Research Projects

Project at a Glance

Project Status: complete

Report Published May 2003:


Title: The effect of smoke from burning vegetative residues on airway inflammation and pulmonary function in healthy, asthmatic, and allergic individuals.

Principal Investigator / Author(s): Colin Solomon

Contractor: UC San Francisco

Contract Number: 97-322


Research Program Area: Health & Exposure

Topic Areas: Health Effects of Air Pollution, Toxic Air Contaminants


Abstract:

It is common practice worldwide to use open field burning to clear agricultural fields of rice straw and other vegetative residues, and for disease and pest control. This burning produces smoke, which contains respirable particulate and gaseous components. Currently, there is no specific information available on the direct effect of rice straw smoke (RSS) exposure on respiratory health effects, even though epidemiological data indicate that this issue requires investigation. The objective of this project was to investigate the effects of controlled exposure to RSS on human respiratory health. Specific Aim One: To determine the effect of a single exposure to RSS at two different concentrations on airway inflammation and spirometric pulmonary function. Specific Aim Two: To determine the effect of the RSS exposure format (single- vs. serial-day) on airway inflammation and spirometric pulmonary function. Specific Aim Three: To determine the effect of asthma and allergic rhinitis status on the airway inflammatory and spirometric pulmonary function responses to RSS exposure. The hypotheses of this project were: 1) that airway inflammation would be increased, and spirometric pulmonary function would be decreased, as a function of increased RSS concentration and dose; 2) that the RSS-induced changes in airway inflammation and spirometric pulmonary function would be increased in asthmatic and allergic individuals as compared to healthy individuals. This project consisted of three separate controlled human exposure experiments. Each experiment utilized 15 subjects; Experiment One used healthy individuals; Experiment Two used individuals with mild to moderate asthma; Experiment Three used individuals with allergic-rhinitis. The exposure conditions were single exposures to Filtered-Air (FA), and RSS at concentrations of 200 mg/m 3 (RSS-200), and 600 mg/m 3 (RSS-600), and three serial-day exposures to RSS at a concentration of 200 mg/m 3 (RSS-3x200). All exposures were of 30 min duration. Bronchoscopy was conducted 6-hr post-exposure, and spirometric pulmonary function was measured pre- and post-exposure, and pre-bronchoscopy. Results: Cells: Experiment One: In the bronchial fraction [(Bfx); first 15 ml of bronchoalveolar lavage (BAL)], for both RSS-600 and RSS-3x200, compared to FA, there was a significantly higher total leukocyte concentration, and for RSS-600, compared to FA, there was a significantly higher macrophage concentration. In the Bfx, for RSS-3x200, compared to both FA, and RSS-600, there was a significantly higher percent, and concentration of lymphocytes, and significantly lower percent of macrophages. Experiment Two: In the Bfx, for RSS-3x200, compared to RSS-600, there was a significantly higher neutrophil concentration. In the BAL, for RSS-3x200, compared to both FA, and RSS-600, there was a significantly higher lymphocyte concentration. Experiment Three: In the BAL, for RSS-600 compared to both FA, and RSS-3x200, there was a significantly lower percent, and concentration of epithelial cells. FA Condition: The Asthma subject group, compared to both the Healthy subject group, and the Allergic Rhinitis subject group; in the BAL had a significantly higher percent, and concentration of neutrophils. RSS-600 Condition: The Allergic Rhinitis subject group, compared to the Healthy subject group; in the BAL had a significantly higher percent, and concentration of lymphocytes. RSS-3x200 Condition: The Asthma subject group, compared to both the Healthy subject group, and the Allergic Rhinitis subject group; in the BAL had a significantly higher percent, and concentration of neutrophils; and compared to the Allergic Rhinitis subject group, in the Bfx, had significantly higher percent, and concentration of neutrophils. The Allergic Rhinitis subject group, compared to the Healthy subject group, in BAL, had a significantly higher percent of neutrophils. Cytokines: Experiment One: In the Bfx, for RSS-3x200, compared to RSS-600, there was a significantly higher interleukin (IL)-8 concentration. Experiment Two: In the Bfx and BAL, for all of the conditions, there were no significant differences in the tumor necrosis factor-alpha (TNF-a), IL-8, or monocyte chemoattractant protein-1 (MCP-1) concentration. Experiment Three: In the Bfx and BAL, for all of the conditions, there were no significant differences in the TNF-a, IL-8, or MCP-1 concentration. Spirometric pulmonary function: For each of the three experiments, there were no physiologically relevant differences, either with-in or between conditions, or between experiments. The results of this project indicate that RSS is capable of inducing airway inflammation in healthy individuals, and in individuals with asthma, or allergic rhinitis.


 

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