Effect of a diesel engine ban on asthma-related morbidity in Beirut

Background: Diesel emissions contain smaller amounts of CO, CO2 and hydrocarbons than gasoline, but their content in nitrogen oxides and particulate matter is significantly higher. Some of this particulate matter is of the respirable size and penetrates deep into the tracheobronchial tree. Exposure to diesel emissions is associated with respiratory disease.In Lebanon, a rapid expansion in the transportation sector allowed a gradual introduction of diesel fuel-operated vehicles, which had been banned till 1977. Fuel was being imported with little control over its quality. A ban was imposed on light and medium-duty diesel engine on the Lebanese territory as of July 1, 2002.Objective: To determine the effect of the diesel ban on the air concentration of particulate matter and on asthma-related morbidity in children admitted to the emergency room (ER) of the American University of Beirut Medical Center (AUBMC).Methods: Air samples were collected at multiple large intersections of Beirut before and after the ban. Each sample was collected over a period of 30 minutes and analyzed for particulate matter. Air sampling was done during summer, at which time the concentration of particulate matter is at its peak. The average of all the concentrations was computed.The records of all visits to AUBMC-ER were reviewed over a two-year period: Period 1 (Pre-ban: July 1, 2001 to June 30, 2002) and Period 2 (Post-ban: July 1, 2002 to June 30, 2003). All patients 0-15 years of age presenting with acute asthma were identified.Results: The average concentration of particulate matter was 181.3 µg/m3 and 97.1 µg/m3 before and after the ban respectively. The total numbers of ER visits for pediatric patients were 6453 and 6865 in period 1 and period 2, respectively. Of those, 313 were due to asthma in period 1 and 223 in period 2. The number of asthma-related visits was significantly reduced during period 2. Asthma-related visits were significantly reduced during October, November and December of period 2 compared to the same months of period 1, while it was significantly increased during the month of June.Discussion: This study shows that a ban on diesel engine resulted in a decrease in the air concentration of particulate matter and was associated with a reduction in the number of emergency room visits for acute asthma. This reduction was most marked during the season of viral respiratory infections. We postulate that a reduction in the concentration of air pollutants was protective against viral-induced asthma exacerbations