Abstract
In the context of climate change and deforestation, Brazil is facing more frequent and unprecedented wildfires. Wildfire-related PM2·5 is associated with multiple adverse health outcomes; however, the magnitude of these associations in the Brazilian context is unclear. We aimed to estimate the association between daily exposure to wildfire-related PM2·5 and cause-specific hospital admission and attributable health burden in the Brazilian population using a nationwide dataset from 2000 to 2015. In this nationwide time-series analysis, data for daily all-cause, cardiovascular, and respiratory hospital admissions were collected through the Brazilian Unified Health System from 1814 municipalities in Brazil between Jan 1, 2000, and Dec 31, 2015. Daily concentrations of wildfire-related PM2·5 were estimated using the 3D chemical transport model GEOS-Chem at a 2·0° latitude by 2·5° longitude resolution. A time-series analysis was fitted using quasi-Poisson regression to quantify municipality-specific effect estimates, which were then pooled at the regional and national levels using random-effects meta-analyses. Analyses were stratified by sex and ten age groups. The attributable fraction and attributable cases of hospital admissions due to wildfire-related PM2·5 were also calculated. At the national level, a 10 μg/m3 increase in wildfire-related PM2·5 was associated with a 1·65% (95% CI 1·51-1·80) increase in all-cause hospital admissions, a 5·09% (4·73-5·44) increase in respiratory hospital admissions, and a 1·10% (0·78-1·42) increase in cardiovascular hospital admissions, over 0-1 days after the exposure. The effect estimates for all-cause hospital admission did not vary by sex, but were particularly high in children aged 4 years or younger (4·88% [95% CI 4·47-5·28]), children aged 5-9 years (2·33% [1·77-2·90]), and people aged 80 years and older (3·70% [3·20-4·20]) compared with other age groups. We estimated that 0·53% (95% CI 0·48-0·58) of all-cause hospital admissions were attributable to wildfire-related PM2·5, corresponding to 35 cases (95% CI 32-38) per 100 000 residents annually. The attributable rate was greatest for municipalities in the north, south, and central-west regions, and lowest in the northeast region. Results were consistent for all-cause and respiratory diseases across regions, but remained inconsistent for cardiovascular diseases. Short-term exposure to wildfire-related PM2·5 was associated with increased risks of all-cause, respiratory, and cardiovascular hospital admissions, particularly among children (0-9 years) and older people (≥80 years). Greater attention should be paid to reducing exposure to wildfire smoke, particularly for the most susceptible populations. Australian Research Council and Australian National Health and Medical Research Council.
Highlights
Wildfires are a major natural hazard of great public concern worldwide.[1,2] In California in 2020, the US National Interagency Fire Center reported that 46 148 wildfires burned 8·4 million acres—about 2·1 million more acres than the 10-year average.[3]
Implications of all the available evidence The findings of our study suggest that exposure to wildfirerelated PM2·5 was significantly associated with increased respiratory, cardiovascular, and all-cause hospital admissions with greater effects for respiratory diseases
The estimated risks of hospital admission were highest during the first day of exposure and declined thereafter, with positive associations on lag 0, 1, and 2 days for all-cause hospital admissions
Summary
Wildfires are a major natural hazard of great public concern worldwide.[1,2] In California in 2020, the US National Interagency Fire Center reported that 46 148 wildfires burned 8·4 million acres—about 2·1 million more acres than the 10-year average.[3] In Australia in 2019–20, more than 27·2 million acres of bush, forest, and parks were burned[4] with billions of animals killed or displaced, and unprecedented amounts of smoke-related PM2·5 produced.[5] The Instituto Nacional de Persquisas Espaciais has monitored and identified 8·3 million acres of burned area in Brazil per complete year since 2003. A study from 2016 found that the duration of the dry season is lengthening;[10]
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