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What Is Ozone (O3)?

Christine Johnson

Ozone is a molecule that contains three atoms of oxygen (its chemical formula is O3). It occurs high up in the Earth’s upper stratosphere as well as at ground level. Depending on where it is in the atmosphere, ozone affects the Earth in good ways and bad.

Ozone Definition: Ozone is a form of oxygen with the chemical formula O3. Found naturally in the earth's stratosphere, ozone helps absorb the ultraviolet radiation from the sun. 

What is “Good” Ozone?

Naturally occurring ozone in the stratosphere is sometimes referred to as “good” ozone. The stratospheric ozone layer absorbs ultraviolet radiation from the sun. This prevents most of the radiation from reaching the earth’s surface. It occurs through the interaction of solar ultraviolet radiation (UV) with molecular oxygen (O2). This upper layer of ozone lives roughly 6 to 30 miles above the ground.

It’s “good” ozone because it shields the planet from the sun’s harmful ultraviolet rays. Without this ozone in the stratosphere, the ultraviolet light would increase our chances of being sunburned and developing skin cancer.

What is “Bad” Ozone?

Ground-level ozone, or “bad” ozone, is a harmful pollutant. It is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. It produces photochemical smog, which is a major contributor to global air pollution.

“Bad” ozone is usually found in urban areas, but high winds can carry emissions hundreds of miles away from their original sources. Major sources of “bad” ozone ingredients, NOx and VOCs, include:

  • Emissions from industrial facilities
  • Motor vehicle exhaust
  • Gasoline vapors
  • Chemical solvents

There’s a greater risk of ozone developing in hot summer months because it requires sunlight.

Ozone & Air Quality

Ozone negatively affects air quality and inhaling it can create a lot of problems. Breathing in “bad” ozone near the ground may damage our lungs and it’s known to trigger a variety of health issues in broad segments of the population. Some of these effects include:

  • Decreased lung function
  • Inflammation in the airways
  • Tightness in the chest
  • Pain or discomfort when taking a deep breath

Additionally, a lot of research indicates high concentrations of ozone are associated with increased asthma attacks.

How to protect yourself from exposure to ozone 

The best way to protect your health is to find out when ozone levels are forecasted to be high in your area and take simple precautions. Some steps you can take to protect yourself from ozone include:

  • Paying attention to the air quality forecast, particularly in hot weather
  • Limiting outdoor activities until air quality improves
  • Reducing the use of gasoline-powered equipment when possible

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