Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 5 (2008) / Chapter Skim
Currently Skimming:
14 Methanol
14 Methanol
Pages 275-288
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 275... ...
It is used industrially in the manufacture of other chemicals and as a solvent. It is added to a variety of commercial and consumer products, including windshield washing solutions, deicing solutions, glass cleaners, duplicating fluids, solid canned fuels, paint thinners and removers, model airplane fuels, embalming fluids, lacquers, inks, and some formulations of gasohol motor fuel.
|
From page 276... ...
Source: Data from NTP CERHR 2003. TABLE 14-2 Background Blood Methanol and Formate Concentrations in Humans mg of methanol/L, mg of formate /L, Subjects mean ± SD (range)
|
From page 277... ...
1984) published by the National Institute for Occupational Safety and Health that described visual disturbances in 66 teacher aides exposed to methanol vapors from "spirit" duplicating machines during a work week, with exposure durations in individual aides varying from 1 to 40 h/wk.
|
From page 278... ...
No increase in blood formate concentration at rest or exercising. 100 ppm 2h Humans No toxicity reported.
|
From page 279... ...
Serum MeOH concentration increased, but serum formate concentration did not. 200 ppm 4h Humans Serum MeOH increased from 0.9 Osterloh et al.
|
From page 280... ...
The delays seen in development of ocular toxicity in humans who ingest significant quantities of methanol can be attributed to two factors: the time necessary to deplete the body's stores of tetrahydrofolate so that formate metabolism to CO2 is greatly decreased and formate begins to accumulate to concentrations that inhibit mitochondrial cytochrome oxidase in the retinal ganglia, and the time needed for the axonal swelling caused by the inhibition of cytochrome oxidase to reach a point at which vision is affected. Studies of controlled inhalation exposure of humans to methanol vapors, most of which have been published since 1994, describe only brief durations and relatively low concentrations -- for example, 12 volunteers for 75 min at 192 ppm (Cook et al.
|
From page 281... ...
, but that the methanol-derived increase in formate concentration in the blood would be only 0.016 mg/dL, which is small compared with the background value of 0.49 mg/dL in unexposed subjects but is in accord with experimental data from methanol exposures in primates and humans. Because there are no published studies of controlled exposures in humans involving the dose range at which formate metabolism to CO2 becomes saturated and blood formate concentrations begin to increase, the model did not include a saturation term for formate metabolism, and its usefulness is limited to situations in which tetrahydrofolate is not limiting.
|
From page 282... ...
suggest that, although the amount of methanol volunteers inhaled during light exercise is 1.8 times the amount inhaled at rest, the concentration of methanol in the blood is only slightly, but not significantly, increased by light exercise (8.1 µg/mL compared with 7.0 µg/mL at rest and 1.8 µg/mL pre-exposure) , and no increase in blood formate concentration was observed after a 6-h exposure to 200 ppm of methanol either at rest or during exercise (Lee et al.
|
From page 283... ...
TLV STEL, skin 250 ppm (325 mg/m3) Abbreviations: ACGIH, American Conference of Governmental Industrial Hygienists; IDLH, immediately dangerous to life and health; NIOSH, National Institute for Occupational Safety and Health; OSHA, Occupational Safety and Health Administration; PEL, permissible exposure limit; REL, recommended exposure limits; ST, short-term exposure limit (15 min)
|
From page 284... ...
= 23.3 ppm, rounded to 23 ppm The calculated SMAC values are summarized in Table 14-6. SPACEFLIGHT EFFECTS None of the reported adverse effects of methanol exposures is known to be affected by spaceflight, but the 1.7% to 12% reduction in total body water associated with prolonged microgravity would proportionately increase the blood concentration of methanol inhaled.
|
From page 285... ...
TABLE 14-6 Acceptable Concentrations for Methanol (ppm) Uncertainty factor Acceptable concentration, ppm Folate Species and Space- defiEffect Exposure data reference NOAEL Species Time flight ciency 1h 24 h 7d 30 d 180 d 1,000 d Visual 200 ppm, Human 1 1 1 1 1 200 – – – – – disturbance 75 min-6 h = Cook et al.
|
From page 286... ...
1997. 1997 TLVs and BEIs-Threshold Limit Values for Chemical Substances and Physical Agents; Biological Exposure Indices.
|
From page 287... ...
1992. Lack of blood formate accumulation in humans following exposure to methanol vapor at the cur rent permissible exposure limit of 200 ppm.
|
From page 288... ...
149-167 in Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants, Vol.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.