Olympic sponsors have also contributed to the vision of a "Green Olympics," according to the report. All of Coca Cola's 5,658 units of Olympic coolers and vending machines will use HFC-free natural refrigerants. The Chinese home appliance giant Haier will equip the Olympic Village and the Olympic Tennis Center with solar-powered, HFC-free air conditioners.

HFCs, or hydrofluorocarbons, are among the major greenhouse gases targeted by the Kyoto Protocol.

The new environmentally friendly technologies Beijing has adopted are a "huge step" from the technologies currently used in the developing world, said Lo. "Beijing has shown that, when a concerted effort is made, change is possible."

These environmental initiatives and the investment Beijing has made in some areas far exceed those of many cities such as Sydney and Athens, the report says.

Despite its achievements, the report notes that Beijing must persist in working for a better environment. For instance, it should introduce the advanced technologies used in its Olympic venues more broadly across the city. It should also continue to tackle air pollution by strictly regulating vehicle emissions and pushing industry toward clean production.

"There are reasons for everyone to be concerned about the air quality of Beijing," Lo said. "These public concerns, when taken more positively, could be a momentum for Beijing to continue improving its air quality."

At the same time, he stressed the naked eye is not always a reliable indicator of air quality. Low visibility may result from meteorological and geological conditions as well as man-made air pollution, he said. Because Beijing's air quality is unstable and difficult to predict, it is important to look at long-term measures and yearlong averages instead of just one or two days, he added.

The Greenpeace report quotes official figures showing that Beijing's annual air quality has improved steadily since 1998.

The report concludes that the Olympic Games will leave an important environmental legacy for Beijing in such areas as transportation infrastructure, energy efficiency, renewable energy, and water and waste treatment.

Lo expects Beijing to set an example for other Chinese cities. "The lessons learned in the Beijing Olympics are vital for China to move toward sustainable development beyond 2008," he said.