Inhalation Toxicology. 11. The Effect of Elevated Temperature on Carbon Monoxide Toxicity

Laboratory rats were exposed (a) to experimental concentrations of carbon monoxide in air at ambient temperature, (b) to elevated temperature atmospheres from 40 deg C to 60 deg C, and (c) to selected carbon monoxide (CO) concentrations at the elevated temperatures in (b). The incapacitating potency of each of the environments was evaluated by measurements of time-to- incapacitation (t sub i) as a function of CO concentration and/or temperature; incapacitation was defined operationally as loss of ability to walk inside a motor-driven, rotating cage enclosed in an exposure chamber. Comparison of data from the combined (CO + elevated temperature) exposures and exposures to CO and elevated temperatures alone indicated than incapacitation occurred earlier when CO inhalation was combined with a whole-body, elevated temperature environment than was observed for the same exposure parameters applied individually. No evidence for a synergistic effect was noted. An empirical equation was derived that allows the calculation of a predicted t sub i for combinations of CO and temperature within the rangers utilized in the experimental exposures.