I-CLIC Projects

UIOWA UIHC

APLD -- Air Pollution And Lung Structure Study

Lung function growth is frequently quantified using spirometry in environmental epidemiologic studies of air pollution. Many studies have focused on the effects of acute exposures on short-term changes in airway function; however, few have investigated the long-term effects of chronic exposure on childhood lung function. Findings from the Children's Health Study, a 10-year longitudinal study of the chronic effects of air pollution among 6000 children residing in 12 Southern California communities, indicate that current levels of particulate matter, nitrogen dioxide, and vapor acids are associated with reduced lung function growth and lower maximum attained measures of airway flows. The deficits (up to 8-10%) are largest and most consistent for FEV1, MMEF and FEF75, suggesting that flows from small airways are reduced. The magnitude of these deficits is of great concern, as irreversible reduction in airway flows has been associated with increased risk for COPD, cardiovascular disease and all cause mortality. A better understanding of the mechanisms for the deficits is required to determine whether there are long-term risks associated with the deficits in lung function. Although it is essential to identity the mechanism for these deficits, the biologic basis underlying these spirometric deficits has yet to be determined. It is critically important to establish whether the deficits in flows occur as a result of irreversible anatomic changes in the airway structure, size or wall thickness that indicate elevated long-term risk for adverse health outcomes, or whether the deficits arise from potentially reversible physiologic changes that may not influence long-term risk. If the deficits reflect structural changes, then individuals with deficits from air pollution are likely to be at increased risk for developing COPD and perhaps cardiovascular disease. Results from recent studies in primates by Plopper et al. show that air pollution exposure produces marked structural changes in the airways and parenchyma resulting in changes in branching structure as well as wall diameter. These finding indicate that studies of the structural effects of air pollution must consider both large and small-scale changes in airways structure. Recent developments in lung imaging using High-Resolution Computerized Tomography (HRCT) now make it feasible to non-invasively study the structure of small airways as small as 2mm in diameter and the entire airway using volumetric reconstructions. These developments make it possible to investigate the anatomic relationship between air pollution associated deficits in spirometric measures of airway flow and permanent changes in the structure and function of small airways, overall airway geometry and lung parenchymal changes.

In this study, we will:

1. Develop methods and test the feasibility for a study of the effects of air pollution on lung     structure using HRCT to assess small airway diameter, wall thickness and luminal area, air     trapping and parenchymal changes among Children's Health Study participants with contrasting     exposure histories.
2. Determine the relationships between small airway diameter, wall thickness and luminal area, air     trapping and parenchymal changes and childhood pollution exposures (Ozone, NO2, PM10,     PM2.5).
3. Assess the relationships between anatomic CT measurements, lung function deficits, and exhaled     nitric oxide (NO) levels