Experimental woodsmoke exposure during exercise and an evaluation of blood oxidative stress
Type of DegreeDissertation
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Introduction: Woodsmoke exposure and exercise elicit oxidative stress in blood. The purpose of this investigation was to understand the effects of woodsmoke exposure on blood oxidative stress measures. Methods: Ten males 18-40 years were exposed to woodsmoke during 3 trials (separated by 1 week) while exercising on a treadmill to simulate the workload intensity and smoke exposure doses of wildland firefighting. Participants were exposed Clean Air (0 μg/m3, Filtered Air), 250 μg/m3 (Low Exposure) and 500 μg/m3 (High Exposure) woodsmoke particles (particulate matter <2.5 μm, PM2.5) in a randomized counter-balanced crossover fashion while exercising. Blood samples obtained at baseline (Pre), immediately post (Post) and 1 hour following (1Hr) post exposure were assayed for trolox equivalent antioxidant capacity (TEAC), uric acid (UA), lipid hydroperoxides (LOOH), protein carbonyls (PC), nitrotyrosine (3-NT), 8-isoprostane, and myeloperoxidase (MPO) activity and protein content assays. Results: Study participants averaged 14.1 % body fat and had an average aerobic capacity of 53.6 ml.kg-1.min-1. There were no self-reported respiratory complications by participant following the exposure trials. UA values were lower only following Low Exposure (p=0.042), while plasma TEAC levels were elevated Post (Clean Air and High exposure, p=0.015 and p=0.001 respectively) and at 1Hr (Clean Air and High exposure, p=0.001) time points. LOOH levels were decreased 1Hr Post (High exposure, p=0.036), while plasma 8-Iso levels were elevated in Post samples from both smoke doses (Low exposure p=0.004, High exposure p=0.009). There were no increases in plasma PC levels for any of the 3 trials, while 3-NT values were elevated over Clean Air when Low/High Exposure values were combined (p=0.012). Neither MPO activity nor protein content was altered following the 3 trials. Discussion: The current laboratory simulation of wildland firefighting elicited some indications of oxidative stress, although increases were independent of PM2.5 concentrations. Additionally, circulating antioxidants were not consistently depleted and two redox sensitive inflammation markers were unaltered by smoke exposure. Future lab-based woodsmoke exposure studies should employ longer duration exposure times in order to provide an exposure stimulus more related to firefighting scenarios. Future study should continue to identify oxidative biomarkers and physiologic parameters that are most sensitive to woodsmoke exposure leading up to comprehensive field studies.