Before 2008, concentrations of air pollutants in the city of Beijing, China, site of the 2008 Olympic Games, far exceeded acceptable standards, which caused serious concerns in the international community about the health and performance of Olympic athletes. To ensure acceptable air quality during the Olympics (held from August 8-24) and the Paralympics (held from September 6-16), the Chinese government launched a series of aggressive measures to reduce pollutant emissions.1- 3 To reduce industrial emissions, the operations of combustion facilities were restricted in smelters, cement plants, power plants, nonattainment boilers, and construction and petro-chemical industries. To reduce traffic emissions, certain vehicles and trucks were banned, 70% of government-owned vehicles were kept off the streets, and other vehicles could travel through the city only on alternating days.3