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The National Aeronautics and Space Administration (NASA) maintains an active interest in the environmental conditions associated with living and working in spacecraft and identifying hazards that might adversely affect the health and well-being of crew members. Despite major engineering advances in controlling the spacecraft environment, some water and air contamination appears to be inevitable. Several hundred chemical species are likely to be found in the closed environment of the spacecraft, and as the frequency, complexity, and duration of human space flight increase, identifying and understanding significant health hazards will become more complicated and more critical for the success of the missions. NASA asked the National Research Council (NRC) Committee on Toxicology to develop guidelines, similar to those developed by the NRC in 1992 for airborne substances, for examining the likelihood of adverse effects from water contaminants on the health and performance of spacecraft crews. In this report, the Subcommittee on Spacecraft Water Exposure Guidelines (SWEGs) examines what is known about water contaminants in spacecraft, the adequacy of current risk assessment methods, and the toxicologic issues of greatest concern.
Human spaceflight is inherently risky, with numerous potential hazards posed at each phase of a mission. Potential health risks during spaceflights include short-term health consequences from being in microgravity, as well as long-term health consequences that arise, or continue, months or years after a flight. Additional health considerations are risks posed by exposure to environmental contaminants onboard spacecraft. Because the International Space Station and spacecraft are closed environments that require recirculation of air and water supplies, some contamination of the air and water will occur. Even with onboard air and water purification systems, chemicals will accumulate in the air and water as they recirculate or are recycled onboard. Therefore, it is necessary for the National Aeronautics and Space Administration (NASA) to identify hazardous contaminants and determine exposure levels that are not expected to pose a health risk to astronauts. NASA uses spacecraft maximum allowance concentrations (SMACs) and spacecraft water exposure guidelines (SWEGs) to provide guidance on acceptable exposures to air and water contaminants during normal operations and emergency situations. Refinements to the Methods for Developing Spacecraft Exposure Guidelines updates the methods for establishing SMACs and SWEGs and assists NASA with identifying chemicals that need updated SMACs or SWEGs and new chemicals for which these guidelines should be developed.
The International Space Station is a closed and complex environment, so some contamination of its internal atmosphere and water system is expected. To protect space crews from contaminants in potable and hygiene water, the National Aeronautics and Space Administration (NASA) requested that the National Research Council (NRC) provide guidance on how to develop water exposure guidelines and review NASA's development of the exposure guidelines for specific chemicals. NASA selects water contaminants for which spacecraft water exposure guidelines (SWEGs) will be established; this involves identifying toxicity effects relevant to astronauts and calculating exposure concentrations on the basis of those end points. SWEGs are established for exposures of 1, 10, 100, and 1,000 days. This report is the second volume in the series, Spacecraft Water Exposure Guidelines for Selected Chemicals. SWEG reports for acetone, alkylamines, ammonia, barium, cadmium, caprolactam, formate, formaldehyde, manganese, total organic carbon, and zinc are included in this report. The committee concludes that the SWEGs developed for these chemicals are scientifically valid based on the data reviewed by NASA and are consistent with the NRC (2000) report, Methods for Developing Spacecraft Water Exposure Guidelines. SWEG reports for additional chemicals will be presented in a subsequent volume.
The International Space Station is a closed and complex environment, so some contamination of its internal atmosphere and water system is expected. To protect space crews from contaminants in potable and hygiene water, the National Aeronautics and Space Administration (NASA) requested that the National Research Council (NRC) provide guidance on how to develop water exposure guidelines and review NASA's development of the exposure guidelines for specific chemicals. NASA selects water contaminants for which spacecraft water exposure guidelines (SWEGs) will be established; this involves identifying toxicity effects relevant to astronauts and calculating exposure concentrations on the basis of those end points. SWEGs are established for exposures of 1, 10, 100, and 1,000 days. This report is the second volume in the series, Spacecraft Water Exposure Guidelines for Selected Chemicals. SWEG reports for acetone, alkylamines, ammonia, barium, cadmium, caprolactam, formate, formaldehyde, manganese, total organic carbon, and zinc are included in this report. The committee concludes that the SWEGs developed for these chemicals are scientifically valid based on the data reviewed by NASA and are consistent with the NRC (2000) report, Methods for Developing Spacecraft Water Exposure Guidelines. SWEG reports for additional chemicals will be presented in a subsequent volume.
Most people associate fluoride with the practice of intentionally adding fluoride to public drinking water supplies for the prevention of tooth decay. However, fluoride can also enter public water systems from natural sources, including runoff from the weathering of fluoride-containing rocks and soils and leaching from soil into groundwater. Fluoride pollution from various industrial emissions can also contaminate water supplies. In a few areas of the United States fluoride concentrations in water are much higher than normal, mostly from natural sources. Fluoride is one of the drinking water contaminants regulated by the U.S. Environmental Protection Agency (EPA) because it can occur at these toxic levels. In 1986, the EPA established a maximum allowable concentration for fluoride in drinking water of 4 milligrams per liter, a guideline designed to prevent the public from being exposed to harmful levels of fluoride. Fluoride in Drinking Water reviews research on various health effects from exposure to fluoride, including studies conducted in the last 10 years.
U.S. Navy personnel who work on submarines are in an enclosed and isolated environment for days or weeks at a time when at sea. Unlike a typical work environment, they are potentially exposed to air contaminants 24 hours a day. To protect workers from potential adverse health effects due to those conditions, the U.S. Navy has established exposure guidance levels for a number of contaminants. The Navy asked a subcommittee of the National Research Council (NRC) to review, and develop when necessary, exposure guidance levels for specific contaminants. This volume, the third in a series, recommends 1-hour and 24-hour emergency exposure guidance levels (EEGLs) and 90-day continuous exposure guidance levels (CEGLs) for acetaldehyde, hydrogen chloride, hydrogen fluoride, hydrogen sulfide, and propylene glycol dinitrate.
At the request of the Department of Defense and the Environmental Protection Agency, the National Research Council has reviewed the relevant scientific literature compiled by an expert panel and established Acute Exposure Guideline Levels (AEGLs) for several chemicals. AEGLs represent exposure levels below which adverse health effects are not likely to occur and are useful in responding to emergencies, such as accidental or intentional chemical releases in community, workplace, transportation, and military settings, and for the remediation of contaminated sites. Three AEGLs are approved for each chemical, representing exposure levels that result in: 1) notable but reversible discomfort; 2) long-lasting health effects; and 3) life-threatening health impacts. Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 13 includes AEGLs for boron trifluoride, bromoacetone, chloroacetone, hexafluoroacetone, perchloryl fluoride, piperidine, propargyl alcohol, trimethoxysilane and tetramethoxysilane, and trimethylbenzenes.
Extremely hazardous substances can be released accidentally as a result of chemical spills, industrial explosions, fires, or accidents involving railroad cars and trucks transporting EHSs. Workers and residents in communities surrounding industrial facilities where these substances are manufactured, used, or stored and in communities along the nation's railways and highways are potentially at risk of being exposed to airborne EHSs during accidental releases or intentional releases by terrorists. Pursuant to the Superfund Amendments and Reauthorization Act of 1986, the U.S. Environmental Protection Agency (EPA) has identified approximately 400 EHSs on the basis of acute lethality data in rodents. Acute Exposure Guideline Levels for Selected Airborne Chemicals, Volume 20 reviews and updates the technical support document on acute exposure guideline levels (AEGLs) for selected chloroformates. This update focuses on establishing AEGL-3 values for n-propyl chloroformate and isopropyl chloroformate, but will also consider whether any new data are available that would affect the proposed values for the other 10 chloroformates. AEGLs represent threshold exposure limits (exposure levels below which adverse health effects are not likely to occur) for the general public and are applicable to emergency exposures ranging from 10 minutes (min) to 8 h. Three levels - AEGL-1, AEGL-2, and AEGL-3 - are developed for each of five exposure periods (10 min, 30 min, 1 h, 4 h, and 8 h) and are distinguished by varying degrees of severity of toxic effects. This report will inform planning, response, and prevention in the community, the workplace, transportation, the military, and the remediation of Superfund sites.
The present report is the committee's 19th interim report. It summarizes the committee's conclusions and recommendations for improving NAC's AEGL documents for the following chemicals and chemical classes: acrylonitrile, benzonitrile, boron tribromide, BZ (3-quinuclidinyl benzilate), chloroarsenicals, chloroformates, bis-chloromethylether, chloromethylether, chlorosilanes (26 selected compounds), cyanogen, ethyl mercaptan, hexafluoroacetone, lewisites, mercury vapor, nitric acid, nitric oxide, nitrogen dioxide, nitrogen tetroxide, oleum, phenyl mercaptan, propargyl alcohol, selenium hexafluoride, silane, sulfer trioxide, sulfuric acid, tear gas, tert-octyl mercaptan, tetramethoxy silane, thionyl chloride, trimethoxysilane, trimethylbenzenes (1,2,4-; 1,2,5-;and 1,3,5-TMB), and vinyl chloride.
Focuses on the applications of toxicology principles to the practice of industrial hygiene, using case studies as examples.