Is Urban Air Quality a Problem? Ian Longley

The air is cleaner than it was, isn’t it?

Effect of controls on coal burning

Health effects of NO 2 & PM 10 Reduction of 1 g/m 3 in PM 10 could lead to gain in life expectancy of 0.5 weeks at cost of £1bn+ (IGCB Report to DETR, 2001). Saving to NHS order or £1m p.a.

National Air Quality Strategy Objectives (UK) Exceedences allow for unfavourable meteorology

The current state of UK Air Quality

Major determinant of air pollution concentrations is the wind

National / international emission abatement strategies: Engines standardYearcomments Euro I19923-way catalytic conversion Euro II1997 Euro III2000On-board diagnostics Euro IV2005Around 40% of new UK cars

Currently 30 million vehicles registered in UK

Improvements likely to be offset by rise in traffic by 2020

(Inter)national strategies: Petrol/Diesel ULSP/ULSD (<50ppm) available from 2000, all fuel by 2005 EU consulting on 10ppm S limit Low Benzene Petrol (also ULSP) City Diesel (7ppm S, 30% less PM, up to 88% for buses with particle trap)

(Inter)national strategies: Alternative Fuels: Chemical LPG – on the road in UK (including hybrids), 80% less PM for buses CNG – UK has 20 filling stations, 50-90% less PM 140 CNG buses operating in France Biodiesel Best options for LDVs in next years

(Inter)national strategies: Alternative Fuels - Others Hybrid – petrol/electric: Toyota Prius & Honda Insight Electric – Peugeot 106, Bristol park & ride buses, Cambridge solar bus Fuel cells (from 2010? London trial buses in 2003)

Local Air Quality Management Environment Act 1995: Local Authority duty Create Emission Inventories Dispersion modelling to predict concentrations NOW and in 2005 Identify areas where 2005 objectives will NOT be met.

Air Quality Management Areas, e.g. Greater Manchester AQMA declared where 2005 objective for NO 2 will NOT be met.

AQMAs: e.g. Croydon

AQMAs 3 million live within AQMAs, mostly in Greater London. RESULT: most L.A.s report most Objectives WILL be met, EXCEPT NO 2 and PM 10 in urban areas and near major roads. L.A.s must draw up Action Plans for AQMAs.

Action Plan options 1: restrictions Low Emission Zone (e.g. central London predicted 16% reduction in NO x, 25% PM 10 emissions), also Nottingham, Leicester, York, Bath Council vehicle fleets Congestion charging (London, Durham, Bristol, Edinburgh, Manchester) Partial or total road closure Bus/cycle/HGV/high-occupancy lanes Parking controls/changes

Action Plan options 2 Traffic calming Traffic management (signalling, bollards) Changing speed limits Smooth driving styles Rail and light-rail investment Bus and park-and-ride investment Public information and ‘encouragement’

Review & Assessment Monitoring: modelling compared to measurements Models consistently under-predict for NO 2 and PM 10 in urban areas, especially densely-built- up areas. Models perform badly at predicting PM 10.

The problem with PM 10 Fine mode (nm) mostly carbonaceous from exhausts. Main suspect in adverse health effects. Coarse mode (m) often crustal. Concentrations related to wind speed and direction. Much harder to control. Mass measurements (PM 10 ) dominated by coarse mode.

Urban hot-spots Personal exposure study showed half of exposure of PM 2.5 occurred over 15% of time, mostly when travelling (Rea et al, Jl. Air & Waste Manage. Assoc. vol.51, Sep 2001) Epidemiological studies based on monitoring sites – R&A shows under-estimate exposure (Alm et al, Atmos. Env. Vol.35, 2001) How far into surroundings does a hot-spot’s effects penetrate?

Urban hot-spots: where are they?

Street Canyon Aerosol Research - SCAR Particle concentrations and fluxes are dependent upon Wind speed, Wind direction and canyon assymetry, Emission strength, Surface heat emission, Traffic-modified mean winds, Traffic-induced turbulence (especially in low winds), Particle size

Conclusions Urban air quality improved in 1960s, but traffic growth compromised improvements. Technological fixes to engines and fuels delivered big improvements and will do so for next 10 – 20 years, but diminishing returns. Suburban and urban background air pollution is marginal – susceptible populations. Urban hot-spots probably require further measures which may restrict mobility. More research needed (by Atmos Physics post- docs).

But… Of 2.9 billion living in cities around the world 2 billion in ‘less developed’ regions (UN,1999); majority of worst polluted cities in Asia Vehicle emission control technology is expensive Cooking and small fires major sources Many cities are less windy than UK cities Many cities in arid/semi-arid areas – affected by natural dusts 2-5% of all deaths in urban areas caused by air pollution. Demand for transport growing much faster than ever happened in Europe.