Toxicokinetics of inhaled bromotrifluoromethane (Halon 1301) in human subjects

Bromotrifluoromethane (Halon 1301, CBrF3), is used as a fire extinguishant in the Space Shuttle, where several scenarios, such as a fire or a faulty alarm, could lead to its discharge resulting in a Halon 1301 concentration of up to 1 percent in the cabin atmosphere. The effect of Halon 1301 on mental performance and physiologic function was investigated in a NASA-sponsored human inhalation study in which four pairs of male subjects were each exposed in a double-blind fashion for 24 hr to 1 percent Halon 1301 and to air in two exposures about 1 week apart. Blood and breath samples from the exposed subjects were collected to provide dosimetric and toxicokinetic information. Halon 1301 blood levels increased rapidly and approached a steady state within 2 hr of the beginning the exposure; the steady-state concentration was approximately 3-4.5 microg/ml. Breath samples collected during exposures closely reflected chamber concentrations. Analysis of postexposure blood samples revealed that Halon 1301 was eliminated biphasically with an average t(1/2) alpha and t(1/2) beta of 4.5 min and 200 min, respectively.