Dichlorodifluoromethane

CAS number: 75–71–8

NIOSH REL: 1,000 ppm (4,950 mg/m³) TWA

Current OSHA PEL: 1,000 ppm (4,950 mg/m³) TWA

1989 OSHA PEL: Same as current PEL

1993-1994 ACGIH TLV: 1,000 ppm (4,950 mg/m³) TWA

Description of Substance: Colorless gas with an ether-like odor at extremely high concentrations.

LEL:. . Nonflammable Gas

Original (SCP) IDLH: 50,000 ppm

Basis for original (SCP) IDLH: Based on the statement by ILO [1971] that 50,000 ppm induces dizziness in humans, an IDLH of 50,000 ppm is chosen for this draft technical standard.

Existing short-term exposure guidelines: National Research Council [NRC 1984] Emergency Exposure Guidance Levels (EEGLs):

1-hour EEGL: 10,000 ppm

24-hour EEGL: 1,000 ppm

ACUTE TOXICITY DATA

Lethal concentration data:

Species	Reference	LC50 (ppm)	LCLo (ppm)	Time	Adjusted 0.5-hr LC (CF)	Derived value
Mouse Rabbit G. pig Rat	Paulet 1976 Paulet 1976 Paulet 1976 Scholz 1962	760,000 800,000 800,000 600,000	----- ----- ----- -----	30 min 30 min 30 min 2 hr	760,000 ppm (1.0) 800,000 ppm (1.0) 800,000 ppm (1.0) 960,000 ppm (1.6)	76,000 ppm 80,000 ppm 80,000 ppm 96,000 ppm

Other animal data: Serious cardiac arrhythmia was found in 5 of 12 dogs exposed to 50,000 ppm for 5 minutes and injected with epinephrine [Reinhardt et al. 1971]. In another study, respiratory-circulatory effects that included bronchoconstriction and tachycardia were found at 50,000 to 100,000 ppm [Aviado and Smith 1975].

Human data: Exposure up to 60,000 ppm was tolerated for 80 minutes by 1 volunteer [NRC 1984]; when exposed at 40,000 ppm for 14 minutes and then at 20,000 ppm for 66 minutes, another volunteer developed EEG changes and had slurred speech and decreased psychologic test scores [NRC 1984]. It has been stated that 50,000 ppm induces dizziness [ILO 1971]. Volunteers exposed for 2.5 hours to 10,000 ppm showed a 7% reduction in a standardized psychomotor test [Azar et al. 1972].

Revised IDLH: 15,000 ppm Basis for revised IDLH: The revised IDLH for dichlorodifluoromethane is 15,000 ppm based on acute inhalation toxicity data in humans [Azar et al. 1972; ILO 1971] and animals [Aviado and Smith 1975; Reinhardt et al. 1971].

REFERENCES:

1. Aviado DM, Smith DG [1975]. Toxicity of aerosol propellants in the respiratory and circulatory systems. Toxicology 3:241-252.

2. Azar A, Reinhardt CF, Maxfield ME, et al. [1972]. Experimental human exposure to fluorocarbon 12 (dichlorodifluoromethane). Am Ind Hyg Assoc J 3:207-216.

3. ILO [1971]. Fluorocarbons. In: Encyclopaedia of occupational health and safety. 2nd ed. Vol. I (A-K). Geneva, Switzerland: International Labour Office, pp. 560-562.

4. NRC [1984]. Emergency and continuous exposure limits for selected airborne contaminants. Vol. 2. Washington, DC: National Academy Press, Committee on Toxicology, Board on Toxicology and Environmental Health Hazards, Commission on Life Sciences, National Research Council, pp. 34-40.

5. Paulet G [1976]. Les fluorocarbones en question. J Eur Toxicol (Supplement) 9:385-407 (in French).

6. Reinhardt CF, Azar A, Maxfield ME, Smith PE Jr, Mullin LS [1971]. Cardiac arrhythmias and aerosol "sniffing." Arch Environ Health 22:265-279.

7. Scholz J [1962]. New toxicological investigations on certain types of freon used as propellants. Fortschr Biol Aerosol-forsch 1957-61 (in German). Ber Aerosol Kongr 4:420-429. [From ACGIH [1991]. Dichlorodifluoromethane. In: Documentation of the threshold limit values and biological exposure indices. 6th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists, pp. 420-422.]