5 August 2009

Study confirms improved air quality during Beijing Olympics

The air in Beijing during the 2008 Olympics was cleaner than the previous year’s, due to aggressive efforts by the Chinese government to curtail traffic, increase emissions standards, and halt construction in preparation for the games.

A Cornell study led by Max Zhang, assistant professor of mechanical and aerospace engineering, indicates such measures as regulating traffic density and encouraging public transportation can have a significant impact on local air quality.

Leading up to the Olympics, the Chinese government barred more than 300,000 heavy-emission vehicles—mostly trucks—from the roads. The city also implemented rules in which only some people could drive on certain days based on their license plate numbers.

The result was to eliminate 2 million vehicles from the roads. Other mandates involved halting construction and decreasing the use of coal in favor of natural gas for electricity.

Among the researchers’ conclusions: Black carbon pollution is significantly greater at ground level than at higher elevations, and diesel trucks are a major source of black carbon emission during the summer in Beijing. These particles are harmful to the lungs, and they are a global warming compound.

The researchers found car emissions of black carbon were down 33% in 2008 compared with their 2007 readings. Carbon dioxide decreased 47%, and ultrafine carbon-based particles—those that measure less than 100 nanometers—decreased 78%.

The U.S. Environmental Protection Agency and Cornell’s Jeffrey Sean Lehman Fund for Scholarly Exchange with China funded the study.

For related information, go to www.isa.org/environmental.