Astronautical hygiene
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Astronautical hygiene is the application of science and technology to the study of the recognition and evaluation of the hazards and the prevention or control of the risks to health while working in a low gravity environment. John R. Cain (UK Government expert) was the first scientist to define this new discipline. He is a Fellow of the Institute of Biology, a Fellow of the British Interplanetary Society and a Member of the Faculty of Occupational Hygiene. Since 2006, he has been working with relevant individuals to try and establish a School of Space Medicine and Astronautical Hygiene in the UK linked with a major University and/or affiliated with the British National Space Centre (BNSC).
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[edit] Hygiene in space
Issues arise when dealing with low gravity environments. On the International Space Station, there are no showers, and astronauts instead take short sponge baths, with one cloth used to wash, and another used to rinse. Since surface tension causes water and soap bubbles to adhere to the skin, very little water is needed.[1][2] Special non-rinsing soap is used, as well as special non-rinsing shampoos.[3] Since a flush toilet would not work in low gravity environments, a special toilet was designed, that has suction capability.[4] While the design is nearly the same, the concept uses the flow of air, rather than water. In the case of the space shuttle, wastewater is vented overboard into space, and solid waste is compressed, and removed from the storage area once the shuttle returns to earth.[5] The current toilet model was first flown on STS-54 in 1993, and features an unlimited storage capacity, compared to only 14 day capacity of the original shuttle toilets, and the new model has an odor-free environment.[3]
[edit] Future applications
When astronauts return to the Moon, and travel further, to Mars, or other planets, they will be exposed to the dust from the surface. It is possible that an "astronaut hygienist" would go along to assist with hygiene aspects of the mission. The astronautical hygienist would provide information on the type and nature of the dust, calculate the levels of dust in the atmosphere, and assess the exposure risks to health, thereby determining the measures to mitigate exposure. This would ensure that the health of the astronauts are protected from exposure to Martian dust.
[edit] Control of gases in spacecraft
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Toxic gases are produced as an off-gassing from the astronauts, non-metallic materials e.g. surface coatings, adhesives, elastomers, solvents, cleaning agents, heat exchanger liquids etc. The gases if inhaled above specific concentrations could affect the ability of the crew to carry out their duties effectively (Ref: James, J "Toxicological Basis for Establishing Spacecraft Air Monitoring Requirements".. SAE Trans. J. Aerospace 107-1, 1998, pp. 854-89)
Most of the toxicological data on gas exposure is based on the 8-hour work period of the terrestrial worker and is therefore unsuitable for spacecraft work. New exposure times (astronautical hygiene data) have had to be established for space missions where exposure can be uninterrupted for up to 2 weeks or longer with no daily or weekend periods.
Exposure limits are based on:
- "Normal" spacecraft operating conditions.
- The "emergency" situation i.e. during a failure mode.
In the normal conditions there are found trace contaminant gases such as ammonia from normal off-gassing at ambient temperatures and at elevated temperatures. Other gases arise from the breathing gas supply reservoirs and crew members themselves. In emergencies gases can arise from overheating, spills, a rupture (s) in the coolant loop (ethylene glycol) and from the pyrolysis of non-metallic components. Carbon monoxide is a major concern for space crews; this was evident during the Apollo missions. The emitted trace gases can be controlled using lithium hydroxide filters to trap carbon dioxide and activated carbon filters to trap other gases.
Gases in the cabin can be tested using gas chromatography, mass spectrometry and infra-red spectrophotometry. Samples of air from the spacecraft are examined pre-flight and post-flight for gas concentrations. The activated carbon filters can be examined for evidence of trace gases. The concentrations measured can be compared with the appropriate exposure limits. If the exposures are high then the risk of health effects increases.
A large number of volatile substances have been detected during flight mostly within their threshold limit values (TLVs) and NASA Spacecraft Maximum Allowable Concentration Limits (SMACs. If spacecraft cabin exposure to specific chemicals is below their TLVs and SMACs then it is expected that the risks to health following inhalation exposure will be reduced.
[edit] SMACs (Spacecraft Maximum Allowable Concentrations)
SMACs provide guidance on chemical exposures during normal as well as emergency operations aboard spacecraft. Short-term SMACs refer to concentrations of airborne substances such as a gas and vapour that will not comprise the performance of specific tasks by astronauts during emergency conditions or cause serious toxic effects. Long-term SMACs are intended to avoid adverse health effects and to prevent any noticeable changes in the crews performance under continuous exposure to chemicals in the ISS for as long as 180 days (Ref: James, J.T. Spacecraft Maximum Allowable Concentrations for Airborne Contaminants. JSC 20584: NASA Johnson Space Centre, Houston, TX, February, 1995).
Astronautical hygiene data for developing the SMACs are:
- chemical-physical characterisation of the toxic chemical;
- animal toxicity studies;
- human clinical studies;
- accidental human exposures;
- epidemiological studies; and
- in-vitro toxicity studies
Application of astronautical hygiene principles to control exposure to lunar dust
Hazard
Lunar dust or regolith is the layer of particles on the Moon's surface and is <100um (Ref: Lunar Exploration Strategic Roadmap Meeting, 2005). The grain shapes tend to be elongated. Inhalation exposure to this dust can cause breathing difficulties. It is toxic. It can also cloud astronauts visors when working on the Moon;s surface. Furthermore, it adheres to spacesuits both mechanically (because of barbed shapes) and electrostatically. During Apollo, the dust was found to wear the fabric of the spacesuit (Ref: Bean, A.L. et al., NASA SP-235, 1970).
Evaluation of risks
During lunar exploration it will be necessary to evaluate the risks of exposure to the moon dust and thereby instigate the appropriate exposure controls. Required measurements may include measuring exospheric-dust concentrations, surface electric fields, dust mass, velocity and charge and its plasma characteristics.
Control
The use of "high-gradient magnetic separation" techniques should be developed to remove dust from the spacesuits following exploration as the fine fraction of the lunar dust is magnetic (Ref: Taylor, L.A., Deleterious efects of dust for lunar base activities: A possible remedy. New Views of the Moon Workshop, Lunar Planetary Inst., ext. abstr. 2000a.). Furthermore, vacuums can be used to remove dust from spacesuits.
Mass spectrometry
Mass spectrometry has been used to monitor spacecraft cabin air quality (Ref: "Mass spectrometry in the U.S. space program:past, present and future". Palmer, P. T. and Limero, T. F. Journal of the American Society for Mass Spectrometry. Vol 12, Issue 6, June 2001 pp 656-675). The results obtained can then be used to assess the risks during spaceflight for example, by comparing the concentrations of VOCs with their SMACs. If the levels are too high then appropriate remedial action will be required to reduce the concentrations and the risks to health.
[edit] See also
[edit] References
- ^ Ken Jenks (1998). Space Hygiene (English). Space Biomedical Research Institute. Retrieved on September 5, 2007.
- ^ NASA (2002). Personal Hygiene Provisions (English). NASA. Retrieved on September 5, 2007.
- ^ a b NASA. Ask an Astrophysicist (English). NASA. Retrieved on September 5, 2007.
- ^ NASA (2002). Waste Collection System (English). NASA. Retrieved on September 5, 2007.
- ^ NASA (2002). Living in Space (English). NASA. Retrieved on September 5, 2007.
[edit] Sources
- Spaceflight - Letters and emails (September 2006, p 353)
- Spaceflight - Letters and emails (December 2007, p 477)
