The National Aeronautics and Space Administration (NASA) is aware of the potential toxicological hazards to crew members that might be associated with prolonged spacecraft missions. Despite major engineering advances in controlling the atmosphere within spacecraft, some contamination of the air appears inevitable. NASA has measured numerous airborne contaminants during space missions. As the missions increase in duration and complexity, ensuring the health and well-being of astronauts traveling and working in this unique environment becomes increasingly difficult. As part of its efforts to promote safe conditions aboard spacecraft, NASA requested the National Research Council (NRC) to develop guidelines for establishing spacecraft maximum allowable concentrations (SMACs) for contaminants, and to review SMACs for various spacecraft contaminants to determine whether NASA's recommended exposure limits are consistent with the guidelines recommended by the subcommittee. In response to this request, the NRC first developed criteria and methods for preparing SMACs for spacecraft contaminants, published in its 1992 report Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants. Since then, the NRC's Subcommittee on Spacecraft Maximum Allowable Concentrations has been reviewing NASA's documentation of chemical-specific SMACs. This report is the fourth volume in the series Spacecraft Maximum Allowable Concentrations for Space Station Contaminants. The first volume was published in 1994 and the second and third in 1996. Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants: Volume 4 has been reviewed in draft form by individuals chosen for their technical expertise and diverse perspectives in accordance with procedures approved by the NRC's Report Review Committee for reviewing NRC and Institute of Medicine reports. The purpose of that Independent review was to provide candid and critical comments to assist the NRC in making the published report as sound as possible and to ensure that the report meets institutional standards for objectivity, evidence, and responsiveness to the study charge. The review comments and draft manuscript remain confidential to protect the integrity of the deliberative process. Table of Contents Front Matter Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants: Introduction Summary of Report on Guidelines for Developing SMACS Review of SMAC Reports References Appendix A: Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants: Executive Summary Appendix B: Reports on Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants B1 Actone B2 C3 to C8 Aliphatic Saturated Aldehydes B3 Hydrogen Chloride B4 Isoprene B5 Methylhydrazine B6 Perfluoropropane and Other Aliphatic Perfluoroalkanes B7 Polydimethylcyclosiloxanes B8 Dichlorofluoromethane (Freon 21) B9 Chlorodifluormethane (Freon 22) B10 Trichlorofluoromethane (Freon 11) B11 Dichlorodifluoromethane (Freon 12) B12 4-Methyl-2-Pentanone B13 Chloroform B14 Furan B15 Hydrogen Cyanide

Table of Contents:
1 Front Matter; 2 Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants: Introduction; 3 Summary of Report on Guidelines for Developing SMACS; 4 Review of SMAC Reports; 5 References; 6 Appendix A: Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants: Executive Summary; 7 Appendix B: Reports on Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants; 8 B1 Actone; 9 B2 C3 to C8 Aliphatic Saturated Aldehydes; 10 B3 Hydrogen Chloride; 11 B4 Isoprene; 12 B5 Methylhydrazine; 13 B6 Perfluoropropane and Other Aliphatic Perfluoroalkanes; 14 B7 Polydimethylcyclosiloxanes; 15 B8 Dichlorofluoromethane (Freon 21); 16 B9 Chlorodifluormethane (Freon 22); 17 B10 Trichlorofluoromethane (Freon 11); 18 B11 Dichlorodifluoromethane (Freon 12); 19 B12 4-Methyl-2-Pentanone; 20 B13 Chloroform; 21 B14 Furan; 22 B15 Hydrogen Cyanide