Air pollution and retained particles in the lung

Epidemiologic evidence associates particulate air pollution with cardiopulm onary morbidity and mortality. The biological mechanisms underlying these a ssociations and the relationship between ambient levels and retained partic les in the lung remain uncertain. We examined the parenchymal particle cont ent of 11 autopsy lungs from never-smoking female residents of Mexico City, a region with high ambient particle levels [3-year mean PM10 (particulate matter less than or equal to 10 mum in aerodynamic diameter)= 66 mug/m(3)], and 11 control residents of Vancouver, British Columbia, Canada, a region with relatively low levels (3-year mean PM10 = 14 mug/m(3)). Autopsy lungs were dissolved in bleach and particles were identified and counted by analy tical electron microscopy. Total particle concentrations in the Mexico City lungs were significantly higher [geometric mean = 2,055 (geometric SD = 3. 9) x 10(6) particles/g dry lung vs. 279 (1.8) x 10(6) particles/g dry lung] than in lungs from Vancouver residents. Lungs from Mexico City contained n umerous chain-aggregated masses of ultrafine carbonaceous spheres, some of which contained Sulfur, and aggregates of ultrafine aluminum silicate. Thes e aggregates made up an average of 25% of the total particles by count in t he lungs from Mexico City, but were only rarely seen in lungs from Vancouve r. These observations indicate for the first time that residence in a regio n with high levels of ambient particles results in pulmonary retention of l arge quantities of fine and ultrafine particle aggregates, some of which ap pear to be combustion products.