Project Summary
A potential environmental function for vegetation, in general, and trees, in particular, is the reduction of
air pollution, especially in neighborhoods alongside roadways. Ultrafine particles (UFP), the smallest
component of particulate matter, is produced by many processes including the burning of diesel and gasoline
fuels and is associated with cardiovascular effects and pulmonary diseases such as atherosclerosis, asthma,
fibrosis and cancer. Recent in vitro studies have found associations between UFP and elevations in pro-
inflammatory cytokines and both reactive oxygen and nitrogen species leading to oxidative stress in human
bronchial epithelial cells. Pollution reduction strategies can be complex and expensive, which encourages
researchers to explore more affordable and locally designed options for municipalities, school districts and
neighborhoods that may be disproportionately exposed. The overarching goal of this project is to determine if
and under what conditions trees can function to mitigate UFP air pollution and define any difference in
cardiorespiratory effects based on cellular response to exposure.
Studies have documented that a stand of trees next to a roadway, a tree barrier, can reduce near-
roadway UFP and black carbon ([BC] solid soot particles); however research remains limited. Tree barriers
associated with the greatest reductions have been composed of evergreens with branches that extend to the
ground and are sufficiently dense to serve as a filter. Combined tree and noise barriers have also been shown
to reduce UFP concentrations in some studies. We are not aware of any studies, to date, that have evaluated
the impact of UFP collected in the presence of a tree barrier on cellular function. We have developed a novel
assessment, based on experiments in nanotechnology, to measure oxidative stress and inflammation in
human epithelial cells when exposed to UFP.
This study will test the hypothesis that a roadway tree barrier or a tree/noise barrier will reduce near-
roadway UFP concentration, alter composition and lead to decreased reactivity in human epithelial cells.
Multiple sites in the Atlanta metropolitan area will be selected, each alongside a tree barrier, a tree/noise
barrier or no barrier. UFP number, UFP mass and BC concentrations will be measured on road and on site at
each location on non-consecutive days. Primary small airway epithelial cells will be exposed to the particles in
order to evaluate differences in 1) epithelial cell injury; 2) inflammatory response; and 3) phenotypic alterations
including epithelial mesenchymal transitions, which has been linked to environmental asthma.
Over 96 million people live within three blocks (approximately 300 m) of a major roadway. Since trees
often exist near roadways across the country, our study can substantially impact public policy, exposure
assessment and epidemiological studies. We will also document potential mechanisms of effect between UFP
and cardiorespiratory effects and explore how they differ based on composition.
