Spacecraft Water Exposure Guidelines for Selected Contaminants

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 subsequently review NASA's development of exposure guidelines for specific chemicals. The exposure guidelines are to be similar to those established by the NRC for airborne contaminants (NRC 1992; 1994; 1996a,b; 2000a). The NRC was asked to consider only chemical contaminants, and not microbial agents. The NRC convened the Subcommittee on Spacecraft Water Exposure Guidelines to address this task, and the subcommittee's first report, Methods for Developing Spacecraft Water Exposure Guidelines, was published in 2000 (NRC 2000b). A summary of that report is provided. Spacecraft water exposure guidelines (SWEGs) are to he established for exposures of l, 10, 100, and 1,000 days (d). The 1-d SWEG is the concentration of a substance in water that is judged acceptable for the performance of specific tasks during rare emergency conditions lasting for periods up to 24 hours (h). The 1-d SWEG is intended to prevent irreversible harm and degradation in crew performance. Temporary discomfort is permissible as long as there is no effect on judgment, performance, or ability to respond to an emergency. Longer-term SWEGs are intended to prevent adverse health effects (either immediate or delayed) and degradation in crew performance that could result from continuous exposure in closed spacecraft for as long as 1,000 d. In contrast with the 1-d SWEG, longer-term SWEGs are intended to provide guidance for exposure under the expected normal operating conditions in spacecraft.