Ultrafine Particles on and near Roadways: Ultrafine Particles on and ...

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Ultrafine Particles on and near Roadways: E Exposure A Assessment and dM Mechanism h i U Understanding d di

Yifang Zhu , Ph.D. Associate Professor Environmental Health Sciences Department Fielding School of Public Health University of California Los Angeles

Comparison of PM10, PM2.5, and Ultrafine PM

PM2.5 (2.5 μm) PM10 (10 μm)

Ultrafine PM (0.1 μm)

PM2.5 (2.5 μm)

PM10 (10 μm)

Human Hair (60 μm diameter)

Relative size of particles 2

Atmospheric Aerosols: Particulate Matter (PM) Size Distribution Mass Distribution

Ultrafine PM

PM2.5

PM10 Number Distribution

Hinds, 1999, “Aerosol Technology: Properties, Behavior, and Measurement of Airborne Particles”, 2nd edition.

Particle Regional Deposition for Light Exercise

Respiratorry Deposition, fraction

1.0

Number Weighted

.8

.6

Head Airways Alveolar

.4

Mass Weighted

.2 2

Tracheobronchial

0.0

1

10

100

Particle Diameter (nm)

1000

10000 4

Pathways of Particle Translocation Within and Outside Respiratory Tract

Translocation of UFP from NP and TB region along sensory neurons to CNS (neurodegeneration)

•Translocation of UFP to interstitium, capillaries, heart •Uptake by endothelium; platelets •Activation/interaction of endothelial cells platelets and leukocytes cells,

Alveolar inflammation 5

Vehicular emissions usually constitute the most significant g source of UFPs in an urban environment.

6

Recent TrafficTraffic-Related Health Studies ƒ Cardiac and Pulmonary Health Risks from NearHighway Exposures Environmental Health – Tufts Univ. School of Medicine (Brugge 2007)

ƒ Adverse Effects of Traffic Exposure on Children’s Children s Lung Development The Lancet – USC School of Medicine (Gauderman 2007)

ƒ Traffic Exposure and Decreased Lung Function in Adults with Asthma A,. Academy of Allergy, Asthma & Immunology – UCSF (Balmes 2009)

ƒ Residential Proximity to Freeways and Autism in the CHARGE Study Environmental Health Perspectives – USC School of Medicine (Volk, 2011) 7

Near Roadways

I-405 Freeway

I-710 Freeway

Upwind

Downwind

Zhu et al., 2002 “Concentration and size distribution of ultrafine particles near a major j highway”, J. of Air and Waste Management Association, 52:1032-1042.

Key point

Upwind

Downwind

Zhu et al., 2002 “Study of Ultrafine Particles near a Major Highway with Heavy-duty Heavy duty Diesel Traffic”, Traffic , 2002, Atmospheric Environment, 36: 4323-4335.

UFP concentrations decay exponentially downwind of freeways. 8

9

10

Near Roadways Totall Particle Numb ber Concentratiion (cm-3)

2.0e+5 Daytime Dominant Wind

1.8e+5 1.6e+5

Nighttime Dominant Wind

1.4e+5 1.2e+5 1.0e+5 8.0e+4 6.0e+4 4.0e+4 2.0e+4 0.0 500

400

Western Side VA Facility

Key point

300

200

100

0

100

Freeway 405

200

300

400

500

Eastern Side LA National Cemetery

Daily exposure to UFPs: Three folds of Distance from the freeway (m) difference between the two cases.

Zhu et al., 2006, “Comparison of Daytime and Nighttime Concentration Profiles and Size Distributions of Ultrafine Particles near a Major Highway” Environmental Science and Technology 40: 2531-2536. 11

Mechanism Understanding: Near Roadway

Zhu et al., 2002 “Concentration and size distribution of ultrafine particles near a major highway”, J. 12 of Air and Waste Management Association, 52:1032-1042.

Mechanism Understanding: Near Roadway

UFPs in different size ranges have distinct number b concentration t ti decay characteristics

Key Point

Mechanisms for the alteration of the number size distribution may include coagulation.

Zhu et al., 2002 “Concentration and size distribution of ultrafine particles near a major highway”, J. of Air and Waste Management Association, 52:1032-1042.

Mechanism Understanding: Near Roadway

100 nm

Aggregate

Oberdorster et al. 2001

Stearns et al. 2001

Bond and Bergstrom 2006

100 nm

Opaque Sphere p

100 nm

Transparent Sphere p

100 nm

Irregularly Shaped Particle

100 nm

Particle with Multiple Inclusions

Whether UFPs are present as single spheres or aggregated spheres p affects their deposition p efficiency y in the lung. g Morphology may affect how UFPs interact with lung cells cells. Morphology influences particle optical properties and hence, their effect on radiative forcing.

Barone and Zhu, 2008 “Morphology of ultrafine particles on and near freeways”, Atmospheric Environment, 42: 6749-6758.

14

Mechanism Understanding: Near Roadway 1.0

50 nm de Non/Low-Volatile Non/Low-Volatile: Non/Low Volatile: Opaque aggregates, High-Volatile spheres, and irregular particles Encapsulated High-Volatile: Transparent spheres Multiple Inclusions Encapsulated: Opaque particles encapsulated in transparent material Multiple Inclusions: Liquid particle which contains smaller opaque or transparent particles inside or on edge.

Numbeer Fraction

0.8 0.6 0.4 0.2 0.0 I-405

30 m

60 m

90 m

Distance from the I-405 Freeway

• Large fraction (> 90%) non/low-volatile particles encapsulated by high-volatile material •Most (96-99%) particles at least partially associated with volatile material Barone and Zhu, 2008 “Morphology of ultrafine particles on and near freeways”, Atmospheric Environment, 42: 6749-6758.

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0.3

Encapsulated Aggregates

0.2

0.1

p = 0.001

0.0

Number Fractio on of Partic cles with Multiple Inclusions

Number Fraction of ncapsulated Aggregates En

Mechanism Understanding: Near Roadway 0.3

Particles with Multiple Inclusions p < 0.001

0.2

0.1

0.0 I-405

30 m

60 m

90 m

Distance from I-405 Freeway

I-405

30 m

60 m

90 m

Distance from I-405 Freeway

Fraction of encapsulated aggregates significantly less at 90 m than fraction on-freewayy

Fraction of particles with multiple inclusions significantly greater at 90 m than fraction on-freewayy

=> Since aggregates are a primary aerosol (directly emitted), secondary aerosol may be more abundant with increasingg distance from the freewayy

=> Dilution may not prevent particles from colliding and merging. Coagulation may play a role in altering the number size distribution

Barone and Zhu, 2008 “Morphology of ultrafine particles on and near freeways”, Atmospheric Environment, 42: 6749-6758.

16

Mechanism Understanding: Charge Background

Key y Point

Freeway

Concentrations of charged ultrafine particles are approximately pp y ten-fold higher g on the freeway y than in the background air.

Lee, Xu, and Zhu, 2012 “Measurements of Ultrafine Particles Carrying Different Number of Charges 17 in On- and Near-Freeway Environments”, Atmospheric Environment, 564-572.

Mechanism Near-freeway DecayUnderstanding: Charge

Key Point Fractional decay of the charged particles was faster than total particle number concentrations, but slower than total ion concentrations downwind from the freeway.

Lee, Xu, and Zhu, 2012 “Measurements of Ultrafine Particles Carrying Different Number of Charges 18 in On- and Near-Freeway Environments”, Atmospheric Environment, 564-572.

Mechanism Understanding: Charge Effects of Charge Polarity Positive Charges

Key Point

Negative Charges

Near freeways, there are strong net positive charges on nucleation mode particles, suggesting that UFPs were not at steady-state steady state charge equilibrium near freeways

Lee, Xu, and Zhu, 2012 “Measurements of Ultrafine Particles Carrying Different Number of Charges 19 in On- and Near-Freeway Environments”, Atmospheric Environment, 564-572.

Indoor near Roadways ‹ Apartment 1

‹ ApartmentKey 2 point i t

Significant amount of freeway UFPs penetrate into indoor environments environments.

Particle Diameter (nm)

Zhu et al., 2005 “Penetration of freeway ultrafine particles into indoor environments”, 2005, Journal of Aerosol20 Science, 36: 303-322.

In--Cabin on Roadway In

110 FWY

405 FWY 710 FWY

Jetta (2002)

Audi A4 (2004)

PT Cruiser (2005)

Zhu et al., 2007 , “In-cabin commuter exposure to ultrafine particles on Los Angeles freeways”. Environmental Science and Technology. 41: 2138-2145.

21

In--Cabin on Roadway In (a) I-405

Typical contour plots of particle number based size distributions inside a test vehicle hi l d driving i i on freeways. (b) I-710

Key point

Greater particle number concentrations were observed b d on II-710, 710 a di diesell vehicle dominated freeway.

Zhu et al., 2008 “Measurements of Ultrafine Particles and Other Vehicular Pollutants inside a Mobile Exposure System 22 on Los Angeles Freeways” J. of Air and Waste Management Association, 58: 424-434.

In--Cabin on Roadways In

Zhu et al., 2007 , “In-cabin commuter exposure to ultrafine particles on Los Angeles freeways”. Environmental Science and Technology. 41: 2138-2145.

23

In--Cabin on Roadways In

Key point

Fan on & Recirculation on provides the best protection for UFP exposures.

Zhu et al., 2007 , “In-cabin commuter exposure to ultrafine particles on Los Angeles freeways”. Environmental Science and Technology. 41: 2138-2145.

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In--Cabin Model In Source

Penetration Filtration

Sink

Deposition p Recirculation Inhalation Coagulation g Recirculation, Qr P Penetration, t ti QL Breath rate, QF

Supply, Qs

Ci Cmi QS (1−ηS ) +QLP = = C0 C mo QFηF + βV + (QS +QL )

Qs+QL

Deposition, β Filtration, ηs 25

In--Cabin Model In

Model performance under steady-state conditions 1.0 Model range Model average Measured data 1.0

0.6

Model range 0.8

0.4

I/O O ratio

0.2 0.0 0.01

Model average Measured data

1.0 Model range

0.6

0.8

Measured data

0.1

particle diameter,μm

Fan off, RC off

Model average g

0.4

I/O ratio

I/O ratio

0.8

0.2

0.6 0.4

0.0 0.01

0.1

particle diameter,μm

Fan on, RC off

0.2 0.0 0.01

0.1

particle diameter,μm

F on, RC on Fan Bin Xu and Yifang Zhu “Quantitative analysis of the parameters affecting in-cabin to on-roadway (I/O) ultrafine particle concentration ratios”, 2009, Aerosol Science and Technology, 43: 400-410.

In--Cabin Model In

M d l performance Model f under d d dynamic i conditions di i UF FP concentrationn, #/cm3

50000 Outdoor Incabin-measured Incabin-model

40000 30000 20000 10000 0 0

20

40

60

80

100

Time, min Bin Xu and Yifang Zhu “Quantitative analysis of the parameters affecting in-cabin to on-roadway (I/O) ultrafine particle concentration ratios”, 2009, Aerosol Science and Technology, 43: 400-410.

In--Cabin Model In

Fan off, off RC off

Mechanical Airflow Penetration Factor

Fan on, RCKey off point p

F on, RC on Fan

Penetration, Deposition, and Filtration are important factors.

Deposition Efficient Filter Efficiency Respiratory

Xu and Zhu 2009 “Quantitative analysis of the parameters affecting in-cabin to on-roadway (I/O) ultrafine particle concentration ratios”, Aerosol Science and Technology, 43: 400-410.

Penetration ™ Apparatus Configuration M t i l Material

Si Size

C fi Configuration ti

0.8 mm height, 9.5 mm length

straight-through

0.8 mm height, 28.5 mm length

straight-through

1.6 mm height, 9.5 mm length

straight-through

1.6 mm height, 28.5 mm length

straight-through

0.8 mm height, 9.5 mm length

straight-through

0.8 mm height, 28.5 mm length

straight-through

0.8 mm height, 28.5 mm length

double-bend

Rubber-Steel

Rubber Rubber Rubber-Rubber

Rubber-glass

29

Penetration

Penetration factors as a function of particle size under various differential pressures

0.9 1.0

0.8 30 Pa 80 Pa 120 Pa 160 Pa 200 Pa

0.7 0.6

(a) 0.5 10

100

Penetration factor

Pe enetration factor

1.0

0.9

08 0.8

0.7

0.6

Particle diameter, nm

((b))

10 1.0

0.5 10

Penetrattion factor

30 Pa 80 Pa 120 Pa 160 Pa 200 Pa 100

Particle diameter, nm

0.9

0.8

30 Pa 80 Pa 120 Pa 160 Pa 200 Pa

0.7

0.6

(c)

Key point

Penetration factors increase as particle size and differential pressure increase.

0.5 10

100

Particle diameter, nm

Bin Xu, Shusen Liu, and Yifang Zhu “Ultrafine particle penetration through idealized vehicle cracks”, 30 2010, Journal of Aerosols Science, 41(9) 859-868.

Penetration ™Particle penetration factor for ™Particle penetration factor for different crack heights

1.00

1.00

0.95

0.95

Penetration n factor

Penetratio on factor

different crack lengths

0.90 0 85 0.85

0.90 0.85

Penetration factors increase as

0.80

0.80 Key crackmmlength decreases and length-28.5 pointCrack p 0.75 Crack length-9.5 length 9.5 mm crack height increases. increases

0.75 0.70 10

100

Particle diameter, nm

Crack height-1.6 height 1.6 mm Crack height-0.8 mm

0.70 10

100

Particle diameter, nm

Bin Xu, Shusen Liu, and Yifang Zhu “Ultrafine particle penetration through idealized vehicle cracks”, 31 2010, Journal of Aerosols Science, 41(9) 859-868.

Deposition ™ Experimental Setup: Particle generation and measurements Deposition experiment Di Diesel l generator t Dilution blower exhaust

Q-Trak DMA

CPC

32

Deposition 0

(a) 30 nm

(b) 66.1 nm 0

-2

ln(C/C0)

ln(C/C0)

-2 -4 4

-4

-6 -6

-8

natural convencton, Slope=7.64 h -1 -1 V1=0.25 m s , Slope=8.36 h -1

V2=0.45 =0 45 m s , Slope=9.76 Slope=9 76 h

-1

natural convection, Slope=3.28 h -1 -1 V1=0.25 m s , Slope=3.52 h

-1

-1

-8 8

10

-1 1

-1

-1

V3=0.65 m s , Slope=4.05 h

-10 0

-1 1

V2=0.45 m s , Slope=3.90 h

-1

V3=0.65 m s , Slope=11.21 h

20

30

40

50

-1

-10 0

20

40

60

time (min)

80

100

120

140

160

time (min) .7 Fan off RC off

(c) 101.8 nm

Fan on RC off The.6 relationship between ln(C/C0) and time Fan on RC on for .5some specific particle sizes inside the test vehicle (a) 30 nm (b) 66.1 nm (c) 101.8 nm .4

In-cabin air velo ocity (m s-1)

0

ln(C/C0)

-2

-4

The.2 value of the slope is equal to particle deposition rate and increased with .1 increasing in-cabin air velocity. velocity 0.0

-1

-6

natural convection, Slope=2.65 h -1 -1 V1=0.25 m s , Slope=2.73 h -1

-1

-1

-1

V2=0.45 =0 45 m s , Slope=2.84 Slope=2 84 h V3=0.65 m s , Slope=2.97 h

-8 0

50

100

time (min)

.3

150

200

250

10

20

30

40

50

Vehicle speed (mph)

60

70

33

Deposition 18 30 nm 66.1 nm 101.8 nm

-1

Particle deposition rate (h )

16

Satrun SL2 car

14 12 10

Isuzu Rodeo SUV

8 6 4 2 3

4

5

6

7

8

9

10

Surface area to volume ratio (m-1)

The particle deposition rates as a function of surface area to volume ratios for 30, 66.1, and 101.8 nm particles inside two test vehicles. Key point

There is a positive correlation between surface area to volume ratios and ultrafine particle deposition rates. Greater surface area to volume ratio results in higher deposition rate for ultrafine particles.

Longwen Gong, Bin Xu and Yifang Zhu “Ultrafine Particles Deposition inside Passenger Vehicles", 2009, Aerosol Science 34 and Technology, 43: 544-553.

Filtration ™Ultrafine Particle Filtration Efficiency Measurements Air flow meter

SMPS DMA

CPC

Filter Diesel Generator

Fan

Filtration Efficiency = 1 −

downstream concentrat ion upstream concentrat ion 35

Filtration Cabin Filter Performance: The Good, the Bad, and the Ugly

Filtra ation effic ciency

1.0 Filter A Filter B Filter C

0.8

0.6

0.4

0.2

0.0 10

100

1000

10000

Particle diameter, diameter nm Xu, Liu, Liu, and Zhu, 2010 ‘Effects of cabin filter on in-cabin to on-roadway ultrafine particle ratios’ Aerosol Science and Technology, Aerosol Science and Technology, 45:215–224.

Filtration

HEPA: 10 Honda HEPA: 08 Toyota HEPA filter HEPA: 04 Toyota HEPA: 05 Toyota HEPA: 01 Honda New Commercial: 10 Honda New Commercial: 08 Toyota New New Commercial: 04 Toyota commercial N C New Commercial: i l 05 T Toyota t New Commercial: 01 Honda In-cabin filtration has great potential to significantly In-use w/ sealing: 10 Honda Key In-use w/ sealing: 08 Toyota reduce commuters’ exposure to ultrafine particles while In-use In-usesealing w/ sealing: 04 Toyota point In-use w/ sealing: g 05 Toyota y the same time solve the CO2 build up problem. In-use w/ sealing: 01 Honda In-use w/o sealing: 10 Honda In-use w/o In-use nosealing: 08 Toyota In-use w/o sealing: 04 Toyota sealing In-use w/o sealing: 05 Toyota In-use w/o sealing: 01 Honda No Filter: 10 Honda No Filter: 08 Toyota No filterNo Filter: 04 Toyota No Filter: 05 Toyota No Filter: 01 Honda 0

20

40

60

Percent particle reduction (%)

80

at

100 37

School Bus Filtration 25000

1.0 Two Air Purifiers On

15000

Air Purifiers Off I/O=0.83

I/O=0.82

.8

In-cabin particles Ambient particles I/O ratio

3

Total pa articles (#/c cm )

20000

One Air Purifier On

I/O=0.55

.6

I/O=0.40 10000

.4

5000

2 .2

0 06 50 06:50

II/O ratio

Air Purifiers Off

0.0 07 10 07:10

07 30 07:30

07 50 07:50

08 10 08:10

08 30 08:30

Time 38

School Bus Filtration I/O ratio inside school buses without/with air purifiers

Key point

Stand-along air purifiers can significantly reduce particulate matter (PM2.5 and ultrafine particle) levels inside vehicles.

Zhang and Zhu 2011 “Performance of School Bus Retrofit Systems: Ultrafine Particles and Other Vehicular Pollutants”, 2011, Environmental Science and Technology, 45: 6475–6482.

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Summary y UFPs On & Near Roadways have Unique Characteristics: - Morphology and Charge Reducing UFP Exposure Near Roadways: - Meteorology: gy stay y on the upwind p side of major j roadways; - Spatial Profile: stay away from major roadways; - Temporal Profile: avoid heavy traffic hours Reducing UFP Exposure inside Vehicles: - Route: avoid heavy-duty y y vehicle route - In-Cabin Ventilation : close window and turn on recirculation - In-Cabin In Cabin Filtration: use HEPA filter/air purifier

Acknowledgements Co-Authors: C A th Willi William C C. Hi Hinds, d C Constantinos t ti Si Sioutas, t Seongheon Kim, Si Shen, Margaret Krudysz, Thomas Kuhn, John F. Froines, Paul Mayo, Arantza EigurenF Fernandez, d Antonio A t i H. H Mi Miguel, l L Longwen G Gong, Bi Bin X Xu, Shusen Liu, and Qunfang Zhang.

Support Health Effects Institute (HEI) National Science Foundation (NSF) California Air Resource Board (CARB) US Environmental Protection Agency (EPA)