BEIJING, Aug. 17 (Xinhua) -- The average density of PM2.5 in Beijing during the first seven months of this year was 55 micrograms per cubic meter, down 14.1 percent from the same period last year, local authorities said Friday.

The density of PM2.5 in July was 50 micrograms per cubic meter, down 3.8 percent from last year, according to Beijing Municipal Environmental Protection Bureau.

From February to July, the average density for PM10, sulfur dioxide, and nitrogen dioxide were 85 micrograms per cubic meter, seven micrograms per cubic meter and 40 micrograms per cubic meter, down by 9.6 percent, 30 percent and 13 percent from last year.

Car emission is currently the main source of the PM2.5 in Beijing. As of the end of July, the city removed 31,000 diesel trucks from its roads this year. A total of 548 manufacturing companies have been eliminated from the city by the end of July.?