Dichlorodifluoromethane

Carcinogenicity

Description of key information

Results from several long-term studies were available for weight of evidence assessment: a carcinogenicity study by inhalation in rats and mice, and an oral study in rats. No tumors or adverse effects were reported.

Inhalation: Rat chronic administration: NOAEC: 5000 ppm, i.e., 24725 mg/m3

Key value for chemical safety assessment

Carcinogenicity: via oral route

Link to relevant study records

Reference

Endpoint:

carcinogenicity: oral

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

no data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

data from handbook or collection of data

Reason / purpose for cross-reference:

reference to same study

Qualifier:

no guideline followed

Principles of method if other than guideline:

- Principle of test: in a multigeneration study by the oral route, groups of 50 male and 50 female Charles River rats of the F1a generation remained in the test for 2 years, with an interim kill at 1 year. Starting at 6 weeks of age, controls, low-dose, and high-dose groups received CFC-12 in corn oil or corn oil alone daily by gavage for 6 weeks and 5 times / week thereafter
- Parameters analysed / observed: survival, periodic measurements of haematological, clinical chemistry, and urinalysis values, organ weights and histopathological findings.

GLP compliance:

no

Remarks:

Prior to GLP standards

Species:

rat

Strain:

Sprague-Dawley

Remarks:

Charles River CD

Sex:

male/female

Route of administration:

oral: gavage

Vehicle:

corn oil

Analytical verification of doses or concentrations:

not specified

Duration of treatment / exposure:

2 years

Frequency of treatment:

daily

Dose / conc.:

0 mg/kg bw/day (nominal)

Dose / conc.:

15 mg/kg bw/day (nominal)

Dose / conc.:

150 mg/kg bw/day (nominal)

No. of animals per sex per dose:

50

Control animals:

yes

Details on study design:

Multigeneration study. The rats from the F1a generation were dosed for 2 years by gavage. An interim kill of 6 rats/group was made after one year of treatment.

Positive control:

No

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: No data
DETAILED CLINICAL OBSERVATIONS: No data

BODY WEIGHT: Yes
- Time schedule for examinations: frequency not detailed

FOOD CONSUMPTION : No data

HAEMATOLOGY: Yes

CLINICAL CHEMISTRY: Yes

URINALYSIS: Yes

NEUROBEHAVIOURAL EXAMINATION: No data

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Clinical signs:

no effects observed

Mortality:

mortality observed, non-treatment-related

Description (incidence):

No difference in survival between treated and control groups

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

Slight decreased body weight in females of the high dose group.

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

no effects observed

Key result

Dose descriptor:

NOAEC

Effect level:

ca. 150 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Key result

Critical effects observed:

no

Conclusions:

There was no evidence of carcinogenic effects in male and female rats following a 2-year administration by oral gavage.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEL

150 mg/kg bw/day

Study duration:

chronic

Species:

rat

Carcinogenicity: via inhalation route

Link to relevant study records

Reference

Reference 1

Endpoint:

carcinogenicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1975 to 1979

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Taken from publically available data. The study is well documented and contains suitable information for use in the assessment. The full literature report is appended for reference.

Qualifier:

no guideline followed

Principles of method if other than guideline:

CFC-12 was tested by inhalation on Sprague-Dawley rats and Swiss Mice using whole body exposure. The animals were exposed by inhalation, 4 hours daily, 5 days weekly, for 104 weeks (rats: Exp. BT 601, 601 bis) and 78 weeks (mice: Exp. BT 602).
All the animals were kept under control until spontaneous death. The status and behaviour of the animals were controlled three times daily. The animals were submitted to clinical examination for gross changes every 2 weeks. The animals were weighed every 2 weeks during treatment, and then every 8 weeks. Full necropsy was performed on all the animals. The housing and the diet of the animals were the same highly standardized ones adopted in the BT Experimental Unit during the last 15 years before the beginning of this experiment.

GLP compliance:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source of test material: Montedison, Italy
- Purity : 99.98%

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female Sprague-Dawley rats 9 (Exp. BT 601), and 13 (Exp. BT 601 bis) weeks old at the start of the experiment.
The animals were of the breed currently used in the BT Experimental Unit for more than 15 years.
All the animals were kept under control until spontaneous death.
The status and behaviour of the animals were controlled three times daily.
The housing and the diet of the animals were the same highly standardized ones adopted in the BT Experimental Unit during the last 15 years before the beginning of this experiment.

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

air

Details on exposure:

The chambers for inhalation exposure were made of stainless steel, with two glass doors, and they measure 135 x 98 x 65 cm. The volume of each chamber is 860 litres. Continuous air flow provided 12-15 air changes per hour. Before its introduction the air was filtered, and the chamber arrangement was such that air flowed from one part of the chamber to the other without recirculation. The internal pressure was about 1 mm Hg less than that of the room where the chambers were situated to avoid any possible contamination of the outside environment.
FC 12 was tested in rats with two experiments each: BT 601 and BT 601 bis (CFC-12). Experiment BT 601 bis included 60 animals (30 males and 30 females). Experiment BT 601 was started concurrently in rats of the same litters. Experiment BT 601 bis was started concurrently in rats of the same litters after experiment BT 601. At the start of the project, the animals of experiments BT 601 bis were scheduled for interim sacrifice for clinical laboratory analyses and histopathology. Since it was then decided not to perform such exams, all the animals of the experiments were treated and examined in the same way, and therefore are considered as a whole.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations in air were checked by continuous gas chromatographic monitoring-no further details referenced within the publication.

Duration of treatment / exposure:

The animals were exposed by inhalation, 4 hours daily, for 104 weeks (rats: Exp. BT 601, 601 bis)

Frequency of treatment:

5 days weekly

Dose / conc.:

0 ppm (nominal)

Dose / conc.:

1 000 ppm (nominal)

Remarks:

(eq. to 4945 mg/m3)

Dose / conc.:

5 000 ppm (nominal)

Remarks:

(eq. to 24726 mg/m3)

No. of animals per sex per dose:

660 total (330 male & 330 female rats): 90/sex/treatment group, and 150/sex/control group

Control animals:

yes, concurrent no treatment

Details on study design:

Detailed in table form, attached under any other information.

Positive control:

Not specified

Observations and examinations performed and frequency:

The status and behaviour of the animals were controlled three times daily.
The animals were submitted to clinical examination for gross changes every 2 weeks.
The animals were weighed every 2 weeks during treatment, and then every 8 weeks.

Sacrifice and pathology:

Systematic and standardized histopathologic examinations were performed on each animal on the subcutaneous lymph nodes, brain and cerebellum, Zymbal glands, interscapular brown fat, salivary glands, Harderian glands, tongue, thymus and mediastinal lymph nodes, lungs, diaphragm, liver, kidneys, adrenals, spleen, mesenteric lymph nodes, stomach, various segments of the intestine, bladder, uterus, gonads, bone marrow smear, and any other organs with pathologic lesions.
Full necropsy was performed on all the animals.

Other examinations:

Not specified

Statistics:

log rank test

Clinical signs:

no effects observed

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Rats: There was no significant differences in survival linked to exposure to the test substance.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Rats: There was no significant differences in body weight linked to exposure to the test substance.

Food efficiency:

not examined

Water consumption and compound intake (if drinking water study):

not examined

Clinical biochemistry findings:

no effects observed

Organ weight findings including organ / body weight ratios:

not examined

Description (incidence and severity):

Not reported in the publication.

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

The tumors most frequently expected in the rats of the strain used, on the basis of the literature and of the historical controls of the BT Experimental Unit, are mammary tumors (benign and malignant), leukemias, pheochromocytomas and pheochromoblastomas. Moreover, a variety of other miscellaneous tumors are also observed.

FC12: Rats (Exp. BT 601 + 601 bis):
Carcinogenicity; No noticeable differences, related to treatment, were found in the incidence of total benign and malignant, and malignant tumors, and of the most frequent expected or rare tumors.

Relevance of carcinogenic effects / potential:

No statistically significant increases in total number of tumors between treated and control groups. No carcinogenic effects were noted within the study.

Key result

Dose descriptor:

NOAEC

Effect level:

>= 5 000 ppm (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Key result

Critical effects observed:

no

Dichlorodifluoromethane (FC12): Total Tumors in Rats (Exp. BT 601 + 601 bis)

Group No.	Concentration (ppm)	Animals		Percentage of Animals Bearing Tumors		No. of Malignant Tumors per 100 Animals
		Sex	No. at Start	TBMT^a	MT^b
I	5000	M	90	30.0	10.0	10.0
		F	90	80.0	20.0	20.0
		M + F	180	55.0	15.0	15.0
II	1000	M	90	46.7	17.8	17.8
		F	90	78.9	26.7	26.7
		M + F	180	62.8	22.2	22.2
III	0 (Control)	M	150	34.0	16.7	17.3
		F	150	82.7	28.7	31.3
		M + F	300	58.3	22.7	24.3

^aTotal benign and malignant tumors.

^bMalignant tumors.

 

Dichlorodifluoromethane (FC12): Mammary Tumors, Leukemias, Pheochromocytomas and Pheochromoblastomas in Rats (Exp. BT 601 + 601 bis)

Group No.	Concentration (ppm)	Animals		Percentage of Animals Bearing Tumors
		Sex	No. at Start	Mammary Tumors
				BMT^a	MT^b	Leukemias^c	Pheochromocytomas	Pheochromoblastomas
I	5000	M	90	12.2	2.2	3.3	5.5	-
		F	90	74.4	10.0	1.1	1.1	-
		M + F	180	43.3	6.1	2.2	3.3	-
II	1000	M	90	15.5	1.1	7.8	12.2	1.1
		F	90	68.9	14.4	3.3	1.1	-
		M + F	180	42.2	7.8	5.5	6.7	0.5
III	0 (Control)	M	150	12.7	4.0	6.0	4.0	-
		F	150	72.0	13.3	5.3	3.3	-
		M + F	300	42.3	8.7	5.7	3.7	-

^aBenign and malignant tumors.

^bMalignant tumors.

^cThe term “leukemia” includes a variety of hemolymphoreticular neoplastic diseases at different sites.

 

Dichlorodifluoromethane (FC12): Liver Angiosarcomas in Rats

Experiment and Compound	Group No.	Concentration (ppm)	Animals		Percentage of Animals Bearing Liver Angiosarcomas
			Sex	No. at Start
BT 601 + BT 601 bis (FC12)	I	5000	M	90	-
			F	90	3.3
			M + F	180	1.7
	II	1000	M	90	-
			F	90	1.1
			M + F	180	0.5
	III	0 (Control)	M	150	0.7
			F	150	0.7
			M + F	300	0.7

Conclusions:

Under the experimental conditions, the test compound did not show carcinogenic effects.

Executive summary:

The propellant chlorofluorocarbon dichlorodifluoromethane (CFC-12) was administered for 104 weeks to rats by inhalation at a concentration of 5000, 1000 and 0 ppm, 4 hours daily, 5days weekly.

The animals were kept under observation until spontaneous death.

No unexpected treatment-related tumors were observed in rats exposed to CFC-12. No important differences in the incidence of total benign and malignant tumors and of frequently occurring spontaneous tumors were observed in the rats exposed to CFC-12.

Under the experimental conditions, and on the basis of statistical analysis and of the oncological evaluation of the results, CFC-12 failed to show carcinogenic effects.

Reference 2

Endpoint:

carcinogenicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1975 to 1979

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Remarks:

Taken from publically available data. The study is well documented and contains suitable information for use in the assessment. The full literature report is appended for reference.

Qualifier:

no guideline followed

Principles of method if other than guideline:

CFC-12 was tested by inhalation on Sprague-Dawley rats and Swiss Mice using whole body exposure. The animals were exposed by inhalation, 4 hours daily, 5 days weekly, for 104 weeks (rats: Exp. BT 601, 601 bis) and 78 weeks (mice: Exp. BT 602).
All the animals were kept under control until spontaneous death. The status and behaviour of the animals were controlled three times daily. The animals were submitted to clinical examination for gross changes every 2 weeks. The animals were weighed every 2 weeks during treatment, and then every 8 weeks. Full necropsy was performed on all the animals. The housing and the diet of the animals were the same highly standardized ones adopted in the BT Experimental Unit during the last 15 years before the beginning of this experiment.

GLP compliance:

not specified

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source of test material: Montedison, Italy
- Purity : 99.98%

Species:

mouse

Strain:

Swiss

Sex:

male/female

Details on test animals or test system and environmental conditions:

Male and female Swiss mice 8 weeks old at the start of the experiment (Exp. BT 602).
The animals were of the breed currently used in the BT Experimental Unit for more than 15 years.
All the animals were kept under control until spontaneous death.
The status and behaviour of the animals were controlled three times daily.
The housing and the diet of the animals were the same highly standardized ones adopted in the BT Experimental Unit during the last 15 years before the beginning of this experiment.

Route of administration:

inhalation

Type of inhalation exposure (if applicable):

whole body

Vehicle:

air

Details on exposure:

The chambers for inhalation exposure were made of stainless steel, with two glass doors, and they measure 135 x 98 x 65 cm. The volume of each chamber is 860 litres. Continuous air flow provided 12-15 air changes per hour. Before its introduction the air was filtered, and the chamber arrangement was such that air flowed from one part of the chamber to the other without recirculation. The internal pressure was about 1 mm Hg less than that of the room where the chambers were situated to avoid any possible contamination of the outside environment.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations in air were checked by continuous gas chromatographic monitoring-no further details referenced within the publication.

Duration of treatment / exposure:

The animals were exposed by inhalation, 4 hours daily, for 78 weeks (mice: Exp. BT 602).

Frequency of treatment:

5 days weekly

Dose / conc.:

0 ppm (nominal)

Dose / conc.:

1 000 ppm (nominal)

Remarks:

(eq. to 4945 mg/m3)

Dose / conc.:

5 000 ppm (nominal)

Remarks:

(eq. to 24726 mg/m3)

No. of animals per sex per dose:

Mouse: 420 total (210 male & 210 female): 60/sex/treatment group and 90/sex/control group

Control animals:

yes, concurrent no treatment

Details on study design:

Detailed in table form, attached under any other information.

Positive control:

Not specified

Observations and examinations performed and frequency:

The status and behaviour of the animals were controlled three times daily.
The animals were submitted to clinical examination for gross changes every 2 weeks.
The animals were weighed every 2 weeks during treatment, and then every 8 weeks.

Sacrifice and pathology:

Systematic and standardized histopathologic examinations were performed on each animal on the subcutaneous lymph nodes, brain and cerebellum, Zymbal glands, interscapular brown fat, salivary glands, Harderian glands, tongue, thymus and mediastinal lymph nodes, lungs, diaphragm, liver, kidneys, adrenals, spleen, mesenteric lymph nodes, stomach, various segments of the intestine, bladder, uterus, gonads, bone marrow smear, and any other organs with pathologic lesions.
Full necropsy was performed on all the animals.

Other examinations:

Not specified

Statistics:

log rank test

Clinical signs:

no effects observed

Mortality:

mortality observed, non-treatment-related

Description (incidence):

The survival rate varied from group to group, was generally lower in control than in treated groups, and showed statistically significant differences after various periods.

Body weight and weight changes:

no effects observed

Description (incidence and severity):

Mice: no effect on body weight was observed.

Haematological findings:

not examined

Clinical biochemistry findings:

no effects observed

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not specified

Description (incidence and severity):

Not reported in the publication.

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

no effects observed

Histopathological findings: neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

A higher number of the following tumors was observed in treated groups:
- total number of tumors in males and females, dose-related in males;
- pulmonary adenomas in males and females, at 5000 ppm; and leukemias in males, at 5000 and 1000 ppm, and in females at 1000 ppm.
Since the above-mentioned tumors were generally age-related, a statistical method was used, namely the log rank test, which allows for such variations. When such a test was used, no statistically significant increases in total number of tumors, pulmonary adenomas, and leukemias was found in treated male or female mice in comparison with control animals.

Relevance of carcinogenic effects / potential:

no statistically significant increases in total number of tumors between treated and control groups. No carcinogenic effects were noted within the study.

Key result

Dose descriptor:

NOEC

Effect level:

>= 5 000 ppm (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Key result

Critical effects observed:

no

 

Dichlorodifluoromethane (FC12): Total Tumors in Mice (Exp. BT 602)

Group No.	Concentration (ppm)	Animals		Percentage of Animals Bearing Tumors		No. of Malignant Tumors per 100 Animals
		Sex	No. at Start	TBMT^a	MT^b
I	5000	M	60	25.0	11.7	11.7
		F	60	21.7	10.0	10.0
		M + F	120	23.3	10.8	10.8
II	1000	M	60	15.0	6.7	6.7
		F	60	25.0	23.3	23.3
		M + F	120	20.0	15.0	15.0
III	0 (Control)	M	90	10.0	5.5	5.5
		F	90	16.7	10.0	11.1
		M + F	180	13.3	7.8	8.3

^aTotal benign and malignant tumors.

^bMalignant tumors.

 

Dichlorodifluoromethane (FC12): Mammary Carcinomas, Pulmonary Tumors and Leukemias in Mice (Exp. BT 602)

Group No.	Concentration (ppm)	Animals		Percentage of Animals Bearing Tumors
		Sex	No. at Start	Mammary Carcinomas	Pulmonary Tumors		Leukemias^a
					Adenomas	Adenocarcinomas
I	5000	M	60	-	8.3	-	6.7
		F	60	-	5.0	-	10.0
		M + F	120	-	6.7	-	8.3
II	1000	M	60	-	5.0	-	6.7
		F	60	3.3	1.7	-	20.0
		M + F	120	1.7	3.3	.	13.3
III	0 (Control)	M	90	-	3.3	-	3.3
		F	90	1.1	2.2	-	8.9
		M + F	180	0.5	2.8	-	6.1

^aThe term “leukemia” includes a variety of hemolymphoreticular beoplastic diseases at different sites.

 

Conclusions:

Under the experimental conditions, the compound failed to show any carcinogenic effects.

Executive summary:

The propellant chlorofluorocarbon dichlorodifluoromethane (CFC-12) was administered by inhalation for 78 weeks to mice at a concentration of 5000, 1000 and 0 ppm, 4 hours daily, 5 days weekly.

The animals were kept under observation until spontaneous death.

The incidence of all tumors and of some particular frequently occurring spontaneous tumors in mice showed a tendency to increase in animals exposed to CFC-12. The increased incidence was usually observed in one sex and was not always dose-related, possibly due to a longer survival of the treated mice compared with controls.

Under the experimental conditions, and on the basis of statistical analysis and of the oncological evaluation of the results, CFC-12 failed to show carcinogenic effects.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Quality of whole database:

Study is considered to be appropriate for use as it presents well documented results in an appropriate format, despite not being to GLP.
Calculation based on 5000 ppm * 120.91 /24.45 = 24725 mg/m3 where 24.45 is the molar volume as reported into the ACGIH ("2010 TLVs and BEIs, Based on the Documentation of the Threshold LImit Values for Chemical Substances and Physical Agents & Biological Exposure Indices") for conversion ppm vs mg/m3.

Carcinogenicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no study available

Justification for classification or non-classification

The inhalation studies were not conducted to GLP and is not in compliance with current protocols. However these results are considered appropriate for use in a weight of evidence. In addition, results of a chronic oral study were also available.

No adverse effects were reported following the 2-year exposure by inhalation or by oral exposure to the substance.

The above results triggered no classification under the CLP Regulation (EC No 1272/2008). No classification for carcinogenic effects is therefore required.

Additional information

A carcinogenicity study on the substance was conducted. Dichlorodifluoromethane (CFC-12) was administered by inhalation at a concentration of 5000, 1000 and 0 ppm, 4 hours daily, 5 days weekly, for 104 and 78 weeks, to rats and mice, respectively.

As a result of this study, no unexpected treatment-related tumors were observed in rats exposed. No important differences in the incidence of total benign and malignant tumors and of frequently occurring spontaneous tumors were observed in the rats exposed to the tested propellant. The incidence of all tumors and of some particular frequently occurring spontaneous tumors in mice showed a tendency to increase in animals exposed to CFC-12. The increased incidence was usually observed in one sex and was not always dose-related, possibly due to a longer survival of the treated mice compared with controls.

 

Under the experimental conditions, despite study limitations and lack fo details in available sources, CFC-12 failed to show carcinogenic effects in rats and mice.