Spatial Extent of Mobile Source Air Pollution

Transcription

1 Spatial Extent of Mobile Source Air Pollution Ying Zhou, Sc.D. Harvard School of Public Health Northern Transportation and Air Quality Summit Baltimore, MD August 13 1, 28 1

2 Introduction Hot spot Spatial extent How spatial extent is defined in different study types Monitoring study Modeling study GIS-based epidemiological study 2

3 Issues That Cause Variability Absolute vs. relative definition e.g. 1x1-6 risk vs. x% from reference concentration Background concentration Population vs. Individual effects Site characteristics Street canyon 3

4 Objective Determine factors that best explain variability in spatial extent Meta-analysis Simple case study Influence of the multiple factors Representative spatial extent values Street canyon case study Street canyon effect Population exposure effect 4

5 Outline Part I Factors influencing the spatial extent of mobile source air pollution Part II Impact of Urban Street Canyons on Population Exposure to Traffic-Related Primary Pollutants

6 Part I Factors influencing the spatial extent of mobile source air pollution Zhou, Y. and Levy, J. I., 27. Factors influencing the spatial extent of mobile source air pollution impacts: a meta-analysis. BMC Public Health 7: 89. 6

7 Methods Data source Peer reviewed literature 1997 to 2 Keywords related to Air pollution Spatial extent Mobile source Government reports 7

8 Methods (cont d) Pollutants CO, benzene NO x PM (including ultrafine particles) Study types Monitoring Dispersion modeling Epidemiology Land use regression Biomonitoring 8

9 Meta-analysis Variable Study type Spatial extent definition Pollutant type and background concentration Traffic count e.g. above/ below median Wind direction, wind speed Downwind/upwind/parallel, above/below median wind speed One-way and factorial ANOVA 9

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11 Factors Influencing Spatial Extent Spatial extent definition Emission rates Background concentration Meteorological condition Health risk threshold Ctotal = Ci + Cb = 2Q 2π Uσ z + Cb 11

12 Case Study Result Factor under study Spatial Extent definition Emission rate Background concentration Meteorological factor Health risk threshold Emission rate (μg/m s) 2. 1 Background concentration (μg/m 3 ).2 1 Meteorological conditions Wind speed (m/s) Stability class D D D D D D D D D D F B D D D Definition of spatial extent Comparison method Absolute Absolute Absolute Relative Relative Relative Absolute Absolute Relative Relative Absolute Absolute Absolute Absolute Absolute Threshold.2 μg/m 3.1 μg/m 3. μg/m 3 % of reference 2% of reference 1% of reference.1 μg/m 3.1 μg/m 3 % of reference % of reference.2 μg/m 3.2 μg/m 3.2 μg/m 3 2 per million cancer risk 1 per million cancer risk Estimated spatial extent (m) N/A > (beyond domain) 12

13 Part I Conclusion Spatial extent generally within a few hundred meters 1 to 4 m for EC 1 to 3 m for ultrafine particles 2 to m for NO 2 Influential factors Comparison method Threshold value Background concentration Meteorological factors Typical" values are greatly affected by influential factors 13

14 Part I Implication and Limitation Implication High-resolution modeling needed near the source for many traffic-related pollutants if individual risk is of concern Urban planning considering zone of influence Limitation Only concentration or individual risk used Total population exposure definition more relevant for benefit cost analysis Different site characteristics e.g., street canyon 14

15 Part II The Impact of Urban Street Canyons on Population Exposure to Traffic-Related Primary Pollutants Zhou, Y. and Levy, J. I., 28. The Impact of Urban Street Canyons on Population Exposure to Traffic-Related Primary Pollutants. Atmospheric Environment. 42 (13): Also in Environews, Forum: Canyons Up the Pollution Ante. Environmental Health Perspectives. 116 (7): A289. 1

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17 Objective Characterize influence of urban street canyon on population exposure to traffic pollutants Determine its implications on spatial extent from a population risk perspective 17

18 Intake Fraction (if) A measure of population exposure if = Population Intake Total Emissions 1-6 Power plant 1 - to 1-6 Mobile Source 1-3 Indoor Environmental Tobacco Smoke (ETS) 1 Cigarette smoking 18

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20 Pollutants and Street configuration Primary pollutants only Conservative pollutants CO, PM 2., PM 1 Reactive pollutants NO, NO 2 Ultrafine particles Population groups Residents, Daytime workers, Pedestrians, Bikers, Drivers 2

21 Average Diurnal Traffic 1 Traffic Count (vehicles/hour) All vehicles Cars Trucks Hour of Day 21

22 OSPM Model (Operational Street Pollution Model) 22

23 Results if by Population group by pollutant Population Group CO NO x PM 2. PM 1 Particle number Pedestrians Bikers Drivers Residents (night) Workers (day) Total if

24 Part II Conclusion if for traffic pollutants from urban street canyons on the order of 1-3 Although limited in spatial extent Pedestrians and daytime office workers contribute most to if together >8% Traffic exposure from street canyon sensitive to street configuration 24

25 Overall Conclusion Spatial extent generally within a few hundred meters Highly influenced by major factors Comparison method, threshold value, background concentration, meteorological condition Although limited in spatial extent, if from urban street canyons on the order of 1-3 Need high resolution modeling near the mobile source 2

26 Acknowledgement Jonathan I. Levy Gilbert and Ildiko Butler Foundation Environmental Defense 26