Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 2 (1996) / Chapter Skim
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B5 Hydrazine
B5 Hydrazine
Pages 213-234
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From page 213... ...
James, Ph.D Johnson Space Center Toxicology Group Biomedical Operations and Research Branch Houston, Texas PHYSICAL AND CHEMICAL PROPERTIES Hydrazine is a clear, colorless, fuming, oily, hydroscopic, highly polar, flammable liquid with an ammonia-like odor or an extremely irritating gas that is readily adsorbed or condensed onto surfaces and has a high affinity for water (Sevin, 19781. Synonym: Diamine Formula: N2H4 CAS number: 302-01-2 Molecular weight: 32.05 Boiling point: 113.5°C Melting point: 1.4-1 .5°C Liquid density at 1.0045 25°C: Vapor pressure: 14.1 mm Hg @ 25°C (10.4 tort at 20°C)
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From page 214... ...
During missions in which hydrazine contamination of the airlock is a risk, a real-time chemical monitor using ionmobility spectrometry has been flown to ensure that unsafe concentrations of propellants, including hydrazine, are not present before the spacecraft is re-entered (Eiceman et al., 19931. PHARMACOKINETICS AND METABOLISM Absorption Hydrazine was detectable in the plasma of anesthetized dogs within 30 s after applying concentrated hydrazine solutions to their intact skin (Smith and Clark, 1972~.
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From page 215... ...
doses of hydrazine sulfate at ~ mmole/kg of body weight and in rats given 60 mg/kg; the highest concentrations appeared in the kidneys (Dambrauskas and Cornish, 19641. Excretion Anesthetized dogs administered hydrazine sulfate intravenously (i.v.)
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The toxicity of multiple lower doses was cumulative, but surviving animals recovered and lived normal life spans if exposure was discontinued. The LCso for a 4-h exposure to hydrazine is 750 mg/m3 (570 ppm)
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There were no deaths due to acute exposure to hydrazine vapor at a hydrazine factory among all 78 workers exposed for at least 6 mo at an estimated 1-10 ppm (54 of them were exposed for over 2 y)
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in male rats (the most sensitive species and sex) exposed by inhalation, tumors, which were predominantly benign, occurred only late in life in animals showing many other chronic toxic effects, including a greatly increased inflammatory response of the upper airways (Carter et al., 1981~.
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Reproductive Toxicity Hydrazine induces abnormally shaped spermatocytes in treated male mice (Wyrobek and London, 1973~. In the mouse dominant lethal test, hydrazine did not induce early fetal deaths or preimplantation losses at single i.p.
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220 V: ._ ._ x o 1 at; V, o 3 Go .= .o _ no ~ Z .O CQ .° 3 o X o .
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RATIONALE FOR ACCEPTABLE CONCENTRATIONS Hydrazine induces a variety of toxic effects including irritation of the eyes, nose, and throat, contact dermatitis, and, at higher concentrations, dizziness, anorexia, nausea, vomiting, cough, fever, diarrhea, temporary blindness, hepatotoxicity, tremors, hyperexcitability, convulsions, and death. Prolonged exposures to relatively low concentrations have been reported to induce Hepatotoxicity and carcinogenicity (Comstock et al., 1954; House, 1964; Haun and Kinkead, 1973; MacEwen et al., 1974; Carter et al., 1980; MacEwen et al., 1981; Vernot et al., 1985~.
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From page 223... ...
Hepatotoxicity Liver effects induced by inhalation of airborne hydrazine include fatty changes in the liver in several species after 90 d of continuous exposure at 0.S ppm (House, 19641. In calculating an AC, these data were used rather than data on hyperplasia because the fatty changes were seen at a much earlier time for similar concentrations of hydrazine.
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From page 224... ...
= 0.3ppm x 1/7 = 0.04ppm. Focal-Liver-Cell Hyperplasia Liver effects induced by inhalation of hydrazine include a significant increase in the incidence of focal-liver-cell hyperplasia in female rats (but not in male rats, mice, hamsters, or dogs)
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From page 225... ...
Therefore, the following equation, based on Crump and Howe's (1984) multistage model with only the first stage dose-related, was used to calculate the exposure concentrations, D, which would yield a tumor risk of 104 for exposure durations of 24 h, 7 6, 30 4, and IS0 d: d.
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Examination of the methods used for many of the experiments reveals serious short-comings in some of the study designs (number of animals tested; not sham-exposing control animals, etc.~. Despite these potential problems in experimental designs and highly scattered rodent data, the conservative approach would be to use the data for the most sensitive species (mice)
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A study on the relative absorption rates for dermal versus inhalation absorption of hydrazine vapor would aid in estimating the total absorbed dose during exposures. A carcinogenicity study using a continuous exposure protocol including concentrations that do not produce nasal inflammation or necrosis would be helpful.
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228 SMACS FOR SELECTED AIRBORNE CONTAMINANTS high concentrations of hydrazine vapor for 1 h, 24 h, or 7 ~ and then observed for their lifetime would be useful.
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229 Cal g ._ C)
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1964. Tolerance Criteria for Continuous Inhalation Exposure to Toxic Materials, ITI.
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P 5-21 in Emergency and Continuous Exposure Guidance Levels for Selected Airborne Contaminants, Vol.
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AMRL-TR-84-533. Aerospace Medical Research Laboratory, Wright-Patterson Air Force Base, Dayton, Ohio.
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30. Aerospace Medical Research Laboratory-, Wright-Patterson Air Force Base, Dayton, Ohio.
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