Student Research: Jeffrey S. Hogue

, , 1994
Faculty Advisor: Jane Q. Koenig

Characterization of Interpersonal and Intrapersonal Differences in Endogenous Ammonia in Human Respiratory Airways


Abstract

The ecological and environmental impacts of the deposition of aqueous acids, acid gasses, and acidic salts have been of growing concern in the past decade. However, not until recently have the impacts of these acids on human heallth been in the forefront of toxicological research. Several previous studies have shown that acid sulfate aerosols are of primary concern regarding potential adverse respiratory effects. In the ambient atmosphere, ammonium sulfate (NH2SO4), ammonium bisulfate (NH4HSO4), and sulfuric acid (H2SO4) have been identified as the major persistent sulfate species. The ammonium salts are the result of the neutralization of H2SO4 by atmospheric ammonia (NH3). Sulfuric acid aerosols are the products of the dissolution of sulfur diozide (SO2) in water vapor to produce sulfurous acid (H2SO3). Sulfurous acid can then be further oxidized to form H2SO4. Although ammonium sulfate salts have been implicated in respiratory irritation, they have been found to be 10-33 percent less irritating than sulfuric acid. Possible health effects associated with human exposure to acid sulfate aerosols include lung function decrements, respiratory irritation, reduced mucocilliary clearance, eye irritation, and tooth erosion in industrial situations.

An important consideration when evaluating the health effects of acid sulfate aerosols is the ability of the body to reduce hydrogen ion concentration [H+], and thereby decrease harmful respiratory effects. Larson and colleagues have hypothesized that acidity can be reduced by two mechanisms: (i) by dilution of acid sulfate aerosols in the saliva matrix and (ii) by neutralization with endogenours ammonia (NH3). The ammonium ion (NH4+) is present in body fluids and is a normal constituent of the respiratory tract and oral cavity. Because of the chemical properties of NH3 and the physical properties of the respiratory blood/air barrier, ammonia is found in measurable concentrations in exhaled air.

Taken from the beginning of thesis.