An intervention analysis of air quality data at Santiago, Chile

Air quality data at Santiago, Chile (PM10, PM2.5 and ozone) from 1989 to 19 98 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 1 980s, have been essentially aimed at PM10 pollution abatement. The analyses show that fall and winter air quality has been improving consistently, spe cially the PM2.5 levels. The estimated trends for the monthly averages of P M10 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 an num. The monthly averages of ground ozone daily maxima do not have a signif icant trend for two of the downtown monitor sites; at the other three monit oring sites (including the one with the highest impacts) there is a clear d ownward trend between - 5 and - 3% per annum. The seasonal averages of a de climatized ozone production rate show a downward trend from 1988 through 19 95, and no additional improvements have occurred thereafter. These mixed re sults 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 a dditional ozone abatement policies and further research on air pollution ab atement options. (C) 2000 Elsevier Science Ltd. All rights reserved.