Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 5 (2008) / Chapter Skim
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1 Acrolein
1 Acrolein
Pages 13-33
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This document is organized as follows: • The approach taken in developing existing acrolein SMACs is summarized, • Recent data that may affect existing SMACs are examined and the 1,000-d acrolein SMAC is established, and 13
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Table 1-1 summarizes the SMACs established for acrolein using mucosal irritation as the toxicologic end point. SUMMARY OF ORIGINAL APPROACH USED TO SET SMACS Acrolein exposure produces mucosal irritation at concentrations lower than those that produce histopathologic changes in the respiratory tract (Lyon et al.
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(1977) showing a concomitant 2-fold lowering of reported eye irritation when exposure concentration decreased by half.
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and an additional safety factor of 10/ n for potential differences among individuals in a human population; adjustment for small size of the study sample is applied to account for potential uncertainty relative to the results from a small number of study subjects (Equation 3)
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The authors examined mortality, growth, food consumption, hematologic changes, blood chemistry, urinalyses, and organ weight and pathology in these animals. Of the species examined, rats were the most sensitive to acrolein exposure, exhibiting slightly depressed growth and histopathologic changes of the nasal cavity at the lowest concentration (Feron et al.
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Bacteriacidal activity toward S aureus at first decreased 1 d after acrolein exposure but returned to control concentrations 7 d postexposure (Jakab 1993)
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A footnote will be included with the revised acrolein SMAC table describing the concentrations at which the odor of the compound may become a concern. RATIONALE FOR 1,000-DAY SMAC AND REVISION OF 180-DAY SMAC The existing 7-, 30-, and 180-d acrolein SMACs (0.015 ppm, 0.034 mg/m3)
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. Extrapolation factors of 0.25 and 0.71 are proposed to adjust for continuous exposure conditions.
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to set acceptable human exposure guidelines and limits. In particular, this approach is recommended by the NRC for setting spacecraft water exposure guidelines -- and by inference SMACs -- when sufficient and appropriate dose-response data are available (NRC 2000)
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LOAEL-NOAEL methodology in confirming existing acrolein SMACs and for revising and establishing new SMACs. The following section presents an additional explanation of our rationale for using each base and supporting study and provides BMD analysis of these studies when applicable.
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This study is also considered supportive in setting the revised 180-d and the new 1,000-d acrolein SMACs. Morris and co-workers exposed male and female mice to acrolein as part of their study to compare responses in healthy mice and in mice with allergic airway disease.
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program was used to analyze the enzyme activity data. SDs for the dose-dependent nasal epithelium biotransformation enzyme activity of the Cassee et al.
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Statistically significant dose-related changes were reported for body weight and heart, lung, kidney, and adrenal organ weight ratios in rats. A polynomial model with the dose-response data procedure for a continuous data program (EPA BMDS)
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, AC (1,000 d) , End Point ppm ppm ppm ppm Body weight Male 0.050 0.040 0.002 0.002 Female 0.080 0.070 0.004 0.004 Lung weight ratioa Male 0.060 0.050 0.003 0.003 Female 0.012 0.098 0.006 0.006 Heart weight ratio Male 0.130 0.100 0.006 0.006 Female 0.180 0.140 0.008 0.008 Kidney weight ratio Male 0.290 0.210 0.012 0.012 Female 0.130 0.110 0.007 0.007 Adrenal weight ratio Male 0.040 0.040 0.002 0.002 Female 0.100 0.090 0.005 0.005 a Organ weight ratio = g per 100 g of body weight.
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Confidence in the BMD analysis and derivation of subsequent ACs is medium. It is important to point out that the study design involved in producing the data used for the BMD analysis used a limited number of exposure concentrations -- control, low, and medium acrolein for the "basal cell hyperplasia" end point and control, medium, and high acrolein for the biotransformation enzyme activity end point.
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reported, limited number than current or enzyme activity of exposure proposed SMAC concentrations tested, small n in each exposure group (Continued)
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reported, limited number than current or enzyme activity of exposure proposed SMAC concentrations tested, small n in each exposure group Feron et al. 1978 Body weight, adrenal 0.05 0.04 0.002 No BMD-specific 4 times lower weight ratio (180 d)
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Abbreviations: ACGIH, American Conference of Governmental Industrial Hygienists; AEGL, acute exposure guideline level; ATSDR, Agency for Toxic Substances and Disease Registry; CEGL, Continuous Exposure Guideline Level; EEGL, Emergency Exposure Guideline Level; EPA, U.S. Environmental Protection Agency; MRL, minimal risk level; NAC, National Advisory Council; 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; TLV, threshold limit value; TWA, time-weighted average; REL, recommended exposure limit; RfC, reference concentration; SMAC, Spacecraft Maximum Allowable Concentration.
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Current and proposed NASA acrolein SMACs are derived through use of a RfC "threshold dose" method with applicable safety factors applied. The supporting studies from which reference dosages were obtained are based in large part on subjective responses.
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. In terim Acute Exposure Guidelines Levels (AEGLs)
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Pp. 19-38 in Spacecraft Maximum Allowable Concentra tions for Selected Airborne Contaminants, Vol.
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