That's almost half of the entire country, which is alarming! Air pollution is especially common in cities where a lot of traffic and corporate entities emit pollutants into the air. That pollution has to go somewhere, and most times it's right into the air that you breathe.
Climate change is another factor that contributes to pollution. The American Lung Institute has said that warmer temperatures can worsen the air quality and makes ozone damage harder to clean up. You can find air quality reports of your exact zip code by doing some research online.
Living in a city, it can be hard to avoid pollution, even while you're in your own home. If you live in a building that is close in proximity to a business such as a nail salon, huge corporation with billowing smokestacks, or any entity that uses a lot of chemicals, your health could very well suffer. These chemicals can make their way into the air in your home and wreak havoc on your health! This is especially true if they're in the same building as you. Mixed-use buildings are extremely common in large city areas. If you are moving into one of these units, be sure to verify what type of businesses also occupy the structure.