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Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 5 (2008) / Chapter Skim
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18 Trimethylsilanol
Pages 348-355

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From page 348...
... Toxicology Group Habitability and Environmental Factors Division Johnson Space Center National Aeronautics and Space Administration Houston, Texas BACKGROUND AND SUMMARY OF ORIGINAL APPROACH No inhalation toxicity data were available on trimethylsilanol (TMS) at the time the original spacecraft maximum allowable concentrations (SMACs)
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From page 349...
... TMS is commonly found in off-gas tests of flight hardware, presumably from lubricants in hardware joints or from off-gassing from silicone-based seals. TABLE 18-1 Previously Set SMACs for TMS Duration of exposure SMAC, ppm Target toxicity to prevent 1h 150 CNS depression 24 h 20 CNS depression 7d 10 CNS depression 30 d 10 CNS depression 180 d 10 CNS depression Source: Data from Kaplan et al.
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From page 350...
... NEW RISK ASSESSMENT APPROACHES The limited data on TMS toxicity, available primarily in abstract form, consist of nonquantitative clinical observations of the anesthetic effects of orally or intravenously administered TMS. Such nonquantitative data are not suitable for benchmark dose analysis because a dose-response relationship is not reported.
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From page 351...
... of Three Compounds Compared with Their Antimicrobial Activity in Two Strains of Bacteria Minimum lethal Compound/parameter Log OWPC concentration, % TES 2.62 0.2 TMS 1.14 2.5 t-butanol 0.73 12.5 Abbreviation: OWPC, octanol-water partition coefficient; TES, triethylsilanol; TMS, trimethylsilanol. Source: Kim et al.
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From page 352...
... × 1/100 = 0.065 mg/m3 ~ 0.02 ppm where 0.97 is the conversion factor for inhalation rate per kg of body weight (rats to humans) , and a default value of 1 was used for unknown relative absorption efficiency.
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From page 353...
... TABLE 18-3 Comparison of TEELs for TMS and t-Butanol t-Butanol, TEELa Explanation TMS, ppm ppm 0 The threshold concentration below which most 0.15 300 people will experience no appreciable risk of health effects 1 The maximum concentration in air below which it 1.5 400 is believed nearly all individuals could be exposed without experiencing other than mild transient adverse health effects or perceiving a clearly defined objectionable odor 2 The maximum concentration in air below which it 7.5 5,000 is believed nearly all individuals could be exposed without experiencing or developing irreversible or other serious health effects or symptoms that could impair their abilities to take protective action 3 The maximum concentration in air below which it 15 5,000 is believed nearly all individuals could be exposed without experiencing or developing life threatening health effects a It is recommended that, for application of TEELs, the concentration at the receptor point of interest be calculated as the peak, 15-min time-weighted average concentration. It should be emphasized that TEELs are default values, following the published methodology (on Subcommitte on Consequence Assessment and Protective Actions' web page)
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From page 354...
... Revised SMACs 15 2 1 1 1 1 a Because the original SMACs were based on a noninhalation route of administration, a lack of prolonged exposure, data reported in the form of company abstracts, and an insensitive means of assessment of CNS effects, a factor of 10 is applied to compensate for uncertainty. Abbreviations: F, female; IV, intravenous; M, male; N/A, not applicable.
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From page 355...
... 1973. Primate absorption and elimination balance studies including pulmonary, urinary, biliary and fecal excretion of t-butanol, trimethylsi lanol, dimethylsilanol and hexamethyldisiloxane.
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Key Terms

  • dow corning
  • corning corp
  • antimicrobial activity
  • cns effects
  • original approach

  • maximum concentration
  • selected airborne
  • air below
  • inducing cns
  • allowable concentrations

  • intravenous study
  • inhalation rate
  • toxicity data
  • original smacs
  • spacecraft maximum

  • default values
  • maximum allowable
  • partition coefficient
  • tms toxicity
  • compounds compared

  • bacterial strains
  • inhalation uptake
  • abstract form
  • company abstracts
  • body weight

  • noninhalation route
  • unpublished material
  • limited data
  • mild anesthesia
  • intravenously administered


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