Regulatory and Air Quality Implications of Setting Particle

Number Standards

Roy M. HarrisonUniversity 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

Particles of < 100 nm diameter are very numerous in the

atmosphere but have very little mass

NANOPARTICLES

NANOPARTICLESInfluence of Particle Size on Particle Number and Surface Area

for a Given Particle Mass

RELATIVE PARTICLE NUMBER OF RELATIVE DIAMETER PARTICLES SURFACE AREA

10 µm 1 1

1 µm 103 102

0.1 µm 106 104

0.01 µm 109 106

PARTICLE SIZEDISTRIBUTIONMEASURED IN BIRMINGHAM

Particle Size Distributions at Marylebone Road

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

10 100 1000

Night

Morning rush hour

Midday

Afternoon rush hour

28 nm

30 nm

32 nm

26 nm

dN/d

logD

P cm

-3

Particle Diameter (nm)

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

CRAN – R GUI

• REPARTEE II data from the Marylebone Road.

• October 2007.

• SMPS TSI 3080 Classifier and TSI 3776 CPC• APS TSI 3321

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 SCORESMean Concentration (%)

Volume Number

Marylebone Road Emissions

Exhaust - solid mode (factor 3)

Exhaust - nucleation mode (factor 4)

18.8

3.6

38.0

27.4

Solid carbonaceous mode

Diurnal Traffic pattern

Strong LDV association

Morning rush hour

Nucleation mode from dilution of diesel exhaust

Mean Concentration (%)

Volume Number

Marylebone Road Emissions

Exhaust - solid mode (factor 3)

Exhaust - nucleation mode (factor 4)

Brake dust (factor 2)

Resuspension (factor 7)

Sub-total

18.8

3.6

13.7

4.4

40.5

38.0

27.4

1.7

4.8

71.9

Urban Background

Accumulation mode (factor 1)

Suburban traffic (factor 5)

Nitrate (factor 6)

Regional (factor 8)

Cooking (factor 9)

Regional (factor 10)

Sub-total

12.8

2.3

8.4

2.5

6.7

26.8

59.5

6.3

7.6

2.0

2.7

6.6

3.0

28.2

Attribution of mean particle volume and number to tentatively assigned sources

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

60x103

50

40

30

20

10

0

d N

/ d

Lo

g D

p

4 5 6 7 8 910

2 3 4 5 6 7 8 9100

2 3 4 5 6 7 8 91000

Da [ m ]

MR_12

DMPS_12

c

Park Road Tower

Remarkable dynamics of nanoparticle in the urban atmosphere

• 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.

D [nm]

40x103

30

20

10

0d N

/ d

lo

g D

p

2 3 4 5 6 710

2 3 4 5 6 7100

2 3 4 5 6 71000

mobility diameter (m)

20x103

15

10

5

0

60x103

40

20

0

Road

Park

Tower

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.

mobility diameter [nm]

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

0 50 100 150 200 250 300 350 400 450 5000

20000

40000

60000

80000

100000

120000

140000

Marylebone Road: Number v NOx at 100 wind sectors

Oct 05 - Sep 07

Feb 08 - Jan 09

NOx (as NO2) [µg m-3]

Parti

cle

num

ber [

cm-3

]

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).

Richard Atkinson and Ross Anderson (St. George’s Hospital Medical School) used case-crossover time series methodology to estimate the percentage increase in a given health outcome corresponding to the inter-quartile range (75%ile minus 25%ile) of concentration for several particle metrics

London Epidemiological Study

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)(Graph shows % change between 25%ile

and 75%ile concentration and 95% CI)

-20

24

6%

(95

% C

I)

PNCNO3 CL

SO4 BS

GR PM

10

NK PM

10

PM10

GR PM

25

PM25

GR PM

102.

5

PRI10

NONP10

NONP2.5

NONP102.

5

-20

24

6%

(95

% C

I)

PNCNO3 CL

SO4 BS

GR PM

10

NK PM

10

PM10

GR PM

25

PM25

GR PM

102.

5

PRI10

NONP10

NONP2.5

NONP102.

5

Respiratory Mortality (lag 2)(Graph shows % change between 25%ile

and 75%ile concentration and 95% CI)

-20

24

68

% (

95%

CI)

PNCNO3 CL

SO4 BS

GR PM

10

NK PM

10

PM10

GR PM

25

PM25

GR PM

102.

5

PRI10

NONP10

NONP2.5

NONP102.

5

-20

24

68

% (

95%

CI)

PNCNO3 CL

SO4 BS

GR PM

10

NK PM

10

PM10

GR PM

25

PM25

GR PM

102.

5

PRI10

NONP10

NONP2.5

NONP102.

5

Desktop Study of Nanoparticles from Traffic in DelhiPrashant 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 ) University of BirminghamDr David Beddows )Dr Krystal Godri )

Dr Richard Atkinson ) St. George’sProfessor Ross Anderson )

Dr Gary Fuller ) Kings College, LondonDr Ben Barratt )

Dr Prashant Kumar ) University of Surrey

THANK YOU