Air pollution results in over 7 million deaths each year. In this episode of Possibly, we look at the most common way to measure air quality, the Air Quality Index, and what it means for you.
Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall.
If you take a look at your weather app and scroll down, you’ll usually see a number for the day’s air quality. But what does that number mean? And where does it come from?
We had Hamid Torabzadeh and Iman Khanbhai from our Possibly Team look into this question.
Hamid Torabzadeh: Hi, Megan!
Iman Khanbhai: Hello!
Megan Hall: Ok, I know that when there’s a big forest fire, the air outside isn’t safe to breathe. You can see it. But there are other times, like during the summer, when there’s an “air quality” alert, the sky looks normal to me. So, what is air quality really measuring?
Hamid Torabzadeh: To find out, we talked to Cory Zigler, a Professor of Biostatistics at the Brown University School of Public Health. He says changes to air quality can show up in a couple of ways:
Cory Zigler: Usually when people are talking about air quality, it could be something they smell. It could be something they see. It could be something that they neither smell nor see but they’re breathing in.”
Megan Hall: So what exactly is in this air?
Iman Khanbhai: There are a lot of substances that get released into the air that make outdoor air quality worse.
Megan: What are they?
Hamid Torabzadeh: A lot of them come from burning stuff. You have tiny little particles that come from wildfires and the colorless gas that comes from burning things like coal.
Iman Khanbhai: Other harmful toxins come from burning things like the gasoline in cars.
Hamid Torabzadeh: And then, when all of those sources of air pollution react with sunlight, they can create smog.
Megan Hall: So, how bad is our air quality in general?
Iman Khanbhai: Not great.
Hamid Torabzadeh: According to the American Lung Association’s “State of the Air” 2024 report, nearly 40% of Americans live in places with unhealthy levels of air pollution.
Iman Khanbhai: And Cory says because of the way the wind blows, you can be affected by bad air quality even if you don’t live near a raging forest fire or a factory that’s burning coal.
Cory Zigler: “It could come from anywhere. It could come from a car’s tailpipe. It could come from a power plant that’s 400 miles away. It could come from a wildfire that’s 400 miles away.”
Megan Hall: But how do we actually measure the quality of our air?
Hamid Torabzadeh: Cory says the Environmental Protection Agency starts by measuring the composition of samples of air.
Cory Zigler: “Literally little machines or monitoring stations out spread across the country that are measuring exactly what is in the air at that location.”
Iman Khanbhai: There are over 5,000 of these monitors running all across the country.
Hamid Torabzadeh: The EPA then takes the data from these monitors to create the Air Quality Index, or AQI.
Iman Khanbhai: That’s the number you see on your weather app or on TV.
Megan Hall: Got it. And what does the AQI include?
Hamid Torabzadeh: It takes data on five major types of pollutants and merges them into one number, ranging from zero to 500.
Megan Hall: And so AQI is telling us how much of those pollutants are in the air?
Iman Khanbhai: Yeah exactly. And the higher the number, the worse the air quality.
Hamid Torabzadeh: There is also something special about the number 100.
Iman Khanbhai: When air quality reaches 100, the EPA considers that air to be unhealthy for certain sensitive groups of people, like those with lung disease, or even older adults and children.
Megan Hall: Got it. But what do we do when that number reaches 100?
Hamid Torabzadeh: Good question. Cory has some advice:
Cory Zigler: You see things like people wearing masks when they’re outside, or avoiding outdoor activities. That can be particularly important if people have some other type of health condition, respiratory condition, something like this. People with asthma, for example.
Iman Khanbhai: If you are especially worried about your air quality, you can also take some other steps, like buying an air purifier for your home.
Hamid Torabzadeh: The main takeaway: use the AQI to get a general idea of the air quality around you. And if you are especially worried, take whichever step makes sense for you.
Megan Hall: Got it! Thanks, Hamid and Iman!
That’s it for today. You can find more information, or ask a question about the way your choices affect our planet, at askpossibly.org. You can also subscribe to Possibly wherever you get your podcasts or follow us on Instagram, Facebook, LinkedIn, X, or Bluesky at “askpossibly”
Possibly is a co-production of Brown University’s Institute for Environment and Society, Brown’s Climate Solutions Initiative, and The Public’s Radio.
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