THE CARDIOTOXICITY OF INHALED POLYMER PYROLYSIS FUMES

Carbon monoxide and hydrogen cyanide are important toxic constituents of pyrolysis product mixtures. Carbon monoxide (CO) is ubiquitous in fire atmospheres; hydrogen cyanide (HCN) is generated whenever nitrogenous fuels are present. Controlled studies of the effects of these gases, when present in a smoke matrix of other pyrolysis products, are few. Most of the systems for exposing animals to pyrolysis products were designed to permit only the ranking of materials in order of toxicity on a total weight combusted basis.;Three effects were monitored: morphologic alteration expressive of tissue damage; increases in the levels of circulating cardia specific creatine kinase (CPK/MB) activity, a biochemical measure; and increases in the number of ectopic heart beats generated by the intravenous injection of norepinephrine, a functional measure. The cardiotoxicity of the two smoke matrices was evaluated without and with the addition of different controlled levels of CO and HCN to permit the construction of dose-effect relationships.;Increases in plasma CPK/MB activity and in the number of ectopic beats generated by the intravenous injection of norepinephrine were directly related to the concentration of carbon monoxide in either hemlock or polyurethane smoke. The addition of carbon monoxide to either smoke also caused increases in the incidence of cardiomyopathies. However, exposure to hemlock smoke was less cardiotoxic than exposure to polyurethane smoke when both smokes contained approximately the same concentration of carbon monoxide.;The addition of hydrogen cyanide to hemlock smoke to produce a concentration equal to that in polyurethane smoke resulted in cardiotoxicity nearly equal to that associated with polyurethane smoke exposure. Further addition of hydrogen cyanide to either smoke resulted in dose dependent increases in their toxicity. Protection of the animals with a cyanide antidote, chlorpromazine plus sodium thiosulfate, abolished the increase in cardiotoxicity associated with hydrogen cyanide supplementation of hemlock smoke and also abolished much of the cardiotoxic effect of polyurethane smoke exposure. Finally, the cardiotoxicity of polyurethane smoke was found to be approximately equal to that of a comparable mixture of pure carbon monoxide and hydrogen cyanide in air.;To overcome the shortcoming of poorly characterized dose, an apparatus which produces a steady state smoke uniform in composition and reproducible from day to day has been designed and constructed. With this apparatus the cardiotoxic effects in rats of smokes generated by the nonflaming combustion of hemlock and of rigid polyurethane foam have been investigated. The primary aim of this research was to determine whether the greater cardiotoxicity of polyurethane smoke than of hemlock smoke could be attributed to hydrogen cyanide generated during the thermal degradation of polyurethane.;It is concluded that the difference in the cardiotoxicity of hemlock and polyurethane smokes is due primarily to the presence of hydrogen cyanide in the polyurethane smoke matrix.