Astronautical hygiene evaluates, and mitigates, hazards and health risks to those working in low-gravity environments. The discipline of astronautical hygiene includes such topics as the use and maintenance of life support systems, the risks of the extravehicular activity, the risks of exposure to chemicals or radiation, the characterization of hazards, human factor issues, and the development of risk management strategies. Astronautical hygiene works side by side with space medicine to ensure that astronauts are healthy and safe when working in space.
Overview
When astronauts travel in space, they are exposed to numerous hazards, such as radiation, microbes in the spacecraft, and planetary surface toxic dust, etc. During a space voyage, astronautical hygienists work on collecting data concerning a multitude of subjects. Once the data has been collected, they then analyze the data to determine, among other things, the risks to human health due to exposure to the various chemicals within the spacecraft as well as other toxins during their flight. From that, the hygienists can determine the appropriate measures to take to mitigate exposure of the astronauts to the harmful chemicals.
Once on the surface of a moon or planet, the astronautical hygienist would also collect data on the nature of the dust, and the levels of radiation on the surface. From this analysis, they would determine the risks to the astronauts' health and will conclude how to prevent or control exposure.
The main roles of the astronautical hygienist are as follows:
To initiate and participate in research where a competent assessment of the risks to health are critical, e.g., in the development of effective dust mitigation strategies for lunar exploration. To be actively involved in designing hazard mitigation techniques, e.g. spacesuits with low dust retention/release and ease of movement. To provide in-flight troubleshooting e.g. for identifying the hazard, assessing the health risks and for determining the mitigation measures. To advise governments such as the UK Space Agency on the most cost-effective risk mitigation measures for crewed spaceflight. To act as a central link between the other space science disciplines. To provide information, instruction and training on standard-setting, on exposure health effects, on hazard identification, and the use of controls. To provide a holistic approach to protecting an astronaut's health.
The Orion spacecraft (or Multi-Purpose Crew Vehicle) is an American-European interplanetary spacecraft intended to carry a crew of four astronauts to destinations at or beyond low Earth orbit (LEO). Currently under development by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) for launch on the Space Launch System. Orion will contain potentially hazardous material such as ammonia, hydrazine, freon, nitrogen tetroxide, and volatile organic compounds and it will be necessary to prevent or control exposure to these substances during flight. Astronautical hygienists in the United States together with colleagues in the European Union, individual United Kingdom astronautical hygienists and space medicine experts are developing measures that will mitigate exposure to these substances.
Dr. John R. Cain (a UK government health risk management expert) was the first scientist to define the new discipline of astronautical hygiene. The establishment of the UK Space Agency and the UK Space Life and Biomedical Sciences Association (UK Space LABS) see the development and application of the principles of astronautical hygiene as an important means to protect the health of astronauts working (and eventually living) in space.
Cleaning and waste management Personal hygiene
Cleaning and waste disposal 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. Special non-rinsing soap is used, as well as special non-rinsing shampoos. Since a flush toilet would not work in low gravity environments, a special toilet was designed, that has suction capability. While the design is nearly the same, the concept uses the flow of air, rather than water. In the case of the space shuttle, waste water is vented overboard into space, and solid waste is compressed, and removed from the storage area once the shuttle returns to Earth. 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.
Inside the ISS, astronauts wear ordinary clothes. The clothes are not washed, and are typically worn until being considered too dirty, at which point they are taken back to Earth as rubbish, or ejected as waste to burn up in the atmosphere. In 2020, per agreement between NASA and Procter & Gamble, research into space-usable detergents began; in 2021, an experimental detergent was launched aboard SpaceX CRS-24.
Control of gases in spacecraft
Toxic gases are produced as an off-gassing from the astronauts and non-metallic materials e.g. surface coatings, adhesives, elastomers, solvents, cleaning agents, heat exchanger liquids, etc. Above specific concentrations, if inhaled, the gases could affect the ability of the crew to carry out their duties effectively.
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. An "emergency" situation.
In normal conditions, there are trace contaminant gases such as ammonia from normal off-gassing at ambient temperatures and 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 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 both before and after flight for their 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 risks to health increase. The ongoing sampling of the hazardous substances is essential so that appropriate action can be taken if exposure is high.
A large number of volatile substances detected during the flight are mostly within their threshold limit values and NASA Spacecraft Maximum Allowable Concentration Limits. 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.
Spacecraft maximum allowable concentrations
SMACs guide chemical exposures during normal as well as emergency operations aboard spacecraft. Short-term SMACs refer to concentrations of airborne substances such as gas and vapour that will not compromise 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 crew's performance under continuous exposure to chemicals for as long as 180 days.Spacecraft Maximum Allowable Concentrations for Airborne Contaminants. JSC 20584: NASA Johnson Space Centre, Houston, Texas, 1999
Astronautical hygiene data needed for developing the SMACs include: chemical-physical characterization of the toxic chemical animal toxicity studies human clinical studies accidental human exposures epidemiological studies in-vitro toxicity studies
Lunar dust hazards
Lunar dust or regolith is the layer of particles on the Moon's surface and is approximately <100 um.Lunar Exploration Strategic Roadmap Meeting, 2005 The grain shapes tend to be elongated. Inhalation exposure to this dust can cause breathing difficulties because the dust 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 cause wear in the fabric of the spacesuit.Bean, A.L. et al. (1970) Crew Observations. NASA SP-235, p. 29
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, charge, and its plasma characteristics.
Deposition of inhaled particles The extent of the inflammatory response in the lung will depend on where the lunar dust particles are deposited. In the 1G deposition, the more central airways will reduce the transport of the fine particles to the lung periphery. On the Moon with fractional gravity, the inhaled fine particles will be deposited in more peripheral regions of the lung. Therefore, because of the reduced sedimentation rate in lunar gravity, fine particles of dust will deposit in the alveolar region of the lung. This will exacerbate the potential for lung damage.
Controlling dust exposure 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.Taylor, L.A. (2000) Deleterious effects of dust for lunar base activities: A possible remedy. New Views of the Moon Workshop, Lunar Planetary Inst., ext. Abstr. Furthermore, vacuums can be used to remove dust from spacesuits.
Mass spectrometry has been used to monitor spacecraft cabin air quality. 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.
Microbial hazards
During spaceflight, there will be the transfer of microbes between crew members. Several bacterial associated diseases were experienced by the crew in Skylab 1. The microbial contamination in the Skylab was found to be very high. Staphylococcus aureus and Aspergillus spp have commonly been isolated from the air and surfaces during several space missions. The microbes do not sediment in microgravity which results in persisting airborne aerosols and high microbial densities in-cabin air in particular if the cabin air filtering systems are not well maintained. During one mission, an increase in the number and spread of fungi and pathogenic streptococci were found.
Urine collection devices build up the bacterium Proteus mirabilis, which is associated with urinary tract infection. For this reason, astronauts may be susceptible to urinary tract infection. An example is the Apollo 13 mission, during which the Apollo Lunar Module pilot experienced an acute urinary tract infection which required two weeks of antibiotic therapy to resolve.