Air quality and human health improvements from reductions in deforestation-related fire in Brazil

Roughly 15% of the Brazilian Amazon was deforested between 1976 and 2010. Fire is the dominant method through which forests and vegetation are cleared. Fires emit large quantities of particulate matter into the atmosphere, which degrades air quality and affects human health. Since 2004, Brazil has achieved substantial reductions in deforestation rates and associated deforestation fires. Here we assess the impact of this reduction on air quality and human health during non-drought years between 2001 and 2012. We analyse aerosol optical depth measurements obtained with satellite and ground-based sensors over southwest Brazil and Bolivia for the dry season, from August to October. We find that observed dry season aerosol optical depths are more than a factor of two lower in years with low deforestation rates in Brazil. We used a global aerosol model to show that reductions in fires associated with deforestation have caused mean surface particulate matter concentrations to decline by ~30% during the dry season in the region. Using particulate matter concentration response functions from the epidemiological literature, we estimate that this reduction in particulate matter may be preventing roughly 400 to 1,700 premature adult deaths annually across South America.