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Ozone: Good Up High, Bad Nearby
27 May
Summary
- Ground-level ozone is a harmful pollutant, irritating lungs and lungs.
- Ozone forms through pollution reactions, especially in hot, sunny weather.
- Reduce ozone by carpooling, using public transit, and avoiding idling.

While the ozone layer high in the atmosphere shields us from harmful UV radiation, ground-level ozone acts as a dangerous pollutant. This molecule, which is invisible and odorless, forms when pollution from sources like cars and factories undergoes a chemical reaction. The process is exacerbated by direct sunshine and hot temperatures.
Chicagoland is currently experiencing weather patterns conducive to high ozone levels, often occurring during hot, stagnant conditions. These situations trap pollution over populated areas, leading to elevated ozone concentrations, typically peaking in the hottest part of the afternoon.
During an Air Quality Alert for ozone, it is advised to limit strenuous outdoor activity, especially during the hottest hours. Shifting exercise or yard work to cooler parts of the day is recommended. Sensitive individuals, including children and older adults, should take extra precautions.
Reducing the pollution that creates ground-level ozone is a collective effort. Simple actions such as carpooling, utilizing public transportation, minimizing vehicle idling, and delaying refueling can significantly help in cutting down ozone buildup.