Tetrafluoroethylene

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

chronic toxicity: inhalation

Remarks:

combined repeated dose and carcinogenicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline Study

Data source

Reference

Reference Type:

publication

Title:

Unnamed

Year:

1997

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 453 (Combined Chronic Toxicity / Carcinogenicity Studies)

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Tetrafluoroethylene

EC Number:

204-126-9

EC Name:

Tetrafluoroethylene

Cas Number:

116-14-3

Molecular formula:

C2F4

IUPAC Name:

tetrafluoroethene

Details on test material:

- Name of test material (as cited in study report): tetrafluoroethylene
- Substance type: pure active substance
- Physical state: gas
- Analytical purity: >98%
- Impurities (identity and concentrations): d-limonene < 0.56%; perfluorocyclobutane < 1.21%
- Lot/batch No.: 12438-6, 12438-79; 12438-92
- Expiration date of the lot/batch: n/a
- Stability under test conditions: 1 year when stored in the original containers at room temperature
- Storage condition of test material: 10 - 22°C; stability measured during the study by gas chromatography.

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female F344/N rats were obtained from Simonsen Laboratories (Gilroy CA). Rats were quarantined for 15 days before the beginning of the studies. Five male and five female rats were randomly selected for parasite evaluation and gross observation of disease. Rats were approximately 7 weeks old at the begining of the study. The health of animals was monitored during the studies according to the protocols of the NTP Sentinel Animal Program. Rats were housed individually. Feed was available ad libitumduring except during exposure periods and water was available ad libitum. Chambers and cages were rotated weekly.
TEST ANIMALS
- Source: Simionsen Laboratories (CA)
- Age at study initiation: 7 weeks
- Weight at study initiation: 126 g males / 102 g females
- Fasting period before study:
- Housing: Housed individually in stainless steel cages
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: 15 days


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 24.1 to 24.5
- Humidity (%): 53 - 58
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12 dark / 12 light


IN-LIFE DATES: From: 23 June 1988 To: 14 June 1990

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: unchanged (no vehicle)

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: Stainless steel chambers designed at Battelle Pacific Northwest Laboratories. The generation and delivery system incorporated gas distribution under regulated pressure with individual monitoring and chemical flow rate to each chamber.
- Method of holding animals in test chamber: Housed individually in stainless steel cages; changed weekly.
- Source and rate of air:
- Method of conditioning air: Filtered - Single HEPA (Flanders filters inc, San Rafael CA) and charcoal (RSE inc. New Baltimore, MI); changed before the studies back and once yearly thereafter.
- Temperature, humidity, pressure in air chamber: 24.1 - 24.5°C, RH 53 - 58%
- Air change rate: 15/hour



TEST ATMOSPHERE
- Brief description of analytical method used: on-line gas chromatography
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations of tetrafluoroethylene (TFE) were monitored using an on-line gas chromatograph, and samples were drawn and analysed from each exposure chamber, the control chamber, the exposure suite, and an on-line standard. The monthly mean concentrations were all within 10% of the acceptable concentration range.

Duration of treatment / exposure:

104 weeks

Frequency of treatment:

6 hours / day, 5 days / week

Doses / concentrations

Remarks:

Doses / Concentrations:
Males: 0, 156, 312 or 625 ppm. Females: 0, 312, 625 or 1250 ppm.
Basis:
analytical conc.

No. of animals per sex per dose:

60

Control animals:

yes, concurrent no treatment

Details on study design:

- Dose selection rationale: Exposure concentrations for the 2-year study in male rats was based on kidney effects. Although the severity and incidence of kidney lesions were identical for male rats exposed to 625 or 1250 ppm, the absolute and relative kidney weights of males exposed to 1250ppm were significantly greater than those of controls. Therefore the highest exposure concentration selected was 625 ppm, which was expected to cause minimal toxicity in the kidney following 2-year exposure. Although kidney effects were the main toxicological consideration for exposure concentration selection in the two year study in female rats, the highest exposure concentration was selected, in part, based on the number of chambers ot be use in this inhalation study. Female rats shared the same exposure chambers as the mice in the 2 year study and were exposed to 312, 625 or 1250 ppm TFE.
- Rationale for animal assignment (if not random): animals were distributed randomly into groups of approximately equal initial mean body weight.

Groups of 60 male rats were exposed to tetrafluoroethylene at concentrations of 0, 156, 312 and 625ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week., for 104 weeks. Groups of 60 female rats were exposed to tetrafluoroethylene at concentrations of 0, 312, 625 and 1250ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week., for 104 weeks. Following the last day of exposure, rats were observed for approximately 11 days before necropsy. Ten male and ten female rats from each group were evaluated at 15 months for alterations in haematology, clinical chemistry, and urine analysis parameters and organ weights.

Examinations

Observations and examinations performed and frequency:

All animals were observed twice daily. Clinical findings were recorded monthly until the last 13 weeks. when they were recored twice monthly. Animals were weighed before the studies began, weekly for the first 13 weeks, and monthly thereafter, until the last 13 weeks when they were weighed every weeks.
Ten male and ten female rats were designated for interim evaluation at 15 months. Two weeks before the scheduled evaluation designated rats were placed in metabolism cages for a 16 hour urine collection. One week later, male and female rats were placed in metabolism cages for a urine concentrationg study. Rats were deprived of water for 16 hours and urine was expressed from the bladders of animals. urine was then collected for the next 6 hours for a urine concentrating study. At the 15 month interim evaluation, blood was taken from the retroorbital plexus of rats for haematology and clinical chemistry analysis.

Sacrifice and pathology:

Necroscopy was performed on all animals. Organ weighed at the 15-month interim evaluation were the right kidney, liver and lung.

Statistics:

Analysis of continuous variables
Two approaches were employed to assess the significance of pairwise comparisons between exposed and control groups in the analysis of continuous variables. Organ and body weight data, which have approximately normal distributions, were analysed using the parametric multiple comparison procedures of Dunnett (1955) and Williams (1971, 1972). Haematology, clinical chemistry, spermatid, and epididymal spermatozoa data, which have typically skewed distributions, were analysed using the non-parametric multiple comparison methods of Shirley (1977) and Dunn (1964). Jonckheere’s test (Jonckheere, 1954) was used to assess the significance of the dose-related trends and to determine whether a trend-sensitive test (Williams or Shirley’s test) was more appropriate for pairwise comparisons than a test that does not assume a monotonic dose-related trend (Dunnet or Dunn’s test). Prior to statistical analysis, extreme values, identified by the outlier test of Dixon and Massey (1951), were eliminated from the analysis. Average severity values were analysed for significance using the Mann-Whitney U-test (Hollander and Wolfe, 1973). Treatment effects were investigated by applying a multivariate analysis of variance (Morrison, 1976) to the transformed data to test for simultaneous equality of measurements across exposure levels.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

Ophthalmological findings:

effects observed, treatment-related

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Effect levels

Dose descriptor:

LOAEC

Effect level:

638 mg/m³ air

Sex:

male/female

Basis for effect level:

other: Increased incidences of renal tubule degeneration.

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

Groups of 60 male and female F344 rats were exposed (6hr/day, days/week) by inhalation to a range of concentrations of TFE for 103 weeks, with an observation period of 11 days following final exposure. The males were exposed to either 0, 156, 312 or 625 ppm TFE (0, 638, 1275 or 2555 mg/m3) and the females were exposed to either 0, 312, 625 or 1250 ppm TFE (0, 1275, 2555, 5110 mg/m3). Ten male and ten female rats from each exposure group were evaluated 15 months with gross necropsy and histological examination. Survival, body and organ weights, and clinical findings The survival rates of males exposed to 625 ppm TFE, and of all exposed groups of females, were significantly less than those of controls. Mean body weights of males exposed to 625 ppm TFE were lower than those of the controls from week 81 until the end of the study, and the mean body weight of females exposed to 1250 ppm TFE was slightly lower than that of controls at the end of the study. At the 15 month evaluation, the absolute and relative weights of the right kidney of males exposed to 625 ppm TFE were significantly greater than those of the controls, and the absolute weight of the right kidney of females exposed to 625 ppm was significantly greater than that of the controls. Also, the absolute and relative liver weights of femals exposed to 1250 ppm TFE and the absolute liver weigth of females exposed to 625 ppm were significantly greater than those of the controls. The only clinical finding associated with exposure to TFE was opacity of eyes that was increased in incidence in female rats exposed at 1250 ppm TFE. This change was observed microscopically as cataracts. Haematology, clinical chemistry, and urinalysis At the 15 month interim evaluation, there were no differences in haematology, clinical chemistry, or urinalysis parameters considered to be related to TFE exposure. Pathology findings The main findings of the study were an increased incidence of renal tubular adenomas and hepatocellular tumours in both sexes. Findings in the kidney At the 15 month interim sacrifice, increased incidences of renal tubule hyperplasia were observed in males exposed to 312 ppm TFE and in males and females exposed to 625 ppm TFE. At the end of the study, the incidences of renal tubule hyperplasia in males exposed to 625 ppm TFE and females exposed to 1250 ppm were significantly greater than those in the controls. At 15 months and at the end of the study, the incidences of renal tubule degeneration in all exposed groups of males, and in females exposed to 625 adn 1250 ppm TFE, were greater than those in the controls. Renal tubular degeneration was similar to that observed in the 13 week study and was located predominantly at the corticomedullary junction. The severity of the nephropathy generally increased with increasing exposure concentration in male rats exposed for 15 month and 2 years. A statistically significant increase in the incidence of renal tubule adenoma and of renal tubule adenoma or carcinoma (combined) was observed in males exposued to 312 and 625 ppm TFE and in females exposed to 1250 ppm TFE was observed. The effect was confirmed using step sections of the kidney. Findings in the liver At the end of the 2 -year study, increased incidences of hepatic angiecstasis were observed in all exposed groups of female rats. At the 15 month interim evaluation and after exposure for 2 years, the incidences of clear cell and mixed cell foci in all exposed groups of males were greater than those in the controls, as were the incidences of mixed cell foci at 15 months in females exposed to 625 or 1250 ppm, and at 2 years in females exposed to 1250 ppm TFE. At the end of the study, the incidences of hepatocellular carcinoma and hepatocellular adenoma or carcinoma (combined) in males exposed to 312 ppm TFE, the incidences of hepatocellular adenoma and adenoma or carcinoma (combined) in females in all exposed groups, and the incidences of hepatocellular carcinoma in females exposed to 312 or 625 ppm TFE, were significantly greater than those in the controls. Also at 2 years, the incidence of haemangiosarcoma in females exposed to 625 ppm was significantly greater than that in controls ( See 7.7 Carcinogenicity). Mononuclear cell leukaemia Increased incidences of mononuclear cell leukaemia were observed in some of the exposed groups, particularly in females where the increased incidences were statistically significantly different from controls, although the effect was not dose-related in either sex ( See 7.7 Carcinogenicity). The incidence in the control males (68%) was outside the historical control range for the conducting laboratory (38 - 66%), as were the incidences observed in males exposed to 312 ppm (62%) and 1250 ppm (72%), but not 625 ppm (46%) TFE, where also outside the range of historical controls.

Applicant's summary and conclusion

Conclusions:

The only clinical finding related to exposure to TFE in a 2 year study in the rat was opacity of the eyes in females exposed to 1250 ppm, due to the presence of cataracts. Increased incidences of renal tubule degeneration, located predominantly at the cortico-medullary junction were seen in all exposed groups and increased incidences of renal tubule hyperplasia were seen in males exposed to 625 ppm TFE and females exposed to 1250 ppm TFE. In addition, increased incidences of hepatic angiectasis were observed in all exposed groups of female rats.

Executive summary:

Exposure of F344 rats, 6 h/d, 5 d/wk by inhalation to concentrations of TFE, ranging from 156 ppm to 1250 ppm (638 to 5110 mg/m3) for 103 weeks caused reduced survival rates in all exposed groups. The only clinical finding related to exposure to TFE was opacity of the eyes in females exposed to 1250 ppm, due to the presence of cataracts. Increased incidences of renal tubule degeneration, located predominantly at the cortico-medullary junction were seen in all exposed groups and increased incidences of renal tubule hyperplasia were seen in males exposed to 625 ppm TFE and females exposed to 1250 ppm TFE. In addition, increased incidences of hepatic angiectasis were observed in all exposed groups of female rats.