Ozone and PM2.5 exposure and acute pulmonary health effects: a study of hikers in the Great Smoky Mountains National Park

Abstract

To address the lack of research on the pulmonary health effects of ozone and fine particulate matter (</= 2.5 microm in aerodynamic diameter; PM2.5) on individuals who recreate in the Great Smoky Mountains National Park (USA) and to replicate a study performed at Mt. Washington, New Hampshire (USA) , we conducted an observational study of adult (18-82 years of age) day hikers of the Charlies Bunion trail during 71 days of fall 2002 and summer 2003. Volunteer hikers performed pre- and posthike pulmonary function tests (spirometry), and we continuously monitored ambient O3, PM2.5, temperature, and relative humidity at the trailhead. Of the 817 hikers who participated, 354 (43%) met inclusion criteria (nonsmokers and no use of bronchodilators within 48 hr) and gave acceptable and reproducible spirometry. For these 354 hikers, we calculated the posthike percentage change in forced vital capacity (FVC) , forced expiratory volume in 1 sec (FEV1) , FVC/FEV1, peak expiratory flow, and mean flow rate between 25 and 75% of the FVC and regressed each separately against pollutant (O3 or PM2.5) concentration, adjusting for age, sex, hours hiked, smoking status (former vs. never) , history of asthma or wheeze symptoms, hike load, reaching the summit, and mean daily temperature. O3 and PM2.5 concentrations measured during the study were below the current federal standards, and we found no significant associations of acute changes in pulmonary function with either pollutant. These findings are contrasted with those in the Mt. Washington study to examine the hypothesis that pulmonary health effects are associated with exposure to O3 and PM2.5 in healthy adults engaged in moderate exercise. .

Figure 1

Hourly variation in mean and maximum PM_2.5 concentration (μg/m³) at the Newfound Gap trailhead stratified by sampling period (29 days during August–October 2002 and 42 days during May–August 2003). Times shown are Eastern Daylight Saving Time (EDT).

Figure 2

Hourly variation in mean and maximum O₃ concentration (ppbv) at the Newfound Gap trailhead stratified by sampling period (29 days during August–October 2002 and 42 days during May–August 2003). Times shown are Eastern Daylight Saving Time (EDT).

Figure 3

Hikers’ mean posthike percentage change in FVC, FEV₁, and PEF as a function of quintile of PM_2.5 concentration.

Figure 4

Hikers’ mean posthike percentage change in FVC, FEV₁, and PEF as a function of quintile of O₃ concentration.