ABSTRACT
Inhalation as a route of exposure is used extensively in animal studies when it mimics the
likely route of human exposure. In many cases, the effect to be evaluated is on an organ
system other than the respiratory tract. For example, developmental toxicity, reproductive
toxicity, and neurotoxicity have been evaluated in animals following inhalation exposure
because the primary route of exposure for humans to the test substances is by inhalation
(solvents, for example). On the other hand, the effect of interest may be on the lungs and
respiratory tract (irritating gases or particulates, for example). Although the mechanics of
the exposures are the same in both cases, the approach to the study design and the end points
selected for evaluation will be quite different. The following provides some understanding
of the principles that guide study design. The emphasis will be on pulmonary toxicity,
but issues relevant for other end points, such as reproductive or developmental toxicity, will
also be discussed.
