4-methylpent-3-en-2-one

Toxicity to reproduction

Administrative data

Endpoint:

screening for reproductive / developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1992

Report date:

1992

Reference 2

Reference Type:

publication

Title:

Unnamed

Year:

1994

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 422 (Combined Repeated Dose Toxicity Study with the Reproduction / Developmental Toxicity Screening Test)

Deviations:

yes

Remarks:

Neither deviation had a detrimental effect on the outcome of the study

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

4-methylpent-3-en-2-one

EC Number:

205-502-5

EC Name:

4-methylpent-3-en-2-one

Cas Number:

141-79-7

Molecular formula:

C6H10O

IUPAC Name:

4-methylpent-3-en-2-one

Details on test material:

- Supplier: Aldrich Chemical Co., Inc., Milwaukee, WI
- Name of test material (as cited in study report): Mesityl oxide
- Physical state: clear liquid
- Analytical purity: 98.2% (date analyzed 03/28/91); 98.4% (09/19/91); 98.2% (03/28/91); 98.4% (09/19/91)
- Lot/batch No.: CY 00502 HP

Test animals

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Laboratories, Inc. (Kingston, NY)
- Age at study initiation: The male and female rats were 66 days of age at the beginning of the pre-mating phase and 80 days of age at the beginning of the mating phase
- Weight at study initiation: The male and female rats weighed 330.3 ± 10.6 or 218.5 ± 9.2 grams (mean ± SD), respectively, at the beginning of the pre-mating phase.
- Fasting period before study: no
- Housing: During the acclimation period, animals were housed by sex in groups of five in suspended, stainless-steel, wire-mesh cages. During exposure periods, the main study animals were singly housed in multicompartmented, stainless-steel, wire-mesh cages. During nonexposure period, the rats were housed in suspended, stainless-steel, wire-mesh cages in a room separate from the exposure room. Starting at study initiation and continuing through the premating period, and following the mating period, male and female animals were singly housed during nonexposure periods. During the mating period, the animals were housed one male with one female during nonexposure periods. On the 20th day of gestation, solid bottom pans containing bedding material for nesting were put in the nonexposure cages of the female rats.
- Diet: Agwaya Prolab' Animal Diet (RMH 3200 ad libitum
- Water: municipal tap water ad libitum
- Acclimation period: 11 days

ENVIRONMENTAL CONDITIONS
- Temperature (°F): 70-76
- Humidity (%): 36-58
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: To: October 7, 1991 to May 7, 1992

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure (if applicable):

whole body

Vehicle:

air

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: 420 L stainless steel and glass inhalation chambers
- Method of holding animals in test chamber: male and female rats were singly housed and exposed simultaneously
- Air flow rate and air change rate:
Exposure Level Compressed AirFlow (Lpm) Dilution Air Flow (Lpm) Total Air Flow (Lpm) Air Changes Per
Hour
High 40 50-62 89-102 13-15
Mid 25 65-93 90-118 13-17
Low 25 62-68 89-95 12-13
Control 25 65 90 13
- Method of conditioning air: Compressed air (Kodak Park Utilities Division) was passed through silices gel (EM Science, Cherry Hill, NJ) and an oil filter (Deltech Engineering Inc., New Castle, DE).
- System of generating vapors: The test substance was metered by a Sage peristaltic pump Model No. 375A (Orion Research Inc., Cambridge, MA) [high-exposure group] from a graduated cylinder reservoir or by a Harvard syringe pump Model No. 2274 (Harvard Apparatus, South Natick, MA) [mid- and low¬exposure groups] from a 25 mL syringe into a glass distillation column (1.5" o.d. x 17" [high¬exposure group] or 1.0" o.d. x 20.5" [mid- and low-exposure groups] Ace Glass Inc., Vinland, NJ). The liquid trickled over the surface of tightly packed glass beads (4 mm diameter) within the distillation column. The beads were used to increase the surface area and enhance vaporization.
- Temperature, humidity, pressure in air chamber: Chamber temperatures for the high-, mid-, and low-exposure groups and the control group were 23.5 ± 0.6, 24.0 ± 0.6, 23.7 ± 0.7, and 23.5 ± 0.8-C (mean ± SD), respectively, and chamber relative humidity were 49.7 ± 6.9, 50.4 ± 4.4, 52.4 ± 3.7, and 43.6 ± 4.1%, respectively.
- Method of particle size determination: Nongaseous airborne material within the exposure inhalation chambers was measured using a Micro Laser Particle Counter model µLCP-301 at a sampling rate of 0.1 cmf for 10 sec. (Particle Measuring Systems, Inc., Boulder, CO). Airborne particles greater than 0.3 mm. were counted. Samples were collected from a fixed reference position within each chamber at least six days per week during the exposure. The samples collected from the test substance exposure chambers were compared to samples collected from the control chamber. The results indicated the absence of a test substance aerosol.
- Treatment of exhaust air: The effluent from all Chambers was filtered through a coarse prefilter, a HF-PA filter, and a charcoal filter.

TEST ATMOSPHERE
- Brief description of analytical method used:
Chamber vapor concentrations were monitored with an automated multipositional air sampling and analysis system. The system consisted of a MIRAN IA infrared gas analyzer (Wilks Foxboro Analytical, South Norwalk, Cl.), a Perkin-Elmer SIGMA 15 data station, and a four-port multipositional environmental sampling valve (Valco Instruments, Houston, TX). Chamber vapor samples were continuously collected, from a fixed reference position within each chamber, through the four port valves using TEFLON tubing (3/16" i.d.). On Day 10 of the study, the microprocessor of the Pekin-Elmer SIGMA 15 data station (which controls the automatic sampling, analyses, and recording of the chamber concentrations) began to malfunction, and it failed on Day 11. This did not affect the performance of the Miran, but did make it necessary to manually sample and record the concentrations for the duration of the study.
- Samples taken from breathing zone: yes

Details on mating procedure:

Male and female rats were mated 1:1 within the same exposure group. For the second mating, the high-exposure male rats were mated 1:1 with unexposed female stock rats. Female rats not inseminated during the first week of mating were placed during a second week of mating with a male which had successfully mated with a female during the first week. The study and ear tag numbers of the mated pairs were recorded. Copulation was verified through identification of sperm in vaginal smears or by appearance of a copulation plug. The morning of the day a vaginal plug or sperm was observed, was considered Day 0 of gestation. Following copulation, the male and female rats were separated and housed individually until study termination.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

see "Details on inhalation exposure"

Duration of treatment / exposure:

pre-mating (14 days), mating (1-14 days), gestation (21-22 days), and early lactation (4 days) (36 to 49 exposures (females) and 49 exposures (males))

Frequency of treatment:

six hours per day, seven days per week

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
31, 103 and 302 ppm (124, 413 and 1211 mg/m3)
Basis:
analytical conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
35, 10 and 388 ppm
Basis:
nominal conc.

No. of animals per sex per dose:

12

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale:
A range-finding inhalation study in pregnant female rats was conducted 1) to evaluate maternal toxic effects of the test substance following repeated inhalation exposures, and 2) to establish exposure levels for this study.
- Rationale for animal assignment (if not random):
All culling and randomization of the animals was done by computer-generated lists using the Automated Animal Toxicology System (AATS). The male and female rats were assigned to the study groups on the basis of body weights so that the mean body weights were similar among the groups at the start of the study. Within an exposure group, male and female rats were randomly paired for mating. For the second week of mating, the uninseminated female rats were randomly paired with a male from the same exposure group that had inseminated a female the previous week.
- Post-exposure recovery period in satellite groups: none

Positive control:

None

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
For adult animals, clinical observations were made at least once daily. Observations included, but were not limited to, examination of the hair, skin, eyes, mucous membranes, behavior patterns, respiratory patterns, feces, urine, and general activity. Post-partum neonatal observations were conducted similarly. Rats visible through chamber windows were observed for clinical signs during exposure. The dams were observed for the beginning of parturition and this date was used to calculate the gestation period. The day on which the dam had completely finished delivering was considered Day 0 post-partum.

DETAILED CLINICAL OBSERVATIONS: No

BODY WEIGHT: Yes The male rats were weighed on Days 0, 7, and weekly thereafter. Male rats were also weighed the day before euthanasia. Body weight change was calculated for Days 0-7, 7-14, 14-21, 21-28, 28-35, 35-42, 42-48, and 0-48.
The female rats were weighed on Days 0, 7, 14 and 21 of the premating/mating phase, Days 0, 7, 14, and 20 of the gestation phase, and Days 0 and 4 post-partum. Body weight change was calculated for Days 0-7, 7-14, 14-20, and 0-20 of the gestation phase and for Days 0-4 post-partum.
The unexposed female rats used in the second mating of the male high-exposure group were weighed on Days 0 and 20 of gestation. Body weight change between Days 0-20 of gestation was calculated.

FOOD CONSUMPTION: Yes
For male rats, feed consumption was determined between Days 0-7, 7-14, 28-35, 35-41, 41-42, and 42-48. Feed consumption was not determined during the mating period. The male high-exposure group did not have feed consumption determined between Days 42-48 because of the second mating period. Male rats were fasted the day before euthanasia.
For female rats from the main study, feed consumption was determined between Days 0-7, and 7-14 of the pre-mating phase, Days 0-7, 7-14, and 14-20 of the gestation phase, and Days 0-4 post-partum. Feed consumption was not determined during the mating period.
Feed consumption was not determined for the unexposed female rats from the male high¬exposure group second mating.

FOOD EFFICIENCY: No

WATER CONSUMPTION: No

Oestrous cyclicity (parental animals):

Not evaluated

Sperm parameters (parental animals):

Not evaluated

Litter observations:

For litters delivered to female rats from the main study, all pups were examined, without handling, as soon as possible after birth to determine the number of viable and stillborn pups. Daily from Day 0 to Day 4 post-partum, all pups were examined macroscopically for external abnormalities and the pups (alive and dead) were counted. On Days 0 and 4 post-partum, live pups were sexed and litter weights (live pups only) were determined. Mean pup body weights were calculated. Dead pups were fixed in 10% buffered formalin following examination.

Litters delivered to female rats from the high-exposure group second mating, were handled in a similar manner, except that the pups were euthanatized after all Day 0 post-partum data was collected.

Postmortem examinations (parental animals):

GROSS PATHOLOGY: Yes

ORGAN WEIGHTS: Yes
Wet weights of the liver, kidneys, thymus, lungs, testes, and epididymides were collected at necropsy. Paired organs were weighed together. Org/body weight ratios were calculated.

HISTOPATHOLOGY: Yes
The following tissues were collected from adult animals and were fixed in 10% buffered formalin: liver (2 sections), kidneys (1 section/kidney), adrenal glands, brain (3 sections including medulla oblongata, pons, cerebellar cortex, and cerebral cortex), heart, spleen, thymus, trachea, lungs, nasal passages, ovaries, and gross lesions. The testes and epididymides were preserved in Bouin's fixative.
Histological evaluation was conducted on the tissues listed above from control and high-exposure adult male and female animals. If abnormalities or equivocal results were seen in any of these tissues, the same tissues from lower exposure groups were examined. Histopathology was performed on significant gross lesions for all adult animals. Ovaries from any female which failed to complete its pregnancy were examined.

Statistics:

The reproductive performance of the dams was evaluated in a contingency table, using a Chi-square test (p < 0.05).
Mean litter, corpora lutes, and body weight change data were analyzed using Bartlett's test (p < 0.001), a one-way analysis of variance (ANOVA) (p < 0.05), and Tukey's studentized range (HSD) test (p < 0.05) to indicate statistical signi£icance. When Bartlett's test indicated a lack of homogeneity of variance among the groups, the ANOVA and HSD tests were performed after ranking the data. All analyses were two-tailed tests.

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

in all test substance exposure groups

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

in all test substance exposure groups

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Description (incidence and severity):

in all test substance exposure groups

Organ weight findings including organ / body weight ratios:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

in all test substance exposure groups

Other effects:

not examined

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

effects observed, treatment-related

Description (incidence and severity):

at the high-exposure level

Details on results (P0)

MORTALITY
No mortality occurred during the study.

CLINICAL SIGNS
During exposure, effects of the test substance consisted of a transient reduction in activity for the high- and mid-exposure groups, and partially closed eyes for the high-exposure group. An increased incidence of post-exposure porphyrin nasal discharge was observed for all test substance exposure groups with the incidence being slightly higher for the female rats when compared to the male rats. Additionally, post-exposure sialorrhea was observed for 3 of 12 high-exposure male rats. These clinicat signs were indicative of the irritating nature of the vaporized test substance.

BODY WEIGHT AND WEIGHT GAIN
An exposure-dependent reduction in mean body weight was observed for all male and female test substance-exposed groups from the main study.

For male rats, the reduction in mean body weights was statistically significant (p <= 0.05) on Days 7 to 35 for all test substance exposure groups, on Day 42 for the high-exposure group only, and on Day 48 for the high- and low-exposure groups when compared to the control group. Mean body weights for male rats from the mid- and low-exposure groups on Day 42 and from the mid-exposure group on Day 48, while not statistically significantly reduced, continued to be lower than those of the control group. Body weight gain was reduced (p <= 0.05) in an exposure dependent manner between Days 0 and 7 for all male test substance exposure groups and was reduced between Days 7 and 14 and Days 0 and 48 for the male high-exposure group when compared to the control group. During the study, the male high-, mid-, and low-exposure groups gained 29, 11, and 11 % less weight then the control group, respectively.

For female rats from the main study, the reduction in mean body weights was statistically significant (p <= 0.05) for all test substance exposure groups on Days 7 and 14 of the pre-mating phase, Days 0 to 20 of the gestation phase, and on Day 0 of the lactation phase when compared to the control group. Mean body weights for female rats from all test substance exposure groups on Day 4 of the lactation phase were not statistically significantly reduced when compared to the control group, but continued to be lower than those of the control group. Body weight gain, during the gestation and post-partum phases, was comparable between the female test substance exposure groups and the control group.

The body weight gain observed for the unexposed female rats from the male high-exposure group second mating exceeded the body weight gain of all test substance exposure groups, and the control group from the main study.

FOOD CONSUMPTION
For male rats, mean feed consumption was reduced (p <= 0.05) in an exposure-related manner for all test substance exposure groups on Day 7 and for the high- and mid-exposure groups on Day 14 when compared to the control group. For the remainder of the study, mean feed consumption was comparable between the male test substance exposure groups and the control group.

For female rats, mean feed consumption was reduced (p <= 0.05) in an exposure-related manner for all test substance exposure groups on Day 7 and 14 of the pre-mating phase and for the mid¬ and high-exposure groups on Day 7 of the gestation phase when compared to the control group. Feed consumption for all test substance exposure groups remained slightly lower than was observed for the control group through Day 20 of gestation; however, this reduction was not statistically significant. Feed consumption during the lactation phase for all test substance exposure groups was statistically comparable to, though slightly higher than, the control group consumption.

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS)
First Mating:
Copulation was identified in 12/12 control females, 11/12 low- and mid-exposure females and 12/12 high-exposure female rats_ The mean number of dams which delivered a litter was lower (p <= 0.05) for the high-exposure group (7/12) when compared to the control group (12/12). The mean number of dams which delivered a litter for the low- (11/12) and mid-exposure (11/12) groups were comparable to the control group.
Mean gestation length (day of gestation on which dams delivered) was longer for the mid¬exposure group (22.1 days) and high-exposure group (21.7 days) when compared to the control group (21.2 days). Mean gestation length of the low-exposure group was comparable to the control group.

The mean number of total implants and the mean percent prenatal loss (calculated using the number of total implants) for all test substance exposure groups were comparable to the control group.

Second Mating
Copulation was identified in 12/12 unexposed dams bred to the high exposure male rats. For the high-exposure male second mating, the mean number of unexposed dams which delivered a litter (10/12) was comparable to the control group (12/12) from the main study. The data for litters delivered by unexposed dams from the male high-exposure second mating, was similar to the data collected from the litters delivered to control dams from the main study.

ORGAN WEIGHTS
The mean absolute and relative testes and epididymides weights for all male test substance exposure groups were statistically comparable to the control group. However, when Rat 643 (a high-exposure male rat observed to have small testes at the time of necropsy) was eliminated from the analysis, the mean relative testes, for the high-exposure group, and mean relative epididymides weights, for the mid- and high-exposure groups, became significantly higher (p 0.05) than the mean control weights. This difference was probably the result of a decreased body weight for the mid- and high-exposure male rats rather then an effect on the testes or epididymides. All other organ weight measurements for male test substance exposure groups and all organ weight measurements for all female test substance exposure groups were comparable to the control group organ weights.

GROSS PATHOLOGY
No exposure-related changes were detected on necropsy examinations.

HISTOPATHOLOGY (PARENTAL ANIMALS)
The incidence of exposure-related changes observed in the olfactory and respiratory epithelium of the nasal passages are listed in Table below.

Table: Incidence of Exposure-related Changes Observed in the Nasal Passages
Location Male Croups Female Croups
Abnormality within the
Nasal Passages Severity Low Mid High Low Mid High
Olfactory Epithelium
Sero-cellular Exudate Minimal 3 9 9 7 9 3
Sero-cellular Exudate Minor 3
Squamous Metaplasia Minimal 1 1
Respiratory Metaplasia Minimal 2
Respiratory Epithelium
Sero-cellular Exudate Minimal 1 1
Sero-cellular Exudate Minor 2
Squa nous Metaplasia Minimal 3 1 3
Chronic Focal Inflammation Minimal 1
Chronic Focal Inflammation Minor 1

Histopathological examination of nasal passages from the control animals did not exhibit any of these changes.
The sero-cellular exudate, was composed of a proteinaceous serum-like component and a cellular component which contained a small number of polymorphonuclear leukocytes.

No other exposure-related changes were observed during the histopathology examinations.
A single high-exposure male (Rat 643) exhibited decreased spermatozoa and spermatids in the testes and decreased spermatozoa and degeneration of spermatids in the epididymides.

Effect levels (P0)

1

Key result

Dose descriptor:

NOAEC

Remarks:

reproductive toxicity

Effect level:

103 other: ppm analytical (413 mg/m3)

Based on:

other: Vapor cocentration

Sex:

male/female

Basis for effect level:

other: decreased mean number of dams which delivered at 302 ppm

2

Key result

Dose descriptor:

LOAEC

Remarks:

Parental toxicity

Effect level:

31 other: ppm analytical (124 mg/m3)

Based on:

other: vapor concentration

Sex:

male/female

Basis for effect level:

other: effects on feed consumption, body weights, body weight gain, and nasal passage histopathology

Results: P1 (second parental generation)

Effect levels (P1)

Remarks on result:

other: not examined 422

Results: F1 generation

General toxicity (F1)

Clinical signs:

not examined

Mortality / viability:

no mortality observed

Body weight and weight changes:

no effects observed

Sexual maturation:

not examined

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings:

not examined

Details on results (F1)

VIABILITY (OFFSPRING)
First mating:
The mean number of live pups per litter on Days 0 and 4 post-partum was higher (p <= 0.05) for the high-exposure group and was lower (p <= 0.05) for the low- and mid-exposure groups when compared to the control group. The mean number of dead pups per litter on Days 0 and 4 post-partum and the mean percent survival of the pups on Day 0 and between Days 0 and 4 for all test substance exposure groups were comparable to the control group.

The mean number of male pups per litter on Days 0 and 4 post-partum was higher (p <= 0.05) for the low- and high-exposure groups and was lower (p <= 0.05) for the mid-exposure group when compared to the control group. The mean percent of male pups per litter on Days 0 and 4 post-partum was higher (p <= 0.05) for the high-exposure group and was lower (p <= 0.05) for the mid-exposure group when compared to the control group. The mean percent of male pups per litter on Days 0 and 4 post-partum for the low-exposure group was comparable to the control group. The mean number of female pups per litter on Days 0 and 4 post-partum were lower (p <= 0.05) for all test substance exposure groups when compared to the control group.

BODY WEIGHT (OFFSPRING)
First mating:
Mean litter weights for all test substance exposure groups were comparable to the control group on Day 0 post-partum. On Day 4 post-partum, the mean litter weight for the mid-exposure group was lower (p <= 0.05) when compared to the control group. Mean pup body weights for the mid-exposure group on Days 0 and 4 post-partum were higher (p <= 0.05) when compared to the control group. Mean pup body weights for the low- and high-exposure groups on Days 0 and 4 post-partum, and mean pup body weight gain and mean percent pup weight gain between Days 0 and 4 for all test substance exposure groups were comparable to the control group.

GROSS PATHOLOGY (OFFSPRING)
First mating:
A single male pup from a low-exposure litter (Dam 661) was born with physical deformities including a cleft lip (right ride) which extended to the right eye, a cleft palate, anophthalmia (right side), and petechial bruises between the left eye and the back of the neck. This pup was euthanatized on Day 0 post-partum, and fixed in Bouin% fixative.

A variety of minimal abnormalities were noted with a two or three pups from each exposure group. These abnormalities included small bruises (dark areas in the skin), appearing smaller than litter mates, hypothermia, pallor, and skin discoloration. These abnormalities were not believed to be related to exposure to the test substance.

Second Mating:
Minimal abnormalities consisting of small bruines or a small cut were noted in five pups delivered to three unexposed dams from the high-exposure male second mating.

Effect levels (F1)

Key result

Dose descriptor:

NOAEC

Remarks:

Developmental toxicity

Generation:

F1

Effect level:

>= 302 other: ppm analytical (1211 mg/m3)

Based on:

other: vapor concentration

Sex:

male/female

Remarks on result:

other: changes not considered as adverse effet

Overall reproductive toxicity

Reproductive effects observed:

not specified

Applicant's summary and conclusion

Executive summary:

The potential toxicity of the mesityl oxidewas evaluated using a combined repeated dose and reproductive/developmental toxicity screeningtest. The test consisted of four phases: pre-mating (14 days), mating (1-14 days), gestation (21-22 days), and early lactation (4 days). Male and female Sprague-Dawley rats were exposed to mean chamber vapor concentrationsof 0, 31,103, or 302 ppm of the testsubstance (target concentrationsof 0, 30, 100, or 300 ppm) for six hrs/day, 7 days/week for atotal of 36 to 49 exposures for female rats (through Day 20 of gestation) and 49 exposures for male rats. Parameters examined consisted of body weight, body weight change, feed consumption, organ weights, gross pathology, histopathology of reproductive organs, reproductive performance, and litter data.

No mortality of adult animals was observed during the study. An exposure-dependent reduction (p =< 0.05) in feed consumption, and a corresponding reductionin mean body weight were observed during the pre-mating phase for male and female rats from all testsubstance exposure groups, and during the first week of the gestation phase for the high-and mid-exposure female rats. During exposure, effects of the test substance consisted of a transient reduction in activity for the high- and mid-exposure groups, and partially closed eyesfor the high-exposure group. An increased incidence of post-exposure porphyrin nasal dischargewas observed for all test substance exposure groups with the incidence-being slightly higer for the female rats when compared to the male rats. Additionally, post-exposure sialorrhea vas observed for 3 of 12 high-exposure male rats. These clinical signs were indicative of the irritating nature of the vaporized test substanse. A slight reduction in mean serum creatininelevels for all male exposure groups was not considered biologically significant since organ toxicity is associated with increases rather than decrease in serum creatinine level.

Copulation was identified in all twelve female rats from the control and high-exposure groups and in 11/2 females from the low- and md-exposure groups. The number of dams which delivered a litter was comparable between the low- (11/12) and mid-exposure (11/12) groups, and the control group (12/12), but the number of dams which delivered was reduced (p =<0.05) for the high-exposure group (7/12). To further evaluate the reproductive performance of thehigh-exposure male group, a second mating was conducted between the high-exposure male rats(after 42 exposures) and unexposed female rats. This second mating resulted in 10 of 12 unexposed female rats delivering litters. No exposure-related changes were observed during histological examination of the reproductive organs of any of the test substance exposed animals. The cause for the reduction in the number of litters produced for the high-exposure group was not determined; however, it may have seen associated with exposure of the female rats to 302 ppm of the test substance. Any effect on male reproduction should have been exacerbated after 42 exposures (versus 14 exposures for the first mating), yet the second mating of the high-exposure male rats to unexposed female rats yielded fertility rates comparable to normal values. A slight increase in relative (to body weight) testes weights in the high-exposuremale rats was considered related to the reduced body weight gain for these animals. No other organ weight changes were observed for male or female rats.

A slightly longer gestation length (p =< 0.05) was observed for the high- and mid-exposure groups, but the differences were within the normal range for length of gestation (21-23 days) within this laboratory. Thus, the increased gestation length was not considered biologically significant. The number of live pups per lifter and the number of male and female pups per litter for all test substance exposure groups were statistically different (p =<0.05) from the control group, but the differences were not consistent among the exposure groups and were not considered biologically significant. Slightly lower (p =< 0.05) mean litter weight and slightly higher (p =< 0.05) mean pup weights for the mid-exposure group were due to the lower number of pups perlitterin this group.

In summary, fourteen days of exposure to 302 ppm of the test substance reduced the number of litters produced by the mating pairs. Reproductive performance of male rats exposed to 302 ppm of the test substance for 42 days and bred to unexposed female rats was comparable to control values. The number of litters produced by the mating pairs exposed to 103 or 31 ppm of the test substance was comparable to that of the control group. The NOEL for reproductive toxicity was 103 ppm of the test substance under these test conditions.