Environmental Health

Air Quality: Research, Planning and Policy

Measuring and Modeling Traffic Related Air Pollution

Air pollution from cars is greater for those living close to busy roadways. Research shows that living close to high levels of traffic is associated with reduced lung function, increased asthma hospitalizations, asthma symptoms, bronchitis symptoms, and medical visits. The Environmental Health air quality program is attempting to assess the problem of traffic related air pollution in San Francisco in a partnership with UC Berkeley School of Public Health. The project is collecting data on traffic flows from a variety of local and state agencies as well as using aerial photographs to determine the flow of truck and heavy vehicles. This traffic volume data will be utilized to develop maps of areas of San Francisco that may be of increased risk for exposure to traffic exhaust pollutants.

To compliment data on traffic volumes, we are also monitoring particulates and nitrogen dioxide on high volume streets. Measurements will be used to validate predictive models of air pollution exposure based upon traffic analysis. Ultimately, these models will attempt to predict exposures of residents, pedestrians, and bicyclists who must use these streets on a daily basis. This data can be used to help planners and community groups understand potential exposures and craft solutions. We are especially interested in defining the distribution of diesel trucks and busses and their contribution to neighborhood diesel particulate exposures.

Planning for Better Air Quality

Significant portions of newly planned residential housing in San Francisco are being planned in or near high traffic roadways. Greater residential density and greater diversity of land uses promotes air quality and climate change objectives; however, health risks associated with proximity to vehicle traffic may also be addressed in planning.

State and local policy calls on the San Francisco to reduce the impact of traffic-related air emissions on health. The California Air Resources Board’s, “Air Quality and Land Use Handbook: A Community Health Perspective" (pdf) advises that a 300—500 foot buffer should exist between residences, schools, and day care centers and the edge of a freeway or equally busy roadway. The Air Quality Section 3.6, of the San Francisco Planning Department states that planners should locate and design buildings in a way that considers air quality impacts.

In October 2005, Environmental Health Section along with the State Department of Health Services and the Bay Area Air Quality Management District hosted a workshop to identify a range of possible strategies to mitigate air quality concerns from roadway proximity. The workshop brought regional experts working on environmental health, epidemiology, indoor and outdoor air quality, industrial hygiene, and planning and architecture. Participants identified the following strategies to address roadway-related air quality impacts:

• Land use strategies to limit residential construction in proximity to roadways as suggested in the California Air Resources Board recommendations:
• Transportation strategies to reduce or re-route road traffic from residential areas
• Traffic demand reduction measures such as congestion pricing. Building Design strategies to restrict air intake location or require windows to open only to inner courtyards and to filter air.

San Francisco Department of  has subsequently proposed a comprehensive approach to air quality assessment and mitigation for new land use development in San Francisco. The approach is described in the document--Assessment and Mitigation of Air Quality-Land Use Conflicts in Urban Infill Development. Future work in this program will focusing on developing models of traffic-related air quality for the entire City.

Additional Air Quality Information:

The California Air Resources Board web page on air quality, emissions and modeling contains detailed information on local and regional air quality throughout California. The site also has local emissions inventories by source and documentation on modeling methodologies.

The UC Berkeley School of Public Health offers a university course on health impact assessment in which students critically evaluate a local, regional, or state land use or transportation project, identifying health benefits and consequences, potential approaches to quantify or qualify how the project may affect health determinants, and recommendations for alternatives or improvements. The UC Berkeley Health Impact Assessment Group has applied air quality and health effects models to the assessment of several real world development projects including the Oak to Ninth Avenue and the Mac Arthur BART transit village.

San Francisco Department of Public Health has a partnership with the UC Berkeley School of Public Health to develop quantitative tools to predict health effects of motorized vehicle travel. The work integrates innovative GIS tools, existing data sources, and empirical research linking traffic to health outcomes, including respiratory disease, pedestrian injuries, and sleep disturbance. Envisioned tools will allow planners to predict air quality exposures of residents, pedestrians, and bicyclists who must use these streets on a daily basis. This partnership was featured in a recent update of the Center for Occupational and Environmental Health.