Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 3 (1996) / Chapter Skim
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B9: Ethylene glycol
B9: Ethylene glycol
Pages 232-270
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From page 232... ...
. Synonym: Formula: CAS number: Molecular weight: Boiling point: Melting point: Vapor pressure: Saturated vapor concentration at 20°C: Conversion factors at25°C,latm: 1,2-Ethanediol HOCH2CH2OH 107-21-1 62.1 197.6°C -13°C 0.06 tort at 20°C 204 mg/m3 or 79 ppm 1 ppm = 2.54 mg/m3 lmg/m3=0.39ppm OCCURRENCE AND USE Ethylene glycol is used as an antifreeze, an industrial humectant, and a solvent in paint and in the plastics industry (ACGIH, 1986)
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From page 233... ...
g/kg) , the metabolites included glycolic acid, oxalic acid, CO2, and a small amount of hippuric acid.
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The results revealed that glycolic acid was the most abundant, accounting for 12% of the dose. Only 0.3 % of the dose was excreted as oxalic acid in the urine of this monkey.
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In that study, after reaching a peak 6 h following inhalation exposure of rats to ~4C-ethylene glycol, the plasma concentration of ~4C activity declined monoexponentially for the remaining 4 6, with a half-life of 39 h. Evidently, not all the ~4C activity represented ethylene glycol.
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indicates that the three major toxic end points of ethylene glyco} poisoning are mucosal irritation, central-nervous-system (CNS) effects, and renal toxicity.
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Species Dose, g/kg Body Weight, g Mortality Rats 5.0 214 3/10 5.0 380 7/10 Guinea pigs 6.6 268 1/10 6.6 558 9/9 Mice 13.8 14.6 7/10 13.8 27.1 6/10 CNS, Cardiopulmonary, and Renal Toxicity Berman et al.
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Some investigators have studied the CNS effects of ethylene glycol in laboratory animals. Most of its CNS effects can be characterized as CNS depression.
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showed that a decrease in blood bicarbonate concentrations in pigtail monkeys was associated with an increase in the blood concentration of glycolic acid. They also showed that exposure of monkeys to 4-methy~pyrazole, which is an inhibitor of alcohol dehydrogenase, 30 min after the intraperitoneal injection of ethylene glyco} shortened the duration of metabolic acidosis induced by ethylene glycol.
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for up to 28 d. The data on mucosal irritation responses from that report are also included in Table 9-3.
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The major toxic effects in {ong-term exposures are mucosal irritation, CNS effects, and renal toxicity. Mucosal Irritation and Eye Toxicity Mucosal irritation induced by ethylene glyco!
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Ammonia is not known to cause CNS depression and nystagmus (Won", 1993~. So the CNS effects observed by Troisi were probably due to ethylene glyco!
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(1974) , a nearly continuous exposure of 20 men to ethylene glyco} at 30 mg/m3 for 30 ~ failed to produce any adverse changes in kidney functions, as measured by urine specific gravity, serum urea nitrogen, serum creatinine, and creatinine clearance.
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The exposures, however, caused no histological changes in the surviving mice and rats. From the data on inhalation exposures summarized above, the NOAEL, based on ethylene glycol's renal toxicity in humans, is 30 mg/m3 for subchronic inhalation exposures.
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(1986a) also reported detecting mild fatty liver in female rats fed ethylene glyco!
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A continuous exposure of eight monkeys to aerosolized ethylene glyco! at 500 mg/m3 for up to 30 w killed six of them (Harris, 1969~.
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for 30 ~ to 30 mg/m3, TWA. Carcinogenesis A search of the National Library of Medicine's database, Medline, failed to reveal any epidemiological data on tumor incidences associated with ethylene glycol exposures in humans.
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It should be noted that the effects found in the ~ %-dose group might be related to the general toxicity of ethylene glyco! in female mice, because the exposure decreased the body weight of the female mice by about 10% in w 10 (Lamb et al., 1985~.
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In the female mice, ethylene glycol caused no clinical signs and no change in the fertility index. In part B of the screen, untreated female and male mice cohabited 3 ~ to produce time-mated females, which were Savaged with ethylene glycol at the same doses as in part A of the screen on gestational ~ 8-14 (Harris, et al., 1992~.
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via Savage at 0, 100, 500, 1000, or 2000 mg/kg/d on gestational ~ 6 through 19. The highest dose caused serious maternal toxicity, as manifested by a 42% mortality, several early deliveries, and renal toxicity (a presence of oxalate crystals in the lumen of cortical renal tubules accompanied by tubular necrosis, degeneration, and dilation)
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(1987) found that coadministered ethylene glyco} and ethanol in dogs reduced the elimination half-life of ethylene glyco!
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RATIONALE FOR ACCEPTABLE CONCENTRATIONS The SMACs are set with the assistance of guidelines provided by the National Research Council (NRC, 1992a)
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The 15-min NOAEL is estimated from data gathered from only 20 men (WilIs et al., 1974; Harris, 1969) , so it is possible that some sensitive individuals could fee} mucosal irritation at the 15-min NOAEL.
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in dogs and the data of Felts (1969) in monkeys and chimpanzees, 1.1 g/kg is the lowest dose known to cause CNS depression effects in acute ethylene glycol poisoning.
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24-h AC for CNS depression = acute NOAEL x body weight x i/daily respiratory volume x 1/absorption fraction x 1/species factor = 110mg/kg x 70 kg x 1/20 m3 x 1/0.60 x 1/10 = 64 mg/m3. Similarly, the 1-h AC for CNS depression is set using the acute NOAEL of ~ 10 mg/kg, assuming that a 70-kg person breathes 20 m3 of air in 24 h (NRC, 1992b)
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As a result, the calculated airborne exposure concentration of ethylene glyco} equivalent to an oral dose needs to be adjusted for the incomplete inhalation absorption. Theoretical 7-d, 30-d, and IS0-d ACs for renal toxicity = 2-y NOAEL x body weight x 1/species factor x I/daily respiratory volume x i/absorption fraction = 0.2 g/kg/d x 70 kg x 1/10 x 1/20 m3/d x I/0.6 = IlOmg/m3.
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They reported that male rats given ethylene glyco! in drinking water at a concentration of 2620 mg/kg/d for 10 ~ had no changes in blood urea nitrogen and serum creatinine levels, but the exposure significantly increased the following renal histological changes: mild tubular dilatation, minimal tubular necrosis, intratubular birefringent crystals, and acute inflammation.
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From page 260... ...
If ethylene glycol does cause renal injuries via formation of calcium oxalate crystals, it can be argued that, because microgravity is known to increase the renal excretion of calcium (Whedon et al., 1977) , an uncertainty factor for the calcium effect during spaceflight might be needed for an extra safety margin in deriving ACs for ethylene glycol's renal toxicity.
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might cause renal injuries via a mechanism other than calcium oxalate crystallization, one should not set an AC for renal toxicity by calculating the ethylene glyco! exposure concentration required to bring the daily urinary oxalate excretion to the threshold of 45 mg/~.
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Comparing the data of mucosal irritation with those of CNS depression, the conclusion is that the data gap on ethylene glycol's propensity to irritate mucous membranes is larger than that on CNS depression. Currently, the ACs for mucosal irritation in short-term exposures are set using the data of Wills' study (Wilis et al., 1974; Harris, 1969~.
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263 Cal o .
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264 x ,+o~ Cd o Cd V, no Cd .= Cd C)
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1986b. Three-generation reproduction and dominant lethal mutagenesis studies of ethylene glyco} in the rat.
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1992. Assessment of a short-term reproductive and developmental toxicity screen.
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1983. Deposition and fate of inhaled ethylene glycol vapor and condensation aeroso!
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1992a. Guidelines for Developing Spacecraft Maximum Allowable Concentrations for Space Station Contaminants.
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1938. The formation of oxalic acid from ethylene glyco} and related solvents.
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270 ~0 ~ ~ 4~_ ~ item AMow~le Conce~r~ions.
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