Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 5 (2008) / Chapter Skim
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7 Carbon Dioxide
7 Carbon Dioxide
Pages 112-124
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From page 112... ...
, headache, dyspnea and intercostal pain, increases in airway resistance, intolerance to hyperventilation, exercise impairment, and testicular injury. For all end points except testicular injury, the data came from human studies; testicular injury data came from exposed guinea pigs and rats.
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From page 113... ...
= 1.3% where AC is acceptable concentration. This AC was applied to all exposure times because CNS effects would not be acceptable even for brief periods; however, there is no basis for supposing that prolonged exposures would result in an accumulation of CO2 that could have CNS effects.
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From page 114... ...
The long-term ACs to prevent increased airway resistance were calculated by using the small n factor as follows:
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CHANGES IN FUNDAMENTAL NRC RECOMMENDED APPROACHES The primary new tool for interpreting toxicity data is the benchmark dose modeling provided by the U.S. Environmental Protection Agency.
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From page 116... ...
investigated the mental performance of four subjects continuously exposed to 0.7% and 1.2% CO2 in a confined space for 26 d. They used four standardized performance tests: grammatical reasoning, memory search, unstable tracking, and dual task (doing unstable tracking and memory search together)
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From page 117... ...
Wong (1996) pieced together a rational picture of the potential adverse effects of exposure to CO2 and derived a defensible set of SMACs, with which the NRC SMAC Subcommittee agreed.
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From page 118... ...
(1971) changes in organ weights, changes in enzymes, of the data appear to and descriptive histological effects in rats and be quantitative, and guinea pigs exposed to concentrations from 1% they do not yield a to 30% CO2 for various times.
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From page 119... ...
. This is reasonable; industrial workers may need a lower limit because they never get a chance to physiologically adapt to workplace CO2 exposures, whereas physiological adaptation occurs in long-term continuous exposures and astronauts are unaffected by CO2 exposures confined to less than 0.7%.
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Abbreviations: ACGIH, American Conference of Governmental Industrial Hygienists; CEGL, continuous exposure guidance level; EEGL, emergency exposure guidance level; IDLH, immediately dangerous to life and health; NIOSH, National Institute for Occupational Safety and Health; NRC, National Research Council; OSHA, Occupational Safety and Health Administration; PEL, permissible exposure limit; REL, recommended exposure limit; SMAC, Spacecraft Maximum Allowable Concentration; STEL, short -term exposure limit; TLV, threshold limit value. measure such a deficit.
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From page 121... ...
Pp. 46-66 in Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants, Vol.
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From page 122... ...
Pp. 105-187 in Spacecraft Maximum Allowable Con centrations for Selected Airborne Contaminants, Vol.
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From page 123... ...
TABLE 7-3 End Points and Acceptable Concentrations (Wong 1996) Uncertainty Factors Acceptable Concentrations End Point Exposure Data Species and Reference Species Small n 1h 24 h 7d 30 d 180 d Visual impairment, NOAEL at 3%, Human (n = 7, 12)
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From page 124... ...
1988) Testicular injury NOAEL at 3%, Rat and guinea pig 1 -- -- -- 3 3 3 24 h/d, 42 d (Schaefer et al.
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