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How can I tell if it's smoggy?

What is the AQI?

The Air Quality Health Index, or AQHI, measures the level of health risk based on air quality. It is issued by the Ministry of the Environment, which monitors our air quality every day. The AQI evaluates the following 3 air pollutants:

  • ground-level ozone
  • nitrogen dioxide
  • fine particulate matter (particles that can be inhaled, which are less than 2.5 micrometres in diameter)

The AQHI scale ranges from 1 to 10+. Higher numbers mean higher health risks. A reading of 1 to 3 is deemed a "low" health risk, 4 to 6 a "moderate" health risk, 7 to 10 a "high" health risk, and 10 or over a "very high" health risk.

Two kinds of air quality advisories are issued. A Special Air Quality Statement (SAQS) is issued when an Air Quality Health Index value of 7 or greater is expected to last for 1 to 2 hours. A Smog and Air Health Advisory (SAHA) is issued when an Air Quality Health Index value of 7 or greater is expected to last for 3 or more hours. To learn about AQHI levels in your community, contact your provincial ministry of health or go to Environment Canada's website.

Can I tell if it is smoggy by looking outside?

Even without access to a weather report, you can easily get an idea of the air quality. Generally, the hotter the weather is, the worse the ozone smog is likely to be. Similarly, the hazier it is, the higher the concentrations of smog particles. Smog alerts often occur on sunny days without wind or rain (water washes some of the pollution out of the atmosphere). Although smog alerts occur mostly from early May to late September, they can occur at any time of the year, including the winter season.

Since air pollution can cause harm at concentrations well below smog warning levels, it is important to take action if you experience any warning signs of smog-induced health effects.

Look out for these signs:

  • breathing difficulties (especially during exercise), including shortness of breath
  • increased mucus production in the nose and throat
  • chest tightness
  • cough or throat irritation
  • eye irritation
  • light-headedness
  • low energy
  • wheezing

All material copyright MediResource Inc. 1996 – 2024. Terms and conditions of use. The contents herein are for informational purposes only. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Source:

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