The assessment covers short-term effects of fine PM2.5 particles, within days of exposure. CREA separately estimates 1,750 deaths from non-fire pollution sources, bringing the September total to 5,310.
The researchers combine particle concentrations, population exposure and relationships between pollution and mortality. They do not count individually identified victims.
At the month's peak, 57.8 million people were estimated to be breathing air classified as unhealthy to hazardous. According to AFP, the government has neither confirmed nor rejected the mortality estimate.