Dichlorodifluoromethane

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Not specified

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Study report, not conducted to GLP but well documented with methodology and results included.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1973

Report Date:

1973

Materials and methods

Test guideline

Qualifier:

no guideline followed

Principles of method if other than guideline:

See "details on exposure" and "details on test animals and environmental conditions" below.

GLP compliance:

not specified

Limit test:

yes

Test material

Reference

Name:

Unnamed

Type:

Constituent

Test material form:

gas under pressure: liquefied gas

Details on test material:

The test material was supplied by the Freon Product Laboratory of the Organic chemicals Department as two solutions in corn oil; one solution contained 0.2% CFC-12 and was given Haskell No. 6966; the other solution contained 2.0% Freon 12 and was given Haskell No. 6967.

Test animals

Species:

rat

Strain:

other: Charles River-CD

Details on test animals and environmental conditions:

Seventy-eight pregnant (primigravida) albino rats (Charles River-CD) were received from Charles Rivers Breeding Laboratories in two shipments one day apart. From the time of arrival at Haskell Laboratory through the fifth day of gestation, the animals were housed inn suspended stainless steel wire cages, assigned to three groups, and fed ground Purina Laboratory Chow (GPLC) supplemented with 1% corn oil (CO).

Administration / exposure

Route of administration:

oral: gavage

Vehicle:

corn oil

Details on exposure:

On day six of the gestation period, all rats in all groups were given the following diet: 74.25% GPLC + 0.25% CO + 25% Casein + 0.5% vitamin mix. One group, the control, was given 2.0ml of corn oil each day by intragastric intubation for 10 consecutive days; the other two groups were given 2.0ml of Haskell No. 6966 (0.2% solution of Freon 12 in corn oil) or Haskell No. 6967 (2.0% solution of Freon 12 in corn oil), respectively, for the same period of time, i.e., through day 15 of gestation. From day 16 of the gestation period to the time of sacrifice, the control and test rats received their initial basal diet (GPLC + 1% CO).

Analytical verification of doses or concentrations:

not specified

Details on analytical verification of doses or concentrations:

Not specified

Details on mating procedure:

Not specified

Duration of treatment / exposure:

10 days

Frequency of treatment:

Daily

Duration of test:

To day 21 of gestation period.

Doses / concentrations

Remarks:

Doses / Concentrations:
0, 16.6 & 170.9 mg/kg/day
Basis:
actual ingested

No. of animals per sex per dose:

78 rats in total.
Group I (0) - 25
Group II (16.6) - 26
Group III (170.9) - 27

Control animals:

yes, concurrent vehicle

Details on study design:

The animals were sacrificed by chloroform inhalation on the twenty-first day of gestation. Pregnancy was dated by counting as day one the morning on which a copulation plug was found. An incision was made in the abdominal wall and both ovaries and uterine horns were promptly removed, inspected and weighed. The uterus was carefully opened and the foetuses removed. The following observations and measurements were made:
1. Number and location of live foetuses, dead foetuses, and resorption sites in the respective uterine horns.
2. Body weight and crown-rump length of all live foetuses.
3. External examination of all foetuses, from head to tail, under Macro Scope (Ednakite 2½ x) for gross abnormalities.
About two-thirds of the foetuses from each litter were preserved in 95% alcohol for subsequent maceration in 1% aqueous KOH, clearing and staining with Alizarin Red S, and examination to detect skeletal abnormalities. The remaining foetuses were fixed in Bouin’s fluid for free-hand razor-blade sectioning (Wilson Method) and examination for visceral and neural anomalies under the dissecting microscope.

Examinations

Maternal examinations:

Not specified

Ovaries and uterine content:

An incision was made in the abdominal wall and both ovaries and uterine horns were promptly removed, inspected and weighed. The uterus was carefully opened and the foetuses removed.

Fetal examinations:

Number and location of live foetuses, dead foetuses, and resorption sites in the respective uterine horns. Body weight and crown-rump length of all live foetuses. External examination of all foetuses, from head to tail, under Macro Scope (Ednakite 2½ x) for gross abnormalities.

Statistics:

Not specified

Indices:

Not specified

Historical control data:

The data was also compared with the standard values established for Charles River-CD (ChR-CD) rats.

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:no effects

Details on maternal toxic effects:
Body Weight: The oral administration of Freon 12 to pregnant rats during the period of organogenesis had no adverse effect on body weight gain
Food Consumption: There were no meaningful differences among the control and test groups of rats with respect to food intake during any of the time periods measured.

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
Pregnancy Outcome and Fetal Development: The uteri of all females in all groups were free from gross abnormalities. There was no difference in the numbers of implantation sites, viable foetuses and resorption sites per female between the control group and those given Freon 12. Likewise, there was no significant difference in mean weight and length of foetuses. The smaller weight and length in the control group were due to sacrifice of several females on day earlier (20 days). The data was also compared with the standard values established for Charles River-CD (ChR-CD) rats and were found to be in good agreement.
Malformations and Anomalies: No major gross, skeletal or soft tissue abnormalities were detected. Maternal feeding of Freon 12 did not influence the fetal development. The incidence and type of other minor anomalies were compared with those of the control group and with the standard values for ChR-CD rats. They were found to be similar.

Effect levels (fetuses)

1

Dose descriptor:

NOAEL

Effect level:

> 170 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: teratogenicity

2

Dose descriptor:

NOAEL

Effect level:

> 170 mg/kg bw/day (actual dose received)

Based on:

test mat.

Basis for effect level:

other: embryotoxicity

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

TABLE I – AVERAGE BODY WEIGHTS OF PREGNANT RATS RECEIVING FREON 12 DURING ORGANOGENESIS

Group Characteristics	No. of Pregnant Rats No. of Rats Received	Average Body Weight in Grams on Day of Gestation Period
		6	16	21
2 ml corn oil (control)	22/25	199	269	337
2 ml corn oil containing 0.2% Freon 12 (test)	20/26	203	278	345
2 ml corn oil containing 2.0% Freon 12 (test)	25/27	196	271	346

 

TABLE II – AVERAGE FOOD CONSUMPTION DATA OF PREGNANT RATS RECEIVING FREON 12 DURING ORGANOGENESIS

Group Characteristics	No. of Pregnant Rats No. of Rats Received	Average Daily Food Consumption (g/rat/day)
		Control Diet Prior to Day 6	Diet During Dosing Day 6-16	Control Diet Days 16-21
2 ml corn oil (control)	22/25	17.1	17.0	21.0
2 ml corn oil containing 0.2% Freon 12 (test)	20/26	18.7	19.3	22.7
2 ml corn oil containing 2.0% Freon 12 (test)	25/27	17.4	17.8	23.1

 

TABLE III – AVERAGE DOSE OF FREON 12 RECEIVED BY PREGNANT RATS DURING ORGANOGENESIS

Group Characteristics	Average Body Weight In Grams During Day 6-16	Average Dose of Freon 12 (mg/kg/day)
2 ml corn oil (control)	234	-
2 ml corn oil containing 0.2% Freon 12 (test)	241	16.6
2 ml corn oil containing 2.0% Freon 12 (test)	234	170.9

 

TABLE IV – EFFECT OF ORAL ADMINISTRATION OF FREON 12 TO PREGNANT RATS IN THE OUTCOME OF PREGNANCY AND ON VARIOUS PARAMETERS OF FETAL DEVLEOPMENT

	Groups (mg/kg/day of Freon 12)			Standard Values (Range) for Charles River (CD) Rats (1)
	Group I (0)	Group II (16.6)	Group III (170.9)
Number Females Pregnant	22/25 (88.0%)	20/26 (76.9%)	25/27 (92.6%)	90% (62-100)
Number Implantation Sites	201	186	236
Number Implantation Sites / Pregnant Female	9.13	9.30	9.44	10.9 (8.6-14.1)
Number Live Fetuses	197	179	231
Number Dead Fetuses	0	0	0
Number of Live Fetuses/Litter	8.95	8.95	9.24	10.2 (8.2-12.7)
Number Females Showing Complete Resorption	0	0	0	0.3% (0-5.9)
Number Females Showing Premature Birth	0	0	0	0.1% (0-5.9)
Number Females Showing Partial Resorption (Excluding Complete Resorptions)	4 (18.2%)	4 (20.0%)	3 (12.0%)	40.6% (10.5-77.8)
Total Number Resorbed	4 (2.0%)	7 (3.8%)	5 (2.1%)	6.0% (1.2-12.4)
Mean Fetus Weight (g)	3.35	4.19	3.93	3.69 (2.90-4.22)
Mean Fetus Crown-Rump Length (cm)	2.98	3.52	3.36

(1) Personal communication; unpublished data obtained from Charles River Breeding Laboratories, Wilmington, Massachusetts for period 1964 -1969.  

 

TABLE V – GROSS EXTERNAL, SKELETAL AND SOFT TISSUE ABNORMALITIES FOUND IN FETUSES FROM MOTHERS ADMINISTERED FREON 12 DURING FETAL DEVELOPMENT

Abnormalities Found	Groups (mg/kg/day of Freon 12)			Standard Values (Range) of Abnormalities for ChR-CD Rats (1)
	Group I (0)	Group II (16.6)	Group III (170.9)
1. Gross External
Number Fetuses Examined	197	179	231	32915
a. Small, stunted	1 (0.5%)	0 (0%)	4 (1.73%)	0.3% (0-3.5)
2. Skeletal
Number Fetuses Examined	12	117	154	7127
a. Xiphisternum and one or more sternebrae unoissified	10 (7.7%)	10 (8.5%)	17 (11.0%)	11% (5-30)
b. With 14 rib(s)	15 (11.7%)	9 (7.6%)	12 (7.8%)	21% (6.36)
c. Vertebral bipartite centra	1 (0.8%)	1 (0.9%)	0 (0%)	2% (0-4)
3. Soft Tissue (Visceral and Neural)
Number Fetuses Examined	68	*	77
a. Found normal	68	-	77

(1) Personal communication; unpublished data obtained from Charles River Breeding Laboratories, Wilmington, Massachusetts for period 1964 -1969.

* Not examined.

Applicant's summary and conclusion

Conclusions:

Maternal feeding of CFC-12 was not embryotoxic under the conditions of this experiment.CFC-12 was not teratogenic.

Executive summary:

The present study was undertaken, as part of a comprehensive toxicological program, to evaluate the embryotoxic and teratogenic potential, if any, of CFC-12 when it was administered by intragastric intubation to pregnant rats during the period of fetal organogenesis. 

Gastric intubation of dichlorodifluoromethane (CFC-12) to pregnant rats from day six through day fifteen of their gestation period, at average dose levels of 16.6 and 170.9 mg/kg/day, had no effect on the food intake and the gain in body weight of the mothers.

No clinical signs of toxicity were observed in any of the treated animals. The outcome of pregnancy, measured by the number of implantation sites, resorptions and live foetuses per litter, was not adversely affected by the treatment. The treatment did not affect the embryonal development as measured by weight and crown-rump length of the foetuses. The absence of any major external, skeletal, and soft tissue abnormalities in live foetuses and a similar incidence of spontaneous minor anomalies in the control and treated groups indicate that oral administration for CFC-12 was not teratogenic.

CONCLUSIONS

The absence of any effect on the number of implantation sites, resorptions, live foetuses per litter and mean weight and crown-rump length of the foetuses indicate that maternal feeding of CFC-12 was not embryotoxic under the conditions of this experiment.

Likewise, the absence of any major abnormalities in live foetuses and a similar incidence of spontaneous minor anomalies in the control and treated groups indicate that CFC-12 was not teratogenic.