This summer, Canada is experiencing a severe wildfire season that has forced thousands of people from their homes across a number of provinces. Earlier in June, weather conditions caused a haze of smoke to sweep across Canada and the Eastern United States. Now, more wildfire smoke is again clouding the skies, making air quality unhealthy in several states. In fact, Chicago, Detroit and New York have all experienced Air Quality Index (AQI) levels that were among the highest in the world at the time due to particle pollution from the smoke.

In addition, hot summer temperatures can add to the air quality problem. This is because heat and stagnant air during a heat wave can lead to ground level ozone pollution to build up. Climate change is leading both to more particle pollution from wildfire smoke and to more ozone pollution as well as more days with extreme heat.

Unhealthy air quality can be scary, but the Air Quality Index is a valuable tool to help you stay safe. Here is some essential information to help you use it.

What is Air Quality Index (AQI)?

The AQI is a rating system that shows the severity of pollution in the air on a scale from 0 to 500. It’s a complex calculation that is administered by the U.S. Environmental Protection Agency. The rating is created by measuring five major pollutants: ground-level ozone, particulate matter (PM2.5), carbon monoxide, nitrogen dioxide and sulfur dioxide. Ground-level ozone and particulate matter, or particle pollution, are the two air pollutants that are most widespread and pose the greatest risk to our health. Those measurements are then calculated into the 0-500 scale to give you one number that reflects how healthy the air is to breathe that day. Particle pollution from wildfire smoke is driving the high AQIs experienced by Chicago, New York City, and so many other cities this summer.

What is considered good and bad AQI?

An AQI under 50 is considered good air quality, meaning that it is safe for everyone to spend time outdoors without posing a risk to their health. As the AQI number increases however, so does the risk to health. An AQI over 300 is considered hazardous. Consult the chart below for more in-depth explanations:

Daily AQI ColorLevels of ConcernValues of indexDescription of Air Quality 
Green
Good
0 to 50Air quality is satisfactory, and air pollution poses little to no risk.
Yellow
Moderate
51 to 100Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.
Orange
Unhealthy for Sensitive groups
101 to 150Members of sensitive groups may experience health effects. The general public is less likely to be affected.
Red
Unhealthy
151 to 200 Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.
Purple
Very Unhealthy
201 to 300Health alert: The risk of health effects is increased for everyone.
Maroon
Hazardous
300 or higher
Health warning of emergency conditions: everyone is more likely to be affected.

Who is considered in a sensitive group?

High risk groups include children under 18, the elderly, people with chronic heart or lung disease, pregnant people, and people with diabetes. Adults who are active outdoors, including outdoor workers and avid exercisers, can be considered at higher risk as well because of prolonged exposure. All these groups are most likely to be the first to experience the effects of ozone and particle pollution, so they need to take extra steps to protect themselves from harm.

Contact your healthcare provider if:

Symptoms such as coughing, sneezing, itchy or watery eyes, runny nose, sore throat, headaches, extreme fatigue, shortness of breathe or any difficulty breathing may signal a more serious problem.

What can you do to stay safe from poor air quality?

Air pollution can threaten anyone's health, so stay up to date on the AQI in your area. AQI forecasts and real-time information can be found on EPA’s AirNow Website. AQI values at or below 100 are generally thought of as satisfactory but be aware of how you feel and take steps to help protect yourself whenever needed. 

On days when the air quality is orange, red, purple or maroon:

  1. Reduce the time you spend outdoors to under 30 minutes when AQI is high. Also, reduce the intensity of outdoor activity. According to the EPA, the chances of being affected by unhealthy levels of air pollution increase the longer a person is active outdoors and the more strenuous the activity. 
  2. If you must go outdoors, consider wearing a mask. Unfortunately, not all masks are created equal when it comes to particle pollution as a cloth or dust mask are not able to filter out the fine particles. However, well-fitted N95 or KN95 masks have better filtration capabilities and may be beneficial during high AQI days.
  3. Keep your air indoors healthy by keeping the windows and doors closed. Run the air conditioning on the recirculate setting, use a portable HEPA air cleaner or, in severe circumstances, creating a clean room.

Check out other clean air resources on our website.

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