Compact development reduces regional air pollution, may harm local health

Daniel Rodriguez
Daniel Rodriguez

An analysis by a team of UNC-Chapel Hill and NC State environmental and planning researchers concludes that densely populated regions with compact urban development that discourages commuting by car — widely touted as a way to increase public exercise and reduce harmful automobile emissions — may only slightly lower average regional particulate matter (PM) concentrations in the air.

However, such development could raise the risk of adverse health effects and mortality by 39 percent because the clustering of individuals in high PM areas increases exposure. In contrast, sprawling or suburban development may lower the risk of ultrafine PM-related deaths by 33 percent.

Researchers say when transportation and urban planners evaluate alternative infrastructure investments and policies, they may need to account for health effects from local air quality, a consideration that warrants further planning to avoid negative outcomes, according to the researchers.

In a first-of-its-kind study, Theodore J. Mansfield, Daniel A. Rodriguez and Jacqueline MacDonald Gibson from UNC and Joseph Huegy from NC State linked a transportation demand model used by regional planners to health risk models. Their paper, “The Effects of Urban Form on Ambient Air Pollution and Public Health Risk: A Case Study in Raleigh, North Carolina,” was recently posted electronically in the journal Risk Analysis, published by the Society for Risk Analysis. Rodriguez is Distinguished Professor of Sustainable Community Design in the city and regional planning department of UNC’s College of Arts and Sciences; Mansfield and Gibson are from the UNC Gillings School of Global Public Health.

The researchers examined three alternative land development scenarios for the Raleigh-Durham-Chapel Hill area of North Carolina.

Using linked models, they analyzed the annual average ultrafine PM concentrations in the region’s air under each scenario and the related health effects. The first scenario was a base case that used 2010 data for the region, with several dense urban core areas but also generally dispersed development. The second was compact development, based on possible land use distribution in the region if authorities had implemented growth management and land conservation policies, such as density incentives and urban growth boundaries. The third was Increased sprawl, based on typical post-1950’s urban development policies in the United States that supported decentralization and suburbs.

Read more about the study.