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

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 RELATIVE PARTICLENUMBER OFRELATIVE DIAMETERPARTICLESSURFACE AREA 10 µm11 1 µm µm µm

PARTICLE SIZE DISTRIBUTION MEASURED IN BIRMINGHAM

Particle Size Distributions at Marylebone Road dN/dlogD 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 nm  Particle mass reflects particles of > 100 nanometres (usually to 2.5 µm or 10 µm)

UK PM 0.1 Emissions

MERGING SIZE DISTRIBUTIONS AND ELUCIDATION OF PARTICLE SOURCES

MEAN MERGED SMPS-APS SPECTRA CRAN – R GUI REPARTEE II data from the Marylebone Road. October 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, (2010).

NUMBER FACTORS AND SCORES Mean Concentration (%) VolumeNumber Marylebone Road Emissions Exhaust - solid mode (factor 3) Exhaust - nucleation mode (factor 4) Solid carbonaceous mode Diurnal Traffic pattern Strong LDV association Morning rush hour Nucleation mode from dilution of diesel exhaust

Mean Concentration (%) VolumeNumber Marylebone Road Emissions Exhaust - solid mode (factor 3) Exhaust - nucleation mode (factor 4) Brake dust (factor 2) Resuspension (factor 7) Sub-total Urban Background Accumulation mode (factor 1) Suburban traffic (factor 5) Nitrate (factor 6) Regional (factor 8) Cooking (factor 9) Regional (factor 10) Sub-total 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 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, (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, (2012).

Map of Central London

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]

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, (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, (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

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, (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, (2010).

Cardiovascular Mortality (lag 1) (Graph shows % change between 25%ile and 75%ile concentration and 95% CI)

Respiratory Mortality (lag 2) (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, (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 Birmingham Dr David Beddows) Dr Krystal Godri) Dr Richard Atkinson ) St. George’s Professor Ross Anderson) Dr Gary Fuller)Kings College, London Dr Ben Barratt) Dr Prashant Kumar)University of Surrey

THANK YOU