Sign In or Create an Account.

By continuing, you agree to the Terms of Service and acknowledge our Privacy Policy

Guides

The AQI Is Falling. Is It Safe to Go Outside?

Here’s how to think about air quality and safety.

A woman peeking out her window at smoke.
Heatmap Illustration/Getty Images

The smoke that blanketed the East Coast this week is beginning to clear, and you may be wondering if it’s safe to go outside without a mask or whether you should crack a window to air things out.

The answer is likely yes, it's safe to go outside — with a few caveats. But you might want to wait before opening your windows.

The good news is, the Air Quality Index across much of the Northeast is now registering at under 100, putting most places in the “good,” or “moderate” category. But to make smart decisions about your health, it’s helpful to understand what those AQI numbers actually mean.

The categories are pegged to the National Ambient Air Quality Standards, which are set by the Environmental Protection Agency and cover various major pollutants. The Clean Air Act requires that these standards protect public health with an "adequate margin of safety.”

When you check the AQI on the EPA’s website or your weather app, what you’re seeing is a measure of five pollutants: particulate matter, ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide. When the AQI is below 100, that means none one of those pollutants are present at a concentration above the levels deemed protective by the EPA. But when any of the pollutants ticks above those levels, the AQI will change to “unhealthy for sensitive groups,” (orange), “unhealthy” (red), “very unhealthy” (purple), or “hazardous,” (maroon) depending on how bad it is.

For example, the standard for PM2.5, the primary health hazard in wildfire smoke, is a 24-hour average of 35 micrograms per cubic meter. When the AQI is below 100, that means PM2.5 levels are below that concentration. At the height of the smoke crisis on Wednesday, average PM2.5 levels in New York City were at 326 micrograms per cubic meter. That brought the AQI into the “hazardous” range, under which the EPA advises:

Everyone should avoid all physical activity outdoors; people with heart or lung disease, older adults, children, and people of lower socioeconomic status should remain indoors and keep activity levels low.

By contrast, at this moment my AQI in Brooklyn is registering at 54, or “moderate.”

At that level, EPA advises: “Unusually sensitive people should consider reducing prolonged or heavy exertion.”

If you look at the average AQI for the month of June in the New York City metropolitan area over the last decade, it has always hovered around 70. By that measure, today is looking pretty good.

I spoke to Jon Samet, a pulmonologist and epidemiologist and the dean of the Colorado School of Public Health, about how to make sense of these numbers. He said that to some extent, it’s up to the individual to use their best judgment.

“If you go below 100, the world may not be risk free, but it's in a range where the risks have been found to be acceptable,” he told me. “The caveat I would offer is that for those people who have heart and lung disease, or any other condition that makes them potentially susceptible, then they should think carefully.” The same goes for children with asthma, who may be particularly susceptible to air pollution.

The bad news is that it’s basically impossible to make statements like, “when the AQI goes below X number, it’s safe to take your asthmatic kid to the playground,” because it’s an imperfect measurement.

“Part of the challenge right now is that epidemiological studies show that even when you make your way below the standard, there's still evidence of adverse effects,” said Samet. “So far, we haven't found risk-free levels of air pollution.”

The best advice he could offer is that if the AQI is below 100, but you go outside and the visibility is poor, or you start coughing, or your eyes burn, that’s a signal to go back inside or pull out your N95 mask. “Pay attention to your own response,” he said.

Personally, looking at the historical averages in New York City makes me feel comfortable going outside without a mask.

As for opening windows to air out any smoke particles that made it inside, John Volckens, an air quality expert and professor of mechanical engineering at Colorado State University, told me it was a good idea to wait until we’re back in the “Good” zone. “While ‘moderate’ isn’t going to be harmful over the short-term for healthy individuals (i.e., those without respiratory or cardiovascular disease), most of the PM contributing to the moderate level will still be from wildfires, so you won’t really be ‘airing out’ your apartment at that point,” he said.

Guess I’ll have to wait a little bit longer to flush out my apartment — but in the meantime, I’m going for a walk.

Editor's Note: This article was updated to include new comments from John Volckens.

Green

You’re out of free articles.

Subscribe today to experience Heatmap’s expert analysis 
of climate change, clean energy, and sustainability.
To continue reading
Create a free account or sign in to unlock more free articles.
or
Please enter an email address
By continuing, you agree to the Terms of Service and acknowledge our Privacy Policy
Air pollution.
Heatmap Illustration/Getty Images

A federal appeals court on Tuesday cleared the way for the Trump administration to kill former President Biden’s $20 billion green bank program, which would have provided low-cost loans for solar installations, building efficiency upgrades, and other local efforts to reduce greenhouse gas emissions.

The three-judge panel overturned a lower court’s injunction temporarily requiring the Environmental Protection Agency to resume payments, and ruled that most of the plaintiffs’ claims were contract disputes and belonged in the Court of Federal Claims. If the case now moves to the Court of Federal Claims, the plaintiffs would only be able to sue for damages and any possibility of reinstating the grants would be gone. But they could also petition to appeal the decision.

Keep reading...Show less
Green
Politics

AM Briefing: Exxon’s Plastic Counterattack

On uranium challenges, Cadillac’s EV dreams, and a firefighter’s firestorm

Exxon Counterattacks California Over Plastics
Heatmap Illustration/Getty Images

Current conditions: Atlantic hurricane season enters its peak window and a zone west of Africa is under close monitoring for high risk tropical storm development this week • A polar air mass came down from Canada and dropped temperatures 15 degrees below historical averages in the Great Plains and the Northeastern U.S. • Croatia braces for floods as up to 11 inches of rain falls on the Balkans.


Keep reading...Show less
Yellow
Electric Vehicles

The Old EV Batteries Being Used to Make New EVs

Toyota’s new “sweep” system will power a Mazda factory in Japan.

A battery as a factory.
Heatmap Illustration/Getty Images

Toyota is helping to build Mazdas. At least, its aging car batteries are.

Cooperation between rivals is nothing new in the car world. Toyota and Subaru have teamed up to build small sports cars and electric vehicles that are, underneath the skin and the logos, essentially the same. GM and Hyundai have signed a memo of understanding to share new vehicles and clean energy tech, while Honda has used GM’s Ultium platform as the basis of its Prologue EV.

Keep reading...Show less
Blue