What the Air Quality Index doesn’t tell us about the air

The Palisades and Eaton fires in Los Angeles have destroyed over 10,000 structures — homes, businesses, and everything inside from bathroom cleaner to electrical wiring.

Naturally, people in the Los Angeles area are reaching for their phones to see what the Air Quality Index (AQI) says about the air around them. But to the surprise of most people, the AQI has been good or moderate across Los Angeles, even in neighborhoods that have been most impacted by the fires. In Pasadena, the AQI went from a high 293 (a rating of “very unhealthy”) on January 11 to a low of 30 (a “good” rating) the next day. How can that be?

Throughout the week, concerned residents attended calls run by leading organizations like the Coalition for Clean Air and local NRP station KCRW asking more questions, like: When entire neighborhoods full of buildings and cars burn, what’s released into the air? How far do they have to be from the fires to be safe from these pollutants? And how do they protect themselves from bad air?

Air pollution is a silent killer that no one is immune to. Every year, 7 million people all across the globe die prematurely from the effects of air pollution. In the United States, exposure to air pollution is associated with 100,000 to 200,000 deaths annually. Long-term exposure can lead to a range of health effects in almost every organ system of the body, says Ed Avol, professor of clinical medicine at the University of Southern California’s (USC) Keck School of Medicine.

Wildfires play natural, important roles in their ecosystems, particularly in western states like California. But human-caused climate change is causing these blazes to become more severe and more frequent. This means that more humans will be exposed to bad air.

But just how bad is that air? Unfortunately the answer isn’t as straightforward as you might think. But here’s what we do and don’t know about air quality, and how to think about lowering the risk to air pollution.

What the AQI does (and doesn’t) tell us about the air

The Environmental Protection Agency developed the AQI to give the public a tool to understand how good or bad the air is throughout the day. Using data collected by 5,000 air monitors placed all across the country, it tracks the levels of specific pollutants in the air, assigns it a number, and that number corresponds with a color-coded category to help people understand the quality of the air and what activities are safe to do in the outdoors.

You can find the latest AQI on the EPA’s AirNow website or through its AirNow app. They also offer a fire and smoke map, which shows the AQI and what neighborhoods are under smoke outlooks.

As former Vox reporter Rebecca Leber explained:

The AQI is calculated based upon five criteria pollutants regulated by the Clean Air Act: fine particulate matter known as PM2.5, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide. When you look at the AQI on your phone or on a website, the number it shows you represents the primary pollutant. The pollutants that drive the AQI number tend to be PM2.5 and ozone.

In the case of the California wildfires, the pollution source is exposing millions of people in the greater Los Angeles area to smoke. And that smoke contains some pollutants that are outside of the scope of the AQI. “It’s correct that when all these things are burning, there’s a lot more toxic compounds in the air,” says Rima Habre, a professor of population and public health sciences at USC’s Keck School of Medicine.

As fires burn down houses and buildings, the blazes can release certain volatile organic compounds, toxic metals, and toxic gases into our air — all of which the AQI does not account for. That’s causing people to worry about the air, and whether their health will be impacted in the long-term as it was for first responders in the 9/11 attacks.

Ash from the wildfires, which can irritate your skin or lungs, falls out of the air and settles onto the ground and therefore is not accounted for in the AQI, Habre says. So the AQI could say that the air is good, even if there’s visible ash on your house or street.

There are ways to measure the potential harmful pollutants and chemicals in the air that are outside of the AQI — that’s how we know they exist in the first place, Avol says. “But we don’t routinely measure all of these things, all the time, everywhere because that would be unfathomably expensive,” he added.

Is the AQI still useful in the context of wildfires? Yes and no. It’s still an important resource, but it simply wasn’t designed for situations like these unprecedented mega wildfires burning down thousands of buildings and structures. But there are ways to help make choices around safety and risk, even when the AQI can’t tell us the full picture.

How to think about risk and best protect yourself

When I attended air quality information webinars this week, I heard Los Angeles residents ask a lot of the same questions: How far do they have to be from the wildfires to be safe from bad air? How can they keep their families safe?

The uncomfortable truth is that there isn’t a one-size-fits-all answer to these questions. You could live several miles away from the fires, but if the wind is moving in the direction of your home, you could be at risk for exposure to bad air. But both Avol and Habre say you can analyze your risk, and make decisions on how to lower your risk from exposure to bad air.

First, take into account your own personal health and the health of your family. Does anyone have respiratory conditions, like asthma? Is anyone immunocompromised? If so, these are extra reasons to stay cautious of the air, Habre says.

You can then check the AQI and observe your environment. If the AQI says the air is good, but it smells like smoke or there’s a lot of ash present, or if the wind is blowing in your direction while fire is present, take precautions: Limit your time outside, wear a well-fitting N95 mask, which can help filter out PM2.5. And, when you do have to go outside, make sure your shoes and clothes aren’t tracking in ash when entering your home. It’s also a good idea to run air purifiers indoors while keeping windows and doors shut.

Understandably, it’s a difficult and scary time for Los Angeles residents. On top of losing entire homes and neighborhoods, the wildfires have forced us to face an uncomfortable truth, which is that life is not risk-free and that there is no way to completely protect ourselves from the consequences of disasters like these. But it doesn’t mean we’re totally powerless in lowering our risk to short and long-term health consequences. “There’s a lot of agency here,” Habre says. Making informed choices, even imperfect ones, may be the best way to move through this uncertain period.