Traffic- Related Air Pollut

A Critical Review of the Literature on 

Exposure, and Health Effec

Clean Air Act Advisory Comm

Crystal City, VA

October 6 – 7, 2009

Dan Greenbaum, President

Health Effects Institute
Goals of the Review

Summarize and synthesize relevant inforair pollution from traffic and its health ef• Emissions and exposure to traffic air p• Exposure to traffic air pollution and he

• Toxicological data and epidemiologic 

A preprint of the report was released in May 20The final Report, following extensive QA/QC, 

published in fall 2009
HEI Traffic Review Pan

Ira Tager—UC Berkeley, ChairKenneth Demerjian—SUNY, AlbanyMark Frampton—U Rochester Michael Jerrett—UC Berkeley Frank Kelly—King’s College Lester Kobzik—Harvard SPHNino Künzli—IMdM, BarcelonaBrian Leaderer—Yale SPHThomas Lumley—U of Washington SFrederick Lurmann—Sonoma Tech. InSylvia Richardson—Imperial CollegeJon Samet—Johns HopkinsMichael Walsh—Consultant
Emissions from Motor Veh

The Current Context

Significant progress has been made in reduction of pollutant emissions from motor vehicles despite increases in number of vehicles and vehicle miles traveled

Increased urb

urban popul

• Increa

on motraffic 

• Chang

patternmore ptraffic pollut
Report Organization
The

(ovattetrafeffe•Hoall 
1. How should we assess Ex

• Who is likely to be exposed?• What exposure assessment meth

epidemiologic studies?

• Pollutant surrogates for traffic exposures (e

CO, UFPM, benzene, etc.)

• Distance from and/or length of roadways• Estimate of traffic density or intensity• Modeling of primary traffic-generated poll
VOC (TraceAir) Distance Decay Around Highway 401, Toronto

0.00.10.20.30.40.50.60.70.80.91.0

-1000 -800 -600 -400 -200 0 200 400 60

Distance from Expressway (m)

Standardized VOC

Levels

Who is Likely to be Expo

Highest levels within 300 – 500 meters 

Toronto, Beckerman et al. (2
Near Roadway Exposure Can Include Lar

Toronto Example: ~45% 

(within 500 meters of an expressway; 100 meters 
Los Angeles Example: (~44
Portland, Oregon ~3
What Markers or Surroga

• Pollutant surrogates for traffic exp

NO2 , EC/BS, CO, UFPM, benzen

• Criteria for what is a good surroga

1. Traffic as the major source2. Emissions vary with other motor vehic3. Can be measured at low concentrations 

inexpensive and accurate methods

4. Not have independent health effects
NO2 as a surrogate

•There ivariabilconcentlocation•NO2 is surrogatemissioon a fin
PM2.5 as a Surrogate

•Use o

surrogvalue bsourceurban 

concenmixed •Curremonitosufficiresoluthe contraffic 
What Markers or Surroga

• Pollutant surrogates for traffic exp

NO2 , EC/BS, CO, UFPM, benzen

• Criteria for what is a good surroga

1. Traffic as the major source2. Emissions vary with other motor vehic3. Can be measured at low concentrations 

inexpensive and accurate methods

4. Not have independent health effects

• Can provide useful information b

meet all these criteria...
Can We Use Exposure Mod

Models used• Proximity models• Geostatistical 

interpolation models

• Dispersion models• Land-use regression 

models

• Hybrid models

• Combine a model with 

time-activity data, or personal/microenvironment al monitoring

• Proximity m

effective:

• Can be co

SocioecoNoise, ot

• Newer mod

are better

• But shoul

against sodata.
Criteria for Inclusion of Toxico

Epidemiology Studies

• Quality of exposure assessment was key• Studies had to include 1 or more of the 

exposure methods:

• Distance from and/or length of roadways• Estimate of traffic density or intensity• Modeling of primary traffic-generated pollu• Studies of occupations characterized by exp• Pollutant surrogates for traffic exposures (e

CO, benzene, etc.) only if data provided to 

pollutant as a reasonably specific surrogate 
2. What Can We Learn from Toxi

(Example from a somewhat limited da

Effects of Traffic Exposure on Asthmatics (Zh

Lung function decline in asthmatics comparing Hyde Park an

(although symptoms did not increase...
3. What can we learn from epide

Criteria for Causal Inferen

Four categories to test whether traffic cabased on:

- how well studies controlled for confoundin- consistency of the findings with other studi- quality of the method to estimate exposure• Sufficient evidence

• Suggestive but not sufficient

• Inadequate and insufficient evidence

• Suggestive of no association
Epidemiology 

Health Outcomes Evalua

• Mortality (all cause, cardiopulm• Cardiovascular morbidity• Respiratory disease

• Asthma—childhood/adult• General respiratory symptoms• Lung function-childhood/adult/C• Health care utilization

• Non-asthmatic allergy• Birth Outcomes• Cancer
1.13 1.16

1.49

0.87 0.94 1.09 1.09

1.72 1.74

1.13

1.6

2.94

1.58

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

per 10.3 ug/m3 in NO2 - 2nd year of life

per 10.6 ug/m3 in NO2 - 4th year of life 

per 10.6 ug/m3 in NO2 - 4th year of life

(Allergic Children)

per 8.5 ug/m3 NO2 - 1st year of life

per 8.5 ug/m3 NO2 - 2nd year of life

per IQR NO2 - 1st year of life

per IQR NO2 - 2nd year of life

Gauderman 2005: Per 5.7 ppb NO2

Janssen 2003: per 18 ug/m3 NO2

Hirsch 1999: per 10ug/m3 NO2

Nordling 2008: per 44ug/m3 NOx

Van Roosebroeck 2008: per 17ug/m3

Nicolai 2003: >=57.4 vs. < 57.4 ug/m3

Brauer

2002

Brauer 2007 Gehring 2002 Morgenstern 2006 Other Authors

ODDS RATIO (95% CI)

Exacerbation of Asthma Sym

Increase in Wheeze Per Incremen
Traffic Exposure and Doctor-Diagn

Incidence in Children

NO2 Distance Density Spatial

SySusugReStutraanco
Long-Term Traffic Exposur

Cardiopulmonary Mortal

1.22

1.38

1.84

1.70

1.05 1.05 1.04 1.07

1.45

1.39

1.13

1.95

0.9

1

1.11.21.31.41.51.61.71.81.9

2

2.1

Jerrett 2009:

Circulatory

Fickelstein 2005:

Cardiovascular

Fickelstein 2005:

Stroke

Gehring 2006:

Cardiopulmonary

Hoek 2002:

Cardiopulmonary

Maheswaran

2003: Stroke

Beleen 2008c:

Cardiovascular

Beelen 2008c:

Cardiovascular

Beelen 2008c:

Cardiovascular

Jerrett 2009:

Circulatory (All)

Jerrett 2009:

Circulatory

(proximity to

traffic)

Jerrett 2005

Residential distance from major road or highway Per

10ug/m3

BS

Per

10ug/m3

NO2

Per 4 ppb NO2 Per

10ug/m3

PM2.5

Relative Risks (95% CI)

Proximity BS NO2 PM

SScnRTRm
Effects of Traffic Exposur

Birth Outcomes

• • 

0.5

0.75

1

1.25

1.5

1.75

2

Quintile 2 vs. 1 

Quintile 3 vs. 1 

Quintile 4 vs. 1 

Quintile 5 vs. 1 

Quintile 2 vs. 1

Quintile 3 vs. 1

Quintile 4 vs. 1 

Quintile 5 vs. 1 

High SES

Middle SES

Low SES

High SES

Middle SES

Low SES

Quartile 2 vs. 1

Quartile 3 vs. 1

Quartile 4 vs. 1

NO2 per 10ug/m3

NO per 10ug/m3

PM2.5 per 1 ug/m3

<50m Highway

<150m Highway

<50m Major road

NO2 per 10ug/m3

NO per 10ug/m3

PM2.5 per 1 ug/m3

Pre-term birth &

traffic density

(Wilhelm 2003)

Pre-term birth +

LBW & traffic

density (Wilhelm

2003)

Pre-term birth

in summer &

traffic density

(Ponce 2005)

Pre-term birth

in winter &

traffic density

(Ponce 2005)

Birthweight

<3000g &

PM2.5

exposure

(Slama 2007)

Small for gestational age

(Brauer 2008)

LBW at > 37

wks (Brauer

2008)

RR (95% CI)

Pre-Term PT/LBS Summer Winter LBW SGA LBW

Density Density PT, Density PM2.5 NOx PM2.5 Proximity
Conclusions
Exposure

• Traffic-related pollutants impact amb

quality on a broad spatial scale ranginroadside, to urban, to regional backgr

• Based on synthesis of evidence, 300 t

from major road was identified as the area most impacted by traffic; 

• variations exist depending on meteorolo

pollution, and local factors 
Issues for Exposure Asses

• None of the pollutant surrogates considered m

an ideal surrogate

• CO, benzene, and NOx [NO2 ] found in on-road veh

also major components of emissions from all source

• UF PM has not been used in epidemiologic studies 

model them because there are no emission inventori

• Exposure models are important, but have vario

utility to health studies

• The proximity model is the most error-prone • Other models are better:

• Dispersion models (need adequate data)• Land use regression models• Several approaches together (hybrid)
Overall Conclusions

• The data are incomplete on emissio

transformations, and exposure asse

• There were, however, enough studi

• Sufficient evidence for a causal assoc

exacerbation of asthma

• Suggestive evidence for a number of 

effects (mortality, lung function, respsymptoms, and others)
Overall Conclusions I

• Limited evidence of effects but inade

insufficient to infer causal association

• Adult onset asthma• Health care utilization• COPD• Non-asthmatic allergy• Birth outcomes• Cancers
Overall Conclusions I

• A caution: epidemiology studies are b

estimates of exposure

• they may not provide an accurate guide 

health associations in the future

• However, given the large number of 

within 300- 500 meters of a major roconcluded that exposures to primary generated pollutants are likely to be oconcern and deserve attention.
Thank You!

Dan Greenbaum

dgreenbaum@healtheffects