ARB Research Seminar

This page updated June 19, 2013

Spatial Analysis of Traffic-generated Air Pollution and Mortality in Los Angeles and Toronto

Michael Leo Brennan Jerrett, Ph.D., University of Southern California

February 10, 2005
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Los Angeles Study: The assessment of air pollution exposure using only community average concentrations may lead to measurement error that lowers estimates of the health burden attributable to poor air quality. To test this hypothesis, we modeled the association between air pollution and mortality at the intra-urban scale in Los Angeles, California.

Our results suggest the chronic health effects associated with intra-urban gradients in exposure to PM2.5 may be even larger than previously reported across metropolitan areas. We observed effects nearly three times greater than in models relying on between-community exposure contrasts. We also found specificity in cause of death, with PM2.5 associating more strongly with IHD than with cardiopulmonary or all cause mortality.

Toronto Study: In many urban areas, traffic has become the largest emission source of air pollutants. Preliminary epidemiologic evidence now links traffic-generated air pollution to significant health effects ranging from birth outcomes to mortality, but uncertainty in exposure assessment models continues to raise doubts about the validity of these findings. In this context we pursued two objectives: (1) to model intra-urban variation in ambient concentrations of NO2, a marker for traffic pollution, with a land use regression (LUR) model; and (2) to assess the association between NO2 and mortality while controlling for other likely confounders.

Our results suggest high-resolution pollution surfaces can be produced for North American cities with location-allocation and LUR methods. Exposure to traffic pollution exerts large significant effects on the mortality experience in this cohort. Within-city exposure contrasts estimated with the LUR method appear to detect larger health effects than reported from earlier studies based on between-city contrasts.

Speaker Biography

Michael Leo Brennan Jerrett, Ph.D., holds a visiting associate professorship in the Division of Biostatistics, Department of Preventive Medicine, University of Southern California, Los Angeles, and a tenured associate professorship in the School of Geography and Geology, the Health Studies Program, and the Institute of Environment and Health, McMaster University, Hamilton, Canada.

Building on expertise in Medical Geography, Geographic Information Systems, and Spatial Statistics, Dr. Jerrett's currently assesses air pollution-health associations in the United States and Canada, with special reference to the role of social-spatial confounders and effect modifiers. He also pursues research in environmental accounting focusing on the valuation of environmental costs and benefits as well as the determinants of environmental and health expenditures. Dr. Jerrett has designed and analyzed local, provincial, state, and national level health and environment databases in Canada, the United States, Mexico, and Vietnam.

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