Abstract:
Combustion of diesel fuel generates significant quantities of particulate matter, especially that with a diameter of less than one micron. Because of its size, diesel exhaust particulate matter is highly respirable and has a large surface area to volume ratio, making it an exceptional carrier of adsorbed organic and inorganic compounds into the lungs. Consequently, diesel exhaust and its components can be a significant source of exposure to air pollution for children who commute to and from school in diesel school buses. This pilot study assessed the exposures of nine asthmatic and non-asthmatic children in Seattle while they rode to and from school in a variety of makes and models of diesel school buses, including two equipped with an oxidative catalyst to reduce its emissions. Using portable instruments that were validated against standard equipment in a controlled environmental chamber, the study quantified children's exposures to the following parameters: fine and ultrafine particles, trace elements, elemental carbon and organic carbon, sulfur dioxide, nitrogen dioxide and carbon monoxide. Additionally, to test for acute effects of diesel exhaust exposures, subjects performed several respiratory health measurements, including: exhaled breath condensate, exhaled nitric oxide, and pulmonary lung function. This pilot study demonstrated the feasibility of performing a multi-year study which aims to document the change in children's exposure to several of the primary constituents of diesel exhaust as older school buses in the Puget Sound region are retrofitted with emission control technologies or replaced by newer clean-burning buses over the next several years. Additionally, the multi-year study will assess changes in children's respiratory health as the bus fleets' emissions are reduced.