Air Pollution Audrey de Nazelle anazelle@imperial.ac.uk November 5 2013
2 weeks ago: Helen ApSimon on atmospheric sciences Today: taster on regulations, monitoring & modelling, and air pollution control In a few weeks: Susan Hodgson on health
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London 1952 Smog Episode The Big Smoke
The big Smoke and the relationship between air quality and health Public awareness Environmental research Government regulation 1956 UK Clean Air Act (1 st Clean Air Act in the US: 1963)
EU Legislative framework Air quality (concentrations) objectives: Air Quality Directive (2008/50/EC): sets ambient standards Emissions targets: National Emission Ceiling Directive (2001/81/EC): for SO2, NOx, VOCs, NH3 Integrated pollution and prevention control Directive (2008/1/EC): requires permits with emission limit values and conditions based on Best Available Technique (BAT) for high pollution potential industrial and agricultural activities
Risk Assessment: - Hazard identification - Dose response - Exposure assessment - Risk characterization Human activity Sources/ emissions Concentrations Exposure / intake Health impacts Policies / interventions Full chain / Driver-Pressure-State-Impact-Response / source-receptor model, etc.
Air quality ambient standards Concentration limits set to protect public health and the environment Periodically reviewed given new scientific evidence EU: Limit values: legally binding Target values: to be attained where possible by taking all necessary measures not entailing disproportionate costs.
Pollutant EU limit values Concentration Averaging period Permitted exceedences each year 350 µg/m3 1 hour 24 Sulphur dioxide (SO 2 ) 125 µg/m3 24 hours 3 Nitrogen dioxide 200 µg/m3 1 hour 18 (NO 2 ) 40 µg/m3 1 year n/a Particulate Matter 50 µg/m3 24 hours 35 (PM 10 ) 40 µg/m3 1 year n/a Lead (Pb) 0.5 µg/m3 1 year n/a Maximum Carbon monoxide 10 mg/m3 daily 8 hour (CO) mean n/a Benzene 5 µg/m3 1 year n/a PM2.5 25 µg/m3* 1 year *Target value 2010, limit value 2015. Also new exposure reduction index: reduce up to 20% background concentration bet. 2010-2020
Member states can use more stringent standards than the EU s
UK Department for Environment, Food and Rural Affairs (DEFRA) co-ordinates assessment and air quality plans for the UK as a whole. local authorities designate air quality management (LAQM) areas and develop action plans
Sources, effects, policies? Tools: Emission inventories, air pollution modelling, air pollution monitoring
National Atmospheric Emissions Inventory (NAEI) Emissions by sector Emissions factors Activity by sector http://naei.defra.gov.uk/index.php
National Atmospheric Emissions Inventory reports http://naei.defra.gov.uk/reports/
35% from tyre and brake wear 80% contribution from traffic sector London s Mayor Air Quality Strategy 2010
UK: Transport main source of pollution in 92% of all LAQMAs Source: Air Pollution in the UK 2011, DEFRA
Greater London PM2.5 emissions (%) Natural, 7.3% Public/ Domestic Combustion, 4.1% Power Generation, 4.8% Off-road Machinery, 8.5% Industry, 20.6% Other Transport, 3.6% Road Transport, 51.2% Background, 26.0% London Public/Domestic Combustion, 0.4% Local Road Transport, 11.1% London Other Transport, 0.9% London Road Transport, 7.4% London Off-road Machinery, 1.2% Regional Secondary Inorganic Aerosols, 12.2% London Power Generation, 0.0% London Industry, 0.9% London Natural, 0.6% London Secondary Inorganic Aerosols, 7.1% Regional Primary PM2.5, 4.7% Secondary Organic Aerosols, 5.2% European Contribution, 16.0% Shipping, 6.3% Roadside PM2.5 Concentration (%)
Greater London PM2.5 emissions (%) Natural, 7.3% Public/Domestic Combustion, 4.1% Industry, 20.6% Power Generation, 4.8% Road Transport, 51.2% Off-road Machinery, 8.5% Other Transport, 3.6%
Roadside PM2.5 Concentration (%) Transport < 25% Local Road Transport, 11.1% London London Other Public/Domestic Transport, 0.9% Combustion, 0.4% London Road Transport, 7.4% London Off-road Machinery, 1.2% London Power Generation, London 0.0% Industry, 0.9% London Natural, 0.6% London Secondary Inorganic Aerosols, 7.1% Regional Primary PM2.5, 4.7% Background, 26.0% Regional Secondary Inorganic Aerosols, 12.2% Secondary Organic Aerosols, 5.2% European Contribution, 16.0% Shipping, 6.3% About 30% London-based contributions
Modelling (concentrations) Regulatory purposes Environmental research Exposure assessment London s Mayor Air Quality Strategy 2010
Chemical transport large-scale models mathematical equations accounting for chemical and physical processes uses meteorology and emissions inventories Examples: CMAQ, CAMx, UAM
Physical and chemical processes: examples PM can be emitted primarily or formed through chemical and physical processes: SO2 emitted -> SO4 sulfate NH3 emitted -> NH4 Amonium NOx emitted -> NO3 nitrate NH4NO3 (NH4) 2 SO4 Secondary Particles (PM10, PM2.5) Ozone (O3) formation results from a complex set of reactions between VOCs, NOx and sunlight Ozone isopleth NO + VOCs NO 2 NO 2 + UV NO + O O + O2 O 3 NO 2 + VOCs PAN, etc NO + O3 --> NO2 + O2
Physical and chemical processes: examples
Dispersion models Applied to a receptor Mathematical equations to characterize physical dispersion (e.g. Gaussian plume) uses meteorology and emissions inventories Example: ADMS, AERMOD
Dispersion from a single source Unstable: light wind sunny convective mixing Neutral: strong wind mechanical mixing Inversion Stable:night light wind clear sky little mixing
Geostatistical /statistical models Interpolation, e.g. Kriging Land Use Regression model conc = b 0 + b 1 X 1 1+ b 2 X 2 +.+ b k X k + E b 0 = Intercept X = Population density, road network, traffic volume, altitude b = regression coefficients E = error Briggs et al. 1997 Use monitoring data (and land use data)
Trade-offs in choice of models (complexity, temporal and spatial scale, flexibility) For regulatory purposes future projections are needed hence more costly and complex chemical transport and dispersion models are used Increasingly land use regression models are used in the health field
Monitoring Regulatory purposes (statutory monitoring network) Environmental research (including model validation) Exposure assessment
website: www.londonair.org.uk Monitoring: e.g. London Air Quality Network
Ambient air policy framework Monitoring stations used to demonstrate current compliance (or not) Models used to demonstrate future compliance (running policy scenarios) + compliance at unmonitored areas
Complexities of air pollution research and regulation Do limit values really reflect current knowledge? Are we targeting the right pollutants? Are we appropriately assessing exposures? Is the current framework allowing the most efficient means to abate air pollution and promote health?
On the choice of limit values Standards are developed based on scientific knowledge on health impacts of air pollution Epidemiology Toxicology
Air Quality Standards for annual PM2.5 concentration CAL WHO EPA EU
On health: results of APHECOM: compliance of WHO guidlens Exceeding WHO guideline in 25 European cities with 39 million inhabitants results in 19 000 deaths per year Pascal et al. 2013; www.aphekom.org PM2.5 (µg/m3) Gain in life expectancy (months) from complying with WHO guideline
Do limit values really reflect current knowledge? See Review of evidence on health aspects of air pollution REVIHAAP WHO 2013 Are we targeting the right pollutants?
PM mass or composition? Trace metals, quinones, endotoxins, PAHs, black carbon inorganic secondary aerosols, primary and secondary organic aerosols? TOXICITY OF PM COMPONENTS? Kelly et al. HEI 155 2011
PM mass or composition? Oxidative potential: the ability of PM to induce toxicity in biological systems (capacity to oxidize physiologically relevant molecules) London study found PM 10 at roadside locations have greater oxidative activity than PM 10 at background sites: likely due to tire and brake wear (indicated by presence of metals arsenic, barium, copper, iron, manganese, nickel, vanadium) Kelly et al. HEI 155 2011
Particle sizes Nel et al, Science, 2005; 307:1858 38
Effect of different contaminants according to their size 39
Do limit values really reflect current knowledge? Are we targeting the right pollutants? Pollutants such as PM10, PM2.5, or NO2 are convenient to represent exposures in epidemiologic studies and as policy targets for the development of standards, but they are not necessarily the most health-relevant pollutants Are we appropriately assessing exposures?
Traditional approaches for assessing exposures in epemiologic research Air pollution: Fixed monitoring stations Air pollution modelling Typically assign home address exposure
(Schembari et al. 2013 Atmospheric Environment, 64: 287-295) Personal, home indoor and home outdoor measurement Pregnant women in Barcelona Pollutants Measurement (N) Geometric Mean (GSD) Min - Max PM2.5 Personal (53) 24.1 (1.5) 9.9-63.9 μg m -3 Indoor (54) 20.6 (1.6) 6.7-72.9 Outdoor (52) 18.0 (1.6) 7.0-68.9 NO x Personal (65) 61.9 (1.6) 26.8-279.3 μg m -3 Indoor (65) 60.6 (1.7) 26.4-379.5 Outdoor (65) 51.6 (1.6) 23.2-279.3
Exposure estimates for NO 2 Time spent in activities Home concentration (µg/m 3 ) Time weighted average concentration (µg/m 3 ) with Home Work Others InTransit Contribution to inhaled dose Mean 54 67 Standard Deviation 11 22 Time-weighted average concentration: accounts for activity patterns de Nazelle et al. 2013 Environmental Pollution 176: 92-99 Home Work Others InTransit
Exposure measurement error can lead to bias results in exposure-response modelling (epidemiology studies) In the current standard regulatory framework, limit values are compared to concentrations measured at monitoring stations do these represent exposures, and does this approach lead to greatest health benefits?
Public health benefits of limit value vs exposure reduction approach Exposure reduction across the whole population may have greater benefits than regulating high exposures using standards if there is no threshold of effect
Do limit values really reflect current knowledge? Are we targeting the right pollutants? Are we appropriately assessing exposures? Is the current framework allowing the most efficient means to abate air pollution and promote health?
Air pollution control
Air pollution control options Pollution dispersion Cleaner processes more efficient processes End-of-pipe (tail pipe): physical and/or chemical removal Regulatory schemes Consumer demand management
Chimneys help disperse pollutants
Improvement in Efficiency of UK Coal Fired Power Stations Less coal burned to produce the same amount of electricity Reduced atmos. Emissions (Assuming same electrical demand) Analysis of Engineering Cycles, RW Haywood
Relative quantity Use an intrinsically cleaner process Burn gas instead of coal 1.2 1 Comparison of Station Emissions Old coal fired New gas fired CCGT Less pollutants to produce the same amount of electricity 0.8 0.6 0.4 0.2 0 Electricity supplied (TWh) CO2 SO2 NOX HCL Dust Ash Description Reduced atmos. Emissions (Assuming same electrical demand) From 1992 on, decrease in use of coal and increase in gas use
Cooking stoves Household air pollution from solid fuels is 4 th highest risk factor for disease burden worldwide (Lim et al. 2012 Lancet vol 380) Using a chimney stove can reduce exposure to household woodsmoke by half Kirk Smith et al.
Use an intrinsically cleaner process: Low-NOx burners; gas reburning (or gas recirculation); etc
End of Pipe Harmful substances to a store ORIGINAL DIRTY PROCESS Pipe POLLUTION CONTROL TECHNOLOGY Less Harmful substances to a store This will always be an added cost though may bring Reduction in pollution taxes Reduction in harmful substances to the environment
Removal: Physical, chemical or both Chemical process Physical process Convert gaseous pollutant to a solid Extract the solid using a technique for particles Physical process Physical process Dissolve the pollutant in a liquid Extract the liquid
Removing particles Baghouse (filter) system ESP: Electrostatic Precipitator Cyclones Wet vortex scrubber Baffle Chamber
Flue gas desulfurization A wet scrubber uses a limestone slurry to remove sulphur dioxide from flue gas Gypsum can be produced and marketed Common practice since turn of the century
Catalytic converters 1989 Euro 1 standard: effectively mandated fitting of 3-way catalysts to petrol vehicles (CO, Nox and NMVOCs) Reduces Nox by 80-90% Works best on hot engines, 5% fail
Some issues with vehicle emissions control Require engine to use more fuel than required otherwise Lower efficiency More emissions to capture (potentially) More carbon dioxide Can generate other pollutants Ammonia in catalytic converters Increase NO 2 emissions in diesel vehicles with particle traps Cat converters use palladium / platinum Significant increase in demand since cats mandated Environmental impacts in localities where these metal are mined
New European Driving Cycle (test cycle) Vehicles exceeded standards when tested on the road (vs test cycle) Average gaseous emissions during laboratory testing and on-road driving Weiss et al. 2012 Atmospheric Environment 62: 657-665
Trends in emissions
Cold Winters UK Miners Strike Decline of Coal Reduction heavy industry Installation of FGD
UK Growth in road transport Catalytic Converters Euro standards Economic downturn Efficiency increases Decrease in Coal Use Low NOX burners Switch to Gas
UK
Non-purely technological approaches Regulatory schemes Taxes Emissions trading ( cap and trade market-based approach) Consumer demand management Encourage people or businesses to voluntarily change behaviours (and their demand for energy use, vehicle travel, etc)
Low emission zones Vehicles that do no meet a minimum standard are restricted from entering heavy diesel vehicles Sweden, Germany, Italy, Japan, Netherlands London is the largest (2008)
Light commercial vehicles (LCVs - 60% of freight in London LEZ) became subject to LEZ requirements for the first time in 2012 % Registered LCVs not meeting LEZ requirements LONDON LEZ National / other Mean PM10 concentration decreased by 13% in LEZ vs 7% decrease outside the LEZ Ellison et al./ Transportation Research Part D (2013) 25-33
London Congestion Charging Scheme * Introduced in February 2003 (22km 2 ) * Expanded in 2006 (42km 2 ) * 5 GBP initially, 8 GBP in 2005
London Congestion Charging Scheme 18% reduction in traffic volume and 30% reduction in congestion the first year Predicted (ie modelled): 20% reduction in NOx and PM10 emissions, 0.8 µg/m3 decrease in PM10 1.7ppb decrease in NOx, 0.3ppb increase in NO2 (all attributable to the CCS) Kelly et al. 2011 HEI 155
London Congestion Charging Scheme Measurements? Kelly et al. 2011 HEI 155 12% decrease in PM10 at background site and 10 to 25 % decrease in NO, but 2 to 20% increase in NO2 at background site Difficulties in attributing changes in air pollution due to competing impacts: Weather Construction Increase in diesel-powered buses and taxis Trends outside London or the centre of London and other changes in distant sources Number and location of air quality monitors Expected reductions in air pollution concentrations from local level schemes are necessarily relatively small.
Reductions in air pollution concentrations are possible, but assessing impacts of specific interventions in the real world is not easy.
Trade-offs and co-benefits of strategies to reduce ambient air pollution
Climate change: generally (overwhelmingly) a co-benefit from strategies to reduce ambient air pollution, but there are some trade-offs
Radiative forcing of climate change during the industrial era shown by emitted components from 1750 to 2011. IPCC Climate Change 2013: the Physical Science Basis
Purely technological solutions vs demand management? (e.g. reducing vehicle trips) Reduction in vehicle use leads to reductions in non-exhaust emissions and noise Woodcock et al. (2009) Comparison of GHG emission policy scenarios in London: death per million people scenario increased active travel lower carbon emission vehicles physical activity Air pollution Traffic mortality TOTAL -528-21 +11-530 0-17 0-17 Woodcock et al. 2009 The Lancet, v3674, 9705: 1930-1943
Changes in deaths/year for transport scenarios in Barcelona scenario 20% in-city car trip reduction, all replaced by biking 20% in-out city car trip reduction, 20% replaced by biking physical activity Traffic mortality Air pollution travellers Air pollution General population* -33.73 0.08 0.57-5 -49.17-0.71 0.64-9.06 *PM2.5 % reduction 0.32 0.58 Rojas-Rueda et al. Environment International 49 (2012) 100-109
Co-benefits? Trade-offs? Climate change Biodiversity Noise Physical activity Greenspace Traffic injuries Diet Etc Reduction in efficiency Cooling agents Air pollution inhalation Traffic injuries etc
Is the current framework allowing the most efficient means to abate air pollution and promote health?