Date of Award


Degree Name

Doctor of Philosophy


Environmental Science and Engineering


Wen-Whai Li


Traffic-related air pollution can be a major public health concern in any urban area. This problem is compounded in the Paso del Norte region that has experienced rapid economic growth, and a substantial number of people living in close vicinity of major roadways. The desert surroundings, arid weather, frequent temperature inversions, heavy border traffic at the international ports of entry between El Paso and Ciudad Juárez, and poorly maintained vehicle fleet further exacerbates this problem. A growing body of air quality and epidemiologic research has discerned the linkage between traffic emissions and respiratory disorders.

Initial health investigations in the Paso del Norte region have found associations between various air pollutant indicators and adverse respiratory outcomes. However, monitoring traffic pollution as an indicator of population health and the subsequent ability to accurately reflect changes in the respiratory health of sensitive populations like school-going asthmatic children has been challenging in this region. Given the substantial amount of time children spend within school microenvironments, assessing children's school-based exposures is essential for preventing children's health risks to air pollutants. Indeed, the importance of characterizing children's exposures in schools corresponds with the US Environmental Protection Agency's recent initiative to promote outdoor air monitoring network near schools.

As part of a binational health effects study investigating the impact of traffic air pollution on asthmatic children, paired indoor and outdoor concentrations of fine and coarse PM (PM2.5 and PM10-2.5), black carbon, and NO2 were determined for 16 weeks in 2008 at four elementary schools in the international community of El Paso - Ciudad Juárez on the U.S.-Mexico border. Fifty-eight asthmatic subjects from these four schools were recruited. Health outcomes (weekly exhaled nitric oxide [eNO] measurements and daily respiratory symptoms) were recorded for the study period. Two schools (one in each city) were located in high traffic density zones and the other two in zones of low traffic density.

Strong spatial heterogeneity in air pollutant concentrations existed in the region with all outdoor pollutant concentrations, in general, higher in Ciudad Juarez than in El Paso by two-fold or more. Concentrations of all pollutants, except PM in Ciudad Juarez, at high traffic density zones in both cities were higher than those measured at their respective low traffic density zones. Traffic-related PM pollution in Ciudad Juarez was confounded by the ubiquitous fugitive dust emissions from unpaved roads and regional unprotected bare soil such that both PM2.5 and PM10-2.5 measured in the low traffic density zone surpassed those measured in the high traffic density zone. Aided by inter-site and intra-pollutant analyses, concentrations of NO2 and black carbon were confirmed to be better indicators for traffic-related pollution. Indoor air pollution was found to be well associated with outdoor air pollution, although differences existed among all schools in student activities, building tightness, use of ventilation system, temperature control devices, and building materials. Routine cooking and food preparation in classrooms could result in high level of indoor NO2 which pose unintended health risks to school children.

Significant associations between the weekly (96-hr) averages of several measured pollutants and eNO with effects estimates ranging from 1 to 3% increases in eNO per interquartile range increases in pollutant concentrations were observed. Effect estimates from models using indoor pollutant school concentrations were generally more robust than corresponding models using outdoor school or ambient concentrations.

This research characterizes the intra-urban variability in traffic-related air pollutants across four schools with potential implications for epidemiological studies basing their exposure variables on those obtained at central monitoring sites. The spatial variability of pollutants supports the use of spatially resolved environmental indicators of traffic pollutants in range of exposure settings. The results indicate that the adverse impact of air pollutant on the respiratory health of asthmatic children in this border region and substantiates the use of air pollutant monitors in close proximity to schools to track exposure and potential health risk in this border region.




Received from ProQuest

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355 pages

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