What Is Ozone?
What is Ozone?
Ozone, or the “ozone layer,” is a beneficial component of the upper atmosphere.
Ground-level ozone is a pollutant. It causes eye, nose, throat and lung irritation. Permanent lung damage can also occur. Ozone pollution forms from a chemical reaction between sunlight and fumes from fuel, paint, cleaners, tailpipes and vegetation. Typically a summer-time pollutant, ground-level ozone is the most wide-spread air quality problem in the United States.
Stratospheric Ozone is a colorless, mostly odorless gas that forms high in the atmosphere when intense sunlight causes oxygen molecules (O2) to break up and re-form as ozone molecules (O3). (The stratosphere is about 6 to 30 miles above the Earth.) Popularly called "good ozone," it shields people, trees, crops, property, and microorganisms from the harmful effects of the sun's ultraviolet light (UV-B radiation).
Ground-Level Ozone, regularly referred to as “bad ozone,” forms when nitrogen oxide (NOx) and/or volatile organic compounds (VOCs) react with heat and sunlight. These NOx emissions and VOCs come from cars, trucks and other fossil-fueled vehicles, industrial and commercial operations, energy production, and even vegetation. (If ground-level ozone were produced only from those natural sources of emissions, it wouldn’t be a problem because plants, animals and people tolerate natural background levels of ozone.)
Summers in Phoenix provide plenty of heat and sunlight that cook the trapped pollutants into ground-level ozone. The warmer months of April through September make up our Valley’s “ozone season.”