In reaction to air pollutants, asthmatics may experience an ""asthma exacerbation"" characterized by the narrowing of their airways. This may lead to a shortness of breath that may require urgent medical attention. One source of air pollution associated with asthma exacerbations is diesel exhaust. How and why diesel exhaust causes exacerbations is unclear, but one hypothesis is that it causes ""oxidative stress"", which is damage to cells and body tissues due to certain chemical characteristics. Ongoing exposure to traffic-related air pollution can also result in new asthma in previously healthy individuals. Dr. Christopher Carlsten is working to understand how different air pollutants, particularly diesel exhaust, influence asthma. He is trying to determine whether diesel exhaust creates oxidative stress, and, if so, if that stress is responsible for airway narrowing in human asthmatics. In his laboratory, diesel exhaust is generated in concentrations typically found in mining operations or in busy bus terminals. Volunteer subjects inhale the exhaust for two hours – a short exposure time has no permanent effects but does produce mild, temporary changes – and changes in oxidative stress and airway narrowing are measured. In some subjects, other typical environmental allergens such as tree and grass pollen are added to see if they worsen the effect of diesel exhaust. In addition to this work, Dr. Carlsten and colleagues are following a group of more than 20,000 children from birth to see how their exposure to such pollution may lead to new asthma. Dr. Carlsten's research will lead to a better understanding of diesel exhaust-related airways disease and will lead to measures to protect Canadians exposed to traffic-related pollution. This research aims to inform recommendations for or against changes in fuel composition and/or personal measures to bolster anti-oxidant levels. Dr. Carlsten’s work to understand the effects of air pollution on asthma development should inform interventions regarding pollutant exposure in children.