Characterization of Particulate Matter Concentrations (PM10, PM10-2.5, and PM2.5) at High-Altitude School and Residential Mircroenvironments in Quito, Ecuador

Air quality issues in Latin American countries are especially challenging because of the limited availability of resources to address them, lack of stringent standards and the rapid and uncontrolled growth of their cities increasing the number of vehicles on the road and the expansion of the industry. In particular, the city of Quito, Ecuador exacerbates its environmental issues by its high-altitude (2800 m above sea level) coupled by its location around a mountain valley and frequent temperature inversions. This study focused on evaluating the spatial variation of the PM concentrations and the effectiveness of a central monitoring network in representing exposure. To accomplish this, a study was conducted in Quito (Ecuador) to evaluate the effect of transient and long-term ambient PM exposure on systemic inflammation, oxidative stress, and atherogenesis in a group of 300 children. Environmental PM data (PM2.5, PM10-2.5, and PM2.5) were collected to evaluate the association of exposure with inflammation and arterial thickening. Weekly averages were collected at schools and residential sites every month, over a 12-month period at three exposure sites (high, medium, and low). Particulate matter sources in Quito, based on size fraction, can be attributed to quarries, unpaved roads, and soil erosion coming especially from the north (for PM10), while the majority of PM2.5 can be attributed to traffic emissions and industrial sources (CORPAIRE, 2007). Spatial and temporal variations of outdoor coarse PM (PM10-2.5) concentrations were associated with meteorological data observed at a central monitoring network. Indoor concentrations for all PM fractions showed weaker association with meteorological or co-pollutant data collected at a central monitoring station. However, outdoor school and residential measurements showed stronger associations with indoor measurements, making them good indicators for indoor exposures, especially at places with no significant indoor PM sources and good ventilation, such as schools in Quito. Indoor residential levels were the highest levels from all the microenvironments studied, making them a priority for evaluation in future studies. Patterns of PM exposure across the three zones varied depending on PM size fraction, with Zone 2 resulting in higher exposure of PM2.5 because of its location in the urban center of Quito and high traffic emissions, while the northern and southern zones (1 and 3 respectively) yielded higher exposures for PM10-2.5. In the case of PM10, exposure classification could be misinterpreted because it contains both fine and coarse fractions of particulate matter. It is important to separate exposure by each size fraction because size influences patterns of deposition within the respiratory tract as well as source of emission. Coarse particles come primarily from mechanical grinding, windblown dust, agricultural activities, while PM2.5 is more likely to come from combustion processes, therefore their chemical composition is different and health effects would differ also. Future studies should focus on isolating PM10-2.5 levels with health effects, to evaluate the importance of establishing regulatory standards