Significance of mode of exposure in aerosol inhalation toxicity studies - head only versus whole body exposure.

The purpose of this study was to investigate differences in acute inhalation toxicity (LC50 values) using different types of exposure systems with five agricultural chemicals (three insecticides and two herbicides). Rats of both sexes were exposed during a period of four hours and observed for 14 days. During exposure air flow rate, concentration, particle size distribution, temperature, relative humidity and oxygen content were monitored within the inhalation chamber, toxic signs and death rate were recorded during the exposure and observation period. Of the three insecticides tested two were liquid OP type compounds - one of which was hydrophilic and one lipophilic - and one was a moderately hydrophilic solid insecticidal carbamate. Upon whole body exposure the hydrophilic OP was slightly less toxic and the lipophilic OP slightly more toxic. The carbamate was equally toxic regardless of type of exposure. The results demonstrate that it is advisable to have both systems available in view of the importance of exposures under practical conditions of use. For gaseous materials the whole body exposure is preferred.