Research Square · Sep 9, 2026
Interaction Effects of PM2.5 and High Temperatures on the Respiratory Health of Vulnerable Age Groups in the Brazilian Amazon
By COUTO LdOd, Schneider R, Jacobson LV et al.
In the Legal Amazon, wildfire smoke raises PM 2.5 concentrations for months. Hot weather and air pollution may aggravate respiratory diseases in vulnerable age groups in this region. The objective was to assess the effects of the interaction between PM 2.5 and heat on hospitalizations for respiratory diseases in children and adolescents (1-19 years) and on respiratory mortality in older adults (≥60 years). We conducted an ecological study with monthly data from 2009 to 2019, applying hierarchical Bayesian models integrated with distributed lag non-linear models (0-2 months lag) to estimate the delayed effects of this interaction. A positive and significant association was observed, with an immediate response in both groups. At lag 0, mortality increased by 2.5% and hospitalizations by 2.7% for each 10 µg/m³ increase in PM 2.5 under high-temperature conditions in the Amazon. These findings indicate an important risk to respiratory health in the region and reinforce the urgency of reducing biomass burning, strengthening air-quality surveillance, and increasing the resilience of the health system and the population to the current impacts of climate and air pollution.