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A Multi-City Investigation of Exposure to Diesel Exhaust in Multiple Commuting Modes








CATF Special Report 2007-1

A Multi-City Investigation of Exposure to
Diesel Exhaust in Multiple Commuting Modes
Columbus OH, Austin TX, Boston MA, New York City, NY










Version 1.0
February 28, 2007




18 Tremont Street, Suite 530
Boston, MA 02108
Tel. 617-624-0234 / Fax: 617-624-0230


Principal Investigator: L. Bruce Hill, Ph.D. Senior Scientist
Research Assistant: James Gooch
Clean Air Task Force
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Acknowledgements--

Clean Air Task Force field research was supported by following charitable organizations: the
Oak Foundation, the Marisla Foundation, the Gund Foundation, the Prospect Hill Foundation,
the Kendeda Fund and the Beldon Fund. Clean Air Task Force thanks its state partners for
field support, American Lung Association of New York State, Texas Public Citizen, Ohio
Environmental Council and volunteers Andrew Hill and Windy Kelly. We thank Kenneth
and Wilma Johnsen for their assistance in Columbus. CATF is grateful for the help of Tom
Balon and Todd Danos of MJB Associates in the box truck retrofit project.

A Note on Report Versions:

CATF considers this white paper a work in progress which may be updated as new data
become available or as data analysis is further refined. Report versions and dates will be
noted on the cover of the report starting with the initial version 1.0 released February 28,
2007. Only the most recent version will be posted to the CATF web so please check at
www.catf.us/goto/noescape
for updates.




Clean Air Task Force
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Table of Contents

ABSTRACT AND BRIEF FINDINGS4
-Brief Findings 5


PART I: MEDICAL CASE FOR REDUCING DIESEL EXHAUST 8
-Short and Long Term Exposure to Diesel Exhaust 9
-Proximity to Traffic11
-Ultrafine Particles12
-Particulate Polycyclic Aromatic Hydrocarbons (PAH) 12

PART II: COMMUTING AND EXPOSURE TO DIESEL EXHAUST13
-The Changing Face of Commuting in the U.S.13
-Previous Commuter Exposure Studies13
-Commuting May be the Most Common Pathway for Diesel Exposure14

PART III: CATF RESEARCH FINDINGS16
--Methodologies and Instrumentation 16
--Highway Commute Routes 23
--Field Data Observations--by Pollutant24
--Summary Data Tables27-30
--Exposure Factors Table31
--Discussion by Commute Mode32


Cars: Composite Car Commute Plots by City36
--Summary HistogramsHighway/Car Commutes42
--Observations of Busy Truck Routes vs Highways with Few Diesels44
--Diesels Responsible for Elevated Particle Levels in Roadway46
Commuting by City Bus47
Commuting by Rail51
Commuting by Subway60
Walking: Pedestrian Exposure62
Commuting by Ferry66
Special Studies: Bostons Rail and Motor Shicle Tunnels68

PART IV: SOLUTIONS72

--Todays Clean Air Retrofit Technology Means Cleaner Commutes 72
-- Box Truck Retrofit72

END NOTES77 Clean Air Task Force
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ABSTRACT AND BRIEF FINDINGS

Routine exposure to diesel exhaust is not just an occupational hazard for truckers, railroad or
construction workersmost of us breathe it every day in traffic and near major
thoroughfares. In fact, diesel exhaust shortens the lives of an estimated 21,000 people per
year in the U.S. and many more suffer the effects of diesel-related respiratory and
cardiovascular disease. Both long-term and short term exposures to the particles that
characterize diesel exhaust have been shown to result in serious health damage. Moreover,
health researchers have long associated traffic with maladies.

If not at work, when are the rest of us exposed to diesel? According to a University of
California study, highway commuters may receive approximately half of their daily exposure
to ultrafine particles and black carbon soot from diesels while commutingin only about 4-6
percent of the day. CATFs investigations in Columbus OH support this estimate. According
to the Transportation Research Board, half of us--one hundred and fifty million people --go
work in the U.S. daily. Worse, our commutes-and therefore our exposures--are lengthening.

While most people drive to their place of employment, many others take commuter trains or
city buses. Some walk and in some cities a few travel on ferries. Few existing U.S. studies
have examined commuter and in-vehicle exposure to air pollution. But now new monitoring
instruments now make it possible to investigate real time changes in particles and health
impacts. A few of the most recent studies that suggest harm from acute exposures to these
pollutants. One such study of healthy highway patrolmen documented heart rhythm
irregularities using strap-on heart monitors

Seeking to investigate commuter exposures further, Clean Air Task Force researchers set out
to investigate commuter exposures to diesel exhaust in three cities in different modes of
transit. Results confirm that diesel soot dominates roadway particulate matter and that people
commuting regularly to and from work along truck routes are exposed to high levels of diesel
soot. Our study documents diesel particle exposures cars, in older buses, trains, ferries and on
foot on sidewalks along city streets.

Clean Air Task Force began its exposure investigations in 2005 and 2006 .Representative
cities were selected for investigating commuter exposure to diesel exhaust (Austin, TX;
Boston, MA, Columbus, OH and New York City) using methodologies developed at major
universities. Four key constituents of diesel exhaust were tracked with continuous monitors:
fine particles (PM
2.5
), ultrafine particles (PM<0.1um), black carbon, and particulate
polycyclic aromatic hydrocarbons (PAHs). Because CATFs monitoring suggests ultrafine
particles may be the best marker of fresh diesel exhaust across all modes of transit, those
results are highlighted in this report. Graphics were selected to illustrate key findings.
Pollutant exposure data was normalized by subtracting daily ambient background
concentrations. For in-depth results and methodological details see companion white paper
at
www.catf.us/goto/noescape/
. The focus of the effort has been on highway commute runs,
where the most robust data is based on over100 car commute runs. However, the data that
CATF has collected for other modes of transit is also revealing.
Clean Air Task Force
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Car Commutes: In Boston, Austin and Columbus typical commute routes were run in a
2006 minivan equipped with four monitors for a total of 107 runs over 79 hours. CATF
investigated the effects of window position, air conditioning, and recirculation of cabin air.
The results from windows open runs are reported here.
Transit Buses: Researchers boarded buses in Boston and Columbus using monitors
housed in backpacks and roll-around bags.
Commuter Rail: Researchers boarded trains in Boston and New York City with monitors
housed in backpacks and roll-around bags for inbound (locomotive push) and outbound
(locomotive pull) runs.
Ferries: Researchers boarded Boston commuter ferries with monitors housed in a
backpack.
Walking Commutes: With monitors in backpacks, researchers walked from residential to
commercial areas in Boston and Columbus.
Chase Studies: CATF monitored comparative particle levels behind conventional and
DPF retrofit buses in New York City and Boston and behind garbage trucks in New York
City. As a controlled experiment, CATF retrofitted a Class-5 box truck with a DPF,
testing air behind the truck before and after.

Brief Findings
Note: for the findings below, data represent net particle exposures (ambient outdoor air
concentration subtracted to normalize data between days with different regional
background.)

CARS:
Car commuters experience their highest daily exposures to diesel particles on the way to
work (PM
2.5
, ultrafine particles, black carbon soot, and particulate polycyclic aromatic
hydrocarbons (PAH))
Mean exposures to ultrafine particlesfound to be the most sensitive indicator of diesel
exhaust, ranged from 4-8 times the ambient outdoor particle levels averaged across all
runs and all modes of transit.
Averaged peak UFP levels ranged from 19-38 times the ambient outdoor air
concen