Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 5 (2008) / Chapter Skim
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4 Benzene
4 Benzene
Pages 62-72
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From page 62... ...
Toxicology Group Habitability and Environmental Factors Division Johnson Space Center National Aeronautics and Space Administration Houston, Texas Spacecraft maximum allowable concentrations (SMACs) for benzene were initially published in Volume 2 of Spacecraft Maximum Allowable Concentrations for 1-h, 24-h, 7-d, 30-d, and 180-d exposure durations (James and Kaplan 1996)
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From page 63... ...
, along with the National Research Council (NRC) Subcommittee on Toxicology, analyzed the acute and chronic toxicity of benzene by assessing available research.
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A spaceflight factor of 3 was deemed appropriate because of numerous reports on spaceflight effects on immune function in rats and to a lesser extent in astronauts (Taylor 1993)
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From page 65... ...
HR Leukemia Lowest of 0.01% risk Varieties -- -- 3 rad -- 12 1.7 0.4 0.07 estimates at 0.2 ppm, 180 d continuous SMAC 10 3 0.5 0.1 0.07 a Extrapolation to these exposure durations produces unacceptable uncertainty in the values. Abbreviation: HR, Haber's rule; rad, radiation.
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From page 66... ...
benzene ACs. Long-Term AC Data A review of the long-term exposure data since the original SMAC publication primarily focused on identifying biomarkers of benzene exposure in urine.
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From page 67... ...
(2004) study showed a monotonically increasing effect only for platelets and B cells but not for the measured cell lines that might be expected to lead to myeloid leukemic lines; WBC counts and granulocyte counts that showed a reduction in cell number at <1 ppm did not show a further reduction among workers with exposures up to 10 ppm.
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Four single nucleotide polymorphisms were associated with decreased WBCs in the benzene-exposed workers. The NRC Committee on Emergency and Continuous Exposure Guidance Levels for Selected Submarine Contaminants (NRC 2008)
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From page 69... ...
TABLE 4-2 Exposure Limits Set by Other Organizations Recommended Organization, Standard Exposure Level, ppma Reference OSHA NIOSH 2005 PEL, 8-h TWA 1 ATSDR ATSDR 1992 PEL, STEL 5 Action level TWA 0.5 (Continued)
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0.013 a Conversion factors at 25°C, 1 atm: 1 ppm = 3.26 mg/m3; 1 mg/m3 = 0.31 ppm. Abbreviations: ACGIH, American Conference of Governmental Industrial Hygienists; ATSDR, Agency for Toxic Substances and Disease Registry; CEGL, continuous exposure guidance level; EEGL, emergency exposure guidance level; IDLH, immediately dangerous to life and health; NASA, National Aeronautics and Space Administration; NIOSH, National Institute for Occupational Safety and Health; NRC, National Research Council; OSHA, Occupational Safety and Health Administration; PEL, permissible exposure limit; STEL, short-term exposure limit; TWA, time-weighted average; SMAC, Spacecraft Maximum Allowable Concentration.
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Washington, DC: National Academy Press. NRC (National Research Council)
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1997. Benzene poisoning, a risk factor for hematological malignancy, is associated with the NQO1 609C→T mutation and rapid fractional excretion of chlorzoxazone.
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