The ratio of fine dust particles blowing from Incheon and Gyeonggi Province that surrounds Seoul, meanwhile, decreased in the same period from 18 percent to 12 percent, according to the study.

The study was conducted from May 2015 to December 2016 based on the 2013 data of air pollutant emissions released by the National Institute of Environmental Research in June last year. The previous report in 2011 was based on the 2008 data.

In terms of emission sources, the influence from traffic has decreased from 52 percent to 37 percent, while the impact from heating and electricity increased from 27 percent to 39 percent, the report said.

During the period of a fine dust advisory from Oct. 19-22, 2015, China and other foreign countries were blamed for 72 percent of the pollution in Seoul, up 17 percentage points from 55 percent recorded in ordinary times.

The report said the transfer of polluted air from China's industrial regions, such as Hebei Province or Shandong Provinces, seems to have led to the increase.

South Korea has been grappling with worsening air quality every year, as clouds of fine dust particles cover the sky with a yellow haze. They are known to cause various respiratory problems while also affecting the body's immune system.

"We will establish comprehensive measures to improve air quality," city official Hwang Bo-yeon said. "We plan to biennially conduct the study and prepare a management system to protect Seoul citizens from fine dust." (Yonhap)