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Jeremy A. Sarnat,¹ Amit Marmur,² Mitchel Klein,¹ Eugene Kim,³ Armistead G. Russell,² Stefanie E. Sarnat,¹ James A. Mulholland,² Philip K. Hopke,⁴ and Paige E. Tolbert¹

¹Department of Environmental and Occupational Health, Emory University, Atlanta, Georgia, USA; ²Department of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA; ³California Air Resources Board, Sacramento, California, USA; ⁴Department of Chemical Engineering, Clarkson University, Potsdam, New York, USA

Abstract
Background: Interest in the health effects of particulate matter (PM) has focused on identifying sources of PM, including biomass burning, power plants, and gasoline and diesel emissions that may be associated with adverse health risks. Few epidemiologic studies, however, have included source-apportionment estimates in their examinations of PM health effects. We analyzed a time-series of chemically speciated PM measurements in Atlanta, Georgia, and conducted an epidemiologic analysis using data from three distinct source-apportionment methods.

Objective: The key objective of this analysis was to compare epidemiologic findings generated using both factor analysis and mass balance source-apportionment methods.

Methods: We analyzed data collected between November 1998 and December 2002 using positive-matrix factorization (PMF) , modified chemical mass balance (CMB-LGO) , and a tracer approach. Emergency department (ED) visits for a combined cardiovascular (CVD) and respiratory disease (RD) group were assessed as end points. We estimated the risk ratio (RR) associated with same day PM concentrations using Poisson generalized linear models.

Results: There were significant, positive associations between same-day PM_2.5 (PM with aerodynamic diameter ≤ 2.5 µm) concentrations attributed to mobile sources (RR range, 1.018–1.025) and biomass combustion, primarily prescribed forest burning and residential wood combustion, (RR range, 1.024–1.033) source categories and CVD-related ED visits. Associations between the source categories and RD visits were not significant for all models except sulfate-rich secondary PM_2.5 (RR range, 1.012–1.020) . Generally, the epidemiologic results were robust to the selection of source-apportionment method, with strong agreement between the RR estimates from the PMF and CMB-LGO models, as well as with results from models using single-species tracers as surrogates of the source-apportioned PM_2.5 values.

Conclusions: Despite differences among the source-apportionment methods, these findings suggest that modeled source-apportioned data can produce robust estimates of acute health risk. In Atlanta, there were consistent associations across methods between PM_2.5 from mobile sources and biomass burning with both cardiovascular and respiratory ED visits, and between sulfate-rich secondary PM_2.5 with respiratory visits.

Key words: acute, Atlanta, cardiovascular, chemical mass balance, emergency department visits, fine particulate matter, positive matrix factorization, respiratory, source apportionment, tracer. Environ Health Perspect 116:459–466 (2008) . doi:10.1289/ehp.10873 available via http://dx.doi.org/ [Online 14 January 2008]

Address correspondence to J. Sarnat, Rollins School of Public Health of Emory University, Department of Environmental and Occupational Health, 1518 Clifton Rd., Room 260, Atlanta, GA 30322 USA. Telephone: (404) 712-9725. Fax: (401) 727-8744. E-mail: jsarnat@sph.emory.edu

Supplemental Material is available online at http://www.ehponline.org/members/2008/10873/suppl.pdf

We thank the Electric Power Research Institute (EP-P4353/C2124) for supporting earlier work on the emergency department study and Atmospheric Research and Analysis for assistance in using Jefferson Street air quality measurements.

This work was supported by grants to Emory University from the U.S. Environmental Protection Agency (EPA) (R82921301-0) and the National Institute of Environmental Health Sciences (NIEHS) (R01ES11294) , as well as to Georgia Tech (U.S. EPA grants RD832159, RD831076, and RD830960) .

The content is solely the responsibility of the authors and does not necessarily represent the official views of U.S. EPA or NIEHS.

The authors declare they have no competing financial interests.

Received 11 September 2007 ; accepted 10 January 2008.