City Cast

Why Chicago's Air Quality Was Worst in the World

Sidney Madden
Sidney Madden
Posted on June 28   |   Updated on June 27
Hazy smoke covers the Chicago skyline

Chicago's skyline from the John Hancock Building Tuesday. (Kamil Krzaczynski / AFP / Getty)

Chicago had the worst air quality in the world Tuesday. Why? Chalk it up to the smoke from Canadian wildfires that has made its way here.

Chicago’s Air Quality Index was 258 Tuesday at 3 p.m., according to the EPA.

Chicago’s AQI was 258 Tuesday at 3 p.m. (EPA’s Air Now)

What’s going on

An air quality alert went into effect Tuesday as levels became “very unhealthy.” The EPA’s Air Quality Index measures air quality from 0 to 500: the higher the value means the greater the air pollution.

Earlier this month, New York City’s AQI reached 405 at its peak. Chicago’s AQI crept past 250 Tuesday.

So how do you protect yourself?

The city encouraged adolescents, seniors, pregnant people, and individuals with heart or lung disease to avoid strenuous activities and limit time outdoors. All Chicagoans are encouraged to:

  • Break out the masks — the N95s and KN95s
  • Limit outdoor exposure (e.g., close your windows, hang inside, etc.)
  • Don’t smoke, use vacuums, or light candles
  • Limit driving a vehicle
  • Run air purifiers
  • Take shelter at park districts or libraries

Make your own DIY air purifier

Since air purifiers can be pricey, you can make your own.

Get a square fan and a HEPA filter of a similar size. Secure the filter tightly to the fan with duct or packing tape — like Wirecutter did.

What else you should know

Conditions are forecasted to improve over the week, according to the National Weather Service. But going into NASCAR and Fourth of July weekend, car emissions and fireworks can make air quality worse.

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