Air quality
Like many metropolitan areas, the Chicago area is no stranger to air pollution. That is why it is so important for Chicago area residents to understand air pollution, where it comes from, how it can affect us, and, most importantly—what we can do to prevent it. So let’s start with the basics.
Know your air quality
When we breathe, we take in more than just air. On some days, there may be elevated levels of air pollution, specifically ozone and particulate matter, which change the outdoor air quality. Just like the weather, our air quality is forecasted every day. The daily air quality is assigned a category with a corresponding color. Also, there are actions we should take for each category.
» Learn more about the air quality index.
Good ozone vs. bad ozone
Ozone is good when it is high up in the atmosphere. It protects us from ultraviolet (UV) rays that can be damaging to our skin and other living organisms. Ozone is bad when it is close to the ground where we breathe. Ground-level ozone (smog) is formed through a complex chemical reaction involving hydrocarbons, nitrogen oxides and the sunlight. High levels of ground-level ozone typically occur on hot, summer days, but can occasionally occur outside of the summer season.
» Learn more about ground-level ozone
Particulate matter
Unlike ground-level ozone, particulate matter can cause problems year-round. Particulate matter, also known as particle pollution, is made up of tiny solid particles and liquid droplets found in the air. Some particles, such as dust, dirt, soot and smoke, are large enough to see with the naked eye. Others are so small, often less than one-hundredth the width of a human hair, they can only be detected using a microscope.
