How The Air Quality Index Determines Wildfire Smoke Risk, Here Are AQI Limitations

If you live in the Midwestern, Northeastern or Middle Atlantic U.S. and breathe air, there’s a good chance that you’ve heard about the Air Quality Index (AQI) at some point over the past month. That’s because smoke traveling Southwards from the Canadian wildfires has been pushing U.S. AQI numbers up into the unhealthy and even hazardous ranges on multiple occasions. The wildfires are likely to continue throughout much of the Summer and become a more and more frequent occurrence as climate change leaves things hotter and drier. So get used to checking the AQI in your area on a more regular basis. But remember, like any single measure, whether it’s number of points scored, the number of likes on social media, or the number of fish being carried on a Tinder profile, the AQI does have its limitations. So even when you hear that the AQI is in the good or moderate range, take it with a grain of salt—just don’t inhale that grain—and listen to your body as well.

You see the AQI is a rather rough measure of the amount of pollution present in the air in a town, city, county, or region and can range from a low of 0 to a high of 500. It doesn’t represent all the possible pollutants and irritants in the air—just the levels of the following five specific major types of pollutants that are regulated by the Clean Air Act:

• Ground-level ozone: Ozone may sound like something dirty in a sexual kind of way. But it is actually a gas that can be either bad or good, depending on where it comes. Good ozone is present in the Earth’s upper atmosphere and protects everyone from ultraviolet rays from the sun. Bad ozone emerges at the Earth’s ground-level from pollutants reacting chemically with the sunlight.
• Particulate matter (PM) in the air: This is also known as particle pollution and includes both solid and liquid material. This has been the primary problem with the wildfire smoke from Canada as the burning of materials can spew all sorts of particles into the air. The particles can range greatly in size. Of course, gigantic particles—such as a car tire flying at you—can be avoided by ducking. But the same can’t be said about coarse particles, designated as PM₁₀ and defined as particulate matter between 2.5 and 10 micrometers in diameter of course. These can readily get into your respiratory tract and cause all sorts of irritation. Even more concerning are the so-called fine particles (PM_2.5), which are definitely not fine to inhale. These are 2.5 micrometers or less in diameter, small enough to get deep into your lungs. I’ve described previously for Forbes how these can cause all sorts of pulmonary and cardiovascular problems. Over time, they may even cause cancer.
• Carbon monoxide: This is an odorless, colorless gas that is generated when fuel burn as in vehicle operation, industrial processes and wildfires. Carbon monoxide can binds to hemoglobin in your bloodstream and reduce its ability to carry oxygen to your body tissues. This can be especially problematic if you already have cardiovascular or respiratory disease that limit how much oxygen is getting to your body tissues. Even when you are completely healthy, high levels of carbon monoxide can mess with your mental status and vision. Very high levels can kill you.
• Sulfur dioxide: This is also a colorless gas. It results when burning sulfur-containing fuels such as coal and oil. When inhaled, it can cause your airways to narrow, which isn’t good because breathing is kind of important to do stuff like watch cat videos and take selfies.
• Nitrogen dioxide: Just say no to NO_₂, which is the chemical formula for nitrogen dioxide. It can result from various industrial processes such as fertilizer production. Inhaling this gas can irritate your airways and even cause fluid build-up in your lungs. Like carbon monoxide, nitrogen dioxide can also interfere with your hemoglobin’s ability to carry oxygen.

The AQI doesn’t include other bad stuff like benzene, dioxins, asbestos, toluene, cadmium, mercury, chromium, lead, or that cologne worn by your co-worker that causes your eyes to water. So even when the AQI is in the seemingly all clear range, there could still be elevated levels of not-so-great stuff in the air around you.

And it’s not as if the AQI is being measured everywhere at every street corner, every park, every parking lot, and every, well you get the picture. As you probably realize, the air quality outside is more like a mullet rather than a buzz cut haircut. It’s not that even everywhere. Instead, it can vary significantly from one place to another. Putting your face right next to car tailpipe may not the same as being at an outdoors Kanye West concert in the same neighborhood—in terms of air quality at least. The AQI is based on measured levels of the five aforementioned pollutants in samples of air taken from designated locations. In reality, a whole lot of things, ranging from wind patterns to the underlying terrain to the presence and absence of armpits can affect the air quality in a given location at a given time.

There’s actually an AQI for each of these five major air pollutants. So, when you hear the AQI being reported on the news or on the Internet, it’s typically the highest of these five AQIs. That’s because the different AQIs are a bit like the number of ferrets in your pants, the number of marmots in your bed, and the number of times a groundhogs with access to your crypto accounts. For each measurement, things may be fine when the number is low. But the higher the number, the worse things are. And as long as one of these measurements drifts into the bad ranges, things could get bad for you.

Ideally, you want each AQI to be no higher than 50, assuming that you aren’t Hedorah, that Smog Monster from that 1971 Godzilla movie. An AQI of 100 corresponds to the level set as the short-term national ambient air quality standard for that pollutant. So, anytime the AQI for a given pollutant creeps above 100, the level of that pollutant is exceeding the standard for public health safety. B

Naturally, being slightly above the safety standard is not the same as being way above the safety standard, which is not the same as holy-smokes-that’s-way-too-high-above-the-safety-standard. So, the EPA has six different categories that correspond to different levels of increasing health concern. They’ve also assigned each level a different color, because regardless of how many times people claim that they don’t see color, they do see color.

The lowest level is Green (AQI of 0 to 50), which corresponds to the Good Level

At this level, the “air quality is satisfactory, and air pollution poses little or no risk,” according to the EPA’s AirNow website. Like “Green” on a traffic light, this typically means “Go” as in “Go ahead and go outside if you’d like.” In theory, you do not need to take any special respiratory precautions, except the usual ones such as not panting too much when on a first date. However, before you “air” on the side of having false assurance, keep in mind once again that the AQI is based on samples of five very specific pollutants. It doesn’t mean that the air is all clear everywhere. Therefore, it is important to remain conscious of your surroundings. Listen to your body. If you find yourself a bit short of breath when not exercising or viewing a piece of avocado toast, there could still be an unhealthy level of pollutants in the air immediately around you.

The next level is Yellow (AQI of 51 to 100), which corresponds to a Moderate Level of Concern

This isn’t exactly an “All Clear” level. Things are still below the public health safety standards but not exactly where you want things to be. The AirNow website offers the following description of this level: “Air quality is acceptable. However, there may be a risk for some people, particularly those who are unusually sensitive to air pollution.” The EPA AQI Guide adds, “People who are unusually sensitive to ozone or particle pollution may experience respiratory symptoms.”

Even though yellow may mean “Speed up” to some people, yellow as an AQI level here doesn’t mean “Speed up and get outside.” It means that you should approach being outside with an appropriate level of caution if you may be particularly sensitive. Pay attention to how your body may be reacting to the surrounding air. If you feel fine then you probably do not need to take any specific precautions. However, any respiratory symptoms such as wheezing, chest tightness, chest pain or shortness of breath when there’s no other obvious cause may be a sign that you are indeed more sensitive. The same may be true with eye or throat symptoms such as your eyes watering when you are not singing “Nothing Compares 2 U.” If you do sense that you are particularly sensitive—or perhaps particulately sensitive—a Yellow Level may mean that it’s still better for you to reduce your time spent outdoors or at least reduce your exertion levels while outside. If it’s the level of particulate matter is the particular problem, wearing a good quality face mask like an N95 face mask while outside can help. Again listen to your body.

The first level to exceed public health standards is Orange (AQI of 100 to 150), which corresponds to an Unhealthy for Sensitive Groups Level

Yes, orange can be the sign of trouble brewing, whether it’s way too much spray tan or an AQI category. The AirNow website warns that at this level, “Members of sensitive groups may experience health effects. The general public is less likely to be affected.” The EPA AQI Guide offers some more specifics for ozone: “People with lung disease, children, older adults, and people who are active outdoors are considered sensitive and therefore at greater risk.” It also specifies the following for particulate pollution: “People with heart or lung disease, older adults, and children are considered sensitive and therefore at greater risk.” This includes older adults who are sensitive in a different way and act like children. If you do fall into one of these higher risk groups, avoid outdoor activities that involve prolonged exertion.

The next higher level is Red (AQI of 151 to 200), which corresponds to an Unhealthy Level

The word “Unhealthy” is usually a tip off that things are not good as in an unhealthy amount of cat video watching. The AirNow website provides the following general warning: “Some members of the general public may experience health effects; members of sensitive groups may experience more serious health effects.” At this level, you probably want to start taking precautions regardless of who you are. That means limiting physical exertion while outside, limiting the amount of time spent outdoors and wearing a good quality face mask that’s effective against the pollutant that’s the problem when possible when outside. Even if your body seems to say that tings are fine, at this level or higher, you may want to say, “Body, you don’t know what you are talking about.” Once the AQI has reached this level and higher, follow the AQI.

Health alerts begin when it’s Purple (AQI of 201 to 300), which corresponds to a Very Unhealthy Level

You’ve heard of the song “Purple Haze,” right? Well, the Purple level is the first “Yikes” category and usually prompts a “Health Alert.” The AirNow website description goes as follows: “Health alert: The risk of health effects is increased for everyone.” The EPA AQI Guide adds, “AQI values between 201 and 300 trigger a health alert, meaning everyone may experience more serious health effects.” It’s a good idea to cancel outdoor activities at this level.

The highest level of concern is Maroon (AQI of 301 or higher), which corresponds to a Hazardous Level

OK, if someone tells you that something “Hazardous” is fine, you may want to back away from that person. Anything “Hazardous” whether it’s a hazardous amount of cat videos or hazardous air quality is very likely to do harm. The AirNow website indicates the following about this level. “Health warning of emergency conditions: everyone is more likely to be affected.”

All in all, the AQI is a bit like red flags on Tinder and other dating web sites. The absence of warnings doesn’t necessarily meant that everything is all clear. And the presence of warnings should be taken seriously, no matter how you may feel. Air pollution can be problem even when things appear all Green. When the AQI is below 101, you should still pay attention to what your body is telling you and avoid locations where you sense elevated levels of pollution. When the AQI has crept into “Unhealthy” or worse levels, take precautions regardless of what you body says.