Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 5 (2008) / Chapter Skim
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10 Dimethylhydrazine
10 Dimethylhydrazine
Pages 162-189
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From page 162... ...
, and it may ignite spontaneously when in contact with heat, flame, or oxidizers. Table 10-1 describes UDMH's physical and chemical properties.
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From page 163... ...
. TABLE 10-1 Physical and Chemical Properties of UDMH Formula C2H8N2 Chemical name Dimethylhydrazine Synonyms Unsymmetrical dimethylhydrazine U-Dimethylhydrazine UDMH DMH Dimethylhydrazine AS-Dimethylhydrazine Asymmetric dimethylhydrazine ASYM dimethylhydrazine Dimazin Dimazine N,N-Dimethylhydrazine Dimethylhydrazine unsymmetrical CAS number 57-14-7 Physical description Liquid (HSDB 2005)
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From page 164... ...
Skin absorption of liquid UDMH was studied in anesthetized dogs given 5-30 millimoles of UDMH per kilogram of body weight (mmol/kg) applied to a shaved area of the chest (Smith and Clark 1971)
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From page 165... ...
. The authors noted that the oxidative metabolism of UDMH was largely mediated by FAD-containing monooxygenase; this study observed that methimazole, a competitive inhibitor of monooxygenase, decreased the free radical activation of UDMH.
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From page 166... ...
Furthermore, they were conducted before good laboratory practices became widely accepted in toxicity studies, so they typically lack the detail and organization of more recent toxicity studies. Toxicity data of different degrees of completeness are available for numerous species of laboratory animals, including rhesus monkeys, dogs, rats, mice, and hamsters (Weeks et al.
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The authors conducted histopathologic studies on rats sacrificed immediately and 1, 3, and 7 d after exposure. Rats exposed to UDMH demonstrated signs of irritation, including sneezing, eye closure, and restlessness.
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From page 168... ...
Although the relative susceptibilities of various species are unknown, CNS symptoms caused by UDMH exposure appear qualitatively consistent across the species tested. Respiratory Effects Shook and Cowart (1957)
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Back (1963) reported no visible signs of toxicity or body weight changes in surviving ICR Swiss mice, Sprague-Dawley rats, and rhesus monkeys after inhalation exposure to 0.56 ppm of UDMH continuously for 90 d.
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Chronic inhalation exposures to UDMH using conventional protocols in use today have not been published; however, one peer-reviewed study in dogs was published some time ago. Rinehart et al.
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From page 171... ...
An indication of hepatotoxicity in dogs was demonstrated by transitory elevations of serum enzyme levels and liver function values in test subjects exposed to 5 ppm of UDMH. Six- to 12-month exposures resulted in a significantly increased oncogenic response to purified UDMH; this proved particularly true for lung adenomas (rarely seen)
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From page 172... ...
The authors reported a dose-related increase in tumors in female mice for the following tumors: hemangiosarcomas, thyroid carcinomas, and Kupffer cell sarcomas. However, our inspection of the data does not support this conclusion (Table 10-3)
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Reproductive Toxicity The reproductive toxicity of UDMH has been researched in rodents. Toxic effects included testicular abnormalities and fetotoxicity at doses near the LD50; however, this was not noted at lower doses.
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(1982) studied the in vivo and in vitro effects of UDMH on selected immune functions after short-term (six groups of 10 mice each injected i.p.
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(1982) shows that low doses of UDMH enhance immune function, which could possibly offset some of the immune changes associated with the stress of spaceflight.
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Inhalation Toxicity Summary Table 10-4, provides a data summary of UDMH inhalation toxicity studies. EXPOSURE LIMITS Table 10-5 presents exposure limits for UDMH set by other organizations.
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From page 177... ...
1963 tonicoclonic convulsions, and depressed activity 252 4h Rat, M, N/A Sneezing, eye closure, restlessness, Weeks et al. 1963 tonicoclonic convulsions, and depressed activity 1,200 5 min Dog, N/A, mongrel Convulsions, vomiting, tremors, and death Weeks et al.
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From page 178... ...
0.56 90 d, continuous Mouse, N/A, Hemosiderin deposit on Kupffer & liver Back et al. 1963 ICR Swiss cells; cysts in hearts of 2; 6 mice died between days 3 and 41 0.56 90 d, continuous Rat, N/A, Sprague- Vacuolization of renal tubular epithelium; Back et al.
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From page 179... ...
1979 hemangiosarcomas, Kupffer cell sarcomas 5a 6 h/d, 5 d/wk, 6 mo Rat, N/A Increase in squamous cell carcinomas, Haun et al. 1979 lung tumors, and hepatocellular carcinomas 0.5a 6 h/d, 5 d/wk, 6 mo Rat, N/A Islet cell adenomas of pancreas, slight Haun et al.
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1984 Golden Syrian 0.5 6 h/d, 5 d/wk, 6 mo Hamster, M, No toxic effects Haun et al. 1984 Golden Syrian 0.05 6 h/d, 5 d/wk, 6 mo Hamster, M, No toxic effects Haun et al.
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From page 181... ...
; Agency for Toxic Substances & Diseases Registry minimum risk level (inhalation) ; ATSDR MRL; IDLH, immediately dangerous to life or health concentration; NIOSH, National Institute of Occupational Safety and Health; OSHA, Occupational Safety and Health Administration; PEL, permissible exposure limit; REL, recommended exposure limit; TLV, threshold limit value; TWA, time-weighted average.
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1984) wk Anemia 5 ppm LOAEL Dogs, n = 3 10 6 10 3 -- -- -- -- 0.003 6 h/d, 5 d/wk, 24 (Rinehart et al.
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(1963) in nine stressed dogs exposed for 1 h to a concentration of 80 to 120 ppm.
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From page 184... ...
. They exposed dogs, rats, and mice 6 h/d, 5 d/wk to UDMH concentrations ranging from 5 to 140 ppm, and for times ranging from 6 to 26 wk.
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From page 185... ...
where comparisons are possible. The 1-h SMAC of 3 ppm matches the NRC acute exposure guideline level "above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape" (AEGL-2)
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From page 186... ...
for exposure to dogs that were stressed before exposure; one of nine dogs displayed slight tremors and experienced full recovery within 1 h, which calculates to a 1h AC of 3 ppm. The long-term SMACs of 0.017 and 0.003 ppm for 30 and 180 d of continuous exposure compare favorably with the threshold limit value of 0.010 ppm set by the American Conference of Governmental Industrial Hygienists.
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From page 187... ...
Pp. 213-233 in Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants, Vol.
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From page 188... ...
2000. Acute Exposure Guideline Levels for Selected Airborne Chemicals, Vol.
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From page 189... ...
1982. In vivo and in vitro effects of 1,1 dimethylhydrazine on selected immune functions.
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