Seoul City signed an agreement with Beijing Thursday to make joint efforts in tackling air pollution, including hazardous ultrafine dust that has been increasingly affecting Northeast Asia.

The agreement, signed between Seoul Mayor Park Won-soon and his counterpart Wang Anshun during Park's one-day visit to the Chinese capital, calls for the establishment of an environmental team within a joint committee in charge of economic and cultural exchange projects.

The committee, set up by the local governments of the two neighboring countries in April of last year, held its first round of talks in October.

The two cosmopolitan cities also agreed to co-host a forum in a bid to improve air quality in Northeast Asia, which will first be held in Seoul in September, with officials and experts from both countries attending.

"The two cities will make joint efforts to improve air quality in Northeast Asia to protect health of residents in both cities," Park said in a statement.

While in Beijing, Park was to visit a Beijing observatory in charge of measuring pollutants including ultrafine dust and sulfurous acid gas, as well as to attend a forum on air quality involving officials and experts from both countries later in the day.

The Seoul government has revved up efforts to tackle the problem by strengthening its monitoring system and toughening regulations to reduce contaminant emissions, but cooperation with China is deemed necessary as westerly winds carry the smog from China to the Korean Peninsula, which is a key source of air pollution.

China regularly sees hazardous air pollution with levels of particulate matter rising to nearly 40 times the limits set by the World Health Organization during the winter months when Chinese homes and plants burn huge amounts of coal for heating.

Particulate matter refers to a combination of minute particles, both solid and liquid, that can be easily inhaled. The smog is made up of chemicals, metals and dust, among other harmful matter, according to the U.S. Environmental Protection Agency. (Yonhap)