Intratracheal instillation as an exposure technique for the evaluation of respiratory tract toxicity: Uses and limitations

The evaluation of respiratory tract toxicity from airborne materials freque ntly involves exposure of animals via inhalation. This provides a natural r oute of entry into the host and, as such, is the preferred method for the i ntroduction of toxicants into the lungs. However, for various reasons, this technique cannot always be used, and the direct instillation of a test mat erial into the lungs via the trachea has been employed in many studies as a n alternative exposure procedure. Intratracheal instillation has become suf ficiently widely used that the Inhalation Speciality Section of the Society of Toxicology elected to develop this document to summarize some key issue s concerning the use of this exposure procedure. Although there are distinc t differences in the distribution, clearance, and retention of materials wh en administered by instillation compared to inhalation, the former can be a useful and cost-effective procedure for addressing specific questions rega rding the respiratory toxicity of chemicals, as long as certain caveats are clearly understood and certain guidelines are carefully followed.