Registration Dossier

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:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1997
Report date:
1997

Materials and methods

Test guidelineopen allclose all
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.
Qualifier:
according to guideline
Guideline:
EPA OPP 83-3 (Prenatal Developmental Toxicity Study)
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

Constituent 1
Chemical structure
Reference substance name:
Trifluoromethane
EC Number:
200-872-4
EC Name:
Trifluoromethane
Cas Number:
75-46-7
Molecular formula:
CHF3
IUPAC Name:
trifluoromethane
Details on test material:
- Purity: >99%

Test animals

Species:
rat
Strain:
other: Crl:CD®(SD)BR
Details on test animals or test system and environmental conditions:
TEST ANIMALS
- Age at study initiation: 112 days
- Weight at study initiation: Day 1 Mean Weights
Group I (0 ppm) - 256.2 g
Group II (5000 ppm) - 256.9 g
Group III (20000 ppm) - 256.5 g
Group IV (50000 ppm) - 255.5 g
- Fasting period before study: none
- Housing: All rats were housed individually in suspended, wire-mesh, stainless steel cages. Nesting material was not provided because the dams were euthanized prior to parturition.
- Diet: Purina® Certified Rodent Chow® #5002 was available ad libitum, except during exposures.
- Water: Water from United Water Delaware was available ad libitum, except during exposures.
- Acclimation period: All animals were quarantined for at least 6 days, and then released for the study by the Laboratory Animal Veterinarian.


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 23°C ± 1°C
- Humidity (%): 50 + 10%.
- Air changes (per hr): not reported
- Photoperiod (hrs dark / hrs light): 12 hr/12 hr

Administration / exposure

Route of administration:
inhalation: gas
Type of inhalation exposure (if applicable):
whole body
Vehicle:
other: air
Details on exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: The exposure chambers were constructed of stainless steel and glass. The internal nominal volume of the chambers was approximately 150 L. Exposure chambers were cubical with square-pyramidal chamber inlets and outlets (NYU style); a tangential feed at the chamber inlet promoted gas mixing and uniform distribution of the test substance vapor.

- Method of holding animals in test chamber: Each rat was individually housed in a stainless steel, wire-mesh exposure module

- Source and rate of air: The vapor was diluted by house-line air to the desired concentrations for each of the three test chambers. Chamber concentrations of the test substance were controlled by regulating the flow of the test substance through the flow meters. House-line air alone was metered in an identical manner into the control chamber.

- Method of conditioning air: Airflow, temperature, and relative humidity were monitored continually with a Lander Control Systems Toxicology Monitoring System and recorded at approximately 30-minute intervals during each exposure. Oxygen was measured with a Biosystems model 3100R Oxygen Monitor and recorded two times during each exposure.

- System of generating particulates/aerosols: The test substance vapor was generated by metering the test material from the sample cylinder through stainless steel tubing into a liquid trap, and into mass flow meters; a separate flow meter was used for each test chamber. The vapor was diluted by house-line air to the desired concentrations for each of the three test chambers.

- Temperature, humidity, pressure in air chamber:
Temperature: range 21 to 26°C
Humidity: range 26 to 64%
Pressure, not reported

- Air flow rate: range 30 to 41 liters/minute

- Air change rate: not reported

- Method of particle size determination: not applicable

- Treatment of exhaust air: Atmospheres from the test chambers were pulled through exhaust pumps and directly vented into a fume hood and discharged through an exhaust stack.


TEST ATMOSPHERE
- Brief description of analytical method used: The atmospheric concentration of the test substance was determined by gas chromatography at approximately 60-minute intervals during each six-hour exposure. Gas samples were continuously drawn by a vacuum pump from representative areas of the chambers where rats were exposed. Chamber atmosphere samples were analyzed for test substance concentration with a Hewlett Packard model 5880 Gas Chromatograph equipped with a gas sample loop and flame ionization detector. All samples were chromatographed isothermally at 85°C. Nitrogen was used as the carrier gas and samples were chromatographed on a 20 in. x 1/8 in. (inside diameter) Chromosorb W stainless steel column. The atmospheric concentration of HFC-23 was determined by comparing the detector response of the chamber samples to that of gas standards with the use of standard curves.
- Samples taken from breathing zone: yes


Analytical verification of doses or concentrations:
yes
Details on analytical verification of doses or concentrations:
Method of Analysis: Hewlett Packard model 5880 Gas Chromatograph equipped with a gas sample loop and flame ionization detector.

Concentration verification (% of Target))
Conducted on all dose levels: yes
Results:
Week 1: 5000 ppm mean = 5500 ppm; 20000 ppm mean = 20000 ppm; 50000 mean = 50000 ppm
Week 2: 5000 ppm mean = 5600 ppm; 20000 ppm mean = 21000 ppm; 50000 mean = 51000 ppm
Week 3: 5000 ppm mean = 5600 ppm; 20000 ppm mean = 21000 ppm; 50000 mean = 51000 ppm
Week 4: 5000 ppm mean = 5500 ppm; 20000 ppm mean = 21000 ppm; 50000 mean = 51000 ppm












Details on mating procedure:
- Impregnation procedure: cohoused
- If cohoused:
- M/F ratio per cage: 1:1
- Length of cohabitation: Until copulation was confirmed by the presence of a copulation plug in the vagina or on the cageboard
- Proof of pregnancy: presence of a vaginal plug referred to as day 1 of pregnancy
Duration of treatment / exposure:
Gestation Days 7 to 21 (14 days)
Frequency of treatment:
6 hours daily
Duration of test:
Females were euthanized on day 22G
No. of animals per sex per dose:
25 females
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: The exposure levels were provided by the sponsor and are consistent with concentrations tested previously with similar alternative fluorocarbons. The highest level, 50000 ppm, was the highest concentration which could be attained without supplementing chamber oxygen.

Examinations

Maternal examinations:
CAGE SIDE OBSERVATIONS: Yes
- Time schedule: daily
Observations for morbidity and mortality were made daily.

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: daily
Individual clinical signs were recorded each morning on days 1-22G and each afternoon on days 7-21G (the exposure period).

BODY WEIGHT: Yes
- Time schedule for examinations: Prior to the start of exposures, females were weighed and examined within one day of arrival, twice during quarantine, and weekly before the start of the study. During the study, females were weighed on days 1, 7, 9, 11, 13, 15, 17, 19, 21, and 22G.

FOOD CONSUMPTION: Yes, food was weighed on days 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, and 22G


POST-MORTEM EXAMINATIONS: Yes
- Sacrifice on gestation day # 22
- Organs examined: A gross necropsy was conducted on each animal; the organs of the thoracic and abdominal cavities were examined. The uterus was removed, weighed, and opened. The types of implants (live and dead fetuses, and resorptions) were counted and their relative positions were recorded. Then, the empty uterus was weighed. The ovaries were removed and the corpora lutea were counted and recorded. The uterus of each apparently nonpregnant rat was opened and stained with ammonium sulfide to detect very early resorptions; data collected from those animals were used only to determine the incidence of pregnancy and the number of females with total resorptions.

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
- Other: Live fetuses were weighed, sexed, and examined for external alterations. The first live fetus and thereafter every other fetus in each litter was decapitated and examined for visceral alterations and the sex verified. Retarded renal development was classified using the scheme of Woo and Hoar (1972) Teratology 6:191-196. The heads were fixed in Bouin’s fluid and examined. The remaining fetuses were euthanized by an intraperitoneal injection of sodium pentobarbital. All fetuses were fixed in 70% ethanol, eviscerated (if not done earlier during the visceral examination) macerated in 1% aqueous potassium hydroxide solution, stained with alizarin red, and examined for skeletal alterations.
Fetal examinations:
- External examinations: Yes: all per litter
- Soft tissue examinations: Yes: half per litter
- Skeletal examinations: Yes: all per litter
- Head examinations: Yes: half per litter
Statistics:
See Table 1 below

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 mortalities observed at any dose level.

There were no compound-related effects on maternal body weight, weight changes, adjusted body weight, or weight change calculated using the adjusted body weight.

At 50000 ppm, there was a statistically significant increase in body weight gain over days 11-13G followed by a significant decrease over days 13-15G. The significant decrease is not believed to be toxicologically relevant because it appears to have been caused by the preceding significant increase which was approximately equal in magnitude. There were no other corroborating indications of maternal toxicity; maternal body weights and food consumption were unaffected. In addition, there was no biologically or statistically detectable effect on weight gain when evaluated for the entire exposure period. In addition, there was a slight, statistically significant reduction in maternal weight gain over days 19-21G. Average weight gain for the high level during this interval was 29.2 grams compared to an average of 32.2 grams for the control group. This is not believed to a toxicologically relevant finding; the reduction in gain is very small and in fact appears to be due to a very slight but significant reduction in food consumption for that interval. In addition, there is no effect on maternal weight gain at any exposure level when considered for the entire exposure period (days 7-22G).

There were no compound-related effects on maternal food consumption.

At 50000 ppm, there was a slight, statistically significant reduction in maternal food consumption over days 19-21G. Average food consumption for the high level during this interval was 25.9 grams compared to an average of 27.1 grams for the control group. This is not believed to be a toxicologically relevant finding; this reduction is very small and is not corroborated by effects on food consumption over any other interval or for when the exposure period is considered in its entirety (days 7-22G).

There were no significant post mortem findings in the maternal dams at any exposure level.

Effect levels (maternal animals)

open allclose all
Key result
Dose descriptor:
NOEL
Effect level:
50 000 ppm (nominal)
Basis for effect level:
other: maternal toxicity
Key result
Dose descriptor:
NOEL
Effect level:
50 000 ppm (nominal)
Basis for effect level:
other: developmental toxicity

Results (fetuses)

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

Details on embryotoxic / teratogenic effects:
There were no compound-related effects on reproductive outcome parameters (dams with either total resorptions or that delivered early, mean corpora lutea, mean number of implantations, litter size or sex ratio).

There were no compound-related effects on fetal mortality (resorptions, or dead fetuses).

There was no compound-related effect on mean fetal weight.

There were no compound-related effects on the incidence of fetal malformations.

There were no compound-related effects on the incidence of fetal variations.

At 50000 ppm, there was a statistically significant increase in the incidence of small renal papilla (sizes 1, 2, and 3). For the 0, 5000, 20000, and 50000 ppm groups, the incidences were [given as “no. fetuses (no. litters)”] 45 (17), 25 (13), 35 (19) and 47 (19). The increase at the high level is not believed to be biologically significant; although the increase is statistically significant, there does not appear to be a dose-response relationship evident in the data. Additionally, at 50000 ppm, the incidence of this frequently observed and highly variable finding is only slightly higher than that observed for the concurrent control group. Finally, the incidences for all groups on this study fall within the range of historical control data (see Table 2: Historical Control Data above) for eight recently conducted rat developmental toxicity studies.

At 20000 and 50000 ppm, there were statistically significant increases in the incidence of retarded sternebral ossification. For the 0, 5000, 20000, and 50000 ppm groups, the incidences were [given as “no. fetuses (no. litters)”] 2(2), 2(2), 13(6), and 9(5). These increases are not believed to be biologically significant for reasons similar to those outlined above for the kidney findings. Although the incidences for the two high level groups are statistically significantly increased, they are not increased in a dose-dependent fashion. In addition, the control group value for the current study is very low and outside of the range of concurrent historical control data (see Table 2: Historical Control Data above) for this endpoint. Finally, the incidences for the 20000 and 50000 ppm groups are well within the range of recent control data.

Effect levels (fetuses)

Key result
Dose descriptor:
NOAEC
Effect level:
50 000 ppm (nominal)
Based on:
test mat.
Sex:
male/female
Basis for effect level:
other: see "remarks"
Remarks on result:
not determinable due to adverse toxic effects at highest dose / concentration tested

Fetal abnormalities

Abnormalities:
not specified

Overall developmental toxicity

Developmental effects observed:
not specified

Applicant's summary and conclusion

Conclusions:
Under the conditions of this study, maternal and developmental toxicity was not observed at any exposure level tested. The maternal and developmental no-observed-effect level (NOEL) was 50000 ppm. Thus, the results of this study indicate that HFC-23 is not uniquely toxic to the rat conceptus.

This study and the conclusions which are drawn from it fulfill the quality criteria (validity, reliability, repeatability).
Executive summary:

The test substance was administered by inhalation to groups of 25 mated Crl:CD® (SD)BR rats on days 7-21 of gestation at daily exposure levels of 0, 5000, 20000, or 50000 ppm. The highest level, 50000 ppm, was the highest concentration which could be attained without supplementing chamber oxygen.

 

There was no evidence of any maternal or developmental toxicity at any exposure concentration tested. There were no compound-related effects on maternal body weights, weight changes, food consumption, clinical observations, or postmortem findings. There were no compound-related developmental or reproductive effects; the endpoints evaluated included mean fetal weight, mean litter size, measures of pre- and post-implantation embryolethality, and the incidences of fetal malformations and variations. Thus, the maternal and developmental no-observed-effect level (NOEL) was 50000 ppm. Therefore, the results of this study indicate that the test substance was not uniquely toxic to the rat conceptus.