Hydrogen Cyanide Vapour

This book reviews toxicity documents on five chemicals that can be released in the air from accidents at chemical plants, storage sites, or during transportation. The documents were prepared by the National Advisory Committee on Acute Exposure Guideline Levels for Hazardous Substances and were evaluated for their scientific validity, comprehensives, internal consistency, and conformance to the 1993 guidelines report.

On-board fires can occur on submarines after events such as collision or explosion. These fires expose crew members to toxic concentrations of combustion products such as ammonia, carbon monoxide, hydrogen chloride, and hydrogen sulfide. Exposure to these substances at high concentrations may cause toxic effects to the respiratory and central nervous system; leading possible to death. T protect crew members on disabled submarines, scientists at the U.S. Navy Health Research Center's Toxicology Detachment have proposed two exposure levels, called submarine escape action level (SEAL) 1 and SEAL 2, for each substance. SEAL 1 is the maximum concentration of a gas in a disabled submarine below which healthy submariners can be exposed for up to 10 days without encountering irreversible health effects while SEAL 2 the maximum concentration of a gas in below which healthy submariners can be exposed for up to 24 hours without experiencing irreversible health effects. SEAL 1 and SEAL 2 will not impair the functions of the respiratory system and central nervous system to the extent of impairing the ability of crew members in a disabled submarine to escape, be rescued, or perform specific tasks. Hoping to better protect the safety of submariners, the chief of the Bureau of Medicine and Surgery requested that the National Research Council (NRC) review the available toxicologic and epidemiologic data on eight gases that are likely to be produced in a disabled submarine and to evaluate independently the scientific validity of the Navy's proposed SEALs for those gases. The NRC assigned the task to the Committee on Toxicology's (COT's) Subcommittee on Submarine Escape Action Levels. The specific task of the subcommittee was to review the toxicologic, epidemiologic, and related data on ammonia, carbon monoxide, chlorine, hydrogen chloride, hydrogen cyanide, hydrogen sulfide, nitrogen dioxide, and sulfur dioxide in order to validate the Navy's proposed SEALs. The subcommittee also considered the implications of exposures at hyperbaric conditions and potential interactions between the eight gases. Review of Submarine Escape Action Levels for Selected Chemicals presents the subcommittee's findings after evaluation human data from experimental, occupational, and epidemiologic studies; data from accident reports; and experimental-animal data. The evaluations focused primarily on high-concentration inhalation exposure studies. The subcommittee's recommended SEALs are based solely on scientific data relevant to health effects. The report includes the recommendations for each gas as determined by the subcommittee as well as the Navy's original instructions for these substances.

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.