1,1-difluoroethane

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

This study is used for read-across and therefore has been assigned a reliability of 2 (reliable with restrictions). Otherwise the study has a reliability of 1 (reliable without restriction). This study was selected as the key study because the information provided for the hazard endpoint is sufficient for the purpose of classification and labeling and/or risk assessment.

Data source

Reference

Reference 1

Reference Type:

study report

Title:

Unnamed

Year:

1993

Report date:

1993

Reference 2

Reference Type:

publication

Title:

Acute, Subchronic and Developmental Toxicity and Genotoxicity of 1,1,1-trifluoroethane (HFC-143a)

Author:

Brock WJ, Trochimowicz HJ, Farr CH, Millischer R-J, and Rusch GM

Year:

1996

Bibliographic source:

Fund. Appl. Toxicol., 31:200-209

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

no

Remarks:

The study was conducted according to the guideline in effect at the time of study conduct.

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OTS 798.4350 (Inhalation Developmental Toxicity Screen)

Deviations:

no

Remarks:

The study was conducted according to the guideline in effect at the time of study conduct.

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

1,1,1-trifluoroethane

EC Number:

206-996-5

EC Name:

1,1,1-trifluoroethane

Cas Number:

420-46-2

Molecular formula:

C2H3F3

IUPAC Name:

1,1,1-trifluoroethane

Details on test material:

Purity: 99.1481-99.5807%

Test animals

Species:

rabbit

Strain:

New Zealand White

Details on test animals or test system and environmental conditions:

110 sexually mature, virgin female rabbits were received from Hazleton Research Products, Inc, Denver, PA. Animals were housed from 5 to 8 weeks prior to study initiation. Rabbits were individually housed in wire mesh cages in temperature (19-22°C) and humidity (20-42%) controlled rooms with a 12 hr light-dark cycle and approximately 10 fresh air changes per hour. They were given Purina Rabbit Chow #5322 and tap water ad libitum except during exposures. Animals were 4-5 months old upon receipt.

Administration / exposure

Route of administration:

inhalation: gas

Type of inhalation exposure (if applicable):

whole body

Vehicle:

unchanged (no vehicle)

Details on exposure:

Animals were exposed simultaneously in four 1.5m3 stainless steel and glass whole body inhalation chambers (NYU type) operated under dynamic conditions to sustain air flows of 12 to 15 air changes per hour, ensuring a minimum oxygen content of 19% and an evenly distributed exposure atmosphere. One chamber was designated for each group. The control group was exposed to clean, filtered air under conditions identical to those used for the groups exposed to the test substance. The temperature inside the exposure chamber was maintained at approximately 20°C (±2°C). Controls were set to maintain relative humidity between approximately 40 to 60%. Daily mean temperature ranged from 19.1 to 22.8°C and daily mean relative humidity ranged from 12 to 36%. The animals were rotated through the various cage positions in the chamber to ensure a similar cage location for all animals over the duration of the treatment period.

HEPA filter and an activated charcoal bed were used to pretreat room temperature air before it entered the chamber. Mass airflow through the chamber was monitored by Dwyer Magnehelic® Indicating Transmitter pressure gauges. These gauges had been calibrated fro conversion from pressure to airflow in standard liters per minute through use of a Kurz mass airflow meter. Treatment of exhaust air consisted of drawing the air through an activated charcoal bed, a HEPA filter, and a water-spray fume scrubber. Solomat probes and transmitters were used to monitor temperature and relative humidity. Oxygen content was measured by Enmet probes and meters. Mass airflow, temperature, humidity, oxygen content within the chambers were continually monitored and recorded every 30 minutes, and negative pressure within the chambers was continually monitored and recorded. Test atmospheres were generated from low pressure cylinders intowhich the test substance had been transferred from the bulk cylinder. The test material was introduced into the chambers via Linde regulator and flowmeters which were connected to each chamber with ¼” O.D. stainless steel tubing.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Samples of the chamber air were withdrawn at least 3 times during each exposure and analysed by gas chromatography with a flame ionization detector. Nominal concentrations were within 90 to 110% of analytical controls.

Details on mating procedure:

Females were artificially inseminated using pooled seman collected from 8 males from an in-house colony.

Duration of treatment / exposure:

6 hours/day

Frequency of treatment:

daily days 6-18G

Duration of test:

From day of copulation plug until day 29

No. of animals per sex per dose:

24 females

Control animals:

yes, sham-exposed

Details on study design:

- Dose selection rationale: Exposure levels were provided by the sponsor and were selected to provide a margin of safety from the lower explosivity limit.

Examinations

Maternal examinations:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: twice daily for moribundity and mortality

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Days 0 through 29 of Gestation (prior to exposure during the treatment period). Animals were also observed for signs of toxicity during the exposure period and approximately 1 hour following the completion of the exposure period. The configuration of the cages and location of the chamber windows precluded observations during exposure for some animals. However, animal cage positions were rotated on a daily basis allowing all animals to be observed periodically throughout the treatment period. All significant findings were recorded at the post-exposure observation period.

BODY WEIGHT: Yes
- Time schedule for examinations: Gestation day 0, 6 through 19 (daily), 24, and 29

FOOD CONSUMPTION AND COMPOUND INTAKE (if feeding study): Yes
- Food consumption for each animal determined and mean daily diet consumption calculated as g food/kg body weight/day: Yes

WATER CONSUMPTION AND COMPOUND INTAKE (if drinking water study): No

POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day #29
- Organs examined: The thoracic, abdominal, and pelvic cavities were opened by a ventral midline incision and the contents were examined. Maternal tissues were preserved in 10% neutral buffered formalin for possible future histopathological examination only as indicated by the gross findings. The liver, kidneys, and lungs from each dam were excised, trimmed, and weighed and all findings recorded. These organs from all animals were collected and placed in 10% neutral buffered formalin for possible future histopathological evaluation. Females which aborted during the experimental period were necropsied that day. The kidneys, lungs, and liver form all animals that aborted were weighed and then placed in 10% neutral buffered formalin. The number and location of implantation sites and corpora lutea were recorded.

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: [allper litter ]
- Skeletal examinations: Yes: [ all per litter ]
- Head examinations: Yes: [ all per litter ]

Statistics:

Statistical evaluations were conducted at p≤ 0.05 using the litter as the experimental unit when appropriate. Chi-square was used for fetal sex ratios; Fisher's Exact for malformations and variations; Mann-Whitney U-test for early and late resorptions, dead fetuses, and post implantation losses; Kruskal-Wallis test for litter proportions of intrauterine data using the litter as the experimental unit; and One-way ANOVA with Dunnett's test for corpora lutea, total implantations, viable fetuses, fetal body weights, maternal body weights and weight changes, maternal net body weight changes, gravid uterine weights, maternal food consumption, and organ weights.

Historical control data:

Historical control data are available if needed to clarify uncertainties.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
Mean body weight gain in the 40000 ppm group was significantly higher than the control group following the second day of exposure (gestation days 7-8). One female in the 2000 ppm group aborted one early resorption on day 17G. Internal findings at necropsy included a cortical cyst in the right kidney, red foci on the lungs and 2 early resorptions in utero. Brown and/or red foci on the lung and accessory spleens were observed in all groups including controls. Reddened and/or mottled lungs were observed in test animals. Dark areas in the stomach and/or reddened kidneys were also observed.

Effect levels (maternal animals)

1

Dose descriptor:

NOEC

Effect level:

> 40 000 ppm (analytical)

Basis for effect level:

other: maternal toxicity

2

Dose descriptor:

NOEC

Effect level:

> 40 000 ppm (analytical)

Basis for effect level:

other: developmental toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
One female had a completely resorbed litter (2000 ppm). The mean number of implantation sites (7.3/dam) in the 10000 ppm group was higher than the controls (5.3/dam), but was within the test facility historical control data for this parameter (4.6-9.0/dam). The concurrent control group had a notably lower mean number of viable fetuses (4.7/dam) and implantation sites (5.3/dam). These values were within, but were at the lower end of the range of the test facility historical data for these parameters (3.9-84/dam and 4.6-9.0/dam, respectively). External, soft tissue and skeletal malformations were observed in 4, 14, 5, and 5 fetuses in the 0, 2000, 10000, and 40000 ppm groups, respectively. The total malformation rate (expressed as percent per litter) was 3.1, 8.2, 3.4, and 7.1% for these same groups, respectively, which is well within the historical control range for total malformations (0.0-12.9%). No dose-relationship was apparent in either the numbers or types of malformation present in the treatment groups. No external developmental variations were observed. The soft tissue and skeletal developmental variations expressed in the treated groups were not present in a dose-dependent manner, but were generally similar to those present in the control group.

Effect levels (fetuses)

Dose descriptor:

NOEC

Effect level:

> 40 000 ppm (analytical)

Sex:

male/female

Basis for effect level:

other: developmental toxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Applicant's summary and conclusion

Conclusions:

The study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).
There was no evidence of maternal or developmental toxicity at any level tested. The NOAEC was greater than 40000 ppm for the dam and conceptus.

Executive summary:

The potential maternal and developmental toxicity of the test substance were evaluated. Three groups of 24 artificially inseminated New Zealand White rabbits were exposed to the test substance by whole body inhalation for a 6 hour period each day for 13 successive days (gestational days 6-18). Target exposure chamber concentrations were 2000, 10000, and 40000 ppm. Exposure levels were provided by the sponsor and were selected to provide a margin of safety from the lower explosivity limit. A concurrent control group, composed of 24 artificially inseminated females, was exposed to clean, filtered air on a comparable regimen. Throughout gestation, all females were observed at least twice daily for appearance and behaviour. Clinical signs, body weights, and food consumption were recorded at appropriate intervals. All surviving females were euthanized on day 29 of gestation for scheduled laparohysterectomy. The uteri and ovaries were examined and the numbers of foetuses, early and late resorptions, total implantations and corpora lutea were recorded. Mean gravid uterine weights and net body weight changes were calculated for each group. The kidneys, lungs, and liver of each female were weighed. Foetuses were weighed, sexed, and examined for external, soft tissue and skeletal malformations and developmental variations.

Survival was unaffected by compound administration at any concentration tested. A single, apparently spontaneous abortion occurred in the 2000 ppm group on gestation day 17. Upon evaluation of the clinical observations, body weights, gravid uterine weights, food consumption and organ weights, no maternal toxicity was apparent at exposure levels of 2000, 10000, and 40000 ppm test substance. No indication of developmental toxicity was exhibited upon evaluation of the intrauterine data on gestation day 29. No treatment-related malformations or developmental variations were observed. Based on these results, a concentration of 40000 ppm was considered to be the NOAEC (no observable adverse effect concentration) for maternal and developmental toxicity.