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The Impact of Wildfires and Weather on Public Health in Portugal.

Thick, yellow-tinted smoke rises from a fire burning trees on a hillside beyond a couple of structures and a fire truck.

Source: GeoHealth

During the last few decades, there has been an increase in severe wildfires that have spread through forests and tundras on various continents. These fires have caused skies to turn orange and have led to air quality alerts. They often happen alongside heat waves, which are now more common, and the resulting pollution can travel through weather systems to areas far from the fire locations.

Smoke and particles from wildfires can be damaging to human health, particularly affecting the heart and lungs. Those who are elderly, pregnant, or from lower socioeconomic backgrounds are at a higher risk for these negative health effects.

Recently, de Souza Fernandes Duarte and colleagues conducted a study on the impact of wildfires, pollutants, and weather conditions on health in Portugal. This country lies in the area between subtropical and midlatitude climates and is prone to severe droughts, heat waves, and fires.

Two-panel figure showing (left) a satellite view of much of Portugal and a little of western Spain with wildfire smoke plumes and (right) a higher-resolution, false-color satellite view of a small area from the left panel showing the locations of burning wildfires and smoke.

Earlier this year, air quality in Portugal was impacted by smoke from wildfires in the western Spanish region of Extremadura. The accompanying false-color satellite image on the right provides a closer look at the fire locations. Credit for the image goes to Copernicus Sentinel-2, obtained through the Copernicus Open Access Hub.

10), and fine particles with diameters that are generally 2.5 micrometers or smaller (PM2.5)

The scientists specifically studied the connection between mortality rates and various factors such as temperature, humidity, wind speed, burned area, aerosol optical depth, and levels of carbon monoxide, nitrogen dioxide, ozone, PM10, and PM2.5.10), and PM2.5

From 2011 to 2020, the researchers observed particles from fires that covered an area of over 1,000 hectares between the months of June and October. They then analyzed how these factors (fires, pollution, and weather) impacted mortality rates for diseases related to the circulatory and respiratory systems.

They used principal component analysis to create two indices: pollutant-burning interactions (PBI), which correlated with burned area and pollutants, and atmospheric-pollutant interactions (API), which correlated with temperature, relative humidity, and ozone. The team found that cardiorespiratory deaths were highest during the hottest, driest, and most polluted months of the wildfire seasons. In addition, high temperatures, low relative humidity, and high near-surface ozone concentrations increased the overall burden of disease in exposed populations.

The authors highlight the significance of enhancing and refining measures of environmental health, such as PBI and API, in increasing public knowledge about potential health hazards and guiding public health policies. (GeoHealth,, 2023)

“I am a science writer named Sarah Derouin (@Sarah_Derouin).”

Citation: Derouin, S. (2023), How wildfires and weather affect Portugal’s public health, Eos, 104, Published on 12 October 2023.

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