A comparative study of the acute inhalation toxicity of smoke from TiO2-hexachloroethane and Zn-hexachloroethane pyrotechnic mixtures.

Rats was exposed to white smoke generated from mixtures of titanium dioxide-hexachloroethane (TiO2-HC) and zinc-hexachloroethane (Zn-HC), respectively, in an inhalation chamber operated in the static mode. The dose was varied by varying the amount of smoke mixture and/or the exposure time. The acute inhalation toxicity of TiO2-HC smoke was much lower than the Zn-HC smoke. Thus, the animals survived exposure to TiO2-HC smoke, even at relatively high smoke concentrations. This smoke was irritating to the animals and minor, acute inflammatory changes were seen in lung tissue. In contrast, Zn-HC smoke was very toxic and caused lethal injuries to the experimental animals, even at relatively low concentrations. Pulmonary injuries were extensive and death was due to blood congestion with pulmonary oedema. Since the TiO2-HC and Zn-HC mixtures form TiCl4 and ZnCl2, respectively, a separate study was performed in which rats were exposed to TiCl4 gas or ZnCl2 aerosol. No animals died from exposure to TiCl4 at concentrations between 370 and 2900 mg/m3 for 10 min. The LC50 of ZnCl2 was found to be around 2000 mg/m3 during a 10-min exposure period. The difference between the two types of smoke is explained by the difference in toxicity between TiCl4 and ZnCl2.