Gas oils, paraffinic

Developmental toxicity / teratogenicity

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:

1990-08-14 to 1991-04-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: This study is classified as reliable without restriction because the study was conducted according to or similar to OECD 414.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1995

Report date:

1995

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Principles of method if other than guideline:

Information pertinent to the test guideline followed was not available.

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Heavy atmospheric gas oil (CAS# 68915-97-9)

IUPAC Name:

Heavy atmospheric gas oil (CAS# 68915-97-9)

Details on test material:

- Name of test material (as cited in study report): Heavy atmospheric gas oil (HAGO); CAS number 68915-97-9
- Test substance: Heave atomospheric gas oil
- Identification: CRU #86271
- Density: 0.95 g/mL
- Expiration date: 1991-06-01
This substance is very similar in structure to the substance being registered

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Kingston, New York
- Age at study initiation: 9 weeks old
- Weight at study initiation: No data reported
- Fasting period before study: No data reported
- Diet (e.g. ad libitum): Ad libitum
- Water (e.g. ad libitum): Ad libitum
- Acclimation period: Two weeks

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20 to 22°C
- Humidity (%): 40 to 60%
- Air changes (per hr): No data reported
- Photoperiod (hrs dark / hrs light): 12 hours light/dark cycle

IN-LIFE DATES: From: 1990-08-14 To: 1991-04-18

Administration / exposure

Route of administration:

dermal

Vehicle:

unchanged (no vehicle)

Details on exposure:

TEST SITE
- Area of exposure: Dorsal surface
- % coverage: No data reported
- Type of wrap if used: No wrap used
- Time intervals for shavings or clipplings: Clippings once weekly

REMOVAL OF TEST SUBSTANCE
- Washing (if done): No data reported
- Time after start of exposure: No data reported

USE OF RESTRAINERS FOR PREVENTING INGESTION: Yes

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

No data reported.

Details on mating procedure:

Nulliparous female rats were placed with male rats in a ratio of 1:1 and observed daily for presence of expelled vaginal sperm plugs and in situ vaginal sperm plugs. Females positive for sperm plug and spermatazoa in vaginal lavage fluid was considered at day 0 of presumed gestation and individually house. Cohabitation was continued until 84 presumed-pregnant rats were obtained.

Duration of treatment / exposure:

Gestation days 0 to 19

Frequency of treatment:

Once daily

Duration of test:

exposure from gestation days 0 to 19

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 8, 30, 125, or 500 mg/kg/day
Basis:

No. of animals per sex per dose:

12 presumed-pregnant females per dose

Control animals:

yes, sham-exposed

Details on study design:

No data reported.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Presumed-pregnant females were examined daily for signs of pathosis, abortion, premature delivery, dystocia and/or death

BODY WEIGHT: Yes
- Time schedule for examinations: Prenatal females were weighed on days 0, 3, 6, 10, 13, 16, and 20 of gestation

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 20
- Organs examined: Uterus, ovaries, thymus, liver

Ovaries and uterine content:

The ovaries and uterine content was examined after termination: Yes
Examinations included:
- Gravid uterus weight: Yes
- Number of corpora lutea: Yes
- Number of implantations: Yes
- Number of early resorptions: Yes
- Number of late resorptions: Yes

Fetal examinations:

- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: half per litter
- Head examinations: No data

Statistics:

ANOVA was used to analyse maternal biophase data, cesaria section data, and fetal data followed by group comparisons using Fisher's Exact or Dunnett's test in the prenatal and postnatal groups. ANOVA was also used to analyse haematology and clinical chemistry data followed by group comparisons using Tukey's test. Thymus and liver weights were evaluated by Tukey's test. The threshold for significance for all statistical tests is p<0.05.

Indices:

No data reported.

Historical control data:

No data reported.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Red vaginal discharge was observed in 7 of 11 pregnant females in the 500 mg/kg/day group indicative of litter resorption, and this observation was considered treatment-related. One female in the prenatal group and one female in the postnatal group also exhibited red vaginal discharge, but it was unclear whether this effect is related to treatment.

Prenatal groups treated with 125 and 500 mg/kg/day had significantly reduced body weights and body weight gains as compared to control. Postnatal groups at 125 mg/kg/day had significantly reduced body weight gain in the first half of the gestational period, but overall body weight gain was not affected. Mean maternal body weights during postpartum were not affected.

Prenatal and postnatal females exposed to 125 mg/kg/day, and prenatal females exposed to 500 mg/kg/day test material consumed less food throughout gestation as compared to controls.

At necropsy, mean absolute and relative thymus weight in prenatal females given 500 mg/kg/day were significantly lower than control, and mean relative liver weight was significantly higher than control. Postnatal group females at 500 mg/kg/day exhibited significantly increased absolute and relative liver weights.

Platelet count and segmented neutrophils were significantly reduced at dose levels of 500 mg/kg/day and 125 mg/kg/day, respectively. Aberrant serum chemistry values were found in triglycerides, total protein, albumin, calcium, urea nitrogen, and alkaline phosphatase at the 500 mg/kg/day dose level. All components showed linear relationship between dose and serum level when analysed by Pearson’s correlation coefficient, >99% confidence level.

Preimplantation loss in the 125 and 500 mg/kg/day groups were two-fold higher than control but not statistically significant. A significant increase in mean number and percent resorptions and a corresponding decrease in litter size were observed at 500 mg/kg/day, although there was no dose-response observed for this effect.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day (nominal)

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOAEL

Effect level:

30 mg/kg bw/day (nominal)

Basis for effect level:

other: developmental toxicity

3

Dose descriptor:

NOAEL

Effect level:

> 125 mg/kg bw/day (nominal)

Basis for effect level:

other: other:

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:yes

Details on embryotoxic / teratogenic effects:
Mean foetal body weights were significantly reduced in male and female foetuses at 500 mg/kg/day, and male foetuses at the 125 mg/kg/day dose level were also significantly reduced. Incomplete ossification of several skeletal structures was observed at the 125 and 500 mg/kg/day groups. These structures include nasal bones, thoracic centra, caudal centra, sternebrae, metatarsals, and pubis.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The study authors reported a NOAEL of 30 mg/kg body weight/day for maternal toxicity (decreased body weight, haematological changes) and foetal toxicity (increased resorption, incomplete skeletal ossification, decreased foetal weights, decreased litter size) following repeated dermal application of heavy atmospheric gas oil on gestational day 0-19.

Executive summary:

No studies located for other "gas" oils. However information form a dermal study in rats on a straight run gas oil (Heavy atmospheric gas oil; CAS 68915-97-9) may be used as a source of information for read across. Straight run gas oil data can be used as read-across data for other gas oils due to similar physical/chemical properties and composition.  The developmental toxicity of heavy atmospheric gas oil (straight run, high boiling distillate) was investigated by Mobil (1991) using two sets of pregnant SD rats. Animals from the first experimental series (termed the prenatal group) were treated with the test material at doses of 0 (sham control), 8, 30, 125, or 500 mg/kg body weight/day on gestation days (GD) 0-19, and sacrificed on GD 20. The second experimental series (termed the postnatal group) received 0 or 125 mg/kg body weight/day on GD 0-19, were allowed to deliver their pups normally, and both dams and pups were sacrificed on lactation day (LD) 4. In all instances the test material was applied to clipped dorsal skin (area unspecified) commencing when the dams were 11 weeks old (GD 0). There were 12 animals per treatment level, and the dams wore cardboard ("Elizabethan") collars to minimize ingestion of test material. Toxicological evaluations performed during the study included clinical observations, measurement of organ- and bodyweights, examination of reproductive organs, examination of uterine contents, serum chemical/haematological analyses and foetal evaluations (macroscopic, soft tissue, skeletal).

Daily application of heavy atmospheric gas oil produced dermal irritation (erythema, thickening of skin, oedema, flaking, scabbing) at the site of application in some animals (infrequent at the lowest dose) but no irritation scores were provided in the report and hence the impact of these reactions on pregnancy outcome cannot be judged directly. Red vaginal discharge was observed in 7 pregnant females from the 500 mg/kg body weight/day dose prenatal group, and in 1 female given 125 mg/kg body weight/day from both the prenatal and postnatal groups. This finding was considered by the study authors to be test material related and indicative of some degree of litter resorption.

Maternal body weights were decreased significantly by approx. 6% or 26% in dams from the prenatal groups treated with 125 or 500 mg/kg body weight/day, respectively, on gestation days 13 and 20. Females from the postnatal group receiving 125 mg/kg body weight/day also gained significantly less weight during the first half of the gestation period (26-75% reduction in body weight change relative to the controls). Mean relative thymus weight was significantly decreased (by approximately 53% compared to controls), and mean relative liver weight significantly increased (by approximately 17% compared to controls), in prenatal females from the 500 mg/kg body weight/day group. Serum chemistry parameters were altered in high dose animals from the prenatal series, and a linear relationship was observed between dose and serum level for triglycerides, total protein, albumin, calcium, urea nitrogen, and alkaline phosphatase (data tables unavailable for review). The study authors reported that dose-response curves for these parameters fell outside the normal range in comparison to historical data but no further details were provided. There was also a reduction of segmented neutrophils and platelets in animals treated with 125 and 500 mg/kg/bw/day heavy atmospheric gas oil, respectively (data tables unavailable for review).

Pre-implantation loss in both the 125 and 500 mg/kg body weight/day dose groups was more than twice that of the control group (16.1% and 17.6%, respectively, compared to 7.1% in controls) but did not achieve statistical significance. In contrast, a statistically significant increase in mean number/percent of resorptions (108/65.6%) with a corresponding decrease in mean litter size (3.6) was observed at the 500 mg/kg body weight/day dose level when compared to control animals (8/5.0% and 14.9, respectively). All foetuses from the 500 mg/kg body weight/day as well as the male foetuses from the 125 mg/kg bw/day groups (mean body weights 3.0 and 3.6 g, respectively) weighed significantly less than control foetuses (3.8 and 3.9 g, respectively).

Skeletal examination revealed incomplete ossification of a number of structures (nasal bones, thoracic centra, caudal centra, sternebrae, metatarsals, and pubis) in foetuses from the 125 mg/kg body weight/day (83% incidence) and 500 mg/kg body weight/day (100% incidence) groups, which were stated to be significantly increased relative to the controls (66% incidence). The incidence of all of these structural findings was significantly raised in the 500 mg/kg/day group while the occurrence of incompletely ossified nasal bones and thoracic centra was increased in the 125 mg/kg/day group.

No visceral anomalies or adverse effects on pup development or survival were reported, however pup body weight and body weight gain were significantly lower in the 125 mg/kg body weight/day group from the postnatal phase of the study (5.8 g on LD 0; 8.7 g on LD 4) relative to the controls (6.2 g on LD 0; 9.7 g on LD 4).

The study authors reported a NOAEL of 30 mg/kg body weight/day for maternal toxicity (decreased body weight, haematological changes) and foetal toxicity (increased resorption, incomplete skeletal ossification, decreased foetal weights, decreased litter size) following repeated dermal application of heavy atmospheric gas oil on GD 0-19. There were no adverse effects on postnatal development (LD 0-4). Although limited reporting means it is not possible to determine whether dermal irritation contributed to these findings, results from a sub-chronic dermal toxicity study on heavy atmospheric gas oil suggest this would not have been expected to have been present to any significant extent in dams from the 125 mg/kg body weight/day groups, indicating the effects observed at this dose level were test substance-related.