Toxicological Assessment of the International Space Station Atmosphere, Part 2

Space-faring crews must have safe breathing air throughout their missions to ensure adequate performance and good health. Toxicological assessment of air quality depends on the standards that define acceptable air quality, measurements of pollutant levels during the flight, and reports from the crew on their in-flight perceptions of air quality. Air samples from ISS flights 2A.2a, 2A.2b, 3A, and 4A were analyzed for trace pollutants. On average the air during each flight was safe for human respiration. However, there were reports from the crew that they experienced a headache when in certain areas, and strong odors were reported from specific locations of the ISS complex. Inspection of air samples in these locations suggested that several of the solvent-type pollutants (e.g. ethyl acetate, xylenes, and n-butanol) were present in concentrations that would cause a strong odor to be perceived by some individuals. There were large variations in pollutants from selected modules upon first entry; however, the egress samples from each module showed nearly uniform mixing of the atmospheres by the time the ISS was resealed. The Service Module was added during this period and samples of its unscrubbed atmosphere and scrubbed atmosphere show that scrubbing was effective, especially against pollutants that were present in relatively high concentrations.