Modeling of Toxicological Effects of Fire Gases: VI. Further Studies on the Toxicity of Smoke Containing Hydrogen Chloride

Studies of rodent lethality due to exposure to HCl, as well as to mixtures of HCl and CO, have shown different apparent toxicological effects at low and at high concentrations of HCl. At low concentrations of HCl, sensory irritation causes a decrease in respiratory minute volume, with somewhat slower loading of CO and a delay in incapacitation. This effect is observable only at low con centrations of CO. At much higher HCl concentrations, pulmonary irritant ef fects are observed leading to postexposure lethality. An empirical analysis of the data for mixtures of HCl and CO suggests that exposure doses leading to lethality may be additive. The lethal toxic potency (LC ₅₀ ) of PVC smoke may be largely, but not entirely, accounted for by the HCl produced. However, PVC smoke exhibits a greater in cidence of early postexposure deaths. The early deaths, which may be partially attributable to a combined effect of CO and HCl, may also be linked to the pattern of respiratory penetration by the smoke. There is evidence that com ponents other than HCl are present which cause PVC smoke to be more irri tating than HCl alone.