How Wildfire Smoke Is Affecting Air Quality Across North America

Wildfire season has become an increasingly “normal” part of summertime in North America, and the effects of those fires often extend far beyond the communities impacted by the flames. Smoke can travel hundreds or even thousands of miles, affecting air quality in regions far removed from the flames themselves.

That’s exactly what’s happening across multiple American states, as smoke from a recent outbreak of Canadian wildfires continues to billow toward the border. The smoke has triggered a series of air quality warnings across at least a dozen states, as residents in other areas continue to notice increased smoke.

Health officials urged residents in affected areas to limit prolonged outdoor activity as concentrations of fine particulate matter reached unhealthy levels. While the smoke is expected to shift with changing weather patterns, the event serves as another reminder of how interconnected weather, wildfire activity, and public health have become.

Smoke Traveled Hundreds of Miles Across the Border

Canada has experienced a recent increase in wildfires. While some were started by lightning strikes and unusually dry conditions, others were started by humans. Canadian authorities are investigating multiple fires across the country.

According to meteorologists, the smoke spread across portions of the Midwest, Great Lakes, Northeast, and Mid-Atlantic, with air quality alerts issued in numerous states. Some communities experienced hazy skies and reduced visibility, while others saw air quality decline into categories considered unhealthy for sensitive groups. Some areas closer to the borders have been issued air quality warnings for the general public.

Things get even harder to manage because of the wide range of factors that can influence the spread of smoke. Wind speed and direction, atmospheric conditions, and the intensity of the fires all influence how far the smoke spreads. It also influences how conditions can change over the course of a single day.

Why Wildfire Smoke Can Be Harmful

Fine particulate matter, commonly known as PM2.5, is the most notable wildfire smoke health risk. These microparticles are fine enough to penetrate deep into the lungs, and in some cases, can even get into the bloodstream. Even healthy individuals may experience eye irritation, coughing, sore throats, or shortness of breath after prolonged exposure, while people with asthma, chronic lung disease, heart conditions, older adults, and young children face a greater risk of more serious complications.

Dr. John Brownstein, who serves as the chief innovation officer at Boston Children's Hospital, told one news outlet, “Wildfire smoke is different from the pollution we typically see because it contains a complex mixture of gases and tiny particles produced by burning vegetation and other materials." He added that exposure can affect both respiratory and cardiovascular health, particularly during extended smoke events.

Air Quality Index Helps Measure the Risk

Throughout the Canadian wildfire crisis, health officials have encouraged people to monitor the air quality index (AQI) for their area. The AQI converts measurements of common air pollutants into a scale that indicates potential health risks. As the numbers rise, so does the likelihood that smoke could affect people's health.

When conditions reach the “Unhealthy for Sensitive Groups” category, older adults, children, pregnant women, and people with underlying health issues are encouraged to reduce outdoor activity. If the air quality continues to decline, officials may recommend that everyone limit prolonged time outside until conditions improve.

Weather Plays a Major Role

Wildfires may generate the smoke, but it’s the weather that ultimately decides where it travels. Strong upper-level winds can transport smoke across international borders, while temperature inversions may trap polluted air near the ground for extended periods. Rain and changing wind patterns can help disperse smoke, but prolonged dry conditions often allow wildfire activity to continue.

Meteorologists are working with health officials to track air quality conditions as weather systems move across North America. Since there are currently more than 800 wildfires in Canada, the amount of smoke flowing across the US-Canadian border has only intensified.

The amount of smoke is expected to fluctuate as weather patterns change. However, if more wildfires continue to ignite, tracking the smoke will only become more difficult.

Protecting Yourself During Smoke Events

Public health officials recommend taking several practical steps as wildfire smoke continues to pour across the border. Spending more time indoors, keeping windows closed when possible, and using high-efficiency air filters can help reduce indoor smoke exposure. People who must spend extended periods outside may benefit from wearing a properly fitted N95 respirator, which filters many of the fine particles found in wildfire smoke.

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