An intervention analysis of air quality data at Santiago, Chile

Air quality data at Santiago, Chile (PM10, PM2.5 and ozone) from 1989 to 1998 are analyzed with the goal of estimating trends in and impacts of public policies on air quality levels. Those policies, in effect since the late 1980s, have been essentially aimed at PM10 pollution abatement. The analyses show that fall and winter air quality has been improving consistently, specially the PM2.5 levels. The estimated trends for the monthly averages of PM10 concentrations range from −1.5 to −3.3% per annum, whereas the trends for monthly averages of PM2.5 concentrations range from −5 to −7% per annum. The monthly averages of ground ozone daily maxima do not have a significant trend for two of the downtown monitor sites; at the other three monitoring sites (including the one with the highest impacts) there is a clear downward trend between −5 and −3% per annum. The seasonal averages of a declimatized ozone production rate show a downward trend from 1988 through 1995, and no additional improvements have occurred thereafter. These mixed results for ground ozone levels are ascribed to a shift in the magnitude and spatial distribution of emissions in the city, and so there is a need for additional ozone abatement policies and further research on air pollution abatement options.