This paper addresses specific problems that may arise when conducting inhalation toxicology studies for which the validated and recommended test designs are not detailed enough of for which changes are recommended. Among these are the physical and chemical characteristics of test materials and their implications for test design, specific problems with particulate matter such as the phenomenon of "dust overloading of lungs", and the difficulties of defining the maximum tolerated dose (MTD) in inhalation studies with solid particles. Improved documentation of the dosimetry is required in many studies, and the US EPA guidelines for acute inhalation studies need to be revised. In order to study at a sufficient level of sensitivity, an increased use of positive and negative control groups in subchronic and chronic studies may be a valuable complement. (Abstract truncated)
