Safe on Mars Precursor Measurements Necessary to Support Human Operations on the Martian Surface (2002) / Chapter Skim
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4. Chemical Environmental Hazards
4. Chemical Environmental Hazards
Pages 28-36
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From page 28... ...
Cancer is a potential chronic effect caused by the inhalation of Martian particulate matter containing certain toxic metals, asbestos-like fibers, or organic compounds. The committee concluded that the threat of asbestos-like materials being present in Martian dust and soil is not significant based on inferences about
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From page 29... ...
Toxic Metals and Other Inorganic Elements Airborne dust and soil could contain trace amounts of hazardous chemicals, including compounds of toxic metals that are known to cause cancer over the long term if inhaled in sufficient quantities. Soil analyses conducted by the Viking missions established maximum possible concentration limits for a few toxic elements based on the detection capabilities of the 29 TABLE 4.1 Representative Listing of Reference Concentrations for Cancer-Causing Compounds and for the Noncancerous Effects of Those Compounds from EPA's IRIS Database (milligrams per cubic meter)
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From page 30... ...
Should the actual concentration of hexavalent chromium become known, the habitat filtration requirements discussed in this chapter will change accordingly, keeping in mind that other toxic elements, such as arsenic, might then be dominant. Given the severe toxicity and uncertainty of the amount of hexavalent chromium, the committee recommends that NASA conduct an in situ experiment prior to the first human mission to Mars to determine if hexavalent chromium is present in Martian soil and airborne dust at potentially hazardous concentrations.
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From page 31... ...
This measurement can take place at any location on the planet since the airborne dust on Mars is highly mixed and therefore considered to be uniform in composition. 31 If this measurement cannot be made in situ, a sample of airborne dust and fine particles of Martian soil must be returned to Earth to determine if hexavalent chromium will pose a threat to astronauts operating on the surface of Mars.
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From page 32... ...
Filtration systems that maintain a maximum average concentration of 1 mg of particulate matter per cubic meter of air will place astronauts in an ARR of between 1 in 10,000 and 1 in 100,000 of getting cancer during their lifetime from exposure to toxic elements in Martian soil and airborne dust (see Table 4.3~. As noted in Chapter 2, in the section "Establishing Risk Standards," the committee established the ARR as an appropriate risk for astronauts.
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From page 33... ...
The committee believes, based on current filtration standards and the capability demonstrated on the International Space Station, that the filtration levels required to protect astronauts are readily achievable. However, if a filtration system cannot be designed to limit the average particulate inhalation exposure of an astronaut to 1 mg of particulate matter per cubic meter of air in the habitat, then a sample of airborne dust taken from the Martian atmosphere and soil must be analyzed to establish concentration levels of all toxic metals.
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From page 34... ...
If NASA chooses to limit respirable particulate concentrations to below 1 mg/m3, the cancer risk from toxic elements will also be reduced, since the relationship between the risk of getting cancer and the allowable concentration of airborne particulate matter is taken to be linear. This means that if NASA allows 10 mg/m3 of particulate matter in the habitat, the risk range of getting cancer will increase tenfold.
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From page 35... ...
The committee is concerned that the oxidants might dissipate during a sample return transfer unless the sample is maintained in near-Martian conditions during transit. If NASA chooses to measure the oxidizing characteristics of the Martian environment, the committee recommends exposing a variety of materials, such as space suit material, to the Martian atmosphere and observing the effects of oxidants on the materials by optical or other measurement techniques.
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From page 36... ...
The committee expects that the same capabilities would be provided in a human habitat on Mars. In addition, any highly reactive species, such as hydroxide radicals or other highly oxidizing species, created by photochemical processes in the Martian atmosphere by ultraviolet radiation would quickly evolve to less-hazardous chemical forms upon coming into contact with habitat airlock surfaces.
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