Faculty

Professor Emeritus James Ultman | Research

Transport and Transformation of Inhaled Air Pollutants in the Respiratory Tract
Advisor: James S. Ultman

Our current research into the distribution of inhaled air pollutants and their potential health effects, is conducted through an integrated set of projects including measurements on human subjects, experiments on in vitro model systems, and mathematical simulation by chemical engineering transport models.

Gender Effects on the Distribution of Ozone

Ozone is an urban air pollutant produced by the photochemical reaction of automobile emissions. We measured the longitudinal distribution of inhaled ozone within the respiratory tract of 10 healthy men and 10 healthy women using the bolus inhalation technique that was pioneered in our laboratory. During quiet breathing conditions, ozone was removed from respired air almost exclusively within the conducting airways. Therefore, the data were analyzed by estimating an overall mass transfer coefficient of ozone absorption into the conducting airways. Statistical analyses indicated that gender alone did not affect the between-subject differences in the mass transfer coefficient. Rather, differences in the conducting airway volumes of the subjects was found to have a significant effect: those subjects with smaller airways exhibited larger mass transfer coefficients.

Comparison of Ozone and Chlorine Distribution

Chlorine gas is an important raw material in the production of bulk chemicals and pharmaceuticals as well as in the disinfection of drinking and swimming pool water. We measured the longitudinal distribution of inhaled chlorine within the respiratory tract of 10 healthy men and women during oral and nasal breathing at respiratory flows characteristic of quiet breathing as well as light exercise. A parallel set of measurements of ozone distribution was recorded for the same subjects. Because of its extremely large aqueous solubility, chlorine absorption was always confined to the upper airways proximal to the larynx. On the other hand, ozone penetrated to the distal end of the conducting airways during quiet breathing and reached the respiratory zone at elevated respiratory flows. These results help to explain the sites of tissue damage that were previously observed in long-term animal experiments. In particular, tissue damage was focused in the nose of chlorine-exposed rats and nonhuman primates, while tissue damage also appeared in the lower airways of ozone-exposed animals.

Simulation of Inhaled Gas Distributions by a Single Path Model

To simulate the absorption of inhaled reactive and soluble gases such as chlorine and ozone, we have developed a one-dimensional model of diffusion, convection and chemical reaction along the respiratory tract. Most of the input parameters necessary to produce a simulation of gas absorption from this model are available from previous scientific literature, but the validity of such simulations must be demonstrated with independent data. We are currently employing gas distribution data from the chlorine and ozone bolus inhalation experiments for this purpose. It appears from our initial findings that the single-path model is valid during quiet breathing conditions, but may require refinements in its stucture or input parameter values at elevated respiratory flows.

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