Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 5 (2008) / Chapter Skim
Currently Skimming:
16 Propylene Glycol
16 Propylene Glycol
Pages 314-328
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 314... ...
The purpose of this document is to review the existing inhalation toxicology literature on PG and develop maximum acceptable air concentrations for 1 h, 24 h, 7 d, 30 d, 180 d, and 1,000 d of potential exposure to vapors of PG. STRUCTURE OF PROPYLENE GLYCOL PG is a colorless, practically odorless and tasteless, and somewhat viscous liquid (see Table 6-1 for physical and chemical properties of propylene glycol)
|
From page 315... ...
As the general weight of evidence in the toxicology literature supports the conclusion that PG will be less toxic than ethylene glycol, PG-based coolant is strongly considered for use in NASA Constellation Program transport vehicles. PHARMACOKINETICS AND METABOLISM No data, human or animal, describing the toxicokinetics of PG exposure through inhalation are available.
|
From page 316... ...
. Tests conducted within 15 min after the exposures included an estimate of tear-film stability breakup time, nasal patency by acoustic rhinometry, dynamic spirometry, and a symptom questionnaire with 23 yes-or-no questions for ocular and respiratory symptoms (nasal and throat irritation, difficulty in breathing)
|
From page 317... ...
The reported incidence of nasal hemorrhaging and ocular discharge in the second week of exposure to the lowest test concentration, 50 ppm, was only 3%. The authors attributed the observed nasal hemorrhaging and ocular discharge to dehydration of the nasal passages and eyes.
|
From page 318... ...
. No chronic inhalation exposure study exists in which the carcinogenic potential of PG was evaluated.
|
From page 319... ...
No changes in respiratory rates, tidal volume, or minute volume; unremarkable gross pathology of tissues (at necropsy) ; thickening of respiratory epithelium with increased number of goblet cells in medium- and high-dose groups.
|
From page 320... ...
The published animal inhalation studies have not specifically looked at changes in immune system parameters. REPRODUCTIVE AND DEVELOPMENTAL TOXICITY There are no published reports of reproductive or developmental toxicity in humans from inhalation of PG vapors in either an occupational setting or by environmental exposure.
|
From page 321... ...
×1/3 (LOAEL to NOAEL) = 32 ppm TABLE 16-3 Spacecraft Maximum Allowable Concentrations for PG SMAC, Duration ppm Target Toxicity Principal Study 1h 32.0 Eye, throat, and respiratory system Wieslander et al.
|
From page 322... ...
. The authors attributed the observed nasal hemorrhaging and ocular discharge to dehydration by PG of the nasal passages and eyes.
|
From page 323... ...
(1947) , described earlier under "Chronic Inhalation Exposure Studies," no nasal hemorrhaging, ocular discharge, or systemic toxicity was reported in rats or monkeys during a 12to 18-month continuous whole-body exposure to at least 53 and 72 ppm of PG vapor, respectively (note that this study was not used to derive the AC for subchronic and chronic durations)
|
From page 324... ...
Although a species factor was not used for the nasal hemorrhaging end point earlier, a species factor of 3 will be used in this case. The factor is for the uncertainty in the severity of effects due to the differences between humans and rats in the nasal passage respiratory epithelium and the nature of the goblet cells.
|
From page 325... ...
As the nature of the effects (epithelial changes in the nasal passages) seemed to be adaptive, the NRC SEG committee recommended using the 180-d AC without any time extrapolation factors from 180 to 1,000 d.
|
From page 326... ...
= 50 ppm; ten (160, 1,000, 2,200 mg/m3 1989 Berge method or 50, 313, 688 ppm) used Nasal hemorrhage and Inhalation of PG; 6 h/d, 5 Sprague- NOAEL for 1 wk -- -- 9 -- -- -- ocular discharge d/wk; 0.16, 1.01, 2.18 mg/L Dawley rat, = 50 ppm (160, 1,000, 2,200 mg/m3 Suber et al.
|
From page 327... ...
1992. Guidelines for Developing Spacecraft Maxi mum Allowable Concentrations for Space Station Contaminants.
|
From page 328... ...
2001. Experimental exposure to propylene glycol mist in aviation emergency training: Acute ocular and respiratory effects.
|
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.