Dissertation Defense Announcement

The School of Public Health announces the Final Dissertation of

Zhuqing Xue

for the Degree of Doctor of Philosophy

on April 2, 2018 at 9:30 AM in Room 217, Robinson Hall.

Advisor: Chunrong Jia

Human Exposure to Air Toxics in Urban Environments: Health Risks, Sociodemographic Disparities, and Mixture Profiles

ABSTRACT: Exposure to air toxics in urban environments may be of significant health concern because populations and emission sources are concentrated in the same geographic area. The overall objective of this study is to characterize the sources, variations, and mixture profiles of ambient air toxics in urban environments, and examine the sociodemographic disparities in exposures to air toxics in a typical U.S. metropolitan area. A model-to-monitor comparison was performed to evaluate the validity of modeling air toxics data using national datasets. Modeled concentrations in the 2011 National-scale Air Toxics Assessment (NATA) moderately agreed with monitoring measurements, and a sizable portion showed underestimation. Results warranted the need for actual monitoring data to conduct air toxics exposure assessment. Air toxics samples were collected in 106 census tracts in the Memphis area in 2014, and samples were analyzed for 75 volatile organic compounds (VOCs). Ambient VOC levels in Memphis were generally higher than the national averages in urban settings, but were mostly below the reference concentrations (RfCs). Factor analysis identified 5 major sources: manufacturing processes, vehicle exhaust, industrial solvents, refrigerants, and gasoline additives. The major non-cancer risks were from neurological, respiratory, and reproductive/developmental effects. The cumulative cancer risk was 5.9± 3.3 ×10-4, with naphthalene and benzyl chloride as risk drivers. Sociodemographic disparities in cancer risks were examined by regressing cancer risks against socioeconomic, racial, and spatial parameters at the census tract level.