Atlanta Commuter Study

Title:  Examining In-Vehicle Pollution and Oxidative Stress in a Cohort of Daily Commuters

Investigators: Jeremy Sarnat, Sc.D. (PI, Emory), Michael Bergin, Ph.D. (Georgia Tech), W. Dana Flanders, M.D., Sc.D. (Emory), Lou Ann Brown, Ph.D. (Emory), Lyndsey Darrow, Ph.D. (Emory), Anne Fitzpatrick, Ph.D. (Emory), Roby Greenwald, Ph.D. (Emory), Randy Guensler, Ph.D. (Georgia Tech), and Cherry Wongtrakool, M.D. (Emory)

Objectives.Vehicle emissions comprise a complex mixture of particulate and gaseous pollutants that have been linked to numerous adverse health outcomes.  Despite this, there is limited knowledge concerning in-vehicle mixtures and corresponding acute health responses among daily automobile commuters.  A more complete understanding of the pollutant-related health effects in commuters is becoming increasingly necessary, as commuting durations as well as roadway congestion have steadily increased throughout the U.S. during the last 20 years.  To investigate in-vehicle exposures among car commuters, we will conduct a panel-based exposure and health assessment study of 30 healthy and 30 asthmatic adults in the metropolitan Atlanta area.  The primary objective of this study is to examine the associations between particulate mixtures that occur during typical automobile commuting and corresponding oxidative stress-mediated pathways of cardiorespiratory injury.  Our central hypotheses are that: a) commuters are exposed to high levels of in-vehicle particulate pollutant mixtures as compared to other, indoor environments; and that b) these short-term exposures are associated with acute changes in oxidative stress in asthmatic and healthy adults.

Approach.  We will use novel methods for measuring highly chemically-resolved PM, focusing on specific particulate components that contribute to PM oxidative potential including polycyclic aromatic hydrocarbons, transition metal species, elemental carbon and ultrafine particles.  In addition, this study will be among the first to measure several highly-sensitive, non-invasive biomarkers of oxidative stress (i.e., glutathione in exhaled breath) at numerous time intervals, with the goal of following the progression from oxidative stress to clinical response. 

Expected Results.  This project is particularly suited towards examining the health effects of air pollutant mixtures.  Expected exposure science results will further our understanding of: a) in-vehicle concentrations of size- and chemically-resolved PM mixtures within periods of peak traffic; b) the impact of exposure factors such as cabin ventilation and traffic composition on in-vehicle pollutant levels; and c) how exposures to specific ROS generating PM components vary between in-vehicle and other indoor environments.  In addition, this study will elucidate several key health effects questions, including: a) the acute, sub-clinical oxidative stress-mediated responses due to real-world exposures to traffic-related PM, its components and pollutant mixtures using individual-specific metrics of personal exposure; b) the temporality of these exposure-response functions; c) whether daily commuters comprise a potentially vulnerable sub-population to these health effects during commuting; and d) whether baseline health status, and specifically asthma, modifies the risk of traffic PM.