CARCINOGENS IN SPACECRAFT AIR

The health effects of long-term exposure to ionizing radiation during spaceflight are a major concern to NASA, especially for missions beyon d low-Earth orbit. Experiments involving astronauts will be conducted during the next few years to improve the risk assessment for exposures to ionizing radiation during flights; however, concomitant exposure t o certain airborne chemical carcinogens during these experiments could confound the results of radiation experiments. Carcinogens can reach the spacecraft atmosphere from leaking thrusters, from off-gassing mat erials, from chemical experiments and from human metabolism. The Johns on Space Center Toxicology Group routinely analyzes atmospheric sample s collected aboard spacecraft. The exposure limits for radiomimetic co mpounds such as benzene are reduced because of the potential interacti on between radiation and chemical exposures. Analysis of recent spacec raft air samples indicates that the following carcinogens are often pr esent in measurable concentrations: acetaldehyde, dichloromethane, for maldehyde and isoprene. Occasionally, the carcinogens 1,2-dichloroetha ne, acrolein, benzene and furan are found in atmospheric samples. Duri ng normal operating conditions, the low concentrations of and limited periods of exposure to airborne carcinogens are thought to pose minima l health risks to crew members, and should not confound experiments in volving sensitive methods to detect biological effects of ionizing rad iation. (C) 1997 by Radiation Research Society.