Filipe V. de Arruda, Ane A. C. Alencar, Newton C. Monteiro, Vera L. S. Arruda, Ana Carolina M. Pessoa, João P. F. M. Ribeiro, Marcia Macedo, Luiz Felipe M. Martenexen, Renata da Costa, Antônio Willian F. de Melo, Ray P. Alves, Wallace V. Silva, Vanessa S. Ribeiro
The analysis of air quality in the Legal Amazon in 2024-2025 shows strong inter-annual variability in exposure to fine particulate matter (PM2.5), closely associated with fire dynamics and meteorological conditions.
In 2024, the episodes were more intense and persistent, concentrated in the arc of deforestation (especially in the Acre-Rondônia-southern Amazonas corridor and northern Mato Grosso), with municipalities recording up to 138 consecutive days (≈ 139 continuous days) of exceeding the WHO threshold (PM2.5 ≥ 15 µg/m³).
In 2025, there was a significant reduction in both the extent and persistence of these events, as well as a relative shift of the hotspots to the east of the region (Pará and Maranhão). The fraction of the Legal Amazon area with PM2.5 ≥ 15 µg/m³ decreased from 13.85% (2024) to 4.03% (2025) (≈ -71%).
On a state scale, 2024 was marked by higher annual averages and greater recurrence in Rondônia, Acre, Mato Grosso and Amazonas; in 2025, Maranhão and Rondônia recorded the highest aggregate indicators.
These results reinforce the need to integrate air quality monitoring, fire prevention and public health protocols to reduce the health risks associated with smoke from fires.
