What dangers does smoke from wildfires pose? Who is most at risk? Here are some answers to health questions often asked, especially now with fires in France and Spain.

What is in the smoke?
Fires burning vegetation generate gases and particles in the air that are dangerous to our health, notes Anses, France's health safety agency.

Fine particles are especially harmful because they can penetrate deeply into the lungs.

Carbon monoxide is one of the major pollutants released by such fires, the agency says. It also listed other chemical substances, such as carbon dioxide, volatile organic compounds including acrolein, formaldehyde and benzene.

Other pollutants can be mixed in if vehicles or buildings are consumed by flames.

Who is most at risk?
Individuals closest to a fire can display symptoms of respiratory irritation. But effects will be felt more widely among the population if wind carries the smoke over the following hours or several days later, French pulmonologist Bruno Crestani told AFP.

Especially at risk are "vulnerable persons—those who are old, who have a respiratory disease, infants or asthmatics—because this (smoke) can unbalance a situation that was previously under control," said Crestani, who heads France's Respiratory Health Foundation.

The impact is "not only respiratory," he pointed out. "These particles can enter the circulatory system" and possibly trigger diabetes, a stroke or a heart attack, he said.

Because these particles are so fine and light, they can be carried long distances and affect people well away from the fire zone.

In September 2025, the World Meteorological Organization stressed that wildfires can send a toxic mix of pollutants thousands of kilometers. It noted that, in 2024, smoke from wildfires in Canada caused air pollution as far away as Europe.