It’s Not Only Outdoor Pollution That Can Be Harmful

Surprisingly, the indoor air quality of our homes may be more hazardous than the air outside. Here’s how to make sure your indoor space is healthy.

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Improve air quality - cooking with gasLeka Sergeeva /

How to Improve Indoor Air Quality at Home

Ventilate when using gas stoves

More than six million Canadians use natural gas for cooking, heating and electricity. But experts have recently raised concerns about the impact gas stoves can have on indoor air quality: Unlike electric and induction types, gas stoves give off nitrogen dioxide (NO2) when ignited—and often at levels that exceed the safety limit set by the World Health Organization.

The NO2 can cause coughing and wheezing, and people with asthma and chronic obstructive pulmonary disease may experience inflamed airways as well. A 2023 study published in the International Journal of Environmental Research and Public Health found that in the U.S., where two out of five homes use gas stoves, 12.7 percent of childhood asthma cases can be attributed to their use in the home.

To protect your indoor air quality, turn on the extractor fan every time you cook; they’re designed to remove smoke, grease and pollutants that are released during cooking. But less than 20 percent of people use them consistently, says Brady Seals, a co-author of the study and a manager with the environmental think tank RMI in Colorado. “Use the back burners, as they’re closer to the exhaust intake, and open a window—even for just five minutes.”

Indoor air quality - VOC paint rolleririn-k /

Avoid Volatile Organic Compounds (VOCs)

VOCs, including benzene and formaldehyde, are sometimes found in household items like paint, carpeting and detergents. While most VOCs do not pose a significant health risk, a 2005 study published in the Journal of Occupational Health found prolonged, concentrated exposure in workplaces—such as industrial factories or nail salons—to be associated with cancer, liver damage and neurological problems.

To reduce your exposure, choose paint and furnishings that are certified as low or no VOC. When using cleaning products, especially those containing bleach, ventilation is key, says Trevor VandenBoer, an environmental-chemistry researcher at York University in Toronto. “Use an exhaust fan, open a window and give the room time to air out—ideally an hour.”

Many VOCs stick to other particles, such as dust, skin flakes and lint, so VandenBoer recommends an activated carbon filter air purifier. Make sure it can capture particulates less than 2.5 microns in diameter (about one-30th the width of a human hair) because that’s the size that can be inhaled deep into your lungs. And vacuum often with a high-efficiency particulate air (HEPA) filter that traps small particles.

Radon Detector

Use a radon detector

An invisible, odourless gas that comes from the breakdown of uranium in soil, radon leaches into the home from cracks and construction joints in the foundation (whether you have a basement or not) and can waft up several levels. Inhaling high levels of radon, especially over many years, can cause malignant cell growth in the lungs, making radon one of the leading causes of lung cancer worldwide. In Canada, it’s second only to cigarette smoke.

Experts say a radon test kit (above) should be as essential as smoke and carbon monoxide alarms. This hockey puck-shaped item, called a dosimeter, must be placed in your home’s lowest occupied level for at least three months since radon levels can vary daily. If your dosimeter indicates unsafe levels (more than 200 bq/m³), a radon-mitigation expert can fix the problem by installing a ventilation pipe in your home’s foundation.

Bathroom fan - thumbs uptab62 /

Combat mould growth

Common household moulds like aspergillus, penicillium and cladosporium are present in 13 percent of Canadian homes. They’re mostly harmless, but when damp indoor conditions encourage growth, they can release dust-like spores into the air. This can trigger allergic reactions, leading to eye, nose and throat irritation, sneezing, coughing and even asthma attacks.

Patches of black or green specks can appear on walls, tile or ceilings, along with a musty odour. Small patches can be cleaned with white vinegar or dish detergent, but if the affected area is larger than a bath towel, call a mould-removal specialist. Mould hides inside the walls, where it’s not always visible, so it’s best to mitigate the growth.

As a habit, turn on an exhaust fan in the bathroom and run a dehumidifier to keep humidity levels below 50 percent. Most dehumidifiers have a built-in hygrometer that measures the air’s humidity; home-humidity meters are also widely available.

Now that you know how to improve indoor air quality, check out our ultimate healthy home checklist.

Reader's Digest Canada
Originally Published in Reader's Digest Canada