The air quality in Seoul, which had been improving yearly since 2002, deteriorated last year due to the yellow dust storms from China.

Seoul City announced that the density of minute dust fell to 58 micrograms per cubic meter of air in 2005 from 76 micrograms in 2002, but jumped back to 60 micrograms last year.

City officials said this was due to the annual dust storms from China and marine fog in the West Sea, but noted that Seoul's air quality is improving by the year.

However, the density of minute dust in the capital remains above the nation's 50-microgram standard and well exceeds the 20-microgram mark recommended by the World Health Organization.