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Repeated dose toxicity: inhalation

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Administrative data

Endpoint:
sub-chronic toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
January 1981 - April 1981
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Similar to OECD 413 and GLP compliant

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1990
Report date:
1990

Materials and methods

Test guideline
Qualifier:
equivalent or similar to guideline
Guideline:
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:
yes
Limit test:
no

Test material

Constituent 1
Chemical structure
Reference substance name:
Vinyltoluene
EC Number:
246-562-2
EC Name:
Vinyltoluene
Cas Number:
25013-15-4
Molecular formula:
C9H10
IUPAC Name:
1-methyl-2-vinylbenzene
Test material form:
other: liquid
Details on test material:
- Name of test material (as cited in study report): Vinyl toluene (Dow Chemical Company (Midland, Ml))
- Physical state: liquid
- Analytical purity: approx. 99%
- Composition of test material, percentage of components: p-Vinyl toluene and m-vinyl toluene represented 31.6% and 68.4%, respectively, of the mixture
- Lot/batch No.:CH910
- Stability under test conditions: Results ofperiodic analysis by infrared spectroscopy, gas chromatography, determination of inhibitor concentration, and polymer concentration indicated no significant degradation of the study material throughout the studies.
- Storage condition of test material: Stability studies performed by gas chromatography indicated that vinyl toluene was stable as a bulk chemical when stored protected from light for 2 weeks at temperatures up to 25° C.

Refer to Appendix G and Table G1 for more details on specific chemical characterisation of the vinyl toluene used in the study.
Specific details on test material used for the study:
- Name of test material (as cited in study report): Vinyl toluene (Radian Corporation (Austin, TX))
- Physical state: liquid
- Analytical purity: approx. 99%
- Composition of test material, percentage of components: p-Vinyl toluene and m-vinyl toluene represented 31.6% and 68.4%, respectively, of the mixture
- Lot/batch No.:CH910
- Stability under test conditions: Results ofperiodic analysis by infrared spectroscopy, gas chromatography, determination of inhibitor concentration, and polymer concentration indicated no significant degradation of the study material throughout the studies.
- Storage condition of test material: Stability studies performed by gas chromatography indicated that vinyl toluene was stable as a bulk chemical when stored protected from light for 2 weeks at temperatures up to 25° C.

Refer to Appendix G and Table G1 for more details on specific chemical characterisation of the vinyl toluene used in the study.

Test animals

Species:
rat
Strain:
other: F344/N
Sex:
male/female
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Source:Charles River Breeding Laboratories (Kingston, NY)
- Age at study initiation: 7-8 weeks
- Weight at study initiation: 155 ± 2g - 159 ± 3g (males); 122 ± 1g - 125 ± 2g (females)
- Housing: Young and Bertke (Cincinnati, OH); Stainless steel Hazleton 2000* (Hazleton Systems, Aberdeen, MD)
- Diet: NIH 07 Rat and Mouse Ration (Zeigler Bros., Inc., Gardners, PAl; available ad libitum except during exposure periods. See Appendx F for more details on ingredients, nutrient composition and contaminant levels in NIH 07 rat diet
- Water: Automatic watering system (Edstrom Industries, Waterford, WI) or water bottles; available ad libitum
- Acclimation period: 20 days

ENVIRONMENTAL CONDITIONS
- Temperature 69°-81°F
- Humidity: 30%-51%
- Air changes: 10-18 room air changes/h during exposure periods
- Photoperiod: fluorescent light 12 h/d

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Vehicle:
air
Details on inhalation exposure:
GENERATION AND MONITORING OF CHAMBER CONCENTRATIONS
Vapor Generation System
Vinyl toluene vapor was generated by using either a J-tube or a gas dispersion-type system in which heated air was passed through liquid vinyl toluene. The vapor then entered the airstream near the top of the chamber and was mixed in the chamber plenum before entering the exposure area of the chamber. In the 2-year studies, secondary flasks were used to further dilute and mix the vapor with filtered air before it was channeled to the appropriate intake port of the study chambers (Hazleton 2000®, Lab Products, Inc.) (Table G2). An individual generation system contained within an enclosure specifically designed for operation under negative pressure was used for each chamber.

During the study, vinyl toluene was metered from a reservoir via a precision pump into a J-tube containing 1/4-inch glass beads. Compressed air, heated to 60-70°C, was delivered at 30-50 liters/min by a heat torch into the system. The vinyl toluene vapor then entered the airstream at the top of the chamber (Hazleton 2000®, Lab Products, Inc.) and was mixed in the chamber plenum before entering the exposure area of the chamber.

Vapor Concentration Monitoring
The concentration of vinyl toluene in the chambers and the exposure room was monitored by an automatic sampling system coupled to a gas chromatograph (Varian 2700) equipped with a flame ionization detector and a 3% SP2250 column (100% Carbowax 20M-TPA column for the short-term studies). The gas chromatographic system was standardized daily by manually injecting solutions of vinyl toluene in n-hexane. Samples from the study chamber atmospheres were pulled from the chambers by a vacuum pump.

Chamber Atmosphere Characterization
Uniformity of vapor concentration in each exposure chamber and at each position with animals present was measured periodically throughout the studies by the same system used for daily concentration monitoring to validate the use of single-port sampling for daily concentration monitoring. The coefficients of variation were always found to be less than 10%.

Tests were conducted for potential oxidation products and their possible hydration products, including vinyl toluene glycol, m-methylphenethyl alcohol, p-methylphenethyl alcohol, and a,p-dimethylbenzyl alcohol. An analytic sample was collected by passing a 400-ppm vinyl toluene atmosphere through an impinger in a dry ice/acetone bath at 12 liters/minute for 30 minutes; the sample was extracted with chloroform and analyzed by gas chromatography using a flame ionization detector and a 3% SP2250 column. None of the potential degradation products was determined to be present at concentrations greater than 0.05% of the vinyl toluene concentration.

Polymers present in a 1,000-ppm chamber atmosphere were determined after an impinger sample was condensed and the ASTM test (ASTM, 1970) and gel-permeation chromatography were performed on the condensate. The condensate was negative in the ASTM test (less than 0.1% polymer), and no high molecular weight substances were found by gel-permeation chromatography (Waters GPC columns, 254-nm ultraviolet detector, and tetrahydrofuran mobile phase).

The aerosol concentration was determined by drawing a 300-ppm vinyl toluene atmosphere through a seven-stage, multijet cascade impactor. Gas chromatographic analysis performed on the contents of the collection slip of each stage and of the final filter indicated that no aerosol was present on any given stage at greater than 0.037% (w/v) of total vinyl toluene sampled (total less than 0.26% for the seven stages).

Residual concentrations of vinyl toluene were determined in the chambers after the 6-hour exposure period. The concentration dropped rapidly; the residual chemical concentration in the chambers was generally less than the detectable level (0.01 ppm) 3 hours after the generators had been stopped and the chambers purged for 1 hour.

For more information, please refer to Appendix G (Generation and monitoring of chamber concentrations of Vinyl Toluene)
Analytical verification of doses or concentrations:
no
Duration of treatment / exposure:
13 weeks
Frequency of treatment:
6 hours per day, 5 days per week
Doses / concentrations
Remarks:
Doses / Concentrations:
0, 25, 60, 160, 400, or 1,000 ppm
Basis:
nominal conc.
No. of animals per sex per dose:
10 males and 10 females
Control animals:
yes, concurrent vehicle
Details on study design:
FIFTEEN-DAY STUDIES
Groups of five rats of each sex were exposed to air containing vinyl toluene at target concentrations of 0, 200, 400, 800, or 1,300 ppm, 6 hours per day for 10 days over a 15-day period. Rats were observed once per day and were weighed before exposure, after 1 week, and at the end of the studies. A necropsy was performed on all animals. Histopathologic examinations were performed on rats in the 1,300-ppm groups.

All rats lived to the end of the studies (Table 2). Lethargy, excessive lacrimation, and red staining (porphyrin) material around the nose and mouth were observed for rats exposed to 1,300 ppm. The mean body weights at necropsy of rats exposed to 400-1,300 ppm were 13%-19% lower than that of the controls for males and 10%-13% lower for females.

Absolute and relative liver weights were significantly increased for rats exposed to 1,300 ppm (Table I1). Four of five male rats exposed to 1,300 ppm had centrilobular necrosis and focal inflammatory cell infiltration of the liver. Minimal-to-slight centrilobular vacuolization of the liver was seen in 5/5 female rats exposed to 1,300 ppm. Dysplasia of the bronchial epithelium, chronic bronchitis, and lymphoid hyperplasia of the lung were observed in all rats exposed to 1,300 ppm. The severity was minimal to slight in males and minimal in females. Because of decreased weight gain at 1,300 ppm (19% for males, 13% for females), the top concentration selected for the 13-week studies was 1,000 ppm.

Examinations

Observations and examinations performed and frequency:
DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Animals were observed one or two times per day; moribund animals were killed. Clinical signs were recorded once per week.

BODY WEIGHT: Yes
- Time schedule for examinations: Weekly

Sacrifice and pathology:
GROSS PATHOLOGY: Yes - A necropsy was performed on all animals except those excessively autolyzed or cannibalized.
HISTOPATHOLOGY: Yes - Histologic examinations were performed on all rats in the control and 1,000-ppm groups. Tissues and groups examined are: adrenal glands, bone, brain, cecum, colon, duodenum, epididymis/seminal vesicles/prostate/testes or oviduct/ovaries/uterus, esophagus, gallbladder (mice), heart, ileum, jejunum, kidneys, larynx, liver, lungs, mammary gland, mandibular and mesenteric lymph nodes, mesentery, nasal passage, pancreas, parathyroid glands, pituitary gland, preputial or clitoral gland, rectum, salivary glands, skin, spinal cord, spleen, stomach, thymus, thyroid gland, trachea, and urinary bladder.
Statistics:
Mean ± standard error (bodyweight, liver weight); ANOVA with Dunnett’s test for multiple comparisons for liver weights.

Results and discussion

Results of examinations

Clinical signs:
effects observed, treatment-related
Description (incidence and severity):
All rats lived to the end of the studies. Excessive lacrimation, palpebral closure, and rough hair coats were seen in rats exposed to 1,000 ppm.
Mortality:
mortality observed, treatment-related
Description (incidence):
All rats lived to the end of the studies. Excessive lacrimation, palpebral closure, and rough hair coats were seen in rats exposed to 1,000 ppm.
Body weight and weight changes:
effects observed, treatment-related
Description (incidence and severity):
The final mean body weights of rats exposed to 160, 400, or 1,000 ppm were 6%, 8%, or 19% lower than that of controls for males and 5%, 6%, or 12% lower for females.
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:
effects observed, treatment-related
Description (incidence and severity):
Relative liver weights, but not absolute weights, for rats exposed to 1,000 ppm were significantly greater than those for controls.
Gross pathological findings:
no effects observed
Histopathological findings: non-neoplastic:
effects observed, treatment-related
Description (incidence and severity):
A mild nephropathy characterized by increased tubular casts was found in male rats exposed to 160, 400, or 1,000 ppm. No compound-related lesions were observed in female rats.
Histopathological findings: neoplastic:
not examined
Details on results:
All rats lived to the end of the studies (Table 3). The final mean body weights of rats exposed to 160, 400, or 1,000 ppm were 6%, 8%, or 19% lower than that of controls for males and 5%, 6%, or 12% lower for females. Excessive lacrimation, palpebral closure, and rough hair coats were seen in rats exposed to 1,000 ppm. Relative liver weights, but not absolute weights, for rats exposed to 1,000 ppm were significantly greater than those for controls (Table I2) but were not associated with histopathological changes. A mild nephropathy characterized by increased tubular casts was found in male rats exposed to 160, 400, or 1,000 ppm. No compound-related lesions were observed in female rats. There were no reports of local effects.

Effect levels

open allclose all
Dose descriptor:
LOAEC
Effect level:
160 ppm (nominal)
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic
Key result
Dose descriptor:
NOAEC
Effect level:
60 ppm
Sex:
male/female
Basis for effect level:
histopathology: non-neoplastic

Target system / organ toxicity

Critical effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
In a thirteen week inhalation study in male and female F344/N rats with vinyl toluene, the NOAEC value of both sexes was considered to be 60 ppm (289.57 mg/m3 based on molecular weight of 118 g/mol). The LOAEC value for both sexes was considered to be 160 ppm.
Executive summary:

In a subchronic inhalation toxicity study (Similar to OECD 413/GLP) Vinyl toluene (approx. 99%; p-Vinyl toluene (31.6%) and m-vinyl toluene (68.4%)) was administered to 10 male and female F344/N rats by dynamic whole body exposure at concentrations of 0, 25, 60, 160, 400, or 1,000 ppm for 6 hours per day, 5 days/week for a total of 13 weeks .


 


All rats lived to the end of the studies. The final mean body weights of rats exposed to 160, 400, or 1,000 ppm were 6%, 8%, or 19% lower than that of controls for males and 5%, 6%, or 12% lower for females. Excessive lacrimation, palpebral closure, and rough hair coats were seen in rats exposed to 1,000 ppm. Relative liver weights, but not absolute weights, for rats exposed to 1,000 ppm were significantly greater than those for controls, but were not associated with histopathological changes. A mild nephropathy characterized by increased tubular casts was found in male rats exposed to 160, 400, or 1,000 ppm. No compound-related lesions were observed in female rats. There were no reports of local effects.


 


The NOAEC value of both sexes was considered to be 60 ppm (289.57 mg/m3 based on molecular weight of 118 g/mol). The LOAEC value for both sexes was considered to be 160 ppm.


 


This subchronic inhalation toxicity study in the rat is acceptable and satisfies the guideline requirement for a subchronic inhalation study OECD 413 in the rat.