Wildfires: a growing public health crisis involving oxidative stress damage caused by airborne particulates

Wildfires have been getting worse, and the trend is expected to continue. The incidences of (and total land area impacted by) wildfires have been increasing globally over the past 40 years, and fire weather conditions are expected to worsen continuously moving forward1. This sombre reality, paired with humanity’s increasing expansion into wilderness areas, has begun to overcome fire suppression capacity in many areas of the world.

At first when we think of wildfires, we think of towering flames and fast-moving brush fires, driven by a noisy wind, emitting an oily, orange glow. We look at the terrible displacement of people in the fires’ path, and the tragic loss of life that they too often leave in their destructive wake. There is, however, another mechanism by which wildfires impact the health and well-being of humans—one that is so dangerous precisely because it reaches far beyond the heat of the flames.

A fireman rushes towards a burning tree which has fallen to the ground

A firefighter rushes to put water onto a fallen tree that had recently ignited. Here, the combustive and smoke-producing potential of a single tree is demonstrated.

It comes in the form of atmospheric particulate matter emitted by the wildfire—carried off by rising heat as a cloud of smoke. A majority of these particles are very small, known as PM2.5 (Particulate Matter smaller than 2.5 μm, only 5% the diameter of a human hair), which can linger in the air for weeks and travel extremely long distances2. This allows fire emissions to impact large urban areas hundreds of miles away from their source fire, greatly increasing human exposure to damaging particulate matter.

Two pictures beside each other, the first showing clear blue sky in Seattle, and the second showing the sky filled with smoke from a wildfire