Wildfire Smoke

Wildfire smoke contains small particles that cause health concerns. When wildfires are large or long in duration, the resulting smoke can travel across countries, states, and countries.

Wildfires, like those that burned across Canada and the Western United States during the summer of 2023, can lead to large amounts of smoke that lowers air quality. When wildfires are large, the resulting smoke can be carried by air currents across large distances. If wildfires are not brought under control, air quality can remain poor and even dangerous for weeks or months.

Smoke released from wildfires contains small particles from burnt vegetation. These particulates are the main cause of haze, or reduced visibility; these particles also cause health risks.

Small particles, called PM2.5, pose the greatest risk. These particles are four times smaller than dust and pollen or 30 times smaller than the width of an average human hair. PM stands for particulate matter, while 2.5 refers to the size of the particles in microns (represented as µm).

These small airborne particles are bad for human health because they penetrate deep into lung tissue and enter the circulatory system. Breathing in high levels of PM2.5 increases the risk of heart disease, asthma, and other health problems.

Wildfire smoke also contains larger particulate matter (called PM10); these larger particulates are what irritates the eyes, nose, and throat.

During wildfire events, exposure to wildfire smoke is an important health consideration. Wildfire smoke-related health risks are measured and reported in terms of air quality, measured by detection of levels of PM2.5 in the air. You can see current wildfire-related PM2.5 levels in your area by visiting the FireAirNow Website.