Spacecraft Maximum Allowable Concentrations for Selected Airborne Contaminants Volume 4 (2000) / Chapter Skim
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B9 Chlorodifluormethane (Freon 22)
B9 Chlorodifluormethane (Freon 22)
Pages 190-210
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From page 190... ...
B9 ChIorodifluoromethane (Freon 229 Hector D Garcia, Ph.D.
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From page 191... ...
In rabbits exposed by inhalation, blood concentrations of HCFC-22 increased very rapidly, steady state being approached in about ~ min. after which a plateau phase continued throughout a 30-min exposure (Sakata et al.1981~.
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From page 192... ...
Following cessation of exposure to 100,000 ppm or 200,000 ppm, blood concentrations of HCFC-22 in rabbits decreased rapidly up to 50% within 1 min and after 15-20 min. blood concentrations became 8-9,uL/g in all cases, irrespective of inhaled concentration (Sakata et al.
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From page 193... ...
In that epidemiological study of medical students during their pathology residency in a Boston hospital, half of those exposed to HCFC-22 during preparation of frozen sections reported heart palpitations. These consisted of mostly premature atrial contractions and episodes of paroxysmal atrial fibrillation, as confirmed by electrocardiography (Speizer et al.
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From page 194... ...
One of 14 rabbits exposed to HCFC-22 at 60,000 ppm for 5 h/d,5 d/w for ~ w, end receiving sodium phenobarbital at 0.5 g/L of drinking water to stimulate drug-metabolizing enzyme systems, developed "well-defined cardiac arrhythmias of probable supraventricular or ventricular origin" (Van Stee and McConnell 1977a)
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From page 195... ...
Exposure at 24,000-27,000 ppm induced somewhat rapid breathing at 5 min and slight lacrymation with partially closed eyes at 2 h. Exposure at 51,00054,000 ppm induced deep breathing and slight lacrymation at 5 min and irregular breathing, rubbing of their noses, and shaking their heads at 2 h.
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From page 196... ...
reported that mice exposed to HCFC-22 at 14,000 ppm for 6 in/d, 6 d/w for 10 mo weighed 26 ~ 1.5 g compared with controls, which weighed 34 ~ 1.8 g, with decreased weight gains noticeable beginning around the fourth to sixth month of exposure. Mice exposed similarly to HCFC-22 at 2000 ppm were unaffected (Karpov 1963a)
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From page 197... ...
(19Sla) , no exposure-related non-neoplastic organ pathology was observed in rats and mice exposed to HCFC-22 for 5 in/d, 5 d/w at 0, ~ 000, ~ 0,000, or 50,000 ppm for the rodents' lifetimes except for the following mild effects seen at the highest dose: a decrease in body-weight gain in male rats up to w 80; increased liver, kidney, adrenal, and pituitary absolute weights in female rats; and hyperactivity in mice.
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From page 198... ...
discounted the biological significance of the salivary-gland tumors, because they were increased only in males and only at 50,000 ppm. Because spontaneously occurring fibrosarcomas are not uncommon in aging mate rats, they concluded that the apparent increase in the spontaneous-tumor incidence was possibly due to a nonspecific action, such as stress at the high exposure concentration or a weak promotional effect (Litchfield and Longstaff 19841.
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From page 199... ...
found HCFC-22 to be negative in unscheduled DNA synthesis assays in the human heteroploid EUE cell line and in V-79 and CHO Chinese hamster cells. Reproductive and Developmental Toxicity Exposure of rats to HCFC-22 at 50,000 ppm for 5 hid for ~ w did not affect mate fertility or induce dominant lethality (Lee and Suzuki 1981~.
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From page 201... ...
201 cx, ~cd D ~D Us ~_ ~C)
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From page 202... ...
202 x .~ Em lo U, o =O O .m ^O, C=d '==o =m c: d.
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From page 203... ...
203 a~ .~, ~ - oo <,~ ,,, ~ m ~~ ~ ~ ~ ~ ~ m - O ~C ~ ~ e ~ ~ ~ =, ~ ~ ~ ~ ~ ~ ~· ~5 ._ C~ ~ _ .s~ 11 C: ~4 ._ C)
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From page 204... ...
TABLE 9-3 Spacecraft Maximum Allowable Concentrationsa Concentration, Concentration, Duration ppm mg/m3 Target Toxicity 1 h 1000 3500 CNS depression 24 h 1000 3500 CNS depression 7 rib 1000 3500 CNS depression 30 ~1000 3500 CNS depression IS0 ~1000 3500 CNS depression aThese SMACs are ceiling values. Previous 7-d SMAC = 100 ppm (350 mg/m3~.
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From page 205... ...
An additional spaceflight factor of 5 was not applied to this NOAEL because the NRC SMAC Subcommittee concluded that it was unnecessariTy conservative for cardiac sensitization data from epinephrine-challenged test animals (NRC 19961. For exposures to CFCs, cardiac sensitization to arrhythmias is generally dependent on blood concentrations but not on exposure duration after the blood concentration has reached a plateau (usually within 1 h)
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From page 206... ...
Because CNS effects are generally dependent only on blood concentration and independent of exposure time beyond about ~ h, the value for the 1-h AC is used for all exposure durations > 1 h. 1-h, 24-h, 7-d, 30-d, and T80-d AC = 10,000 ppm 10 (species)
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From page 207... ...
Because a response was seen only in one sex of one out of two species tested and only at the highest dose and very late in the study, the investigators concluded that the observed response represents an increase in the spontaneous tumor incidence due to a nonspecific action or a week promotional effect. That interpretation is supported by the lack of nonneoplastic histopathological changes in salivary glands and Zymbal glands in the Tinston et al.~198la)
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From page 209... ...
Pp 282-283 in Documentation ofthe Threshold Limit Values and Biological Exposure Indices. American Conference of Governmental Industrial Hygienists, Cincinnati, OH.
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From page 210... ...
1971. Cardiac arrhythmias and aerosol "sniffing." Arch.
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