Ethylbenzene

Toxicity to reproduction

Administrative data

Endpoint:

one-generation reproductive toxicity

Remarks:

based on test type (migrated information)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study methodology followed was according to OECD TG 415 and in accordance with the Principles of GLP

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2003

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 415 [One-Generation Reproduction Toxicity Study (before 9 October 2017)]

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Ethylbenzene

EC Number:

202-849-4

EC Name:

Ethylbenzene

Cas Number:

100-41-4

Molecular formula:

C8H10

IUPAC Name:

ethylbenzene

Details on test material:

No data

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
- Age at study initiation: approximately 11 weeks
- Weight at study initiation: males - 341-406 g, females - 225-273 g
- Fasting period before study: no
- Housing: individually housed in suspended wire mesh cages
- Diet (e.g. ad libitum): Certified Rodent Lab Diet 5002 (PMI Nutrition International Inc.), ad libitum except during exposure
- Water (e.g. ad libitum): reverse osmosis-treated tap water, ad libitum except during exposure
- Acclimation period: 16 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): controlled to 71 ± 5 ºF
- Humidity (%): 50 ± 20% relative humidity
- Air changes (per hr): 10 air changes/hour
- Photoperiod (hrs dark / hrs light): 12 hours light/dark cycle

Administration / exposure

Route of administration:

other: inhalation exposure 6 hours/day; gavage thrice daily at 2 hour intervals

Type of inhalation exposure (if applicable):

whole body

Vehicle:

other: Vehicle: conditioned air for inhalation exposure, corn oil for oral exposure.

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Rats were exposed in 2 m3 stainless steel and glass whole-body inhalation chambers
- Method of holding animals in test chamber: not specified
- Source and rate of air: not specified
- Method of conditioning air: not specified
- System of generating particulates/aerosols: not specified
- Temperature, humidity, pressure in air chamber: not specified
- Air flow rate: not specified
- Air change rate: not specified
- Method of particle size determination: not specified
- Treatment of exhaust air: not specified

TEST ATMOSPHERE
- Brief description of analytical method used: GC
- Samples taken from breathing zone: not specified
- Monitoring of test atmosphere: Concentrations of ethylbenzene in the inhalation chambers were measured at least 10 times per exposure day by an automatic sampling system coupled to a gas chromatograph

PREPARATION OF DOSING SOLUTIONS: not specified
The inhalation/gavage females received the vehicle, corn oil, or the test article in the vehicle via oral gavage at a constant dose volume of 1 mL/kg for gavage exposure. An aliquot from each formulation was taken on the first day of dose administration and once during the gavage exposures and analyzed by GC. Stability was determined over 10 days (room temperature

VEHICLE
- Justification for use and choice of vehicle (if other than water): corn oil, (divided into 3 equal doses, approximately 2 hours apart)
- Concentration in vehicle: not specified
- Amount of vehicle (if gavage): constant dose volume of 1 mL/kg
- Lot/batch no. (if required): not specified
- Purity: not specified

Details on mating procedure:

- M/F ratio per cage: 1:1 (male:female)
- Length of cohabitation: 2 weeks
- Proof of pregnancy: [vaginal plug / sperm in vaginal smear] referred to as [day 0] of pregnancy
- Further matings after two unsuccessful attempts: [no]
- After successful mating each pregnant female was caged: individually

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Inhalation
0, 100, 500 and 1000 ppm
Actual mean exposure concentrations achieved in the chambers were:
F0 (P) generation 99, 500, and 1008 ethylbenzene.
F1 generation 101, 498, and 1002 ethylbenzene

Gavage
0, 90, 342 and 621 mg/kg
Dosing formulations were analyzed demonstrating the formulations were homogeneous and stable (up to 10 days).
Results of periodic concentration analyses returned the following mean concentration ranges (mg/L):

Target Actual
30 29.9 - 33.7
114 112 - 122
207 205 - 231

Duration of treatment / exposure:

Inhalation + gavage on lactation days 1-4 for half of the dams.
F0 (P) Daily, 6 hour-exposures. Males were exposed to test atmospheres for a minimum of 4 weeks. Females were exposed for a minimum of 2 weeks prior to mating, throughout the mating period, and from gestation day 0 through gestation day 20. At this time, one-half of the F0 females were selected for the inhalation/gavage phase and the remaining females selected for the inhalation phase only.
Inhalation only LD1-4: exposure of the F0 females was suspended from gestation day 21 through lactation day 4.

Oral gavage LD1-4: The inhalation/gavage females received the vehicle, corn oil, or the test substance in the vehicle via oral gavage. (divided into 3 equal doses, approximately 2 hours apart)

Post LD4: Inhalation exposure of the F0 females in both phases was re-initiated on lactation day 5 and continued through the day prior to euthanasia

F1 - The F1 offspring were potentially exposed to the test subtance in utero and through nursing during lactation until weaning. On lactation days 21 and 28, pups were weaned and selected (one pup/sex/litter) for inhalation exposure to the same concentration of the test subtance as their dam beginning on postnatal day 22 or 29 and lasting through postnatal day 33

Frequency of treatment:

daily

Details on study schedule:

- F0 parental animals not mated until 13 weeks
- Selection from F1 generation when pups were [21/28] days of age.
- Weight at mating of the animals in the study: males [339-443 g], females [222-301 g]

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
0 ppm (inhalation) and 0 mg/kgt (oral by gavage)
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
100 ppm (inhalation) and 90 mg/kg (30 mg/l - oral by gavage)
Basis:
analytical conc.
99 and 101 ppm (P and F1 generation - inhalation) and 29.9-33.7 mg/l (oral by gavage)

Doses / concentrations 3

Remarks:

Doses / Concentrations:
500 ppm (inhalation) and 342 mg/kg (114 mg/l - oral by gavage)
Basis:
analytical conc.
500 and 498 ppm (P and F1 generation - inhalation) and 112-122 mg/l (oral by gavage)

Doses / concentrations 4

Remarks:

Doses / Concentrations:
1000 ppm (inhalation) and 621 mg/kg (207 mg/l - oral by gavage)
Basis:
analytical conc.
1008 and 1002 ppm (P and F1 generation - inhalation) and 205-231 mg/l (oral by gavage)

No. of animals per sex per dose:

20 male +20 female/dose

Control animals:

yes

Details on study design:

No data

Positive control:

not applicable

Examinations

Parental animals: Observations and examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily (prior to exposure and within 1 hour after completion of each exposure period)

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: once weekly

BODY WEIGHT: Yes
- Time schedule for examinations: P generation - Male body weight were recorded weekly until euthanasia. Female body weight and feed consumption were recorded weekly until mating, on 8 occasions during gestation (3 day intervals) and 7 occasions during lactation (3-7 day intervals).

FOOD CONSUMPTION: Yes
- Time schedule for examinations: same as above

Oestrous cyclicity (parental animals):

None

Sperm parameters (parental animals):

None

Litter observations:

STANDARDISATION OF LITTERS
- Performed on day 4 postpartum: [yes]
- If yes, maximum of [10] pups/litter ([5]/sex/litter as nearly as possible); excess pups were killed and discarded.

PARAMETERS EXAMINED
The following parameters were examined in [F1] offspring:
[number and sex of pups, stillbirths, live births, postnatal mortality, presence of gross anomalies, weight gain, physical or behavioural abnormalities]
- Each pup was subject to a detailed physical examination on postnatal days 1, 4, 7, 14, 21 and 28.
- Pup body weights were recorded on postnatal days 1, 4, 7, 14, 21 and 28
- Weaning and selection - Each dam and litter remained housed together until weaning on lactation day 28 except for one pup/sex/litter that was weaned on postnatal day 21. The day following weaning (postnatal day 21 or 28), one male and one female per litter that were randomly selected were directly exposed to the same concentration of the test article as their dam through postnatal day 33. Direct inhalation exposure periods for the selected pups were postnatal days 22-33 (F1 postnatal days 22-33) or postnatal days 29-33 (F1 postnatal day 29-33).

GROSS EXAMINATION OF DEAD PUPS:
[yes, for external and internal abnormalities; possible cause of death was determined for pups born or found dead.]

Postmortem examinations (parental animals):

- Necropsy - Adults P(F0): All parental animals were subject to gross examination at sacrifice which was after mating for males and after weaning for females. Unscheduled deaths were also subject to necropsy. For females that delivered the number of former implantation sites were recorded. For females that failed to deliver, non-gravid uteri were opened and placed in 10% ammonium sulfide solution for detection of implantation sites. Organ weights were recorded for livers and kidneys

Postmortem examinations (offspring):

- Necropsy - Pups F1: A gross necropsy was performed on all pups on PND 28 for unselected pups and on PND 34 for pups selected for further toxicity evaluation.

Statistics:

Chi-square test with Yates' correction factor: parental mating and fertility indices
Parametric one-way analysis of variance (ANOVA) for homogeneous and normal data or Kruskal-Wallis nonparametric ANOVA for non-homogeneous or non normal data: mean parental (weekly, gestation and lactation) and F2 offspring body weight, food consumption and food efficiency data, organ weight data, maternal estrous cycle data, pre-coital intervals, gestation lengths, implantation sites, unaccounted sites, numbers of pups born, and live litter size.
Kruskal Wallis nonparametric ANOVA: mean litter proportions (percent per litter) of postnatal pup survival, sex ratio at birth (percentage of males per litter.
Nested analysis of covariance (ANCOVA): pup weights through weaning

Reproductive indices:

Mating Index, Fertility Index, Mean pre-coital interval (days) and gestation length

Offspring viability indices:

Live litter size, number of live pups and males/litter (%)

Results and discussion

Results: P0 (first parental generation)

General toxicity (P0)

Clinical signs:

no effects observed

Body weight and weight changes:

effects observed, treatment-related

Food consumption and compound intake (if feeding study):

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Other effects:

not examined

Reproductive function / performance (P0)

Reproductive function: oestrous cycle:

not examined

Reproductive function: sperm measures:

not examined

Reproductive performance:

no effects observed

Details on results (P0)

CLINICAL SIGNS AND MORTALITY (PARENTAL ANIMALS) - F0/P animals - There were no test article-related deaths. There were no test article-related clinical observations.

BODY WEIGHT AND FOOD CONSUMPTION (PARENTAL ANIMALS) - F0 (P) Body weight gain was decreased in the 500 and 1000 ppm group males and females during the first week of exposure (p<0.05 or p<0.01) and continued to be reduced in the 1000 ppm group males during the second week of exposure (not statistically significant). As a result of the reduced body weight gain during the first 2 weeks of exposure, mean body weights in the 1000 ppm group F0 males were reduced 4.2-4.7% during study weeks 2-4 (p<0.05). In the F0 females the reduction was not of sufficient magnitude to produce a reduction in mean body weight relative to control. Body weight parameters were unaffected in the low exposure group.

REPRODUCTIVE PERFORMANCE (PARENTAL ANIMALS) - Ethylbenzene did not adversely affect reproductive performance in either sex.
(results given by dose group: 0, 100, 500, 1000 ppm)
- Mating index (%):
F0 males: 100, 100, 100, 95
F0 females: 100, 100, 100, 95
- Fertility index (%)
F0 males: 75, 85, 100, 95
F0 females: 75, 85, 100, 95
- Mean pre-coital interval (days)
F0: 3.4, 2.7, 3.2, 2.4
- Gestation Length
The mean length of gestation was unaffected by treatment.
F0: 22.1, 21.8, 21.9, 21.8

ORGAN WEIGHTS (PARENTAL ANIMALS) - Organ Weights (F0)
Mean liver (males and females) and kidney (males only) weights were increased in the 500 and 1000 ppm (generally statically significant, p<0.01). Relative liver weights were increased 13.1 and 26.6% in the 500 and 1000 ppm male groups, respectively. Relative kidney weights were increased 10.5 and 19.0% in the same respective groups. In females, relative liver weights were increased 21.9 and 37.6% at 500 and 1000 ppm, respectively, inhalation phase only and 14.0 and 25.8% for these same groups for inhalation/gavage phase (generally statistically significant p<0.05 or p<0.01).

GROSS PATHOLOGY (PARENTAL ANIMALS) - Necropsy Observations
At the scheduled necropsies, no macroscopic findings related to test article exposure were observed at any exposure concentration.

OTHER FINDINGS (PARENTAL ANIMALS) - Implantation sites: The mean number of implantation sites did not differ between the groups:
(by dose group: 0, 100, 500, 1000 ppm)
- F0: 15.9, 15.5, 15.7, 15.5

Effect levels (P0)

Dose descriptor:

NOAEC

Effect level:

1 000 ppm

Sex:

male/female

Basis for effect level:

other: Ethylbenzene at an exposure level of 1000 ppm did not adversely impact reproduction (F0).

Results: F1 generation

General toxicity (F1)

Clinical signs:

no effects observed

Mortality / viability:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Sexual maturation:

no effects observed

Organ weight findings including organ / body weight ratios:

not examined

Gross pathological findings:

no effects observed

Histopathological findings:

not specified

Details on results (F1)

VIABILITY (OFFSPRING) - F1 Pup Survival PND 1-4
Postnatal survival was slightly reduced from birth to postnatal day 4 in the 500 and 1000 ppm groups (inhalation phase) and in the 1000 ppm/621 mg/kg bwt/day group (inhalation/gavage phase) compared to concurrent and historical controls:
By dose group: 0/0, 100/90, 500/342, 1000/621 ppm/mg/kg bwt/day

From birth to postnatal day 4 (pre-selection): (%)
- F1 inhalation phase: 99.1, 91.7, 86.5, 84.1* (* not statistically significantly different but lower than concurrent and historical control data and occurred in presence of other adverse effects to pups, hence considered treatment-related)
- F1 Inhalation/gavage phase: 95.1, 97.2, 94.6, 88.7

F1 weanlings exposed from PND 22-33
Several exposure-related deaths were observed in the 500 (1/9M) and 1000 ppm (2/9M) group (inhalation phase) weanlings and the F1 1000 ppm/621 mg/kg bwt/day (inhalation/gavage) phase weanlings (3/9 M and 1/9F). Other deaths occured which were not considered exposure related.

F1 weanlings exposed from PND 29-33
No deaths were noted in the F1 weanlings exposed to ethylbenzene beginning on postnatal day 29 (postnatal days 29-33) at any dose level

CLINICAL SIGNS (OFFSPRING) - F1 weanlings exposed from PND 22-33. Exposure-related clinical signs were observed one hour following exposure to 500 ppm, 1000 ppm or 1000 ppm/621 mg/kg and included labored respiration, eyelids half-closed, prostration, righting difficulty, rocking, lurching, and swaying while ambulating. These findings were generally noted in the first several days of exposure only. No adverse effects were observed on clinical signs in the F1 weanlings exposed to 100 ppm of ethylbenzene alone beginning on postnatal day 22.

F1 weanlings exposed from PND 29-33
No adverse effects were observed on clinical signs in the F1 weanlings exposed either by inhalation only or by inhalation and gavage


BODY WEIGHT (OFFSPRING) - F1 weanlings exposed from PND 22-33
F1 weanlings exposed to 500 and 1000 ppm beginning on postnatal day 22 showed a reduction in mean body weight gain in both the inhalation and inhalation/gavage phases (postnatal days 22-33 animals)(p<0.05 or p<0.01). Reductions in mean body weights ranged from 3-14% in the 500 ppm animals and 9-27% in the 1000 ppm animals. Slightly reduced mean body weights were noted in the F1 weanlings exposed to 100 ppm beginning on postnatal day 22 in both the inhalation (4-14%) and inhalation/gavage (6-16%) phases. The only statistically significant difference(p<0.05) from the control group at 100 ppm was noted on postnatal day 31 for females in the inhalation phase.

F1 weanlings exposed from PND 29-33
These F1 weanlings exhibited reduced mean body weight gain at 500 or 1000 ppm in both the inhalation and inhalation/gavage phases. The differences from the control group were statistically significant (p<0.05 or p<0.01) for the inhalation only animals. At 1000 ppm by postnatal day 34, body weights were reduced by 6-13% and, at 500 ppm by postnatal day 34, body weights were reduced by 5-9%. Mean body weights and body weight gains in the F1 weanlings exposed to 100 ppm of ethylbenzene beginning on postnatal day 29 were similar to control group values.

ORGAN WEIGHTS (OFFSPRING) - no data

GROSS PATHOLOGY (OFFSPRING) - No treatment-related changes were apparent in the pups

OTHER FINDINGS (OFFSPRING)
- LITTER DATA
No statistically significant differences were present in litter parameters. Combined Phase by dose group: 0/0, 100/90, 500/342 and 1000/621 ppm/mg/kg bwt/day
- Live litter size:
F1: 14.2, 14.5, 13.8, 13.7
- No. live pups:
F1: 14.3, 14.7, 14.6, 14.4
Males/litter (%):
F1: 48.5, 48.1, 46, 49

- Pup body weight:
Pup weight reductions occurred in the 1000 ppm inhalation exposure groups and were more pronounced in the inhalation/gavage phase (14.8 and 10.9% in male and female pups, respectively, on postnatal day 28)(p<0.05 or p<0.01) than in the inhalation phase (3.4 and 4.3% in the male and female pups, respectively, on postnatal day 28) during the pre-weaning period. These results suggest that at the top dose level the gavage dosing of the dams on lactation days 1 to 4 affected the growth of the offspring

Effect levels (F1)

Dose descriptor:

NOEC

Generation:

F1

Effect level:

100 ppm

Sex:

male/female

Basis for effect level:

other: Based on evidence of reduced weight gain at 500 ppm and 1000 ppm in the F0 generation and on reduced pup survival (F1) through lactation, reductions in pup weights at 1000 ppm and to a lesser extent at 500 ppm

Overall reproductive toxicity

Reproductive effects observed:

not specified

Any other information on results incl. tables

None

Applicant's summary and conclusion

Conclusions:

Ethylbenzene at an exposure level of 1000 ppm did not adversely impact reproduction (F0). Based on evidence of reduced weight gain at 500 ppm and 1000 ppm in the F0 generation and on reduced pup survival (F1) through lactation, reductions in pup weights at 1000 ppm and to a lesser extent at 500 ppm. These effects were observed with and without gavage administration on PND's 1-4.

Clinical signs of toxicity and reduced survival and reduction in bodyweight gain were observed only in the F1 generation exposed from PND 22 particularly at the top dose level and to a lesser extent at 500 ppm.

Executive summary:

In this pilot study, 20 male and 20 female Sprague Dawley rats (P/F0 generation) were exposed via the inhalation route to vapors of ethylbenzene at levels of 100, 500 and 1000 ppm (6 hours/day); males exposed for a minimum of 4 weeks and females exposed to a minimum of 2 weeks prior to mating and via oral by gavage route at dose levels of 90, 342 and 621 mg/kg (divided into 3 equal doses, approximately 2 hours apart).

 

Analytical verification of the doses indicated a good agreement between the nominal and analytical concentrations.

 

Animals were paired on a 1:1 basis after treatment for at least 2 weeks. Each pair was examined daily and mating was confirmed by the presence of a copulatory plug or presence of sperm in a vaginal smear (assigned gestation day 0).

 

Parameters observed were clinical signs, body weights, food consumption, litter observation and pathology (gross). Oestrous cyclicity and sperm examinations were not performed during the study.

 

P/F0 generation - There were no test article-related deaths and no test article-related clinical observations. Body weight gain was decreased in the 500 and 1000 ppm group males and females during the first week of exposure (p<0.05 or p<0.01) and continued to be reduced in the 1000 ppm group males during the second week of exposure (not statistically significant). As a result of the reduced body weight gain during the first 2 weeks of exposure, mean body weights in the 1000 ppm group F0 males were reduced 4.2-4.7% during study weeks 2-4 (p<0.05). In the F0 females the reduction was not of sufficient magnitude to produce a reduction in mean body weight relative to control. Body weight parameters were unaffected in the low exposure group.

 

Ethylbenzene did not adversely affect reproductive performance in either sex and the mean length of gestation was unaffected by treatment.

 

The mean number of implantation sites did not differ between the groups.

 

At the scheduled necropsies, no macroscopic findings related to test article exposure were observed at any exposure concentration.

 

Mean liver (males and females) and kidney (males only) weights were increased in the 500 and 1000 ppm (generally statically significant, p<0.01). Relative liver weights were increased 13.1 and 26.6% in the 500 and 1000 ppm male groups, respectively. Relative kidney weights were increased 10.5 and 19.0% in the same respective groups. In females, relative liver weights were increased 21.9 and 37.6% at 500 and 1000 ppm, respectively, inhalation phase only and 14.0 and 25.8% for these same groups for inhalation/gavage phase (generally statistically significant p<0.05 or p<0.01).

 

F1 generation - Postnatal survival was slightly reduced from birth to postnatal day 4 in the 500 and 1000 ppm groups (inhalation phase) and in the 1000 ppm/621 mg/kg bwt/day group (inhalation/gavage phase) compared to concurrent and historical controls.

 

Several exposure-related deaths were observed in the 500 (1/9M) and 1000 ppm (2/9M) group (inhalation phase) weanlings and the F1 1000 ppm/621 mg/kg bwt/day (inhalation/gavage) phase weanlings (3/9 M and 1/9F) during postnatal days 22-23.

 

No deaths were noted in the F1 weanlings exposed to ethylbenzene beginning on postnatal day 29 (postnatal days 29-33) at any dose level.

 

F1 weanlings exposed from PND 22-33. Exposure-related clinical signs were observed one hour following exposure to 500 ppm, 1000 ppm or 1000 ppm/621 mg/kg and included labored respiration, eyelids half-closed, prostration, righting difficulty, rocking, lurching, and swaying while ambulating. These findings were generally noted in the first several days of exposure only. No adverse effects were observed on clinical signs in the F1 weanlings exposed to 100 ppm of ethylbenzene alone beginning on postnatal day 22.

F1 weanlings exposed from PND 29-33
No adverse effects were observed on clinical signs in the F1 weanlings exposed either by inhalation only or by inhalation and gavage.

 

F1 weanlings exposed from PND 22-33
F1 weanlings exposed to 500 and 1000 ppm beginning on postnatal day 22 showed a reduction in mean body weight gain in both the inhalation and inhalation/gavage phases (postnatal days 22-33 animals)(p<0.05 or p<0.01). Reductions in mean body weights ranged from 3-14% in the 500 ppm animals and 9-27% in the 1000 ppm animals. Slightly reduced mean body weights were noted in the F1 weanlings exposed to 100 ppm beginning on postnatal day 22 in both the inhalation (4-14%) and inhalation/gavage (6-16%) phases. The only statistically significant difference(p<0.05) from the control group at 100 ppm was noted on postnatal day 31 for females in the inhalation phase.

F1 weanlings exposed from PND 29-33
These F1 weanlings exhibited reduced mean body weight gain at 500 or 1000 ppm in both the inhalation and inhalation/gavage phases. The differences from the control group were statistically significant (p<0.05 or p<0.01) for the inhalation only animals. At 1000 ppm by postnatal day 34, body weights were reduced by 6-13% and, at 500 ppm by postnatal day 34, body weights were reduced by 5-9%. Mean body weights and body weight gains in the F1 weanlings exposed to 100 ppm of ethylbenzene beginning on postnatal day 29 were similar to control group values.

 

No statistically significant differences were present in litter parameters observed.

 

Pup weight reductions occurred in the 1000 ppm inhalation exposure groups and were more pronounced in the inhalation/gavage phase (14.8 and 10.9% in male and female pups, respectively, on postnatal day 28) (p<0.05 or p<0.01) than in the inhalation phase (3.4 and 4.3% in the male and female pups, respectively, on postnatal day 28) during the pre-weaning period. 

 

No treatment-related changes were apparent in the pups at necropsy.

 

Based on the results of the study, Ethylbenzene at an exposure level of 1000 ppm did not adversely impact reproduction (F0) and was considered as NOAEL for the P/F0 generation.

 

Based on evidence of reduced weight gain at 500 ppm and 1000 ppm in the F0 generation and on reduced pup survival (F1) through lactation, reductions in pup weights at 1000 ppm and to a lesser extent at 500 ppm, the NOEL was considered as 100 ppm.