The following blog is a summary of the technical report recently released by the California Department of Public Health (CDPH). The full report can be found here.
Climate change linked to greenhouse gas (GHG) emissions is the preeminent public health threat of the 21st century. California is the 12th largest GHG emitter in the world, and emissions from automobiles account for 30% of its GHGs. Strategies to reduce automobile-related GHG include low carbon driving (e.g. electric cars and biofuels) and reducing vehicle miles traveled. Walking and bicycling alone or in combination with public transit (active transport) can substitute for short car trips and provide physical activity, which is known to reduce the risks of chronic diseases and obesity. Both low carbon driving and active transport also reduce air pollution from cars. Thus, both GHG-reducing strategies generate benefits to health, or what we call, co-benefits.
The California Department of Public Health (CDPH) and Bay Area transportation and air quality organizations teamed up with researchers from the London School of Hygiene and Tropical Medicine, who developed a model that helps answer the question: "How big are the health benefits or harms of active transport or low carbon driving?" This model was applied to the health and travel patterns of Bay Area residents. The model used statistical data on deaths, illness, injury and disability for major health conditions strongly linked to physical activity, traffic injuries, and air pollution. The researchers considered several travel scenarios that by 2035 would increase the daily walking and bicycling of an average Bay Area resident, as well as increase the share of electric cars and alternative fuels.
At high levels of active transport, the model predicted annually 13% fewer premature deaths and 15% fewer years of life lost for cardiovascular disease and diabetes, and 5% reductions in several other chronic diseases. After accounting for a 19% increase in the disease burden from traffic injuries to pedestrians and bicyclists, the Bay Area would still experience 2,236 fewer deaths and 22,807 years of life gained per year. By reducing air pollution, low carbon driving yielded 22 fewer deaths and a gain of 232 life years from heart and respiratory disease. Increased physical activity accounted for almost all of the potential health co-benefits. Low carbon driving was estimated to reduce GHG emissions from 9% to 33.5%.
Reducing risks from chronic disease of the magnitude suggested by this research would rank among the most notable public health achievements in the modern era. Increasing active transport and low carbon driving could reduce the estimated $34 billion annual cost in California from cardiovascular disease and other chronic diseases, and help achieve the U.S. Surgeon General's recommendation on physical activity. Measures to enhance the safety of pedestrians and bicyclists will facilitate the adoption of active transport. Together, the ambitious scenarios of active transport and low carbon driving could put California on track to meets its goals for reducing greenhouse gas emissions while making major improvements to public health.
 Maizlish NA, Woodcock JD, Co S, Ostro B, Fairley D, Fanai A. Health Co-Benefits and Transportation-Related Reductions in Greenhouse Gas Emissions in the Bay Area - Technical Report. Sacramento, CA: California Department of Public Health; Available at: http://www.cdph.ca.gov/programs/CCDPHP/ Documents/ITHIM_Technical_Report11-21-11.pdf. November 21, 2011.