1-chloro-1,1-difluoroethane

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP-compliant near-guideline study, available as unpublished report, no restrictions, fully adequate for assessment (SIDS score: 1b)

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1978

Report date:

1978

Materials and methods

Principles of method if other than guideline:

Exposure of pregnant female rats by inhalation to different concentrations of the test material on Days 6 through 15 of gestation

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1-chloro-1,1-difluoroethane

EC Number:

200-891-8

EC Name:

1-chloro-1,1-difluoroethane

Cas Number:

75-68-3

Molecular formula:

C2H3ClF2

IUPAC Name:

1-chloro-1,1-difluoroethane

Details on test material:

Name of test material: 1-chloro 1,1-difluoroethane
The test-material was presented as compressed form in 2 gas cylinders labelled as "Aerosol Grade Isotron 142b CClF3CH3 Monochlorodifluoroethane" (purity level not stated).
Supplier: Pennwalt Corporation
Date of receipt: October 11, 1977
Batch number: LBI No. 1876

Test animals

Species:

rat

Strain:

other: CRL: COBS CD (SD) BR

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc., Portage, Michigan
- Age at study initiation: 10 weeks
- Housing: individually in wire cages in a temperature-controlled animal room
- Diet: Purina Laboratory Chow, ad libitum
- Water: fresh, ad libitum
- Acclimation period: 13 days

ENVIRONMENTAL CONDITIONS
- Photoperiod (hrs dark / hrs light): 12 / 12

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure chamber: 0.25 cubic meter stainless steel and plexiglass chamber operated under negative pressure
- Exposure generation: the test material was metered into the chamber through a calibrated glass rotameter and diluted with room air.
- Method of holding animals in test chamber: caged

TEST ATMOSPHERE
- Brief description of analytical method used: Scott Model 216 Hydrocarbon Analyzer

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Scott Model 216 Hydrocarbon Analyzer, calibrated with known concentrations of monochlorodifluoroethane, with methane used as internal standard.

Details on mating procedure:

- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1
- Proof of pregnancy: copulatory plug referred to as day 0 of pregnancy

Duration of treatment / exposure:

day 6 through day 15 of gestation

Frequency of treatment:

6 hours per day; an additional 45 min was allowed at the end fo the exposure to account for initial chamber equilibrium (determined by the air flow and the following formula: t = 4.6 (chamber volume/chamber flow)

Duration of test:

until day 20 of gestation

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm (analytical)

Doses / concentrations 2

Dose / conc.:

3 259 ppm (analytical)

Doses / concentrations 3

Dose / conc.:

9 420 ppm (analytical)

No. of animals per sex per dose:

20 mated females/dose

Control animals:

yes, concurrent vehicle

Details on study design:

Dose selection rationale: the dose levels of 2000 and 10000 ppm were proposed by sponsor, but difficulty was encountered in maintaining the lower concentration due to the absence of pressure regulators for the compressed gas tanks.

Examinations

Maternal examinations:

CLINICAL OBSERVATIONS
-The female rats were observed daily for changes in general appearance, behavior and condition

BODY WEIGHT:
-The mated female rats were weighed on Days 0, 6, 15 and 20 of gestation

FOOD CONSUMPTION
- Food consumption fwas measured during the period 0-6, 6-15 and 15-20 days of gestation

POST-MORTEM EXAMINATIONS:
- Sacrifice on gestation day 20
- Organs examined: visceral and thoracic organs.

Ovaries and uterine content:

The uterus was removed and opened. The number of implantation sites and their placement in the uterine horns, live and dead fetuses, and resorption sites were recorded.

Fetal examinations:

- Body weight.
- The fetuses were removed, examined externally for abnormalities and weighed.
- One third of the fetuses of each litter were fixed in Bouin's fluid. These were later examined for changes in the soft tissues of the head, thoracic and visceral organs. The remaining fetuses of each litter were examined for skeletal abnormalities following staining with Alizarin Red S.

Statistics:

Dunett's t-test (for difference between means with near-normal distribution); 
2x2 contengency table with Yates correction (for ratios); 
Wilcoxon Rank Sum (for discontinuous parameters).

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
There were no deaths throughout the duration of the study. All animals were normal in appearance throughout the duration of the study except one female rat (nr. 3509) in 10000 ppm dose, which was found to be without water on Day 11 of gestation and showed a red crusty material on all extremities and around the nose. The toes of all extremities were swollen and the skin on the bottom of the right fore extremity was missing. On Day 12 of gestation the distal 3 cm of the tail was missing and on Day 13 a red vaginal discharge was observed. Body weights recorded on this animal at Days 15 and 20 of gestation showed a weight loss. This change was not considered to be compound-related.
All female rats were normal in appearance at necropsy, except for 2 animals at 10000 ppm dose level, one of which showing mottled lunges and another a mottled liver. These changes were not considered significant.
Mean body weight and food consumption indicated no significant differences between control and treated pregnant rats.

Effect levels (maternal animals)

Dose descriptor:

NOAEL

Effect level:

> 9 420 ppm (analytical)

Based on:

act. ingr.

Basis for effect level:

other: maternal toxicity

Maternal abnormalities

Abnormalities:

no effects observed

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
The total number of resorption sites and the number of litters with resorptions was significantly reduced in the 2000 ppm dose level as compared to the controls. This change was not considered to be compound related. In addition, the one female (nr. 3509) in 10000 ppm group showed 17 resorption sites only. This was attributed to the poor health of the animal. The concurrent control and historical control data were considered to be acceptably similar.

- Number pregnant per dose level: 15/20, 18/20, 20/20 for control, low and high dose group, respectively
- Number aborting: none in all groups
- Number of resorptions, early/late: 15, 8 and 31 for control, low and high dose group, respectively
- Number of implantation sites: 106/106, 109/137 and 131/ 129 for control, low and high dose group, respectively (Left horn/Right horn)
- Litter size : 15/15 , 18/18 and 19/2O 20 for control, low and high dose group, respectively; there were no statistically significant difference of the mean weight of fetuses between treated and control groups
- Number viable (number alive): 197, 238 and 229 for control, low and high dose group respectively. There was no dead fetus in any group.
- Sex ratio : no statistical difference between exposed and control group

Grossly visible abnormalities:
1) external: one pup in each of the two litters in both the control and the high dose groups had subcutaneous hematomas. These changes were not considered to be compound-related.
2) soft tissue: examination of the Bouin's fixed specimens revealed no abnormalities.
3) skeletal abnormalities: 1, 1 and 2 fetuses with unsual skeletal variations for control, low and high dose group, respectively; there was also an increased incidence of delayed ossification of the supraoccipital bone in both exposure groups; this effect was not observed in the control group. However the authors stated about a number of changes including the delayed ossification of supra-occipital bone, that, while not strictly normal, such findings are frequently observed in 20-day old rat fetuses of this strain and source in their laboratory. So they clearly concluded that there was no evidence of compound-induced embryotoxicity or inhibition of fetal growth and development.

Effect levels (fetuses)

Dose descriptor:

NOAEC

Effect level:

> 9 420 ppm (analytical)

Based on:

act. ingr.

Basis for effect level:

other: Developmental toxicity : no treatment -related effects

Fetal abnormalities

Abnormalities:

effects observed, non-treatment-related

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

Exposure of pregnant female rats to average airborne concentrations of 1-dichloro 1,1difluoroethane at 3259 and 9420 ppm produced no effect on the pregnant dams. There was no evidence of compound-induced terata, variation in sex ratio, embryotoxicity or inhibition of fetal growth and development at the highest dose tested.

Executive summary:

Pregnant female rats were exposed to average graded airborne concentrations (0, 3259 and 9420 ppm) iof the test material on days 6 through 15 of gestation for 6 h. There were no changes in the dams that indicated an adverse compound-related effect. There was no evidence of compound-induced terata, variation in sex ratio, embryo toxicity or inhibition of fetal growth and development. The NOAEL for developmental and maternal toxicity was established to exceed 9420 ppm (the highest dose tested).