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In a study at the University of California Davis. Dr Edward Schelegle and colleagues recruited 31 healthy nonsmoking individuals to participate in 6.6-hour sessions during which they were exposed to ozone at 60, 70, 80 or 87 parts per billion (ppb) or filtered air while undergoing six 50-minute bouts of moderate exercise followed by 10-minute breaks. A 35-minute lunch break separated the third and fourth bouts of exercise. Lung function for each subject was assessed before, during and after exposure, and each individual answered a questionnaire evaluating their subjective symptoms. Of the four levels of ozone concentration tested, Dr Schelegle and colleagues found significant decrements in both lung function and subjective respiratory symptoms at 70 ppb and above, beginning at 5.6 hours after exposure. The results suggest that even at levels currently below the air quality standard (75ppb), healthy people may experience decreased lung function after just a few hours of moderate to light exercise such as bicycling or walking, although the changes were reversible within a few hours. However, the study would seem to be particularly relevant for lung function in asthmatics given the acute rise in the hospitalisation of asthmatics during high ozone periods. Although the study also supported the previously reported smooth dose-response curve associated with ozone (the higher the level of ozone, the greater the decrease in lung function) the response of the healthy subjects in the study was very variable with a few exhibiting strong sensitivity to ozone concentrations although the researchers had no idea why..
American Thoracic Society's American Journal of Respiratory and Critical Care Medicine August 09
Click here for more research on possible treatments for asthma First Published in July 2009 |
