It is difficult to assess inhalation toxicity without using any animal models. "The Promise and Reality of Alternative Methods in Inhalation Toxicology and the Development of Inhaled Therapeutics" symposium session campaigned for some methods to evaluate inhalation toxicity and addressed issues that are still unsolved.
An important criteria for inhalation toxicity is to evaluate both acute and repeated exposures, and in vitro methods must be able to successfully receive the exposure and to mimic how the response is observed in humans. Most of the presenters addressed this issue by introducing multiple ways to culture cells.
In vitro models also must contain the same cells found in the lung. However, cells in the upper respiratory tract differ from cells in the lower tract. In addition, the thickness of the epithelium changes according to the location, which interrupts distribution. Multiple presenters overcame this issue by introducing in vitro models that cultured with various cells, such as a layer of dendritic cells followed by epithelial cells. These cultures were found to overcome some current issues. However, a better model must be designed before we can replace in vivo studies.