VOLATILE ORGANIC CONTAMINANTS FOUND IN THE HABITABLE ENVIRONMENT OF THE SPACE-SHUTTLE - STS-26 TO STS-55

The health and performance of spacecraft crews can be adversely affect ed by contaminants present in the respirable air. Contaminants origina te from hardware offgassing, crew and microbial metabolism, use of uti lity chemicals, leakage from fluid systems and payload experiments, an d from electrical overheating. The quality of Shuttle air is measured by collecting contaminants in evacuated cylinders or on sorbent resin for later ground-based analysis by gas chromatography (GC) and GC mass spectrometry (MS). The results of those analyses are presented for 28 missions, including 5 Spacelabs which were flown in the payload bay o f the Shuttle. The major contaminants were relatively nontoxic alcohol s (ethanol, isopropanol), ketones (ae etone, diacetone alcohol), alkan es, halocarbons (Halon 1301, Freon 113), and siloxanes. Occasionally, more toxic contaminants, such as methanol, acetaldehyde, and tetrachlo roethene, were present at low concentrations (below 1 mg/m(3)). The co ntaminant concentrations measured in spacecraft air were compared to s pacecraft maximum allowable concentrations (SMAC's) which are set to p rotect the crew from adverse health effects or performance decrements. Aggregate toxicity assessments (T values) of the contaminants present during each mission, calculated by summing the ratios of measured con centrations to each contaminant's SMAC, showed that air quality consis tently met the criterion that the T value be less than 1.