What you need to know to understand air quality warnings in Canada

Wildfires are becoming more common in Canada and that means more smoke and air quality warnings. Here’s what you need to know about air quality to better understand how it could impact your health and outdoor activities. What is the Air Quality Health Index? In Canada, the Air Quality Health Index (AQHI) is a scale developed to help people understand what the current air quality means for your health. It is an initiative among Environment Canada, Health Canada and the provincial governments. “When we look at the AQHI, it’s really an indication of the impact of the air quality on our health,” said Dr. Samantha Green, a family physician at Unity Health Toronto. The index takes into consideration three pollutants to determine the air quality. First, ground-level ozone, which is formed by photo-chemical reactions in the atmosphere. Second, particulate matter, which can be emitted by vehicles, industries and forest fires, forming a mix of particles that we can inhale. Finally, nitrogen dioxide comes from vehicle emissions and power plants that rely on fossil fuels, and this can normally be found near high-traffic roads. Those three pollutant levels contribute to how good or bad the air quality is in a certain area. How do we know when the air quality is good or bad? “The AQHI is measured in different air monitoring stations, and can provide a very accurate measurement in real time of the air quality in a particular location and it can guide us in making decisions about spending time outdoors and activity levels,” said Green. The bigger the number, the higher risk it has to your health. When the AQHI is low (1-3) or moderate (4-6), outdoor activities can continue as normal, and should only be modified if the person feels symptoms like coughing, for example. When the levels get a bit higher, between 7 and 10, it is advised to reconsider strenuous outdoor activities if you’re already experiencing symptoms. Whenever the levels get higher than 10, it is recommended that people reduce or reconsider strenuous outdoor activities, especially if they have symptoms. People at higher risk and children should reconsider outdoor activities when the level is seven and above and avoid the outdoors when the level is above 10, according to Air Quality Ontario. Who is at a higher risk? People at a higher risk of the impacts of air quality include , but are not limited to: seniors, pregnant people, children, and people with existing illnesses or health conditions, like cancer, diabetes, lung or heart conditions, and other chronic conditions. What are the possible health impacts? The immediate health impacts of poor air quality can include difficulty breathing, eye and throat irritation, cough, wheezing and chest tightness, and it can worsen any pre-existing symptoms of respiratory conditions, such as asthma. When it comes to long-term impacts, there’s still research to be done on the impact of exposure to wildfire smoke. However, preliminary results show “an impact on lung function, a slight increased risk of lung cancer, brain tumours, potential increased risk of Alzheimer’s disease and dementia, and a potential effect on childhood development and developmental disorders of childhood,” said Green. “Wildfire smoke likely has negative health impacts on all body systems and we should avoid repeated and long term exposure,” said Green. What is causing the poor air quality? On July 14, until 11 a.m., Toronto had an AQHI of 10, meaning it was better to stay indoors, while in Halifax, the AQHI was 2, an ideal air quality for outdoor activities. The poor air quality in many parts of the country, like Ontario, Manitoba and Saskatchewan, was caused mainly by the forest fires over Northern Ontario and the Prairies. Do masks filter out air pollution? “An N95 mask will filter out a large portion of the particulate matter. It’s not going to filter out those other air pollutants, like nitrogen dioxide and ozone and it’s not a long term solution,” Green said. However, a surgical mask won’t help, only an N95 worn correctly. “If someone must be outside and the AQHI is high, I would say, sure, yes, it will protect you if you wear an N95 mask,” said Green.

• Why is the air quality so bad? What to know about the health dangers of wildfire smoke
• Chris Selley: Let your kids outside, for God's sake, even if it's a bit smoky

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