Basic Continuing Education Course on Inhalation Toxicology Gets off to a “Fiery” Start

By Gary Rankin posted 03-24-2014 19:03


One of the first Continuing Education (CE) Courses offered at the 53rd Annual Society of Toxicology meeting in Phoenix, Arizona, was AM05 Inhalation Studies: Challenges and Complexities. This CE course, chaired by Drs. Willie J. McKinney and Gregory Baker, provided an outstanding background in the basic elements of conducting an inhalation study. The five speakers covered a wide range of topics, including comparisons of methods of exposure, test material characterizations, dose predictions, toxicological endpoints, and regulation guidance.

The stage was set for this CE Course by co-chair Dr. McKinney from Altria Client Services, Inc., who gave a description of the need and benefits of conducting inhalation studies. He also gave an overview of the topics to be covered during the morning. However, as the first speaker, Dr. Robert Phalen from the University of California Irvine, began his presentation, an emergency alarm sounded and the entire Phoenix Convention Center had to be evacuated. We soon learned that the reason for evacuating everyone was a fire at one of the food court restaurants. Although the fire was quickly extinguished, we still had to wait for Phoenix firemen to arrive and determine that everything was safe. After about 15 minutes, the firemen arrived to check out the situation, and the “all clear” was given a few minutes later.

Dr. Phalen soon resumed and completed his topic, which compared the use of whole body exposure and nose-only exposure—the common models used to conduct inhalation studies. The next speaker, Dr. Gregory L. Baker from Battelle, covered the different types of test materials (gases, aerosols, particles) used in inhalation studies and how to generate and characterize them. Dr. Michael J. Oldham from Altria Client Services, Inc., was the last speaker before the break, and he discussed selecting test subjects and making dose predictions. Following the break, Dr. Jack Harkema from Michigan State University talked about how to pick the biological endpoints needed to properly conduct and monitor a meaningful inhalation study. Lastly, Dr. Mark Higuchi presented the regulatory aspects of conducting inhalation studies.

For anyone beginning to conduct inhalation studies or for those looking for a refresher course, AM05 did an excellent job of providing the needed information. There were several important basic concepts covered by this course:

  • What to consider in model selection. When to use a whole body exposure method or a nose-only model was well covered.
  • What are you exposing your subject to and how do you characterize the components in the exposure mixture. The various methods to characterize particle size were compared with their pluses and minuses presented.
  • How to pick a model for an inhalation study. It turns out that lungs from all mice (and rats) are not the same size, which can inform the results observed between strains. A new fact for me was that the ferret has lungs more like humans than other animal models such as mice, rats, and non-human primates. It was also interesting that in many inhalation exposure studies, the particles go primarily to the head rather than the lungs and may end up being cleared into the gastrointestinal tract.
  • How to pick biological endpoints that have human relevance. During the study, it is important to look for relevant clinical signs of toxicity via pathological examination, respiratory function test, and bronchiole-alveolar lavage.
  • A reminder that there are regulatory guidelines from agencies such as the Environmental Protection Agency that must be followed when generating inhalation study data.

Clearly, humans are exposed to many chemicals via the inhalation route, and it is essential that investigators follow basic and appropriate guidelines to get the most accurate and representative data possible.