Development of a large-scale computer-controlled ozone inhalation exposure system for rodents

Abstract

Objective: Complete systems for laboratory-based inhalation toxicology studies are typically not commercially available; therefore, inhalation toxicologists utilize custom-made exposure systems. Here we report on the design, construction, testing, operation and maintenance of a newly developed in vivo rodent ozone inhalation exposure system.

Materials and methods: Key design requirements for the system included large-capacity exposure chambers to facilitate studies with large sample sizes, automatic and precise control of chamber ozone concentrations, as well as automated data collection on airflow and environmental conditions. The exposure system contains two Hazelton H-1000 stainless steel and glass exposure chambers, each providing capacity for up to 180 mice or 96 rats. We developed an empirically tuned proportional-integral-derivative control loop that provides stable ozone concentrations throughout the exposure period (typically 3h), after a short ramp time (∼8 min), and across a tested concentration range of 0.2–2 ppm. Specific details on the combination of analog and digital input/output system for environmental data acquisition, control and safety systems are provided, and we outline the steps involved in maintenance and calibration of the system.

Results: We show that the exposure system produces consistent ozone exposures both within and across experiments, as evidenced by low coefficients of variation in chamber ozone concentration and consistent biological responses (airway inflammation) in mice, respectively.

Conclusion: Thus, we have created a large and robust ozone exposure system, facilitating future studies on the health effects of ozone in rodents.

Keywords:

• Ozone
• air pollution
• inhalation
• exposure
• computer-controlled
• exposure system

Acknowledgements

We thank the following individuals who were instrumental to the success of this project: Ian Gilmour at The United States Environmental Protection Agency’s National Health and Environmental Effects Research Laboratory (NHEERL), Chris Gregory from the Department of Genetics at The University of North Carolina at Chapel Hill, and William Robertson and Artie Neese of Facilities Services at The University of North Carolina at Chapel Hill.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by the National Institute of Environmental Health Sciences under award numbers R01 ES024965, T32 ES007126-35, and P30-ES-010126.