Toxicity of Alternatives to Chlorofluorocarbons HFC-134a and HCFC-123 (1996) / Chapter Skim
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3 EXPOSURE GUIDANCE LEVELS FOR HYDROFLUOROCARBON-134a
3 EXPOSURE GUIDANCE LEVELS FOR HYDROFLUOROCARBON-134a
Pages 23-40
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From page 23... ...
134a or 1,1,1,2 tetrafluoroethane is a gaseous halocarbon that is being considered as a prime candidate for replacing other halocarbon materials, such as Freon 12 (dichioroctifluoromethane) and Freon 22, for use in air conch tioning and refrigeration systems anct possibly as an aerosol pro pellant or foam expansion agent.
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From page 24... ...
96 psia at 25°C (77°C) Nonflammable 0.15% in water; soluble in ether Pow= 1.06 1 mum= 238 ppm; 1 ppm= 4.2 mg/m3 The major uses of HFC 134a are in mobile air conditioning anct
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From page 25... ...
Toxic effects observed in animals following oral and inhalation exposures to HFC 134a indicate that it is absorbed by the lungs and gastrointestinal (GI) tract (Salmon et al., 1980~.
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From page 26... ...
HFC 134a at high concentrations appears to be a develop mental toxicant (slight delays in skeletal ossification and lower body weights)
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Two of 4 dogs exposed at 100,000 ppm showed marked responses, one with multiple consecutive ventricular beats, the other with ventricular fibrillation leading to cardiac arrest. In summary, Mullin ant!
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. Urinary fluoride concentrations were increased after the ninth exposure, suggesting metabolic conversion of the retained halocarbon (Silber and Ken nedy, 1979b)
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. Changes in liver, kidney, and gonad weights were noted; these were con fined to male rats exposed at 50,000 ppm except for a liver weight increase, which was also seen at 10,000 ppm.
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From page 30... ...
There was a significant re Suction in fetal weight and significant increases in several skeletal variations following exposure of clams to HFC 134a at 300,000 ppm. Maternal toxicity was observed following exposure of clams at both 100,000 ppm (effects were reduced responses to noise stim uli and uncoorclinatec!
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From page 31... ...
Reproductive Toxicity In a 28 day inhalation study, 16 male rats were exposed to HFC 134a at 0, 1,000, 10,000, 50,000 ppm for 6 hr/day, 5 days/wk (Riley et al., 1979~. The rats exhibited decreased gonad weights at the 50,000 ppm exposure concentration.
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From page 32... ...
The authors reported that none of these effects occurred following exposure of male rats at 10,000 ppm. Genotoxicity There is no eviclence to suggest that HFC 134a induces either genetic or chromosomal mutations, and hence, there is no reason to suspect that HFC 134a might incluce heritable effects in hu mans.
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From page 33... ...
Thus, the NOAEL or upper limit of animal exposure for nontoxic effects of HFC 134a is about 50,000 ppm. In a 52 week study, male and female rats were exposed to HFC 134a.
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34 ~ is .
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From page 35... ...
at 40,000 ppm. Although fetotox~c effects were observed in rats and rabbits at lower exposure concentrations, the NOAELs (20,000 ppm for rabbits exposed for 78 hr and 10,000 ppm for rats exposed for 240 hr)
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He fetotox~city observed in rats during gestation was used to develop the 24 hr EEGh whereas the 90 day CEGL was recom mended on the basis of no adverse effects observed in rats chroni cally exposed to 50,000 ppm. The similarity of the exposure guid ance levels recommended for 24 hr and 90 day exposures is consis tent with the fact that blood concentrations of this class of com pounds reach maximal levels within minutes of the onset of expo
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CTL/P/ 2422. Central Toxicology Laboratory, Imperial Chemical Industries, AlclerIey Park, Macclesfie1d, Cheshire, U.K Hardy, C.~., 1.~.
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CTL/P/437. Central Toxicology Laboratory, Imperial Chemical In dus tries , Alderl ey Park, M accles field, Cheshire, U.K Litton Bionetics.
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From page 39... ...
422 79. Haskell Laboratory, Wilming ton, Del.
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