A Method to Determine the Potential Toxicity of Smoke from Burning Polymers: II. The Toxicity of Smoke from Douglas Fir

Mice were exposed for 30 minutes to smoke from burning Douglas fir under flaming conditions using the UPitt II apparatus for evaluation of flaming combustion/toxicity of smoke. The burning conditions were selected to provide a range from sufficient energy and oxygen to just sustain flaming above the specimens up to efficient flaming conditions of high flame height above the specimens. Under inefficient burning conditions carbon monoxide evolved slowly and was found to be the principal toxicant. Under highly efficient burn ing conditions deaths also occurred but not due to CO. Combining all burning conditions an average LC ₅₀ of 113 mg/L (95% confidence interval was 108 to 118 mg/L) was obtained from smoke from Douglas fir. No deaths were observed at a smoke exposure concentration below 76 mg/L for a 30 minute exposure. Lethality data were also analyzed for time to death to obtain median time to death, survival distribution function and cumulative hazard. These showed that although the smoke LC ₅₀ was similar for the burning conditions in vestigated, the time to effect was different. The cumulative hazard was highest under the most efficient flaming conditions producing low CO. Thus, the lethal effect of smoke from Douglas fir was not predicted from analysis of CO as was previously suggested.