As thick smoke from climate-change driven wildfires continues to spread across parts of Canada and the United States, public health officials are urging people not to underestimate the health risks posed by poor air quality, even if the flames are hundreds of miles away.
Several cities have hazardous levels of smoke
At 8am on Wednesday, Detroit was the most polluted major city in the world with an air quality index rating of 518, well over the 300 rating considered to be hazardous to health according to the tracking website IQAir. Toronto and Minneapolis rounded up the top three and were all considered hazardous, while Chicago ranked as “very unhealthy” in spot four.
Wildfire smoke contains a complex mixture of gases and microscopic particles produced by burning trees, vegetation, buildings and other materials. The greatest concern is fine particulate matter, known as PM2.5, which is small enough to travel deep into the lungs and enter the bloodstream.
Exposure to wildfire smoke has been linked to worsening asthma and chronic obstructive pulmonary disease (COPD), while also increasing the risk of cardiovascular events including heart attacks and strokes. People may notice burning eyes, coughing, sore throats, headaches and fatigue after spending time outdoors when smoke levels are high. Chronic exposure to wildfire smoke increases the risk of developing several types of cancer.
As climate change contributes to longer and more intense wildfire seasons, smoke has become an increasingly common public health hazard across North America. So what can you do to protect yourself?
Monitor air quality where you are
One of the most important steps people can take is to monitor local air quality before heading outside. Air quality forecasts provide an indication of how much particulate pollution is in the air and whether it is safe to exercise or spend extended periods outdoors. When air quality reaches unhealthy levels, experts recommend limiting outdoor activity, particularly vigorous exercise, which increases the amount of polluted air inhaled.
Stay indoors whenever possible and clean the air
Staying indoors can significantly reduce exposure, but only if the indoor air is relatively clean. Keeping windows and doors closed, running air conditioning on recirculation mode and using portable HEPA air purifiers can substantially lower indoor concentrations of smoke particles. Homes with central heating or cooling systems may also benefit from high-efficiency furnace filters designed to capture fine particulates.
Wear a respirator
For people who cannot avoid being outside, masks are recommended, but not all masks offer the same level of protection. Cloth masks and standard surgical masks, which became familiar during the Covid-19 pandemic, do little to filter the tiny particles found in wildfire smoke. Instead, public health agencies like the CDC recommend wearing a well-fitting N95, KN95 or equivalent particulate respirator certified by NIOSH. These masks are designed to filter at least 95% of airborne particles when they form a tight seal around the face. Medical staff working in high risk environments like with patients with dangerous infectious diseases typically wear these respirators.
But respirators only work if they fit properly. Gaps around the cheeks or nose, or facial hair that interferes with the seal, can substantially reduce protection. Several different sizes and brands are available as they are not typically one-size fits all. Respirators are also not recommended for everyone. Young children often cannot achieve an effective fit, and some people with significant heart or lung disease may find them difficult to wear for prolonged periods.
While wearing a properly fitted respirator can reduce exposure outdoors, experts stress that masks should not be viewed as a substitute for avoiding smoke altogether. The most effective protection remains reducing time spent outside, improving indoor air quality and paying close attention to air quality alerts.
With wildfire smoke now affecting communities far away from fires, N95 respirators and air purifiers may become an increasingly routine part of preparing for summer in areas of the U.S. and Canada.
