Local meteorological conditions exert a strong influence over day-to-day variations in air pollutant concentrations. Therefore, the meteorological fluctuations have to be removed in order for air quality planners and managers to examine underlying emissions-related trends and make better air quality management decisions for future. In this study, the meteorologically adjusted $PM_{10}$ trends in Seoul are investigated over the period $1999{sim}2006$ using Kolmogorov-Zurbenco (KZ) filter. The result indicated that meteorologicaJ variability accounts for about 25% of $PM_{10}$ variability. Both the meteorologically adjusted and unadjusted Jong-term daily $PM_{10}$ concentrations had a significant downward trends and the difference between the meteorologically adjusted and unadjusted was small. So it was assumed that in long-term daily $PM_{10}$ changes, localized changes in emissions is more important than the changes caused by meteorological conditions.