The atmospheric concentration of dust particles in Seoul hit 49 micrograms per cubic meter on average last year, an all-time low since the air pollution test was started in 1995, the city government said Wednesday, indicating a steady improvement in the capital's air quality.

   The capital's dust density level has fallen for the third consecutive year after peaking at 61 micrograms per cubic meter in 2007, the Seoul Metropolitan Government said.

   Under the current air quality law, a dust density reading of 50 micrograms is recommended.

   Last year, the so-called "clean days," when the dust density level remains below 20 micrograms, totaled 44 days, up from 28 in 2006, whereas the so-called "high-density" days with over 100 micrograms was reduced to 19 from 33 in 2006, the government said.

   The municipal government said that it will further tighten emissions controls and reduce emissions of dust particles in the city in order to drop the pollution level to 45 micrograms by 2014.

   The government has replaced fuel for most city buses from diesel to compressed natural gas and is planning to expand the supply of electric and hybrid cars, as part of the clean air drive.