A system for the long‐term continuous exposure of laboratory animals to mixtures of air pollutants1

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Abstract
A facility has been developed for the continuous chronic exposure of large numbers of animals to various levels of air pollution mixtures. It consists of four large environmental rooms which are self‐contained, each constituting a large exposure chamber. The rooms are suitable for housing almost any species of laboratory animals. A main air handler conditions and cleans outside air which is distributed to the four rooms and hallway. Air flow, temperature and humidity are precisely controlled independently in each room. Actual air pollution involves large numbers of trace substances and is impractical to reproduce entirely. For the present, a controlled mixture is being used, consisting of submicron sulfate aerosol and major gaseous pollutants in proportions similar to those in urban atmospheres. The mixture is introduced into three of the four exposure rooms at three pre‐determined levels; low (typical of average air pollution), high (alert or episodic levels) and exaggerated (or emergency levels). Pollutant concentrations are automatically regulated by a programmed feed‐back control system. The fourth room, into which no pollutants are introduced, serves as a clean air control. The primary objective of the investigation is to study effects of air pollution on animals with respiratory and cardiovascular diseases. In addition, any adverse effects on healthy animals can be assessed since suitable control animals are included for each disease model.