Beijing announced it will adopt the national V emissions standard, the tightest one in China, for diesel-powered vehicles this month, becoming the first city in China to adopt standards for both gasoline and diesel-powered vehicles.

It is projected that nitrogen oxide, or NOx, could drop by 40 percent in the city because of the plan. There are approximately 22,000 heavy diesel vehicles in Beijing, accounting for 50 percent of NOx and 90 percent of particulate matter in the city, two major polluters of Beijing's air.