Spacecraft Maximum Allowable Concentrations for 1-Propanol

1-Propanol is a volatile organic compound commonly used as a solvent for industrial and pharmaceutical products. It has been consistently detected at low concentrations in the International Space Station. Although there are published spacecraft maximum allowable concentrations (SMACs) for its less toxic isomer 2-propanol, no SMACs were previously established for 1-propanol. This document reviews existing literature on 1-propanol inhalation toxicity to derive acute and long-term SMACs applicable to off-nominal and nominal scenarios, respectively.

Electronic databases and published literature were searched for relevant toxicity data on 1-propanol inhalation. Keywords "1-propanol" and "n-propanol" were used, and hits were further screened by the key phrase "inhalation toxicity."

Most studies identified were acute inhalation toxicity using animal models. Mice exposed to 3250 ppm of 1-propanol for 1.5-2 h experienced central nervous system depression mimicking alcohol intoxication. No adverse effects were reported in mice or rats exposed to 1600 ppm for 120 h, but exposure to 7000 ppm for 294 h resulted in reduced male fertility.

To preclude central nervous system depression, 1-h and 24-h SMACs for 1-propanol were set at 205 and 100 ppm, respectively. A limit of 60 ppm for 7 d was based on lack of effects at 1600 ppm for 120 h. SMACs for 30, 180, and 1000 d were set at 35 ppm to preserve male fertility. Resulting values are approximately half of the recently updated SMAC values for 2-propanol, which is consistent with the trend between the other published exposure limits of these two isomers. Ryder VE, Yap DA. Spacecraft maximum allowable concentrations for 1-propanol. Aerosp Med Hum Perform. 2026; 97(1):60-63.