... highway”, J. of Air and Waste Management Association, 52:1032-1042. .....
Filtration. HEPA: 04 Toyota. HEPA: 08 Toyota. HEPA: 10 Honda. HEPA filter. N. C
.
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 Cardiac and Pulmonary Health Risks from NearHighway Exposures Environmental Health – Tufts Univ. School of Medicine (Brugge 2007)
Adverse Effects of Traffic Exposure on Children’s Children s Lung Development The Lancet – USC School of Medicine (Gauderman 2007)
Traffic Exposure and Decreased Lung Function in Adults with Asthma A,. Academy of Allergy, Asthma & Immunology – UCSF (Balmes 2009)
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.
15
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.
24
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.
39
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)