Abstract

Airborne particulate matter (PM) has been recognized as a major anthropogenic pollutant and health hazard, in particular in urban settings. Large urban centers routinely monitor PM10 and PM2.5 levels and implement pollution abatement policies and measures to reduce population exposure. However, respirable PM monitoring has only been performed in the past 2-3 decades. PM10 concentrations in Santiago, Chile have been measured in air filters since 1988. We collected tree samples from a park in central Santiago and measured elemental concentrations in tree rings from 1930 to 2008 and use these data to reconstruct PM10 variability before monitoring started. We train regression models in the time span from 1989 to 2008 and reconstruct PM10 levels since 1930. We show that PM10 levels remained generally high since 1930 and started to fall only since the mid-1990s when democracy was restored and the government started implementing various decontamination plans. This is the first time air quality data has been reconstructed from tree rings. This method may allow the reconstruction of decades to centuries of air quality variability for many urban centers.