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Toxicological information

Developmental toxicity / teratogenicity

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Administrative data

Endpoint:
developmental toxicity
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1985
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Acceptable, well documented study report equivalent or similar to OECD guideline 414:

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1987
Report Date:
1987

Materials and methods

Test guideline
Qualifier:
equivalent or similar to
Guideline:
OECD Guideline 414 (Prenatal Developmental Toxicity Study)
Principles of method if other than guideline:
Pregnant Sprague-Dawley rats by single dose exposures through three separate routes of exposure; inhalation (1000 mg/m3), dermal (2000 mg/kg bw/day), oral gavage (5000 mg/kg bw/day) with exposures on gestation days 6-19.
GLP compliance:
not specified
Limit test:
yes

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Type:
Constituent
Details on test material:
Test Material - Stock 461 white oil
Manufacturer - Witco Chemical Company
Density - 0.88 g/ml
White oil was made by severely hydrotreating a dewaxed feed stock

Test animals

Species:
rat
Strain:
Sprague-Dawley
Details on test animals and environmental conditions:
TEST ANIMALS
- Source: Charles River Breeding Laboratories, Lakeview, NJ
- Diet: Purina Certified Rodent Chow #5002 (Meal)
- Water: Tap water via automatic water system ad libitum
- Acclimation period: 3 weeks
- Age at study start - Approximately 12 weeks

Administration / exposure

Route of administration:
other: Oral gavage, dermal and aerosol inhalation
Type of inhalation exposure (if applicable):
whole body
Vehicle:
water
Details on exposure:
Dermal application
Stock 461 was applied once daily to the clipped, intacti dorsal skin of the rat at a dose level of 2000 mg/kg body weight/day (maximum practical dose dermally applicable). Application sites were not covered. Stock 461 was drawn up into a 1 cc syringe (calibrated in 0.01 cc) and dispensed evenly on the the clipped skin using the tip of the syringe without the needle. To minimize ingestion, rats were fitted with cardboard Elizabethan-style collars on gestation day 0 and replaced as necessary. Collars were lined with latex tubing to minimize the development of irritation or lesions. Rats were clipped on gestation day 5 and again on day 12.

Inhalation
Presumed-pregnant rats were exposed to 1 mg/l (1000 mg/m3) of stock 461 for 6 hr/day on days 6-19 of gestation. Aerosol was generated by stainless steel Laskin nebulizers inside a glass vessel containing test substance. Setup was designed to allow the maximum proportion of respirable particles (< 5 um in diameter) to pass into the exposure chamber while larger particles impacted the walls of the glass vessel and deposited. Airstream was passed through an elutriator to remove majority of remaining large aerosol droplets. Aerosol-laden air was then mixed with incoming airstream before entering the exposure chamber. Exposures were performed in 400-liter chambers with individually housed animals. Airflow was set for at least 12 air changes per hour.

Oral gavage
21 presumed-pregnant rats were orally dosed with 5000 mg/kg body weight/day of test substance on days 6-19 of gestation. Rats were dosed with a 3 cc syringe fitted with a 16-gauge stainless steel gavage needle.
Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Oral and dermal applications - Amount of stock administered to each rat was calculated using the most recently recorded body weight for each animal, dose level and density of test substance

Inhalation exposure - Mean aerosol concentration determined gravimetrically matched the target concentration of 1 mg/l. Mass median aerodynamic diameter of particles was 1.2 um with a geometric standard deviation of 1.8 um. Particles were determined to be weill within respirable range (less than 5-10 um)
Details on mating procedure:
During the mating period, female rats which had not previously borne pups were placed with adult male rats from their corresponding treatment group in a ratio of 1:1 and observed daily for evidence of having engaged in breeding activity. Each morning during the period of cohabitation, the drop-pan papers under the animal cages were checked for the presence of expelled vaginal sperm plugs; additionally, each female rat was examined for the presence of in situ vaginal sperm plugs. Vaginal lavage fluid was obtained from each female which exhibited a vaginal sperm plug in situ or on the drop-pan papers, and was examined for the presence of spermatozoa. Females that were positive for sperm plug as well as for spermatozoa were considered to be at day 0 of presumed gestation and were placed in individual housing units. The cohabitation was continued until 122 presumed-pregnant female rats were obtained.
Duration of treatment / exposure:
Gestation days 6-19
Frequency of treatment:
Inhalation - 6 hr/day

Oral/dermal - Once/day
Duration of test:
Inlife test period - Feb 12-23 1985 to March 5-15, 1985
Doses / concentrationsopen allclose all
Remarks:
Doses / Concentrations:
2000 mg/kg bw/day
Basis:
other: Dose dermally applied
Remarks:
Doses / Concentrations:
5000 mg/kg bw/day
Basis:
actual ingested
Oral
Remarks:
Doses / Concentrations:
1000 mg/m3
Basis:
nominal conc.
Inhalation exposure
No. of animals per sex per dose:
Dermal application - 20 rats/group
Oral gavage - 21 rats/group
Inhalation exposure - 20 rats/group
Control animals:
yes, sham-exposed

Examinations

Maternal examinations:
All animals in each group were monitored at least once a day throughout gestation until sacrifice for changes in appearance, behavior, excretory function, ill-health, mortality or abortion. Body weight of each presumed-pregnant female was measured to the nearest 0.1 gram on days 0, 6, 8, 10, 13, 16, 18 and 20 of gestation. Food consumption was measured for gestation day intervals of 0-6, 6-8, 8-10, 10-13, 13-16, 16-18 and 18-20.
Ovaries and uterine content:
Ovaries and uterus of each rat were excised and examined grossly. Number of corpora lutea per ovary were counted and recorded. Uterine content of each pregnant rat were exposed and the number and location of implantations, early, mid and late resorptions, live and dead fetuses were recorded.
Fetal examinations:
Each live fetus was gendered, weighed and measured for crown-rump distance and grossly examined for external anomalies. Fetuses in each litter were distributed randomly into 2 groups: one half fixed in Bouin's solution and examined for soft tissue anomalies. The other half were peeled, eviscerated, fixed in 95% ethanol, macerated in pottasium hydroxide, differentially stained for cartilage and bone, cleared in glycerin and examined for skeletal anomalies.
Statistics:
Maternal biophase and cesarean section data and fetal data were evaluated by ANOVA followed by group comparisons using Fisher's exact or Dunnett's test. Differences following comparison of experimental data were considered statistically significant at p value < 0.05.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:
Maternal toxic effects:no effects

Details on maternal toxic effects:
Dermal irritation (erythema, flaking and scabbing) of skin was noted in the dermally exposed rats. MAternal parameters such as food consumption and body weight gain were not adversely affected by test substance exposure. Reproductive parameters such as number of implants, number of resorptions, number of viable fetuses were not affected by test substance exposure.

Effect levels (maternal animals)

open allclose all
Dose descriptor:
NOAEL
Effect level:
>= 2 000 mg/kg bw/day (actual dose received)
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEL
Effect level:
>= 5 000 mg/kg bw/day (actual dose received)
Basis for effect level:
other: maternal toxicity
Dose descriptor:
NOAEC
Effect level:
>= 1 000 mg/m³ air (nominal)
Basis for effect level:
other: maternal toxicity

Results (fetuses)

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

Details on embryotoxic / teratogenic effects:
Fetal parameters such as body weight, crown-rump length were changed compared to controls. There was no evidence of teratogenicity in external, skeletal and visceral evaluations of fetuses.

Effect levels (fetuses)

open allclose all
Dose descriptor:
NOAEL
Effect level:
>= 2 000 mg/kg bw/day (actual dose received)
Basis for effect level:
other: teratogenicity
Dose descriptor:
NOAEL
Effect level:
>= 5 000 mg/kg bw/day (actual dose received)
Basis for effect level:
other: teratogenicity
Dose descriptor:
NOAEC
Effect level:
>= 1 000 mg/m³ air (nominal)
Basis for effect level:
other: teratogenicity

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
NOAEL for teratogenicity was ≥ 2000 mg/kg bw/day (dermal), 1000 mg/m3 (inhalation) and 5000 mg/kg bw/day (oral gavage).
Executive summary:

A series of studies were conducted to evaluate the teratogenic effects of a C16-C30 light mineral oil in pregnant Sprague-Dawley rats by three separate routes of exposure; inhalation (1000 mg/m3), dermal (2000 mg/kg bw/day), oral gavage (5000 mg/kg bw/day) with exposures on gestation days 6-19. Due to low vapor pressure, the mineral oil was delivered as an aerosol for the inhalation study though aerosol particle size generated was well within the respirable range. There were no observable maternal effects (food consumption, body weight gain) irrespective of route of exposure. No adverse effects on reproductive parameters (implantation number, resorptions, fetal viability) or fetal parameters (body weight, crown-rump length) were observed in any of the studies. There was a clear lack of teratogenicity with regard to abnormal ossification, and adverse effects to external or soft tissue. Spontaneous anomalies were noted in some exposure groups but were not considered exposure related since incidence of such occurrences were similar in the sham-exposed groups. NOAEL for developmental toxicity was ≥ 2000 mg/kg bw/day (dermal), 1000 mg/m3 (inhalation) and 5000 mg/kg bw/day (oral gavage).