Toxicity evaluation of degradation products of refrigerants

Abstract

1.はじめに 1974年にローランドとモリーナが、成層圏に 達したフロンが紫外線によって分解されて発生 した塩素によるオゾン層破壊の可能性を指摘し た(Molina and Rowland, 1974.)。1985年にはウ ィーン条約が締結され、1987年には「モントリ オール議定書」が採択され、ヒトの健康及び環 境保護のために、冷媒として使用されている特 定フロン[Chlorofluorocarbon(CFC)の5物質] を1996年末までに全廃することとされた。特定 フロンに代わって、「塩素を含まないこと、含 んでいても分子内に水素を有し、成層圏に達す る前に消滅しやすいこと」、「地球温暖化への影 響が少ないこと」及び「毒性がないこと」を条 ABSTRACT The present paper summarizes the data available in the literature concerning toxicity of the degradation products of 1,1,1,2-tetrahydrofluoroethane(HFC-134a),which is widely used worldwide as a refrigerant, and 2,3,3,3-tetrafluoropropene(HFO-1234yf),which is developed as a refrigerant for new generation. There are many studies available for toxic effects of carbon dioxide(CO2)and carbon monoxide(CO)in humans and animals. General toxicity of excessive CO2 exposure in humans is well reported. However, information on reproductive and developmental toxicity of CO2 in humans and animals is inadequate for risk assessment. As for CO, further studies are required to evaluate the adverse effects of chronic exposure to low and near ambient levels of CO on development of fetuses and newborn infants in marginal condition because of high susceptibility to hypoxic effect in fetuses and newborn infants. There is a lack of information on toxicity of trifluoroacetic acid, carbonyl fluoride, hydrogen fluoride, and formic acid in humans and animals. Animal studies remain necessary for risk assessment of chemicals because it is difficult to find alternative methods to determine the toxic effect of chemicals.