considered to be 1000 ppm, equivalent to 81 mg/kg/day, and the no observed effect level for cell proliferation is considered to be 24000 ppm, equivalent to 1400 mg/kg/day.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
LOAEL
31 mg/kg bw/day
Study duration:
chronic
Species:
rat
Quality of whole database:
Reliable studies conducted in accordance with OECD guidelines and GLP are available.
System:
other: Site of contact tissues
Organ:
oral cavity

Carcinogenicity: via inhalation route

Link to relevant study records

Referenceopen allclose all

Endpoint:
carcinogenicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP compliant, near guideline study, available as unpublished report and as a publication in the peer reviewed literature, minor restrictions in design and/or reporting but otherwise adequate for assessment.
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
yes
Remarks:
clinical pathology from 10 animals/group at interim kills in weeks 51, 81 and 104 only.
GLP compliance:
yes
Species:
mouse
Strain:
other: Crl:CD-1(ICR)BR, Swiss-derived, outbred strain
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Uk Ltd, Margate, Kent, UK
- Age at study initiation: Approximately 6 weeks
- Weight at study initiation: 22.4-35.5 g (males), 16.0-28.5 g (females)
- Housing: Individually in stainless steel mesh cages suspended over cardboard-lined trays
- Diet: SQC Rat and Mouse Maintenance Diet No. 1, expanded (Special Diets Services, Witham, UK.) ad libitum except during exposure or preclinical evaluation fasting periods
- Water: Tap water ad libitum
- Acclimation period: 17 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19-25°C
- Humidity: 40-70%
- Air changes (per hr): At least 15/hr
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 5 January 1984 To: 6 February 1986
Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Milled steel and glass exposure chambers; volume approximately 8 m3.
- Vapour was generated by metering liquid vinyl acetate into a nebuliser within an expansion chamber of the generator module. The aerosol produced was mixed with the filtered exposure chamber air and introduced to the chamber as a vapour. The concentration in the diluent air was controlled by altering the flow rate of the metering pumps.
- The chambers reached target concentrations within 15 minutes.
- Method of holding animals in test chamber: in stainless steel wire mesh cages
- Air flow rate: Approximately 1500 to 2000 L/min
- Source and rate of air: Chamber air was drawn from filtered room air.
- Temperature, humidity in chamber: Chamber temperatures maintained between 19-25°C on 96% of occasions. Chamber humidity was maintained between 40-80% on 96% of occasions.

TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of vinyl acetate in all chambers was measured once every 15 min using a gas and flame ionisation detector. Quantification was by comparison of peak areas with a standard mixture of vinyl acetate in nitrogen.
- Samples taken from breathing zone: yes
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Mean daily chamber vinyl acetate concentrations in the 50, 200 and 600 ppm groups were 49.4±2.4, 200.5±9.7 and 594.7±16.8 ppm, respectively, and were within the protocol ranges on at least 95% of the occasions.
Duration of treatment / exposure:
104 weeks
Frequency of treatment:
6 h/day, 5 days/week
Post exposure period:
Satellite group - 70 weeks of exposure followed by 15 (males) or 16 (females) weeks exposure free.
Remarks:
Doses / Concentrations:
0, 50, 200 or 600 ppm (v/v)
Basis:
other: target concentrations
Remarks:
Doses / Concentrations:
49, 201 or 595 ppm
Basis:
analytical conc.
Remarks:
Doses / Concentrations:
0, 178, 714 or 2142 mg/m3 (as reported in EU RAR, 2008)
Basis:
nominal conc.
No. of animals per sex per dose:
60/sex for the main study and 30/sex for satellite groups.
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: Based on the results of an earlier 90-day study.
- Satellite animals were used for laboratory investigations (except at wk 104) and interim kills of 10 males and 10 females from each group after 52 and 82 weeks of exposure.
- Following the results of the 52 week interim kill it was decided by the sponsor to institute a 16 week recovery group. Therefore, in week 70 the remaining satellite animals not designated for sacrifice after 82 weeks of exposure plus any required from the main study to make a total of 10/sex/group underwent a recovery period until being killed in week 85 or 86.
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Immediately before and after exposure for a mortality and morbidity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animals received a detailed examination, including palpation for masses, once weekly. Any lesions or tissue masses observed at this examination were recorded for each animal and subsequent progress monitored. A record was kept to show the location, size and characteristics of any observed masses.

BODY WEIGHT: Yes
- Time schedule for examinations: Main study and satellite animals: Individual body weights were recorded pre-dose, at weekly intervals to week 28 and at 4 weekly intervals thereafter.
- Recovery animals: Individual body weights were recorded weekly during weeks 71 to 74 and at intervals of 4 weeks thereafter.

FOOD CONSUMPTION: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Blood samples were collected from satellite animals in weeks 51 and 81 and from 10 main study animals in week 104. These animals were subsequently killed and necropsied at the corresponding interim/terminal kill so that no animal was sampled on more than one occasion.
- Blood samples were collected by orbital sinus puncture under halothane anaesthesia following an overnight period without food.
- The following parameters were measured on blood collected into lithium heparin (except prothrombin time which was measured on blood collected into 3.13% trisodium citrate): haemoglobin, mean cell volume, red blood cell count and indices: (cell haemoglobin, packed cell volume, cell haemoglobin concentration), total and differential white blood cell count.

CLINICAL CHEMISTRY: Yes
- Blood samples were collected from satellite animals in weeks 51 and 81 and from 10 main study animals in week 104. These animals were subsequently killed and necropsied at the corresponding interim/terminal kill so that no animal was sampled on more than one occasion.
- Blood samples were collected by orbital sinus puncture under halothane anaesthesia following an overnight period without food .
- The following parameters were measured on blood collected into lithium heparin: glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, alkaline phosphatase, creatinine phosphokinase, sodium, potassium, chloride, calcium, glucose, blood urea nitrogen, total protein, albumin, albumin/globulin ratio.

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- A complete gross examination was performed on all animals.

ORGAN WEIGHTS: Yes
- Adrenals, gonads, kidneys, lungs, spleen, brain, heart, liver & thyroids.

HISTOPATHOLOGY: Yes
- With the exception of eyes which were fixed in Davidson's fluid ,the bone marrow smear which was fixed in methanol, and testes which were fixed in Bouin's solution, samples of the following tissues and organs were fixed in 10% neutral buffered formalin:- adipose tissue, adrenals, aorta, bone marrow smear, brain (medullary, cerebellar and cortical section), caecum, colon, duodenum, ear canal, eyes (and optic nerve), fallopian tubes, femur, ganglia (lumbar, sacral and dorsal), Harderian glands, heart, hind limbs (post-distal portions for examination of tibial and plantar nerves), ileum, jejunum, kidneys, larynx, liver, lymph nodes (mandibular, mediastinal, mesenteric and bronchial), lungs, mammary gland, muscle (quadriceps), nasal turbinates ( 6 levels), oesophagus, ovaries, pancreas, pituitary, prostate, rectum, salivary gland (submaxillary), sciatic nerves, seminal vesicles, skin, spleen, spinal cord (high cervical), stomach (glandular and forestomach), testes (with epididymides), thyroids (with parathyroids, where identified), thymus (where present), tongue, trachea, urinary bladder, uterus (including cervix), gross lesions and tissue masses.
- All tissues listed, from all animals in the control and high dose groups and from all animals that died or were killed in extremis were embedded in paraffin wax BP, sectioned at a nominal thickness of 5 µm, stained with haematoxylin and eosin and examined.
- In addition, as the respiratory tract was identified as being the target organ these tissues from animals in the low and intermediate dose groups were similarly processed and examined.
- Two histopathological evaluations were conducted. The first was done at Hazleton Laboratories, UK. A second, independent and more detailed review of the respiratory tract tissues was conducted at the TNO-CIVO laboratories in the Netherlands.

Statistics:
One-way analysis of variance, followed by pair wise t-tests of treated groups against control was performed on body weights, body weight gain, haematological and blood clinical chemistry parameters, terminal body and organ weights and relative organ weights. RBC, PCV and WBC counts and all clinical chemistry data were log-transformed before analysis. Survival probability functions were estimated by the Kaplan-Meier technique and compared by the log-rank procedure. Tumour incidence data were evaluated across groups using the Cochran-Armitage trend test. Non-neoplastic and neoplastic lesions were evaluated between groups using the Fisher's exact test.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
no effects observed
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
- There was no increase in mortality
- Clinical signs associated with treatment were rough haircoat and hunched posture seen at all concentrations.

BODY WEIGHT AND WEIGHT GAIN
- A statistically significant reduction in weight gain was noted for animals exposed to 600 ppm. By week 104 the absolute weights showed reductions in the region of approximately 15% in comparison with the controls. Body weight gain of mice exposed to 200 ppm was significantly lower than controls throughout the study. Mice in the 50 ppm group showed reductions in weight gain to about week 52, but were not different to control at the end of the study.
- During the recovery phase, male mice in the 600 ppm group and female mice in all exposure groups showed a statistically significant increase in weight gain.

ORGAN WEIGHTS
- With the exception of lung weight, the changes seen in organ weights did not fall into any biologically significant pattern.
- Increases in absolute and relative lung weights were restricted to the 600 ppm group males. At the 83-week kill, these changes were seen in the 200 and 600ppm males and 600 ppm females. At termination, significant increases were seen in 600 ppm males and females.
- Recovery animals showed no differences in absolute or relative organ weights between the groups.

HISTOPATHOLOGY: NON-NEOPLASTIC
- Exposure-related effects were confined to the respiratory tract. There was no evidence of systemic toxicity or systemic oncogenicity.
- Histopathological changes were noted in the nasal cavity. In the olfactory epithelium the main non-neoplastic changes included epithelial atrophy, regenerative effects (squamous metaplasia and respiratory metaplasia of olfactory epithelium), basal cell hyperplasia, and epithelial nest-like infolds.
- Squamous metaplasia at the naso/maxilloturbinate region was prevalent in mice.
- Nonneoplastic changes were similar in the recovery groups.

HISTOPATHOLOGY: NEOPLASTIC
- No treatment-related tumors were observed in the nose, larynx, trachea, or other tissue besides lung of mice of the main study group nor in any airway tissue or other tissue of mice in the satellite groups.
- A single moderately invasive squamous cell carcinoma was found in a major bronchus of the lung of a male of the 600 ppm group while a single adenocarcinoma occurred in a male of the control group.
Dose descriptor:
NOAEC
Remarks:
local
Effect level:
50 ppm
Sex:
male/female
Basis for effect level:
other: 176 mg/m3. Non-neoplastic lesions in regions of nasal cavity lined by respiratory and olfactory epithelium; statistically significant at 200 and 600 ppm. (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Dose descriptor:
NOAEC
Remarks:
systemic
Effect level:
50 ppm
Sex:
male/female
Basis for effect level:
other: 176 mg/m3. Body weight reduction at 200 and 600 ppm. (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Conclusions:
Following inhalation exposure to vapours of vinyl acetate for two years, the no observable adverse effect concentration (NOAEC) for systemic and local effects was 50 ppm in the mouse, equivalent to 176 mg/m3. (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)
Executive summary:

In a 104 week inhalation toxicity study, 4 groups of mice were exposed for 6 hours per day, 5 days/week, to vinyl acetate vapour at concentrations of 0, 50, 200 and 600 ppm v/v. Body weights were reduced throughout the two year period in mice exposed to 200 or 600 ppm but there was no overall effect on survival. Mice exposed to 200 or 600 ppm vinyl acetate developed treatment-related lesions in the nasal cavity, including degenerative lesions of the olfactory mucosa. These localised changes are considered to be indicative of respiratory irritation. One squamous cell carcinoma was found in the lung of a 600 ppm group mouse. There was no evidence of systemic oncogencity at any exposure level. At 50 ppm (v/v) there were no microscopic changes to indicate respiratory tract irritation. The no observable adverse effect concentration (NOAEC) for all effects was 50 ppm in the mouse, equivalent to 176 mg/m3. (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)

Endpoint:
carcinogenicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Reason / purpose:
reference to same study
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)
Deviations:
yes
Remarks:
clinical pathology & urinalysis from 10 animals/group at interim kills in weeks 51, 81 and 104 only.
GLP compliance:
yes
Species:
rat
Strain:
other: Crl:CD(SD)BR
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Uk Ltd, Margate, Kent, UK
- Age at study initiation: Approximately 6 weeks
- Weight at study initiation: 115.5-243.2 g (males), 127.6-189.1 g (females)
- Housing: 5/sex in stainless steel mesh cages suspended over cardboard-lined trays
- Diet: SQC Rat and Mouse Maintenance Diet No. 1, expanded (Special Diets Services, Witham, UK) ad libitum except during exposure and overnight prior to blood sample collection
- Water: Tap water ad libitum except during exposure and overnight prior to urine collection
- Acclimation period: 17 days

ENVIRONMENTAL CONDITIONS
- Temperature: 19-25°C
- Humidity: 40-70%
- Air changes (per hr): At least 15/hr
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: From: 5 January 1984 To: 6 February 1986
Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Milled steel and glass exposure chambers; volume approximately 8 m3.
- Vapour was generated by metering liquid vinyl acetate into a nebuliser within an expansion chamber of the generator module. The aerosol produced was mixed with the filtered exposure chamber air and introduced to the chamber as a vapour. The concentration of vinyl acetate in the diluent air was controlled by altering the flow rate of the metering pumps.
- The chambers reached target concentrations within 15 minutes.
- Method of holding animals in test chamber: in stainless steel wire mesh cages
- Air flow rate: Approximately 1500 to 2000 L/min
- Source and rate of air: Air flow into chambers was drawn from filtered room air.
- Temperature, humidity in chamber: Chamber temperatures maintained between 19-25°C on 96% of occasions. Chamber humidity was maintained between 40-80% on 96% of occasions.

TEST ATMOSPHERE
- Brief description of analytical method used: The concentration of vinyl acetate in all chambers was measured once every 15 min using a Sigma 4 gas chromatograph fitted with a single-loop gas injection valve and flame ionisation detector. Quantification was by comparison of peak areas with a standard mixture of vinyl acetate in nitrogen.
- Samples taken from breathing zone: yes
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
The daily mean concentrations of vinyl acetate in the low, intermediate and high dose chambers were within the following ranges: 43 to 57 ppm (v/v), 180 to 220 ppm(v/v) and 540 to 660 ppm (v/v), respectively, on at least 95% of the occasions.
The daily mean concentration of vinyl acetate in the room and control chamber did not exceed 1.9 ppm (v/v), the lower level of detection was 0.5 ppm (v/v) during the course of the study.
Duration of treatment / exposure:
104 weeks
Frequency of treatment:
6 hr/day, 5 days/week
Post exposure period:
Satellite group - 70 weeks of exposure followed by 15 (males) or 16 (females) weeks exposure free.
Remarks:
Doses / Concentrations:
0, 50.200 or 600 ppm (v/v)
Basis:
other: target concentrations
Remarks:
Doses / Concentrations:
49, 201 or 595 ppm
Basis:
analytical conc.
Remarks:
Doses / Concentrations:
0, 178, 714 or 2142 mg/m3 (as reported in EU RAR, 2008)
Basis:
nominal conc.
No. of animals per sex per dose:
60/sex for the main study and 30/sex for satellite groups.
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: Based on the results of an earlier 90-day study.
- Satellite animals were used for laboratory investigations (except at wk 104) and interim kills of 10 males and 10 females from each group after 52 and 82 weeks of exposure.
- Following the results of the 52 week interim kill it was decided by the sponsor to institute a 16 week recovery group. Therefore, in week 70 the remaining satellite animals not designated for sacrifice after 82 weeks of exposure plus any required from the main study to make a total of 10/sex/group underwent a recovery period until being killed in week 85 or 86.
Observations and examinations performed and frequency:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Immediately before and after exposure for a mortality and morbidity.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: All animals received a detailed examination, including a palpation for masses, once weekly. Any lesions or tissue masses observed at this examination were recorded for each animal and subsequent progress monitored. A record was kept to show the location, size and characteristics of any observed masses.

BODY WEIGHT: Yes
- Time schedule for examinations: Main study and satellite animals: Individual body weights were recorded pre-dose, at weekly intervals to week 28 and at 4 weekly intervals thereafter.
- Recovery animals: Individual body weights were recorded weekly during weeks 71 to 74 and at intervals of 4 weeks thereafter.

FOOD CONSUMPTION: No

WATER CONSUMPTION: No

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: Yes
- Blood samples were collected from satellite animals in weeks 51 and 81 and from 10 main study animals in week 104. These animals were subsequently killed and necropsied at the corresponding interim/terminal kill so that no animal was sampled on more than one occasion.
- Blood samples were collected by orbital sinus puncture under halothane anaesthesia following an overnight period without food.
- The following parameters were measured on blood collected into EDTA for rats (except PT which was measured on blood collected into 3.13% trisodium citrate): haemoglobin, mean cell volume, red blood cell count and indices: (cell haemoglobin, packed cell volume, cell haemoglobin concentration), total and differential white blood cell count, and prothrombin time (only in week 104).

CLINICAL CHEMISTRY: Yes
- Blood samples were collected from satellite animals in weeks 51 and 81 and from 10 main study animals in week 104. These animals were subsequently killed and necropsied at the corresponding interim/terminal kill so that no animal was sampled on more than one occasion.
- Blood samples were collected by orbital sinus puncture under halothane anaesthesia following an overnight period without food .
- The following parameters were measured on blood collected into lithium heparin anticoagulant: glutamate oxaloacetate transaminase glutamate pyruvate transaminase, alkaline phosphatise, creatinine phosphokinase, sodium, potassium, chloride, calcium, glucose, blood urea nitrogen, total protein, albumin, albumin/globulin ratio.

URINALYSIS: Yes
- Urine samples were collected overnight (about 12 hr) from satellite animals in weeks 51 and 81 and from 10 main study animals in week 104. Immediately after exposure on the day of sampling, the rats were allowed free access to food and water for approximately 2 hr. Individual urine samples were then collected and the following parameters were measured: volume, specific gravity, pH, protein, glucose, ketones, bilirubin, blood, urobilinogen, reducing substances, microscopy of spun deposits.

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:
GROSS PATHOLOGY: Yes
- A complete gross examination was performed on all animals.

ORGAN WEIGHTS: Yes
- Adrenals, gonads, kidneys, lungs, spleen, brain, heart, liver, pituitary & thyroids.

HISTOPATHOLOGY: Yes
- The following tissues were submitted in appropriate fixatives: bone marrow, brain (medullary, cerebellar and cortical section), duodenum, eyes (and optic nerve), femur, Harderian glands, heart, ileum, jejunum, kidneys, larynx, lungs, mammary gland, muscle (quadriceps), nasal turbinates (4 or 6 levels), ovaries, pituitary, rectum, sciatic nerves, seminal vesicles, spinal cord (high cervical), stomach (glandular and forestomach), thyroids (with parathyroids, where identified), urinary bladder, gross lesions and tissue masses, caecum, colon, +ear canal, fallopian tubes, +ganglia (lumbar, sacral and dorsal), +hind limbs (post-distal portions for examination of tibial and plantar nerves), liver, lymph nodes (mandibular, mediastinal, mesenteric and bronchial), oesophagus, pancreas, prostate, salivary gland (submaxillary), skin, spleen, testes with epididymides, thymus (where present), tongue, trachea, uterus (including cervix), gross lesions and masses.
- All tissues listed, except for those indicated (+) from all animals in the control and high dose groups and from all animals that died or were killed in extremis were routinely processed, stained and examined.
- In addition, as the respiratory tract was identified as being the target organ, these tissues from animals in the low and intermediate dose groups were similarly processed and examined. Additionally gross abnormalities were examined from some animals in these groups. At the terminal kill special attention was given to the lungs with all 5 lung lobes being sectioned longitudinally in the plane of the major airways.

OTHER:
- Initially, 4 sections of the nasal turbinates were taken and examined. The locations of the sections was more closely defined and 2 further sections (making 6 in total) were taken and examined for all rats necropsied to week 52.

Two histopatholgical evaluations were conducted. The first was done at Hazleton Laboratories, UK. A second, independent and more detailed review of the respiratory tract tissues was conducted at the TNO-CIVO laboratories in the Netherlands.


Other examinations:
Nasal lesions were recorded for 5 anatomical regions of the nasal cavity in the TNO review.
Statistics:
One-way analysis of variance, followed by pair-wise t-tests of treated groups against control was performed on body weights, body weight gain, haematological and blood clinical chemistry parameters, urine volume, terminal body and organ weights and relative organ weights. RBC, PCV and WBC counts and all clinical chemistry data were log-transformed before analysis. Urine specific gravity and pH were analysed by Kruskal-Wallis test followed by the Wilcoxon rank-sum test. Survival probability functions were estimated by the Kaplan-Meier technique and compared by the log-rank procedure. Tumour incidence data were evaluated across groups using the Cochran-Armitage trend test. Non-neoplastic and neoplastic lesions were evaluated between groups using the Fisher's exact test.
Clinical signs:
effects observed, treatment-related
Mortality:
mortality observed, treatment-related
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
no effects observed
Clinical biochemistry findings:
effects observed, treatment-related
Urinalysis findings:
effects observed, treatment-related
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
effects observed, treatment-related
Gross pathological findings:
not specified
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
effects observed, treatment-related
Details on results:
CLINICAL SIGNS AND MORTALITY
- Clinical signs associated with treatment were rough haircoat and hunched posture seen at all concentrations.
- The incidence of superficial palpable masses showed an increase in all treated female rats from week 89 onwards, and reached a maximum in week 102 (5 in controls versus 20 and 22 in low and high dose). There were no other noteworthy differences between controls and treated animals.
- There was no increase in mortality associated with vinyl acetate exposure in rats. There was an increase in survival in female rats exposed to 600 ppm (64%) compared to controls (36%) at the end of the 104 week period.

BODY WEIGHT AND WEIGHT GAIN
- A statistically significant reduction in weight gain was noted for animals exposed to 600 ppm. By week 104 the absolute weights showed reductions in the region of approximately 10% in comparison with the controls. Body weight gain of rats exposed to 50 or 200 ppm was similar to controls throughout the study.
- During the recovery phase, only high dose males showed a statistically significant improvement in weight gain.

HAEMATOLOGY AND CLINICAL CHEMISTRY
-There were no treatment related changes in haematological parameters.
- Statistically significantly lower glucose levels were noted in high dose female rats at weeks 51, 81 and 104.

URINALYSIS
- A statistically significant reduction in urine volume was noted for rats exposed to 600 ppm at weeks 51 (males only), 81 and 104 (both sexes). Concomitant effects such as increased specific gravity and decreased pH were noted but did not always reach levels of statistical significance. Similar effects (although not always statistically significant) were seen in the lower dose groups. This effect was thought to be related to reduced food and water consumption (though these parameters were not measured) and not to be toxicologically significant.

ORGAN WEIGHTS
-There was a statistically significant increase in lung weight in high dose animals.
-There were no other statistically significant effects on other organ weights.
- Recovery animals showed no differences in absolute or relative organ weights between the groups.

HISTOPATHOLOGY: NON-NEOPLASTIC
- Exposure-related effects were confined to the respiratory tract. There was no evidence of systemic toxicity or systemic oncogenicity.
-There were a number of significant nonneoplastic lesions of the respiratory tract. In the respiratory epithelium of the nasal cavity, no nonneoplastic changes were observed.
-The most prominent and consistent compound related nasal lesion consisted of olfactory atrophy (thinning of the olfactory epithelium) accompanied by basal cell hyperplasia in animals exposed to 200 or 600 ppm. In most animals exposed to 600 ppm, these changes were associated with submucosal oedema and loss of nerve bundles and Bowman's glands or with hyperplasia of glandular structures. In animals exposed to 200 ppm these lesions were located in the anterior part of the dorsal meatus whereas at 600ppm, they extended to the posterior part of the olfactory epithelium. Focal squamous metaplasia of olfactory epithelium (without keratinisation) was observed in many 600 ppm exposed rats. Regeneration of olfactory epithelium was evident in many rats exposed to 200 ppm and in some exposed to 600 ppm.
- No compound-related non-neoplastic changes were seen in the larynx or trachea.
-Treatment-related pulmonary changes were observed in rats exposed to 600 ppm and generally involved the bronchi and bronchioli (brochial exfoliation of the lining epithelium).
- in general, treatment related nasal and pulmonary lesions, similar to those seen in the main study, were present in the interim and recovery groups and occurred to about the same incidence and degree as in the main study. In the lungs, however, bronchial exfoliation was not observed in any of the interim or recovery groups.

HISTOPATHOLOGY: NEOPLASTIC (Table 1)
- A total of 12 tumours of the nasal cavity were found:
- 4 were classified as benign inverted, endophytic papillomas and were found in 600 ppm males only; 1 was classified as a benign exophytic papilloma and was found in 1 male at 200 ppm. The papillomas were characterised by pseudoacinar structures with cuboidal to columnar epithelium and multilayered epithelium with atypical cells and flattening in some areas and were seen in various parts of the nose.
- The other nasal tumours were all observed in the 600 ppm group and were classified as malignant carcinoma in situ (1 case) or squamous cell carcinomas with varying degrees of keratinisation (6 cases). Three large squamous cell carcinomas were observed in female rats exposed to 600 ppm, they obstructed one side of the nasal cavity and were characterised by invasive growth in nasal bones, soft tissues and the maxillary sinus.
- In the larynx a squamous cell carcinoma was found in 1 female rat at 600 ppm.
- No tracheal or treatment-related lung tumours were found i the terminal sacrifice animals nor were any neoplasma observed in the 53-week, 83-week or recovery groups.

Dose descriptor:
NOAEC
Remarks:
local
Effect level:
50 ppm (nominal)
Sex:
male/female
Basis for effect level:
other: 176 mg/m3. Degenerative lesions of the olfactory mucosa at 200 & 600 ppm. Squamous cell carcinoma in olfactory regions at 600 ppm. (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)
Remarks on result:
other: Effect type: carcinogenicity (migrated information)
Dose descriptor:
NOAEC
Remarks:
systemic
Effect level:
200 ppm (nominal)
Sex:
male/female
Basis for effect level:
other: 704 mg/m3. Body weight depression & olfactory squamous cell carcinoma at 600 ppm. (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)
Remarks on result:
other: Effect type: carcinogenicity (migrated information)

TABLE 1 Summary of Statistically Significant Neoplastic Changes in Lungs and Nose of Rats: Main Study (Bogdanffy et al, 1994)

Incidence of tumours (numeric)

Males

Females

Concentration (ppm)

Control

50

200

600

Control

50

200

600

Lungs 

(58)

(59)

(60)

(60)

(60)

(60)

(60)

(59)

Well-differentiated adenoma [B]

0

0

0

0

1

0

0

0

Nose

(59)

(60)

(59)

(59)

(60)

(60)

(60)

(59)

Inverted papilloma [B]

0

0

0

4

0

0

0

0

Squamous cell carcinoma [M]

0

0

0

2

0

0

0

4

Papilloma [B]

0

0

1

0

0

0

0

0

Carcinoma in situ [M]

0

0

0

1

0

0

0

0

Total benign tumours

0

0

1

4

0

0

0

0

Total malignant tumours

0

0

0

3

0

0

0

4

Total nasal tumours

0

0

1

7**

0

0

0

4

Larynx

(59)

(60)

(60)

(60)

(60)

(60)

(60)

(59)

Squamous cell carcinoma [M]

0

0

0

0

0

0

0

1

KEY:

Values in parenthesis represent the number of animals from which this tissue was examined microscopically.

[B], benign; [M], malignant.

Significance of differences in a pair wise (Fisher's) test between each treatment and control incidence is represented by ** (p < 0.01).

Conclusions:
Following inhalation exposure to vinyl acetate vapours for 2 years, the NOAEC in rats was considered to be 50 ppm v/v, equivalent to 176 mg/m3 in air for all effects. At 200 ppm and above, local degenerative lesions were present in the nasal epithelium and were indicative of irritation. (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)
Executive summary:

In a 104 week inhalation toxicity study, 4 groups of rats were exposed for 6 hours per day, 5 days/week, to vinyl acetate vapour at concentrations of 0, 50, 200 and 600 ppm v/v. Rats exposed to 200 or 600 ppm v/v vinyl acetate developed treatment-related lesions in the nasal epithelium, including degenerative lesions of the olfactory mucosa. These localised changes are considered to be indicative of respiratory irritation. There was no evidence of systemic carcinogenicity. Oncogenic responses to vinyl acetate exposure were mainly confined to the nasal cavity in rats and included squamous cell carcinoma, carcinoma in situ in olfactory regions and enophytic papilloma in respiratory regions. The tumorigenic response appeared to be nonlinear and suggests that specific risk extrapolation models should be developed for vinyl acetate.

There was no evidence of systemic toxicity at any exposure level. At 50 ppm (v/v) there were no microscopic changes to indicate respiratory tract irritation. The no observable adverse effect concentration (NOAEC) for all effects was 50 ppm in the rat, equivalent to 176 mg/m3 (RAR, 2008) and the NOAEC for systemic toxicity was 200 ppm (equivalent to 704 mg/m3 air). (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)

Endpoint:
carcinogenicity: inhalation
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Non-GLP, non guideline animal experimental study, published in peer reviewed literature, minor restrictions in design and/or reporting but otherwise adequate for assessment.
Reason / purpose:
reference to same study
Qualifier:
no guideline followed
Principles of method if other than guideline:
Evaluation of nasal epithelial cell proliferation.
GLP compliance:
not specified
Species:
rat
Strain:
Sprague-Dawley
Sex:
male
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Laboratories, Wilmington, NC, USA
- Age at study initiation: 5 -6 wks
- Weight at study initiation: 140-220 g
- Housing: stainless steel, wire-mesh cages suspended above animal cage boards.
- Diet: Purina certified rat chow 5002 (chunk) ad libitum except during exposures.
- Water: tap water ad libitum except during exposures

ENVIRONMENTAL CONDITIONS
- Temperature: 21±2ºC
- Humidity: 40-60%
- Photoperiod: 12 hrs dark / 12 hrs light

IN-LIFE DATES: Not reported
Route of administration:
inhalation: vapour
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 150 L stainless steel and glass exposure chambers operated in a one-pass flow-through mode at slight negative pressure.
- Method of holding animals in test chamber: in holding cages
- Source and rate of air: Filtered compressed air
- Method of conditioning air:
- System of generating particulates/aerosols: Filtered, compressed air passed over liquid vinyl acetate and mixed with make-up air which flowed directly to the chamber
- Temperature, humidity, oxygen content in air chamber: approximately 22-26ºC, 17-52%, 20-21%
- Air flow rate: approximately 35 L/min controlled by a Brooks mass flow controller
- Air change rate:
- Treatment of exhaust air: pulled through a sodium hydroxide trapping solution and then exhausted to a fume hood.

TEST ATMOSPHERE
- Brief description of analytical method used: Gas chromatography with flame ionisation detector
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Chamber atmospheres were analysed directly by gas chromatography and were sampled automatically every 30 minutes. Chamber concentrations were determined by comparison of peak areas with the standard curves. Concentrations of vinyl acetate and acetaldehyde were measured for each exposure chamber.
Duration of treatment / exposure:
1 day, 5 days or 4 weeks
Frequency of treatment:
5 days per week, 6 hr per day
Post exposure period:
18 hr
Remarks:
Doses / Concentrations:
0, 50, 200, 600 or 1000 ppm
Basis:
other: target concentrations
Remarks:
Doses / Concentrations:
0, 50.8, 199.6, 598.5 or 1007.3 ppm
Basis:
analytical conc.
No. of animals per sex per dose:
5
Control animals:
yes, sham-exposed
Details on study design:
- Dose selection rationale: previous 3 month and 2 year inhalation studies in rats and mice
- Rationale for animal assignment : rats assigned to test groups by computerised, stratified randomisation
Observations and examinations performed and frequency:
DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: 3 times per week

BODY WEIGHT: Yes
- Time schedule for examinations: 3 times per week

Sacrifice and pathology:
GROSS PATHOLOGY: Yes - respiratory tract tissues
HISTOPATHOLOGY: Yes - respiratory tract tissues and duodenum (positive control for BrdU procedure).
Nasal cavities were removed and fixed, decalcified, trimmed and embedded in paraffin and sections cut. Five cross sections of the nose (I-V) were evaluated for histopathological change, corresponding to levels 5, 6, 9, 11 and 23 (Mery et al 1994).
Sections of duodenum were also cut.
Other examinations:
Cell proliferation - immunocytochemistry was carried out using the single stain BrdU procedure and the avid-biotin peroxidase complex to visualise the anti-BrdU antibody.
Level 6 was chosen for evaluation as it corresponded to the region with most pronounced lesions on histopathological examination.
A total of 1000 cells of the upper airway epithelium of the 2 different regions was evaluated for BrdU incorporation.
The labelling index was expressed as the number of cells with BrdU incorporation into nuclei per 1000 cells evaluated.
Statistics:
Multiple group comparisons of bodyweight, body weight gain and labelling index were analysed by one-way analysis of variance. When the test for differences among test group means (F-test) was significant, pair wise comparisons were made with Dunnett's test.
Clinical signs:
no effects observed
Mortality:
no mortality observed
Body weight and weight changes:
effects observed, treatment-related
Food consumption and compound intake (if feeding study):
not examined
Food efficiency:
not examined
Water consumption and compound intake (if drinking water study):
not examined
Ophthalmological findings:
not examined
Haematological findings:
not examined
Clinical biochemistry findings:
not examined
Urinalysis findings:
not examined
Behaviour (functional findings):
not examined
Organ weight findings including organ / body weight ratios:
not examined
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Histopathological findings: neoplastic:
no effects observed
Details on results:
CLINICAL SIGNS AND MORTALITY
There were no reported clinical effects.

BODY WEIGHT AND WEIGHT GAIN
Mean body weights of rats exposed to 1000 ppm vinyl acetate were significantly reduced by approximately 11% compared to controls. Maximal reduction (14%) was on day 5 of exposure.
There were no significant differences in mean body weight of rats exposed to 50, 200 or 600 ppm vinyl acetate.

GROSS PATHOLOGY
There were no treatment related gross findings

HISTOPATHOLOGY: NON-NEOPLASTIC
Microscopic lesions were evident in the olfactory epithelium of rats exposed to concentrations of 600 or 1000 ppm vinyl acetate. The severity of these lesions was dose-related and decreased along an anterior-posterior gradient.
Lesions were characterised according to duration of exposure as follows:
Single exposure: degeneration, necrosis and exfoliation of olfactory epithelial cells.
5 or 20 exposures: post necrotic repair and adaptation. Lesions characterised by regenerative hyperplasia of olfactory epithelium, attenuation and/or disorganisation of the olfactory mucosa. After 20 exposures, there was degeneration and atrophy of olfactory nerve bundles in the olfactory lamina propria.

Incidences and severity of lesions in the respiratory epithelium were low in all groups. Rats exposed to 600 ppm and 2 exposed to 1000 ppm showed minimal regenerative hyperplasia of respiratory epithelium.

The nasal cavities of rats exposed to 50 or 200 ppm vinyl acetate were histologically normal.

HISTOPATHOLOGY: NEOPLASTIC
Occasional areas of squamous metaplasia in the olfactory epithelium were present in rats exposed to 1000 ppm following 5 or 20 exposures.
1 rat exposed to 1000 ppm had a minimal squamous metaplastic change in the respiratory epithelium, after 20 exposures.
CELL PROLIFERATION
A dose related increase in cell labelling was seen in both respiratory and olfactory epithelium following a single 6 hr exposure, primarily in the basal cells of the epithelial cell layer. This was statistically significantly different from controls in the 600 ppm and 1000 ppm groups.
After 5 exposures, there were no statistically significant differences in labelling index.
After 20 exposures, the response in the respiratory epithelium was similar to controls but that of the olfactory epithelium was increased at 600 and 1000 ppm. The cells proliferating in the olfactory epithelium were basal cells, although in regions of regenerating epithelium there was qualitatively more labelling of cells in the adluminal regions of the epithelium.
Dose descriptor:
NOAEC
Effect level:
200 ppm (analytical)
Sex:
male
Basis for effect level:
other: (704 mg/m3) cell proliferation in respiratory and olfactory epithelium at 600 and 1000 ppm (The conversion of ppm to mg/m3 is based on Rm of 86.09, 25 deg C, 1 atmosphere.)
Remarks on result:
other:
Remarks:
Effect type: other: Cell proliferation (migrated information)
Conclusions:
Inhalation exposure of rats to vapours of vinyl acetate at concentrations of up to 1000 ppm, for up to 20 exposures, caused evidence of cell proliferation in the olfactory and respiratory epithelium after a single exposure. A second wave of proliferation was also apparent after 20 exposures. The NOAEC was 200 ppm, equivalent to 704 mg/m3.
Executive summary:

Groups of rats were exposed to vinyl acetate by inhalation, at concentrations of 0, 50, 200, 600 or 1000 ppm, for 1, 5, or 20 exposures and killed 18 hr after the last exposure. Microscopic lesions were evident in the olfactory epithelium of rats exposed to concentrations of 600 or 1000 ppm vinyl acetate. The severity of these lesions was dose-related and decreased along an anterior-posterior gradient. The respiratory tract was evaluated for cell proliferation as assessed by BrdU uptake. In respiratory epithelium, cell proliferation rates were elevated after a single exposure but returned to control levels after 5 or 20 exposures. In olfactory epithelium, cell proliferation rates also increased after initial exposure and subsided after 5 exposures but then showed a second wave of proliferation after 20 exposures. The NOAEC for all effects was 200 ppm, equivalent to 704 mg/m3.

Endpoint conclusion
Endpoint conclusion:
adverse effect observed
Dose descriptor:
NOAEC
176 mg/m³
Study duration:
chronic
Species:
other: Rat and mouse
Quality of whole database:
Reliable studies conducted in accordance with OECD guidelines and GLP are available.
System:
other: Site of contact tissues
Organ:
nasal cavity

Carcinogenicity: via dermal route

Endpoint conclusion
Endpoint conclusion:
no study available

Mode of Action Analysis / Human Relevance Framework

Incorporation of the WHO/IPCS Template Mode of Action Analysis / Human relevance framework not applicable.

Additional information

1. CARCINOGENICITY STUDIES

INHALATION ROUTE OF EXPOSURE

In a combined chronic toxicity and carcinogenic study (Hazleton, 1988b; Bogdanffy et al., 1994b), male and female Sprague-Dawley rats and CD-1 mice were exposed by inhalation to vinyl acetate vapour in concentrations of 0, 50, 200, and 600 ppm over a period of 2 years (6 hours/day, 5 days/week). In addition to the 60 animals per sex per dose in the main study, three satellite groups of 10 of each species and sex were included for interim evaluation at week 53 and week 83 and recovery studies (70 weeks of exposure followed by 15/16 weeks of recovery).

Exposure-related tumour response was observed in the nasal cavity of rats only. Concomitant degenerative, hyperplastic and metaplastic changes of the upper respiratory tract were reported in both species. There was no evidence of treatment-related tumour response in other organs of rats and mice.

A total of 11 nasal cavity tumours classified as papilloma, squamous cell carcinoma, carcinoma in situ in olfactory regions, and papilloma and squamous cell carcinoma in respiratory or anterior non-olfactory regions were evident in 7 males (11.9%) and 4 females (6.7%) of the high dose rat group. In the intermediate dose groups, a single tumour (benign papilloma of the olfactory region) was found in a male rat. In the larynx, a squamous cell carcinoma was found in a high dose female. No treatment-related tracheal or lung tumours were observed. No respiratory tract tumours were reported in the low dose groups and a single adenoma of the lung was reported in a control female.

Drinking water route of exposure

A drinking water study reported by Hazleton (1988a) and Bogdanffy et al., (1994a) evaluated the carcinogenic potential of vinyl acetate following oral exposure. Vinyl acetate was administered to male and female Sprague Dawley rats (60 offspring/sex/dose of the main study and 10 offspring/sex/dose for interim sacrifices at week 52 and week 78) via drinking water in concentrations of 0, 200, 1000, and 5000 ppm (average vinyl acetate consumption: 0, 10, 47, and 202 mg/kg/day in males, 0, 16, 76, 302 mg/kg/day in females) over a period of 2 years.

To address potential issues associated with the hydrolysis of vinyl acetate to acetaldehyde, the test solutions were prepared daily. Rats of the 1000 and 5000 ppm groups consumed less water and rats of the 5000 ppm groups had decreased food consumption. Mean body weight gain of 5000 ppm males was significantly reduced compared to controls during the first (-11%) and second year (-17%). Mean body weight gain of 5000 ppm females was depressed (-11%) only during the second year. No treatment-related effect was seen for the mortality rates, or the test parameters of haematology, clinical chemistry or urinalysis. There was no evidence of systemic target organ toxicity.

The authors concluded that there was no treatment-related oncogenic effect. Squamous carcinomas were seen in the oral cavity of two high dose males and additional single other oral cavity tumours were observed in treated animals (fibrosarcoma in one low and mid dose males each, an odontoma in a mid dose female, and a malignant schwannoma in a high dose female). In addition, a single sarcoma was found in the stomach of a high dose male. All reported tumours were considered to be within normal rates and within the biological variation of the strain and age of rat.

Due to the reduced body weight gain at 5000 ppm, the NOAEL for non-neoplastic effects was 1000 ppm (47 mg/kg bw/d in male rats, 76 mg/kg bw/d in female rats).

An OECD Guideline carcinogenicity study (Umeda et al., 2004) conducted a similar oral study but using even higher exposure levels. Groups of 50 male and female F344/DuCrj rats received drinking water containing 0, 400, 2000, and 10000 ppm vinyl acetate (98% pure) for 104 weeks. The (analysed) dose was equivalent to 21, 98 and 442 mg/kg/d in males and 31, 146 and 575 mg/kg/d in females. Groups of 50 male and female Crj: BDF1 mice also received drinking water containing 0, 400, 2000, 10000 ppm vinyl acetate for 104 weeks (equivalent mean dose levels were 42, 202 and 989 and 63, 301 and 1418 mg/kg bw/d in males and females respectively).

In rats, higher incidences of tumour rates in the oral cavity, oesophagus, and stomach were considered to be treatment-related although at comparatively lower overall incidence (7/50 for males and 3/50 for females) than mice. The increased incidences of squamous cell carcinomas of the oral cavity in high dose males and females rats were considered relevant as spontaneous tumours of this type are rare at this site. Single squamous carcinomas were reported at 400 and 2000 ppm and were not significantly different from the control group. Preneoplastic changes were not seen in 400 and 2000 ppm groups of either sex at these levels.

In mice, tumours associated with the vinyl acetate treatment were observed in the oral cavity, oesophagus, forestomach and larynx in the high dose group. In the 10000 ppm group, squamous cell carcinomas of the oral cavity occurred in 13/50 males and 15/49 females (both significant) and squamous cell papilloma occurred in 4/50 males and 34/49 females (total incidence of squamous cell tumours in males 32% and in females 37%), but no squamous cell tumours were seen in the control and low dose groups.

The authors concluded that vinyl acetate given in drinking water to rats and mice caused squamous cell tumours in areas of the upper digestive tract with direct contact (predominantly in caudal and exterior regions of the mandible that were highly exposed) and squamous cell hyperplasia, basal cell activation and epithelial dysplasia represented early stages of squamous cell tumours. The lowest concentration associated with squamous cell tumours was 400 ppm (31 mg/kg/d) in female rats and 2000 ppm (301 mg/kg/d) in female mice.

(Note: The 400 ppm LOEL in female rats is equivalent to 31 mg/kg/d, not 21 mg/kg/d as cited in the EU RAR, 2008 (page 194) for male rats. Male rats had a tumour NOEL of 2000 ppm.)

It is important to note that unlike the Bogdanffy et al., (1994a) drinking water study, test solutions were only prepared twice weekly. Concerns have been expressed over the lack of study control groups for vinyl acetate hydrolysis (low pH drinking water group), which could explain the difference between the results reported in Bogdanffy and the Umeda studies (See Letter to Editor, J. Occup. Health Vol. 46: 249, 2004).

Also noted in the EU RAR, 2008: “The vinyl acetate concentrations in the drinking water measured 4 d after the preparation were found to decrease to 72 -80% of the initial concentrations for rats and 86 -96% for mice. The acetic acid concentration and the pH measured 4 d after the preparation were 9.2 ppm and pH 4.0 for the 400 ppm vinyl acetate-formulated drinking water, 47 ppm and pH 4.2 for the 2000 ppm water and 263 ppm and pH 3.6 for the 10000 ppm water at the end of the 4-day administration period.”

2. MODE OF ACTION INVESTIGATIONS

The potential mechanism(s) of carcinogenicity of vinyl acetate have been extensively evaluated and reported (EU RAR, 2008). Some information, key to the current understanding of the mechanism of carcinogenicity of vinyl acetate, is summarised below. Overall, the weight of evidence indicates that, for animal carcinogenicity, a threshold mechanism is applicable for vinyl acetate via both inhalation and oral routes of exposure (EU RAR, 2008).

Vinyl acetate is rapidly hydrolysed by ubiquitous carboxylesterases to two naturally occurring products, acetic acid and acetaldehyde (Hazleton 1980a, Bogdanffy & Taylor, 1993, Hinderliter et al., 2005). The local formation of acetic acid nets production of 3 mole equivalents of protons per mole of vinyl acetate and may result in an increase in intracellular acidity, which is believed to be a critical event leading to local irritation, cytotoxicity and cell proliferation. Acetaldehyde itself is subsequently oxidised, by aldehyde dehydrogenase, to acetic acid (Bogdanffy et al., 1998). As described below, acetaldehyde can be genotoxic, mutagenic and mitogenic at concentrations exceeding physiological levels and may contribute comparatively more to the tumorigenic activity of vinyl acetate than acetic acid. Prolonged exposure to acetic acid may lead to cell death, cell proliferation, hyperplasia and eventually localised tumours, via a threshold mode of action although there is some uncertainty on the role of intracellular acetic acid for non-olfactory tissues. Nonetheless, in the absence of initial cytotoxic insult and corresponding reparative or mitogenic cell proliferation, the cascade of events leading to tumour formation for olfactory tumors, cannot be completed.

The local concentration of the other vinyl acetate metabolic product, acetaldehyde, is key to understanding its toxicological effects, particularly with respect to its potential genotoxicity, tissue injury and carcinogenicity. Acetaldehyde is rapidly oxidized by the NAD+-dependent aldehyde dehydrogenase (ALDH) enzymes in liver and mucosal tissues of the respiratory tract to acetic acid. The metabolic product, acetate when buffered at physiological pH, can enter the citric acid cycle and is further processed to carbon dioxide and water (Asmussen et al., 1948; Lundquist et al., 1962). However, as a highly reactive electrophile, acetaldehyde has the potential to react with nucleophilic groups, such as amino and sulfhydryl moieties of proteins to form adducts (Tuma and Sorrell, 1985; Feron et al., 1991; Gapstur et al., 1992; Lindahl, 1992; Nicholls et al., 1992; Niemelä, 1993; Worrall et al., 1993). It is most likely that acetaldehyde-mediated toxicity is due to this reaction with cellular macromolecules prior to removal (Morris et al., 1996; Environment Canada, 2000).

Acetaldehyde, administered orally to rats, has been reported to cause hyperplastic and hyperproliferative changes in epithelia of the upper gastrointestinal tract prior to the appearance of tumours (Homann et al., 1997). Acetaldehyde is a naturally occurring substance of the metabolic pathways of animals and humans (metabolism of ethanol and sugars). Since it is present in many foods at low concentrations and also in animal and human blood and tissues, it is reasonable that an acetaldehyde concentration threshold must exist and only when the normal physiologic concentrations are exceeded might its carcinogenic potential be manifested. Thus, at high acetaldehyde concentrations, ALDH activities will not be adequate to oxidize exogenously generated acetaldehyde. Consequently, acetaldehyde accumulates intracellularly and may cause interference with protein and enzyme function, increased cell proliferative activity, increased DNA adduct formation and DNA damage (clastogenicity). Whilst it appears that acetaldehyde may express this potential in cases of metabolic overload, the exact concentration (threshold) of vinyl acetate where production of acetaldehyde and its removal starts to be imbalanced, cannot be reliably estimated from data available. However, the absence of rat nasal tumours at 50 ppm vinyl acetate in air, suggests that, at least this concentration is not sufficient to overcome cellular homeostasis (SCCNFP 2004). Similarly, tumours in the upper digestive tract are also thought to arise by the same mechanism; although there is some uncertainty with the NOAEC, a threshold of 400 ppm vinyl acetate in drinking water has been chosen for female rats.

The localised metabolism of vinyl acetate to acetic acid and acetaldehyde indicates that the site of potential tumour development induced by vinyl acetate in animal studies is the site of first entry; this may be the nasal epithelium following inhalation exposure or oral cavity/upper digestive tract following drinking water exposure. There are striking similarities in the biological consequence of acetaldehyde overload and prolonged vinyl acetate exposure. When rats were exposed to acetaldehyde by inhalation, tumours of the site of first entry, the respiratory tract, particularly adenocarcinomas and squamous-cell carcinomas of the nasal mucosa, resulted. Similarly, alcohol consumption in humans is a well-known risk factor for squamous cell cancer of the oropharynx, larynx and oesophagus, the site of first entry of the alcohol. It has been speculated that microbially produced acetaldehyde in saliva may explain the tumour-inducing effect of ethanol on these epithelia (Homann et al., 1997).

Thus there are two potential carcinogenic mechanisms that could act either alone or in concert, following vinyl acetate exposure. Clearly the environment at the site of first entry, and in particular local enzyme activities of the carboxylesterases and aldehyde dehydrogenases, will play a significant role in defining the concentrations of the metabolites, acetic acid and acetaldehyde and thus also defining which threshold mechanism may play a dominant role. The weight of evidence implicates a cytotoxicity mode of action, initiated by acetic acid formation, in the formation of the olfactory tumours in rats following prolonged inhalation exposure to vinyl acetate and a more dominant mode of action involving cellular proliferation and genotoxic contribution from acetaldehyde operative for non-olfactory respiratory tract tumour types and tumours associated with the oral exposure route.

From the limited studies available, experience from human exposure did not give indication that vinyl acetate exposure was associated to increased tumour rates (EU RAR, 2008).

The EU RAR (2008) provides an in-depth discussion of the support for a threshold mode of action.

A comprehensive and detailed review of the potential mode of action of VAM point of contact carcinogenesis and its relationship to acetaldehyde is available (Albertini, R. 2013). This paper also summarises the available data on VAM in its relation to genotoxicity and carcinogenicity. It concludes that VAM is a direct acting DNA reactive mutagen which is capable of inducing gene and chromosome level mutations but only through its acetaldehyde metabolite. Acetaldehyde itself is produced endogenously in cells as a product of metabolism and is present at physiologic concentrations. The proposed sequence of key events leading to gene mutation from VAM is the rapid cellular metabolism to acetaldehyde which results in a saturation of detoxification permitting intra-cellular acetaldehyde concentrations to increase greater than standard physiological levels. This is then followed by cellular proliferation with a shortened time for DNA repair in certain cell types resulting in mutations.

3. QUANTITATIVE ASSESSMENT – NOAEC DERIVATION

Part 1. Tumours of the olfactory region of respiratory tract

Based on the available mechanistic information, cytotoxicity appears to be a good surrogate for a threshold concentration for tumour development for the olfactory region. The table below summarises the effect and no-effect levels for cytotoxicity, hyperplasia and tumour response using the female rat as the most sensitive responder to vinyl acetate exposure. The following table is an abridged version of that presented in EU RAR, 2008.

Effective concentrations for toxic and proliferative responses to vinyl acetate at olfactory tumour sites.  

Cytotoxicity

Epithelial degeneration/necrosis/atrophy

Rat = 200 ppm

No-adverse-effect concentration for toxic effects

Rat = 50 ppm

Preneoplasias and Neoplasias

Hyperplasias Metaplasias

Rat = 200 ppm

Weak or questionable tumour response

Rat = 200 ppm

Clear tumour response

Rat = 600 ppm

Concentration without tumour response

Rat = 50 ppm

The data are derived from Hazleton 1988b (Bogdanffy et al., 1994b). Subchronic inhalation studies did not reveal any indication on proliferative response at concentrations of 50 ppm, and this concentration was verified in carcinogenicity studies. Therefore, the concentration of 50 ppm is considered as NOAEC for risk characterisation on carcinogenicity via inhalation. The concentration without adverse cytotoxicity and hence proliferative response is 50 ppm.

Part 2. The non-olfactory region of the respiratory tract

The mechanistic pathways of tumour development in the non-olfactory respiratory tract and the upper gastrointestinal tract are expected to be similar (see part 3, below). However, the respiratory epithelium of rats was less sensitive than the olfactory tissue to damage, showing no lesions up to 600 ppm (Bogdanffy, Dreef-Van den Meulen et al., 1994), the lowest concentration with respiratory epithelial damage was 1000 ppm vinyl acetate after 4 weeks of inhalation (Bogdanffy et al., 1997). Lesions of the lower parts of the respiratory tract (larynx, trachea, bronchi, bronchioli) were seen at 600 ppm vinyl acetate in rats. Since no biological response in the respiratory mucosa was observed in long-term inhalation studies at concentrations up to 200 ppm vinyl acetate exposure, it is concluded that the cellular integrity is not disrupted (EU RAR, 2008). Within the olfactory region of rats, the concentration without adverse cytotoxicity was defined as 50 ppm. This lower value is therefore considered to be protective of the other, non-olfactory areas of the respiratory tract.

Part 3. The upper digestive tract

It is proposed to select the most sensitive biological effect with putative toxicological relevance as a starting point to estimate a threshold. Since there is some uncertainty over the NOAEC from oral exposure, the vinyl acetate concentration (400 ppm) inducing the single tumours in the rat oral cavity, was chosen as the LOAEC (EU RAR, 2008). The following table is adapted from EU RAR, 2008.

Effective concentrations for proliferative responses to vinyl acetate in the upper digestive tract in rats.

Preneoplasias and Neoplasias# 

Hyperplasias Metaplasias

Mouse = 2000 ppm

Rat = 400 ppm

Weak or questionable tumour response

Mouse = 2000 ppm

Rat = 400 ppm

Clear tumour response

Rat = 10000 ppm

Concentration without tumour response

Rat LOAEC = 400 ppm

#Umeda et al., 2004. (Note: as no cytotoxicity has been identified in the upper digestive tract from rat and mouse studies up to dose levels of 24,000 ppm, cytotoxicity data has been omitted for clarity.)

4. ENDOCRINE DISRUPTION POTENTIAL

Three guideline-conform (chronic toxicity-) carcinogenicity studies, two of which were further GLP-compliant, did not provide any indication for endocrine or adverse affects on endocrine oragns cause by vinyl acetate

- Upon oral exposure via drinking water in either F344/DuCrj rats or Crj:BDF mice (Umeda et al., 2004); or

- After in utero exposure of the test animals (Sprague Dawley CD rats) that were then treated orally via the drinking water (Hazleton, 1988a; as also published in Bogdanffy et al., 1994a); or

- Upon inhalation exposure in either Sprague Dawley CD rats or Crl:CD-1(ICR)BR mice (Hazleton, 1988b; as also published in Bogdanffy et al., 1994b).

For further information, please check Section 13.2 of the IUCLID dossier.

5. CONCLUSION

The concentration of 50 ppm (176 mg/m³) is considered as a NOAEC for risk characterisation on carcinogenicity via inhalation. (The conversion of ppm to mg/m³ is based on Rm of 86.09, 25 °C, 1 atmosphere.) For the oral route, no NOAEC was estimated (400 ppm for female rats) but this value was proposed as the LOAEC for risk characterisation. However, since oral exposure is not an envisioned exposure scenario, no oral cancer risk value is to be proposed.

REFERENCES

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- Bogdanffy, M.S., Dreef-van der Meulen, H.C., Beems, R.B., Feron, V.J., Cascieri, T.C., Tyler, T.R., Vinegar, M.B., Rickard, R.W. (1994b): Chronic toxicity and oncogenicity inhalation study with vinyl acetate in the rat and mouse. Fund Appl Toxicol 23: 215-229

- Bogdanffy, M.S., Gladnick, N.L., Kegelman, T., Frame, S.R. (1997): Four-week inhalation cell proliferation study of the effects of vinyl acetate on rat nasal epithelium . Inhalation Toxicology 9: 331 -35.

- Bogdanffy, M.S., Tyler, T.R., Vinegar, M.B., Rickard, R.W., Carpanini, F.M.B., Cascieri, T.C. (1994a): Chronic toxicity and oncogenicity study with vinyl acetate in the rat: In utero exposure in drinking water. Fund Appl Toxicol 23: 206-214

- Bogdanffy, M.S., Sarangapani, R., Kimbell, J.S., Frame, S.R., Plowchalk, D.R. (1998): Analysis of vinyl acetate metabolism in rat and human nasal tissues by an in vitro gas uptake technique. Toxicol. Sci. 46: 235-246

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- Hazleton, 1988a. Vinyl acetate: 104-week oral (drinking water) combined chronic toxicity and carcinogenicity study in the rat following in utero exposure; Hazleton, UK; for: The Society of the Plastics Industry Inc, USA; Hazleton Report no 5531 -51/16; Feb 1988; study director D.C. Shaw

- Hazleton, 1988b. Vinyl acetate: 104-week oral (drinking water) combined chronic toxicity and carcinogenicity study in the rat and mouse (Volumes 1 and 2); Hazleton, UK; for: The Society of the Plastics Industry Inc, USA; Hazleton Report no 5547 -51/15; Nov 1988; study director P.E. Owen.

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- Umeda, Y., Matsumoto, M., Yamazaki, K., Ohnishi, M., Arito, H., Nagano, K., Yamamoto, S., Matsushim, T., (2004a) Carcinogenicity and chronic toxicity in mice and rats administered vinyl acetate monomer in drinking water. J. Occup. Health 46:87-99

Justification for classification or non-classification

According to Regulation (EC) No 1272/2008, the classification of vinyl acetate is Category 2, H351: Suspected of causing cancer. This is in line with the CLP Annex VI harmonised classification.