Measuring Bicyclists’ Uptake of Traffic-Related Air Pollution

Alex Bigazzi PSU Transportation Seminar Feb. 28, 2014

Miguel Figliozzi Jim Pankow Wentai Luo Lorne Isabelle

Urban Bicyclists' Pollution Uptake 1

Bicycle & Health Promotion

Public Health

Exercise

Crashes Pollution

Emissions

Exposure/ Dose

2 Urban Bicyclists' Pollution Uptake

Framework

3

Adapted from Ott, Stieneman & Wallace, 2007

Vehicle Emissions

Air Quality

Traveler Exposure Inhalation

Uptake Health Effects

Urban Bicyclists' Pollution Uptake

Outline

Lit. review & early results:

1. Exposure concentrations

2.  Inhalation

3. Uptake doses

4. Health effects

4 Urban Bicyclists' Pollution Uptake

Bicyclists’ Exposure to Air Pollution

5 Urban Bicyclists' Pollution Uptake

Traveler Exposure

Bicyclists’ Exposures

6

0 5 10 15 20

Ultrafine PM

Fine PM

Coarse PM

Black Carbon

CO

VOC

NO2

# studies measuring on-road bicyclists’ exposure concentrations

Pollutant

9k – 94k pt/cc

0.5 – 13 ppm

5 – 88 µg/m3

42 studies

Urban Bicyclists' Pollution Uptake

3 in U.S. since 1970’s

Modal Comparisons of Exposure

•  Majority of bike exposure research •  Inconsistent results

– Bicyclists lower if separated

•  Inconsistent comparisons – Available bicycle facilities & routes

•  Exclude other modal factors – Origins & destinations, weather…

7 Urban Bicyclists' Pollution Uptake

High-Traffic/Low-Traffic Routes

8 Urban Bicyclists' Pollution Uptake

-50%

0%

50%

100%

150%

200%

250%

CO VOC UFP PM2.5 PM10 BC

Expo

sure

Inc

reas

e on

H

igh-

Traf

fic R

oute

s

N=6 N=11 N=8 N=6 N=3 N=5

PSU Bike Exposure Research

9 Urban Bicyclists' Pollution Uptake

Going beyond bike versus car.

How can we reduce exposure risks for bikers?

Urban transportation

system

Bicyclists’ uptake of air

pollution

Sampling Equipment

10 Urban Bicyclists' Pollution Uptake

CO

Cameras

CO2

TVOC Sampler Pump

Breath Bags

Sample Cartridge

Smart phone

Cycle computer

PM

ACE Device

The Portland ACE

Portable, Low-cost and Networked Device for Assessing Cyclists’ Exposure

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On-Road Sampling

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13

Exposure Data coverage

Urban Bicyclists' Pollution Uptake

~40 hours of data over 13 days

Exposure Early Results

0% 50% 100% 150% 200% 250% 300%

m,p-Xylene

Ethylbenzene

Toluene

Benzene

Concentration Increase (over Tabor)

Major Arterials Minor Arterials Local Roads I-205 Path

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Bicyclists’ Inhalation Doses

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Inhalation

Urban Bicyclists' Pollution Uptake

Inhalation

Exposure Conc’n Respiration Duration Intake

Dose

16

mg/m↑3   m↑3 /sec  sec mg

Urban Bicyclists' Pollution Uptake

𝑉↓𝑇       ×       𝑓↓𝐵 

(breaths/sec )

(m↑3 /breath )

Respiration and Exercise

•  Ventilation strongly related to workload and heart rate

•  ln (𝑉↓𝐸 ) =𝑎+𝑏∙𝐻𝑅 –  𝑅↑2 ≈0.97

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25

50 Ventilation

(VE)

90 120 Heart Rate

(HR)

Mermier et al. (1993)

Bicyclists’ Exertion

•  External work – Speed & acceleration – Weight & slope – Wind & drag – Rolling resistance (tires, road)

•  Personal factors (minor effects) – Basal metabolic rate – Fitness (exercise response)

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Respiration & Bicycle Studies

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57 studies assess bicyclists’ exposure

Ignored 38

Constant 16

Assumed 7

Modeled 8

Measured 1

Variable 3

Modeled 2

Measured 1

Res

pir

atio

n:

Urban Bicyclists' Pollution Uptake

Bicyclists’ Respiration

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0

1

2

3

4

5

0 5 10 15 20 Ratio

of Bic

ycle

/Mot

oriz

ed

Trav

eler

Res

pira

tion

Bicycle Speed (mph)

All Men Women

Modal Comparisons of Intake

•  Bicyclists’ respiration 2-5x higher than passengers

•  Often longer duration •  Greater intake doses for bicyclists

•  Respiration is a major factor for dose

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Modal Comparisons of Dose

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-100%

-80%

-60%

-40%

-20%

0%

20%

40%

60%

Pedestrian Car/Taxi Bus

Dif

fere

nce

fro

m B

icyc

list

Dos

e

CO UFP PM2.5

N

(3)

(3)

(5)

Duration vs. Respiration

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•  For active modes (bike/ped), speed:

•  Duration dominates: faster travel reduces intake / mile

Respiration

Duration

PSU Research

•  Second-by-second on-road respiration rate & amplitude

•  8% correlation between 1-second TVOC and breathing rate – Bad for intake doses – Missed with constant respiration rates – e.g. at intersections & hills

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Bicyclists’ Uptake Doses

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Uptake

Lung Fun Facts!

•  Gas exchange area is about ___ sq-ft. – And ~0.2 µm thin!

•  During exercise, a red blood cell spends ___ seconds in the gas-exchange area. – Yet O2 fully exchanged in this time!

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800

¼

What happens to inhaled gas?

1.  Immediately expired (dead space)

2. Absorbed/desorbed into lung lining – Water-soluble compounds

3. Absorbed/desorbed into blood – Rapid diffusion to/from blood cells

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What happens to inhaled PM?

1.  Immediately expired

2. Trapped/expelled (Large PM)

3. Deposits on lung lining (Medium PM) – Muco-ciliary clearance

4. Deposits in alveoli (Tiny PM) – Lymphatic/blood clearance

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Factors Influencing Uptake

Uptake increases with: Exposure Inhalation dose

Pollutant Smaller particles Blood-soluble compounds

Respiration & Physiology

Deeper breathing Oral breathing Cardiac output Metabolic rate

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Exercise and Uptake

•  Uptake dose increases with exercise – Primarily through ventilation

•  Compared to intake doses – PM uptake doses increase more

•  40% greater effect than breathing alone – Gas uptake doses increase less

•  Limited by blood/air equilibrium

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Bicyclist Uptake Studies

•  Blood/urine samples (x1) – Metabolites of BTEX compounds (VOC) – Urban bikers > rural bikers

•  Induced sputum samples (x1) – Lung-deposited black carbon – Bicyclists > transit riders

•  Modeled uptake (x4) – Doses increases with exertion

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PSU Uptake Research

•  New approach •  High-resolution uptake measurement •  Breath sampling in bags

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Breath Sampling

•  Developed as medical screening •  End-tidal breath good proxy for blood

concentrations – Low water-solubility VOC – Hydrocarbons like benzene, toluene,…

•  Requires very precise instrumentation

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Data Collection

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•  75 breath VOC samples •  9 days •  3 subjects •  123 compounds

On-Road Sampling Example

Paired subjects; ambient & breath VOC (20-30 minutes, 3-5 miles)

35 Bigazzi Dissertation Proposal Defense

1

2

Breath

Breath

Breath

Early Results

•  The method works: exposure predicts breath concentrations – Breath elasticity to exposure: 0.3-0.5 – For traffic-related VOC

•  Significant history effects

•  Minimal subject-specific effects

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Early Results

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Breath

Ambient

Major ArterialLocalI-205

Benzene

% concentration increase (vs. Tabor)

0 50 100 150 200 250 300

path

Health Effects

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Health Effects

Bicycle Biomarker Studies

•  Inconsistent results – Insignificant acute effects (4) – Some cardiovascular, respiratory, or

neurological biomarker changes (7)

•  Health implications? •  Chronic effects for commuters?

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Net Health Effects Estimates

•  Health impacts for bicyclists: – Physical activity benefits dominate

•  By a factor of 9-96 – Outweigh crash & pollution risks

•  Still, we can & should reduce pollution risks

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Conclusions

•  Low-traffic facilities have much lower exposure concentrations

•  Respiration is the big factor for bikes – And insufficiently studied

•  Uptake rates & health effects are still unclear

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Future Work

We have a novel data set of empirical uptake measurements

– Much more analysis work to do!

1. Bike exposure & respiration models 2. Bicycle network/facility design

guidance for pollution dose impacts 3. Extend to pedestrians

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Thank you!

abigazzi@pdx.edu alexbigazzi.com

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Acknowledgements: City of Portland Metro NITC OTREC NSF

Urban Bicyclists' Pollution Uptake

•  Bigazzi, A. and M. Figliozzi, “Review of Urban Bicyclists’ Intake and Uptake of Traffic-Related Air Pollution.” Transport Reviews, Forthcoming 2014.

•  Bigazzi, A., W. Luo, M. Figliozzi, J. Pankow, and L. Isabelle, “Measuring urban bicyclists’ uptake of traffic-related volatile organic compounds using ambient and breath concentrations.” 93rd Annual Meeting of the Transportation Research Board, Washington D.C., January 2014.