The treatment of Beijing's air pollution needs the cooperation of neighboring areas, experts said on Friday when the city reported a modest improvement in its air quality in 2012.

The report, published by the Beijing Municipal Environmental Protection Bureau, showed that the sulfur dioxide, nitrogen dioxide and inhalable particle density in the air has decreased 1.5 percent, 5.5 percent and 4.4 percent, respectively, from the previous year.

The emission load of sulfur dioxide, nitric oxide, and ammonia nitrogen has decreased 4.12 percent, 5.75 percent and 3.95 percent compared with 2011, according to the report.