What is in the smoke?

The smoke from a fire contains gas and particles that are hazardous to our health, according to Anses, France's health safety agency. Fine particles are particularly harmful as they can reach deep into the lungs. Carbon monoxide is one of the primary pollutants emitted by burning vegetation, alongside carbon dioxide and volatile organic compounds like acrolein, formaldehyde, and benzene. If buildings or vehicles burn, additional contaminants may be mixed into the smoke.

Individuals in close proximity to a fire may experience respiratory irritation, but the effects can also be felt more broadly in the population if the smoke is carried by wind over several hours or days. French pulmonologist Bruno Crestani warns that vulnerable groups such as the elderly, those with respiratory diseases, infants, and asthmatics are at higher risk, as these particles can disrupt conditions that were previously manageable.

The impact of wildfire smoke extends beyond the respiratory system. These fine particles can enter the circulatory system, potentially leading to diabetes, strokes, or heart attacks. Due to their size and lightness, these particles can travel long distances, affecting areas far removed from the fire. Last September, the World Meteorological Organisation highlighted that wildfires can disseminate a toxic mix of pollutants across thousands of kilometers, citing smoke from Canadian wildfires in 2024 that impacted air quality in Europe.

In its annual health risks report, The Lancet estimated that exposure to wildfire smoke caused approximately 154,000 deaths worldwide in 2023, primarily due to fine particulate matter. For France, the charity Oxfam estimated that about 2,800 early deaths annually result from air pollution linked to wildfires. Crestani emphasizes the importance of considering long-term effects on the entire population, not just vulnerable individuals.