Asthma and Summer Smog in Toronto: Staying Safe During Air Quality Alerts

How Summer Smog Triggers Asthma Flare-Ups

Ground-level ozone and fine particulate matter (PM2.5) are the two biggest culprits behind smog-related asthma attacks in Toronto. On hot, sunny days, vehicle exhaust and industrial emissions react with sunlight to produce ozone, the primary component of urban smog. When wildfire smoke drifts into southern Ontario from northern forests or even from fires across the continent, PM2.5 levels can spike dramatically. Both of these pollutants irritate and inflame your airways, making them swell, produce excess mucus, and tighten. For someone with well-controlled asthma, a bad air quality day can undo weeks of stability in a matter of hours.

The Air Quality Health Index (AQHI) is your most reliable tool here. Published by Environment and Climate Change Canada and updated hourly, the AQHI rates conditions on a scale of 1 to 10+. At a 4 or above, people with asthma or other respiratory conditions should start modifying their outdoor activities. At 7 or above, even people without a lung condition may feel the effects. You can check the AQHI for Toronto at any time through weather apps or the Ontario government website. Making this a daily habit during summer months is a small step that can prevent a trip to the emergency room.

What Your Asthma Action Plan Should Include for Poor Air Quality

Most asthma action plans are written for general flare-ups. They tell you when to increase your controller medication and when to use your rescue inhaler. But they often don't include specific guidance for environmental triggers like wildfire smoke or smog events. If your plan doesn't address what to do when the AQHI climbs above 6, it's worth getting it updated by your Nurse Practitioner before summer is in full swing.

A smog-ready action plan typically covers a few key areas. First, it should outline when to pre-treat with your rescue inhaler before going outdoors on high-AQHI days. Second, it may include a temporary step-up in your controller medication during extended poor air quality periods. Third, it should clarify the specific symptoms that mean you need to seek urgent care rather than managing at home. Your NP can tailor these recommendations based on your asthma severity, your medication history, and how your lungs have responded to past environmental triggers. At Care& Family Health, members working through Chronic Disease Management can book visits to review and update their action plan as often as needed.

Practical Steps to Reduce Your Exposure

Staying indoors with windows closed and air conditioning running is the single most effective way to reduce PM2.5 exposure during a smog advisory. If your home doesn't have central air, a portable HEPA air purifier in your bedroom can make a meaningful difference. Keep car windows up and recirculate interior air when driving. If you exercise outdoors, shift your workouts to early morning when ozone levels are typically lowest, or move them indoors entirely on advisory days. N95 or KN95 masks do filter fine particulate matter effectively if you need to be outside, but only when they form a proper seal against your face.

Medications and Seasonal Adjustments

For many people with asthma, summer isn't just about smog. It's a collision of triggers. Pollen counts peak, humidity rises, and then poor air quality stacks on top. Your healthcare provider may recommend stepping up your inhaled corticosteroid dose starting in late May or early June and continuing through September. This kind of proactive seasonal adjustment is common in asthma management, and it's far more effective than reacting after symptoms spiral.

Your rescue inhaler (typically salbutamol) should be within arm's reach on any day the AQHI reads 4 or higher. Check the expiry date now. A surprising number of people carry expired inhalers through the summer without realizing it. If you're using your rescue inhaler more than two to three times per week outside of exercise, that's a sign your asthma isn't well controlled, and your treatment plan likely needs adjustment. Leukotriene receptor antagonists like montelukast may also be considered for some patients, though Health Canada has issued an advisory about potential neuropsychiatric side effects including mood changes and sleep disturbances. Your provider can help you weigh the benefits against those risks.

If you're pregnant, breastfeeding, or planning a pregnancy, check with your healthcare provider before starting any new asthma medication or changing your current regimen. Poorly controlled asthma during pregnancy poses risks to both parent and baby, so adjustments should be made carefully rather than avoided altogether. For children with asthma, management during smog events may differ from adult protocols. A pediatric-focused assessment with your NP can ensure the right medications and doses are in place.

When to See Your Nurse Practitioner

If you've been caught off guard by a smog day more than once, or if your rescue inhaler use has been creeping up as summer settles in, it's time to get your asthma plan reviewed. Your NP can assess your current control level, adjust medications proactively, and make sure your action plan accounts for air quality triggers. You can see your family healthcare provider through OHIP if you have one, but many Torontonians don't have a family doctor at all, or can't get a timely appointment when seasonal adjustments are needed. Care& Family Health offers a Family Practice membership that includes unlimited visits with the same Nurse Practitioner, so you can revisit your asthma management as conditions change throughout the summer rather than waiting months for a single follow-up. The membership is $450+HST per year and is not covered by OHIP. You can learn more about how it works and whether it fits your needs.

Frequently Asked Questions