Transcript PARTICULATE MATTER: METRICS, HEALTH EFFECTS AND …

Regulatory and Air Quality
Implications of Setting Particle
Number Standards
Roy M. Harrison
University of Birmingham and
National Centre for Atmospheric Science
CONTENT
• Particle size distributions and the meaning of
particle number concentration
• Sources and environmental behaviour of
nanoparticles
• Epidemiology of nanoparticle exposures
• Conclusions
NANOPARTICLES
Particles of < 100 nm diameter
are very numerous in the
atmosphere but have very
little mass
NANOPARTICLES
Influence of Particle Size on Particle Number and Surface Area
for a Given Particle Mass
PARTICLE
DIAMETER
RELATIVE
NUMBER OF
PARTICLES
RELATIVE
SURFACE AREA
10 µm
1
1
1 µm
103
102
0.1 µm
106
104
0.01 µm
109
106
PARTICLE SIZE
DISTRIBUTION
MEASURED IN
BIRMINGHAM
Particle Size Distributions at
Marylebone Road
90000
dN/dlogDP cm-3
80000
28 nm
70000
30 nm
60000
50000
40000
32 nm
Night
26 nm
Morning rush hour
Midday
Afternoon rush hour
30000
20000
10000
0
10
100
Particle Diameter (nm)
1000
Particle Number, Surface Area and Mass
Measuring:
 Particle number reflects particles < 100
nanometres primarily
 Particle surface area reflects mainly particles of
50-1000 nm
 Particle mass reflects particles of > 100
nanometres (usually to 2.5 µm or 10 µm)
UK PM0.1 Emissions 1970-2008
MERGING SIZE DISTRIBUTIONS
AND ELUCIDATION OF
PARTICLE SOURCES
MEAN MERGED SMPS-APS SPECTRA
• REPARTEE II data from the Marylebone Road.
• October 2007.
• SMPS TSI 3080 Classifier and TSI 3776 CPC
• APS TSI 3321
CRAN – R GUI
An Enhanced Procedure for the Merging of Atmospheric Particle Size Distribution Data Measured Using
Electrical Mobility and Time-of-Flight Analysers, D.C. Beddows, M. Dall’Osto and R.M. Harrison, Aerosol
Sci. Technol., 44, 930-938 (2010).
NUMBER FACTORS AND SCORES
Mean Concentration (%)
Volume
Number
Exhaust - solid mode (factor 3)
18.8
38.0
Exhaust - nucleation mode (factor 4)
3.6
27.4
Marylebone Road Emissions
Solid
carbonaceous
mode
Strong LDV
association
Diurnal Traffic
pattern
Nucleation
mode from
dilution of
diesel exhaust
Morning rush
hour
Attribution of mean particle volume and
number to tentatively assigned sources
Mean Concentration (%)
Volume
Number
Exhaust - solid mode (factor 3)
18.8
38.0
Exhaust - nucleation mode (factor 4)
3.6
27.4
Brake dust (factor 2)
13.7
1.7
Resuspension (factor 7)
4.4
4.8
Sub-total
40.5
71.9
Accumulation mode (factor 1)
12.8
6.3
Suburban traffic (factor 5)
2.3
7.6
Nitrate (factor 6)
8.4
2.0
Regional (factor 8)
2.5
2.7
Cooking (factor 9)
6.7
6.6
Regional (factor 10)
26.8
3.0
Sub-total
59.5
28.2
Marylebone Road Emissions
Urban Background
TAKE-HOME MESSAGE
Vehicle exhaust nanoparticles comprise two
types:
• nucleation mode – mainly condensed
lubricating oil, centred on 20 nm diameter
• solid mode – graphitic carbon – centred on
50-60 nm diameter
PMF Analysis of Wide-Range Particle Size Spectra Collected on a Major Highway, R.M.
Harrison, D.C.S. Beddows and M. Dall’Osto, Environ. Sci. Technol., 45, 5522-5528 (2011).
THE REPARTEE
EXPERIMENT
Atmospheric Chemistry and Physics in the Atmosphere of a Developed Megacity (London): An Overview
of the REPARTEE Experiment and its Conclusions, R.M. Harrison, M. Dall’Osto, D.C.S. Beddows, A.J.
Thorpe, W.J. Bloss, J.D. Allan, H. Coe, J.R. Dorsey, M. Gallagher, C. Martin, J. Whitehead, P.I. Williams,
R.L. Jones, J.M. Langridge, A.K. Benton, S.M. Ball, B. Langford, C.N. Hewitt, B. Davison, D. Martin, K.
Petersson, S.J. Henshaw, I.R. White, D.E. Shallcross, J.F. Barlow, T. Dunbar, F. Davies, E. Nemitz, G.J. Phillips,
C. Helfter, C.F. Di Marco and S. Smith, Atmos. Phys. Chem., 12, 3065-3114 (2012).
Map of Central London
Remarkable dynamics of nanoparticle in the urban atmosphere
60x10
3
Park
Road
Tower
d N / d Log Dp
50
40
30
20
10
0
4
5 6 7 8 9
10
•
•
•
2
3
4
5 6 7 8 9
[ m ]
Da[nm]
D
100
2
3
4
5 6 7 8 9
1000
The typical size distribution measured at the Road site peaking between 20 and 30 nm
diameter.
In contrast, data from the Park site showed a mode which had shifted downwards to below
10 nm diameter.
There is almost complete loss of the sub-30 nanometre mode at the BT Tower site.
60x10
3
Road
40
20
d N / d log Dp
0
40x10
3
30
Park
20
10
0
20x10
3
Tower
15
10
5
0
2
3
4 5 6 7
2
10
3
4 5 6 7
2
100
3
4 5 6 7
1000
mobility
diameter
mobility
diameter(m)
[nm]
On distance scales of the order of 1 km and travel times of around 5 minutes upon moving away
from major emissions sources very significant loss of the nanoparticle fraction is observed which
manifests itself in a shift to smaller sizes within Regents Park and an almost complete loss of the
sub-30 nanometre mode at the BT Tower site.
TAKE-HOME MESSAGE
• The nucleation mode particles in traffic
exhaust are semi-volatile and evaporate as
they are carried downwind of source, or mixed
upward in the atmosphere
Remarkable Dynamics of Nanoparticles in the Urban Atmosphere, M. Dall’Osto, A. Thorpe,
D.C.S. Beddows, R.M. Harrison, J.F. Barlow, T. Dunbar, P.I. Williams and H. Coe, Atmos. Chem.
Phys., 11, 6623-6637 (2011).
Particle Nucleation
• New particle formation in the atmosphere can
lead to huge bursts of nanoparticle concentration
• Highly prevalent in southern Europe, but less so in
the UK
• Health impacts of particles formed by regional
nucleation are not known
New Considerations for PM, Black Carbon and Particle Number Concentration for
Air Quality Monitoring Across Different European Cities, C. Reche, X. Querol, A. Alastuey,
M. Viana, J. Pey, T. Moreno, S. Rodriguez, Y. Gonzalez, R. Fernandez-Camacho,
A.M. Sanchez de la Campa, J. de la Rosa, M. Dall’Osto, A.S.H. Prevot, C. Hueglin, R.M. Harrison
and P. Quincey, Atmos. Chem. Phys., 11, 6207-6227 (2011).
BIRMINGHAM, JUNE 1999
Contrasting Behaviour of PM Mass
and PM Number
If there were a temporary cessation of PM emissions
and secondary formation:
• Particle mass would be conserved and diminish only
slowly due to deposition processes
• Particle number would not be conserved. It would
diminish due to:
- evaporation
- coagulation
- surface deposition
Or, might increase due to nucleation!
TEMPORAL TRENDS IN PARTICLE
NUMBER CONCENTRATIONS
Marylebone Road: Number v NOx
at 100 wind sectors
140000
Oct 05 - Sep 07
Particle number [cm-3]
120000
Feb 08 - Jan 09
100000
80000
60000
40000
20000
0
0
100
200
300
NOx (as NO2) [µg m-3]
400
500
TAKE-HOME MESSAGE
• Nanoparticle concentrations have fallen
sharply since late 2007, especially at roadside
sites
• The cause is most probably the transition to
“sulphur-free” diesel fuel
A Large Reduction in Airborne Particle Number Concentrations at the time of the Introduction
of “Sulphur Free” Diesel and the London Low Emission Zone, A.M. Jones, R.M. Harrison,
G. Fuller and B. Barratt, Atmos. Environ., 50, 129-138 (2012).
London Epidemiological Study
Richard Atkinson and Ross Anderson (St.
George’s Hospital Medical School) used casecrossover time series methodology to
estimate the percentage increase in a given
health outcome corresponding to the interquartile range (75%ile minus 25%ile) of
concentration for several particle metrics
Urban Ambient Particle Metrics and Health: A Time Series Analysis, R.W. Atkinson, G.W. Fuller,
H.R. Anderson, R.M. Harrison and B. Armstrong, Epidemiology, 21, 501-511 (2010).
Cardiovascular Mortality (lag 1)
PM
10
N
K
PM
10
PM
G
10
R
PM
25
PM
G
R
PM 25
10
2.
5
PR
N I10
O
N
P1
N
0
O
N
N
O P2 .
N
P1 5
02
.5
BS
R
G
4
SO
C
L
3
N
O
PN
C
-2
0
% (95% CI)
2
4
6
(Graph shows % change between 25%ile
and 75%ile concentration and 95% CI)
Respiratory Mortality (lag 2)
PM
10
N
K
PM
10
PM
G
10
R
PM
25
PM
G
R
PM 25
10
2.
5
PR
N I10
O
N
P1
N
0
O
N
N
O P2 .
N
P1 5
02
.5
BS
R
G
4
SO
C
L
3
O
N
PN
C
-2
0
% (95% CI)
2
4
6
8
(Graph shows % change between 25%ile
and 75%ile concentration and 95% CI)
Desktop Study of Nanoparticles from Traffic in Delhi
Prashant Kumar and co-workers examined particle number
emissions in Delhi and three scenarios:
 Present day (2010)
 Business as usual (2030)
 Best estimate scenario (2030)
Impacts on mortality were estimated using two sources of
exposure-response functions:
 Atkinson et al. (2010)
 Stolzel et al. (2007)
Preliminary Estimates of Nanoparticle Number Emissions from Road Vehicles
in Megacity Delhi and Associated Health Impacts, P. Kumar, B.R. Gurjar, A.K
Nagpure and R.M. Harrison, Environ. Sci. & Technol., 45, 5514-5521 (2011).
Estimated excess deaths annually in Delhi for different air quality scenarios and
exposure response functions – central estimate and 95% confidence intervals
Excess deaths are derived from the ambient ToN concentrations (after losses) and figures in
parentheses are 95% CI values
Note: Based solely on acute effects as chronic effects of UFP exposure are not known
CONCLUSIONS
• It would be possible to use the results of studies such as
Atkinson et al. (2010) and Stolzel et al. (2007) to set air
quality standards for (traffic generated) particles by number.
• The differential toxicity of ultrafine particles from different
sources is not known.
• Nanoparticles behave less conservatively in the atmosphere
relative to the larger particles which comprise most of the
particle mass, making the relationship between abatement
measures and airborne concentrations more difficult to
define.
• It is difficult to know whether an AAQS for particle number
would offer additional protection of public health relative to
the present PM mass standards.
ACKNOWLEDGEMENTS
Dr Alan Jones
Dr Manuel Dall’Osto
Dr David Beddows
Dr Krystal Godri
)
)
)
)
Dr Richard Atkinson
Professor Ross Anderson
)
)
St. George’s
Dr Gary Fuller
Dr Ben Barratt
)
)
Kings College, London
Dr Prashant Kumar
)
University of Surrey
University of Birmingham
THANK YOU