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Safety assessment of HCFC-141b: use as a blowing agent for insulation in building construction and refrigeration.

We have performed a risk assessment to evaluate potential risk to human health that might be associated with the use of HCFC-141b (1,1-dichloro-1-fluoroethane) in rigid foam insulation boards for home sheathing and in foam insulation for refrigerators. Risks presented by the blowing agent itself and its potential contaminants and breakdown products (HCFC-151a, HCFC-1131a, and vinylidene chloride) were evaluated following the standard procedures outlined by the National Academy of Sciences. HCFC-141b showed an equivocal tumorigenic effect in rats (an increase in benign testicular tumors that was not dose related), while vinylidene chloride was associated with an increase in tumor incidence (kidney tumors in mice) in a single study out of 19 in which its carcinogenicity has been investigated. The other two contaminants have not been tested for carcinogenicity, but do show some evidence of genotoxicity in short-term tests. However, even if all of these substances are treated as potential carcinogens, under the anticipated conditions of human exposure the maximum theoretical risk to a resident is less than one in one million (10(-6)). Also, no other toxic effects would be anticipated.