Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 3 (1996) / Chapter Skim
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B1: Bromotrifluoromethane
B1: Bromotrifluoromethane
Pages 21-52
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Chiu-Wing Lam, Ph.D. Johnson Space Center Toxicology Group Biomedical Operations and Research Branch National Aeronautics and Space Administration Houston, Texas PHYSICAL AND CHEMICAL PROPERTIES Synonyms: CAS number: Formula: Molecular weight: Melting point: Boiling point: Vapor pressure: Trifluorobromomethane, Freon 1301, Freon 13B1 Fluorocarbon 1301 75-63-8 CBrF3 148.9 -167.7°C -57.8°C Exists as a gas at ambient temperature Concentration conversion 1 ppm = 6.1 mg/m3; at 25°C: 1 mg/m3 = 0.16 ppm OCCURRENCE AND USE Bromotrifluoromethane, a gaseous fluorocarbon, is commonly known as Halon 1301.
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TOXICOKINETICS AND METABOLISM Toxicokinetics An inhalation study sponsored by NASA was conducted with eight pairs of human subjects exposed to 1% (10,000 ppm) Halon 1301 for
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Tissue concentrations and uptake and elimination kinetics of Halon 1301 in the heart and brain (two major target organs) were investigated in rats exposed to 71-76% Halon 1301 for 5 min (Van Stee and Back, 1971a)
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TOXICITY SUMMARY Owing to its inertness, Halon 1301 is low in toxicity (Reinhardt and Reinke, 1972~. The toxicity of Halon 1301 has been extensively reviewed (DuPont, 1971; NAS, 1972; Haskell Laboratory, 1974, 1978; Van Stee, 1974; NRC, 197S, 1984; Graham, 1981~.
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The cardiovascular effects probably are due in part to the sensitization of the heart to epinephrine, a phenomenon that can be induced by exposures to high concentrations of hydrocarbons and halogenated hydrocarbons (Van Stee and Back, 1969; Hanig and Herman, 1991~. Acute and Short-Tenn Exposures Human Exposures CNS Effects An accidental discharge of 1200 Ib of Halon 1301 for 30 s was triggered by a fire alarm in a hospital facility.
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Subjects exposed to 4% Halon 1301 also showed performance decrements, although to a lesser degree. The effect of Halon 1301 on sensory-motor test performance was also evaluated in groups of four or six subjects exposed to I.25%, 2.5 %, 5 %, and 10% Halon 1301 for 22 min in an inhalation chamber (Hine et al., 1968, 1969~.
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Because no studies had been conducted in which humans were exposed to Halon 1301 for more than several hours, NASA sponsored a double-blind human inhalation study in which four pairs of subjects were each exposed for 24 h to Halon 1301 or air (NASA, 1989; Calkins et al., 1993~. Six cognitive performance assessments and a motor function test, which produced 13 measurements of accuracy and reaction time, were administered before, during, and after the inhalation exposures.
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Cardiac effects have not been detected in subjects exposed at lower concentrations. The cardiovascular toxic signs and incidence reported by hospital workers exposed to a nominal concentration of 5% Halon 1301 during an accidental discharge were shortness of breath (36%)
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Dogs exposed to 10% Halon 1301 showed no toxic signs (Hine et al., 1968; Van Stee and Back, 19691. CNS effects were also observed in rats exposed to 30-53% Halon 1301 for 10 min (Clark and Tinston, 1982~.
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Van Stee and Back (1969) observed an increase in heart rates in dogs exposed to 20-30% Halon 1301 or more.
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. In a repeated-exposure study, 20 mice, 10 rats, and 10 guinea pigs were exposed to 50% Halon 1301 2 h daily for 15 consecutive days; one mouse and one guinea pig died.
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for 10 ~ and studied clinical toxic signs, clinical chemistry, gross pathological changes of all organs, and microscopic histopathological changes of selected organs (lungs, liver, heart, kidneys, and spleen) of these animals.
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also observed that adrenal weights in Halon 1301-exposed guinea pigs were not statistically different from those of air-exposed guinea pigs. Therefore, the effects of Halon 1301 on the adrenal glands in rats are questionable, and these results would not be considered in setting the exposure limit.
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These effects were not considered compound-related. Halon 1301 was not considered a developmental toxicant under these test conditions (NRC, 1984; Haskell Laboratory, unpublished data, cited in NRC, 1984, and Graham, 1981~.
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are outlined in Guidelines for Developing Spacecraft Maximum Allowable Concentrationsfor Space Station Contaminants (NRC, 1992~. Studies Not Considered in Setting ACs Studies on "Impure" Halon 1301 A study using the commercial grade of Haion 1301 available at that
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(1968) suggested that the eye and nasal irritation reported by some of their human subjects in their study was due to Halon 1301 thermal decomposition products.
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(1982) reported that exposing six human subjects to 7% Halon 1301 for 3 h produced transient light-headedness, mild euphoria, and considerable performance decrements.
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(1993) observed that Halon 1301 blood concentrations in exposed human subjects increased rapidly and approached a steady state within 2 h of starting the exposure; thus, the cardiac effects would be expected to be relatively independent of exposure time shortly after the initiation of exposure.
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(1953) observed moderate diffuse congestion in the respiratory tracts of rats exposed to 2.3% Halon 1301 for 30 d.
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47 to o C)
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32016. Medical Sciences Division, Space and Life Sciences Directorate, NASA Johnson Space Center, Houston, Tex.
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in human subjects. Fundam.
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1992. Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants.
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Van Stee, E.W., and K.C.
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46-68. Haskell Laboratory, E.T.
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