Toxicokinetics of inhaled bromotrifluoromethane (Halon 1301) in human subjects

Bromotrifluoromethane (CBrF3), commonly known as Halon 1301, is used as a fire extinguishant in the Space Shuttle. 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% in the spacecraft cabin atmosphere. To examine the effects of Halon 1301 on mental performance and physiologic function, the National Aeronautics and Space Administration sponsored a human inhalation study. Four pairs of adult male subjects were each exposed in a double-blind fashion for 24 hr to 1% (10,000 ppm or 60,875 mg/m3) Halon 1301 and to air in two separate exposures approximately 1 week apart. Mental performance and physiologic function were assessed and the results are reported in a companion paper (D. S. Calkins, J. J. Degioanni, M. N. Tan, J. R. Davis, and D. L. Pierson. Fundam. Appl. Toxicol. 20, in press). Blood and breath samples from the exposed subjects were also collected to provide dosimetric and toxicokinetic information, which is presented here. Blood Halon 1301 levels increased rapidly and approached a steady state within 2 hr of beginning the exposure; the steady-state concentration was approximately 3-4.5 micrograms/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 t1/2 alpha and t1/2 beta of 4.5 min (range 2.5-8.1 min) and 200 min (range 131-347 min), respectively. Halon 1301 concentrations in fat and soft tissues were also estimated. Subsequently, the end-tidal breath/blood/tissue/fat partition coefficients were calculated to be 17/1/0.5/33.(ABSTRACT TRUNCATED AT 250 WORDS)