Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 3 (1996) / Chapter Skim
Currently Skimming:
B12: Xylene
B12: Xylene
Pages 321-344
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 321... ...
The three isomers of xylene are very similar in physical, chemical, and toxicological properties. The odor threshold for vapors of mixed xylenes was determined by a pane} of six people to be on the order of ~ ppm (Carpenter et al., 1975~.
|
From page 322... ...
Both products are mixtures of three isomers. Commercial xylene frequently contains ethy~benzene and traces of toluene, phenol, thiophene, pyridine, and small amounts of nonaromatic hydrocarbons.
|
From page 323... ...
of unchanged xylene appear in the urine after exposure at concentrations of 46 or 92 ppm (Sedivec and FIek, 1976~. At retained body burdens of 0.019 g/kg in humans, essentially all the conjugated xylene in the urine was in the form of glycine-bound toluic acid (methy~hippuric acid)
|
From page 324... ...
Kinetic data in humans showed that well-perfused tissues, such as the brain, should reach xylene equilibrium within m~nutes and muscles within a few hours. Calculation of partition coefficients suggests that brain xylene concentrations should closely follow blood xyiene concentrations (Riihimaki and Savolainen, 1980~.
|
From page 325... ...
Fatigue, drowsiness, headache, dizziness, dyspepsia, and nausea have been reported during repetitive daily exposure to unmeasured atmospheric concentrations (Browning, 1965~. Acute Exposures Seven human volunteers reported minimal degrees of subjective responses (eye, nose, or throat irritation; dizziness or lightheadedness; and tearing)
|
From page 326... ...
with signs suggesting CNS effects: the sequential development of salivation, ataxia, tonic and clonic spasms, anesthesia, and death (Carpenter et al., 1975~. The only lesions reported that were considered significant in any of the acute inhalation studies were atelectasis, hemorrhage, and interIobular edema of the lung in rats that died after inhaling mixed xylenes at 9900 ppm for several hours (Carpenter et al., 1975~.
|
From page 327... ...
The magnitude of these changes was minor compared with the effects seen in general anesthesia or in long-term occupational exposure to hexane (Seppalainen et al., 1989~. In a complicated study, inhalation of m-xylene at 100 to 400 ppm was reported to cause impairment of body balance and increase of reaction times in eight human volunteers (Riihimaki and Savolainen, 1980~.
|
From page 328... ...
The first paper reported a negative correlation between atmospheric m-xylene concentration and changes in body sway and a lack of correlation between m-xylene blood concentrations and changes in body sway. The second paper reported a positive correlation between m-xylene blood concentrations and changes in the eyesclosed-to-eyes-open ratios of both average and maximal body sway.
|
From page 329... ...
was classified as negative in the ChernoffKavIock developmental toxicity screen (Seidenberg and Becker, 1987~. In a Hungarian study using rats, however, exposure to o-, m-, or p-xylene at 35, 350, or 700 ppm for 24 hid from ~ 7 to 14 of pregnancy was reported to produce the following effects for the three isomers: toxic effects in the dams exposed at 700 ppm and maternal deaths of 4 of 30 rats seen only for m-xylene at 700 ppm; reduced fetal weight at 700 ppm for all isomers and at 350 ppm for o-xylene; increased incidence of skeletal retardation for o-xylene at 700 ppm, for p-xylene at all three concentrations, but not for m-xylene; and decreased activity of several liver and thymus enzymes at the highest dose for all the isomers (Ungvary et al., 1980~.
|
From page 330... ...
Male rats exposed to m-xylene vapor at concentrations of 49, 393, and 735 ppm for 6 in/d, 5 d/w, for 2 w showed evidence of accumulation of m-xylene in some tissues. Xylene concentrations in brain and perirenal fat increased in proportion to the exposure concentrations between w ~ and 2 of exposure (Savolainen and Pfaffli, 1980~.
|
From page 331... ...
XYZENE 33 1 Gastrointestinal Effects in Humans Workers exposed to commercial xylene vapors in concentrations above 200 ppm have complained of nausea, vomiting, heartburn, and loss of appetite (Browning, 1965~.
|
From page 333... ...
333 oo~ it, ~ - ~ ~_ ~` ~ ax _ _ _ ~_ Ce _ _ _ ~Cd - ~ ~Cal Cd Cd Cd ~ ^ ~Cd ~ Ct V]
|
From page 334... ...
The guidelines established by the National Research Council (NRC, 1992) were used to compare the resulting ACs for the various end points, and the lowest AC at each exposure duration was selected as the SMAC.
|
From page 335... ...
The atmospheric concentration of xylene in the confined space was estimated to be 10,000 ppm on the basis of the volume of paint applied to the walls, the volume of the confined space, and the poor ventilation. Despite the poor ventilation, Morley et al.
|
From page 336... ...
Thus, ACs for lethality were not calculated for exposure times greater than 24 h. Throat Irritation One of seven human volunteers exposed for 15 min to m-xylene reported mild throat discomfort during the first minute and again during the seventh minute of inhalation at 106 ppm and during the first minute of inhalation at 230 ppm, but none reported discomfort while inhaling 460 ppm (Carpenter et al., 1975~.
|
From page 337... ...
Eye Irritation One of seven volunteers exposed for 15 min to m-xylene reported intermittent mild eye irritation at 230 ppm (Carpenter et al., 1975~. The degree of irritation reported in this study was minor but dose related.
|
From page 338... ...
Examination revealed no differences at any dose from air-exposed controls in body weight, blood and urine analyses, and histopathological changes of tissues from the adrenal, brain, pituitary, trachea, thyroid, parathyroid, lung, heart, liver, kidney, spleen, stomach, duodenum, pancreas, ileum, jej unum, colon, skeletal muscle, sciatic nerve, and bone-marrow impression smear (Carpenter et al., 19751. To calculate the ACs for 7 ~ and 30 it, the 810ppm value was divided by 10 for species extrapolation, multiplied by 16.25 (= 6 hid x 65 ~ .
|
From page 339... ...
be of clinical concern due to reduced cardiac output (R. Billica, chief, Medical Operations, NASA Johnson Space Center, Houston, Tex., personal commun., 1992~.
|
From page 340... ...
340 SMACS FOR SELECTED AIRBORNE CONTAMINANTS SPACEFLIGHT CONSIDERATIONS Of the end points induced by exposure to xylenes, only cardiac output possibly would be affected by launch, microgravity, or re-entry. The decrease in the force of contraction of the left ventricle would tend to counteract the increased susceptibility to arrhythmia induced by spaceflight.
|
From page 341... ...
o o o o I1 0 0 1 ° ~ ~ _1 ~- 1 - V3^ ~o o o ~ O 1 1 0 0 0 0 ~ .° ~1 1 ~- ~- so ~ ~ 1 1 ° ° o O to o ~ ~ o o o o o o _ ~ _ ~ o ~o ~ _ ~ _ ~_ _ o C)
|
From page 342... ...
1986. The developmental toxicity of xylene and xylene isomers in the hydra assay.
|
From page 343... ...
1992. Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants.
|
From page 344... ...
1985b. Conversely exposure-related effects between atmospheric m-xylene concentrations and human body sense of balance.
|
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.