Indicator ES.4.a Proportion of households living within potential traffic-related air quality hazard area

ES.4.a Proportion of households living within potential traffic-related air quality hazard area

Download PDF map.

Data Source

Map prepared by City and County of San Francisco, Department of Public Health, Environmental Health Section using ArcGIS software. Field measurements were combined with use of models USEPA’s  CAL3QHCR Line Source Dispersion Model and CARB’s vehicle emissions model were to estimate air pollution concentrations.

Table data is presented by planning neighborhood. While planning neighborhoods are larger geographic areas than census tracts, census tracts do not always lie completely within a planning neighborhood. SFDPH used ArcGIS software and a 'centroids within' methodology to convert census blocks to geographic mean center points. We then assigned census blocks to planning neighborhoods based on the spatial location of those geographic mean center points and calculated the planning neighborhood totals for the table. Detailed information regarding geographic units of analysis, their definitions, and their boundaries can be found in the HDMT at the following links:

http://www.thehdmt.org/etc/Geographic_Units_of_Analysis.September_2009.pdf

http://www.thehdmt.org/data_map_methods.php

Explanation and Limitations

The above map was created by SFDPH using the California Air Resources Board’s, EMFAC 2007 vehicle emissions model and the USEPA approved CAL3QHCR Line Source Dispersion Model to model PM 2.5 exposures. CAL3QHCR is a Gaussian dispersion model which estimates air pollution concentrations based on physical characteristics of emissions, meteorology, topography, and receptor horizontal and vertical location. The map show potential roadway exposure zone, which means those areas within the City and County of San Francisco which, by virtue of their proximity to freeways and major roadways, may exhibit high PM 2.5 concentration attributable to Local Roadway Traffic Sources.

In June 2008, San Francisco Supervisor Tom Ammiano proposed a new ordinance requiring public agencies take regulatory action to prevent future air quality health impacts from new sensitive uses proposed near busy roadways. The regulation requires that developers screen sensitive use projects for proximity to traffic and calculate the concentration of PM 2.5 from traffic sources where traffic volumes suggest a potential hazard. If modeled levels of traffic-attributable PM 2.5 at a project site exceed an action level (currently set at 0.2 ug/m3) developers would be required to incorporate ventilation systems to remove 80% of PM2.5 from outdoor air. The regulation would not place any requirements on proposed sensitive uses if modeled air pollutant levels fall below the action threshold.
 
The San Francisco Health Code, Article 31- Hunter's Point Shipyard ordinance is designed to protect human health and safety and the environment at the former Hunters Point Shipyard during and after development and to facilitate redevelopment as envisioned in the Hunters Point Shipyard Redevelopment Plan, which the Board of Supervisors adopted in 1997, and its Environmental Impact Report.

The San Francisco Health Code, Article 22.B - Construction Dust Control Requirements apply to any site preparation or construction activities taking place within the City and County of San Francisco that has the potential to create dust or that will expose or disturb soil. Applicants for projects over a half acre in size shall submit a map showing the location of the project and clearly identifying all surrounding sensitive receptors and particularly noting those within 1,000 feet of the project. The Director of Health shall review this map and any other information available to the Director to verify compliance with this submittal requirement. If no sensitive receptors are determined to be within 1,000 feet of the project, then the Director of Health may issue a waiver to the Applicant that specifies that the project is not required to have a site-specific dust control plan.

Vehicle emissions are not the same as exposures to air pollution. While traffic volumes are proportional to air pollutant emissions, it is the exposure to emissions that matters for health. The proximity to busy roadways is only rough measure of exposure and potential health hazards. Weather, wind, geography, and buildings all affect how vehicle emissions are dispersed and their resulting concentrations in the air. Dispersion modeling can help estimate airborne concentrations of pollutants from vehicle sources.

The importance of the exposure to health risk also depends on the combination of multiple air pollutants, the relative toxicity of the pollutants, and many other factors." For more information, visit: http://www.arb.ca.gov/ch/chapis1/chapis1.htm Exposure also varies depending on the activities of the exposed individual.

Why is this a Community Health Indicator?

Epidemiologic studies have consistently found that proximity to high traffic density or flow results in reduced lung function and increased asthma hospitalizations, asthma symptoms, bronchitis symptoms, and medical visits.b Children appear to be the most sensitive to adverse effects. California freeway studies show about exposure levels approach background levels after a distance of 500 feet.a Specific epidemiologic research findings include:

Motor vehicle emissions, power plants, and refineries are the predominant sources of fine particulate air pollution (PM2.5). Several large-scale studies demonstrate that increased exposure to PM2.5 is associated with detrimental cardiovascular outcomes, including increased risk of death from ischemic heart disease, higher blood pressure, and coronary artery calcification.h

According to a prospective study of 3399 participants in Germany, living within 150m of major roads is associated with an increased risk of coronary heart disease over time even after adjusting for individual risk factors and background air pollution.i

  1. California Air Resources Board. Air Quality and Land Use Handbook: A Community Health Perspective. 2005. Accessed at: http://www.arb.ca.gov/ch/landuse.htm
  2. Brauer M, Hoek G, Van Vliet P, et al. Air pollution from traffic and the development of respiratory infections and asthmatic and allergic symptoms in children. American Journal of Respiratory and Critical Care Medicine. 2002;166:1092-1098.
  3. Brunekreef B, Janssen NA, de Hartog J, Harssema H, Knape M, van Vliet P. Air pollution from truck traffic and lung function in children living near motorways. Epidemiology. 1997;8:298-303.
  4. Lin S, Munsie JP, Hwang SA, Fitzgerald E, Cayo MR. Childhood asthma hospitalization and residential exposure to state route traffic. Environ Res. 2002;88:73-81.
  5. Venn A, Lewis SA, Cooper M, Hubbard R, Britton J. Living near a main road and the risk of wheezing illness in children. American Journal of Respiratory and Critical Care Medicine. 2001;164:2177-2180.

  6. Kim JJ, Smorodinsky S, Lipsett M, Singer BC, Hodgson AT, Ostro B. Traffic-related air pollution and respiratory health: East Bay Children's Respiratory Health Study. American Journal of Respiratory and Critical Care Medicine. 2004;170: 520-526.

  7. English P, Neutra R, Scalf R, Sullivan M, Waller L, Zhu L. Examining Associations Between Childhood Asthma and Traffic Flow Using a Geographic Information System. Environmental Health Perspectives. 1999;107(9):761-767.

  8. Simkhovich BZ, Kleinman MT, Kloner RA. Air Pollution and Cardiovascular Injury: Epidemiology, Toxicology, and Mechanisms. J Am Coll Cardiol. 2008;52(9):719-26.

  9. Hoffmann B, Moebus S, Stang A, et al. Residence close to high traffic and prevalence of coronary heart disease. Eur Heart J. 2006;27(22):2696-2702.