Research

Human-caused fires in the Amazon are a major source of fine-particulate pollution. We ask whether it reaches Brazil's South and Southeast, more than 1,000 km downwind, and harms health there. An atmospheric-transport model traces fire emissions to their destinations and condenses them into a single fire-attributable PM2.5 index. Ground monitors confirm the index captures real airborne particulate: a one-standard-deviation rise in predicted exposure lifts measured PM2.5 by 0.055 and PM10 by 0.030 standard deviations, while pollutants unrelated to fire register nothing. That exposure produces an acute respiratory response. Admissions rise about half a percent per standard deviation, concentrated on the dry days when rain does not scavenge the plume, with clean placebos.