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The Basics

A single atom can make a big difference in the way a molecule works — so can its location. The everyday air we breathe has two atoms of oxygen (O2) in it. Ozone is a gas made up of three atoms of oxygen (O3). And while we need oxygen to survive, ozone can either help us or hurt us — depending on where it is.

What’s the difference between helpful and harmful ozone?

Ozone can be helpful or harmful to your health and the environment, depending on its location in the atmosphere. Helpful ozone exists naturally high above the Earth’s surface and protects us from the sun’s ultraviolet rays (radiation). Human-made air pollutants damage the helpful ozone.

Harmful ozone is close to the ground. It comes from human activities that release chemicals into the air, which react with sunlight to create ground-level ozone.

How can ozone affect my health?

When human-made air pollutants destroy helpful ozone, people may receive too much ultraviolet radiation. This may cause:

  • Cataracts (clouding of eye lens, which leads to poor vision)
  • Problem with immune system (the system that fights diseases)
  • Skin cancer
Too much ultraviolet radiation may also damage crops (plants we grow for food) and other plants.

Contact with harmful ozone can cause:

  • Coughing
  • Irritated throat
  • Worsening in respiratory (breathing) disorders, such as asthma and bronchitis
Regular contact with ozone can also cause permanent damage to the lungs, especially in children, because their lungs are still developing.  


Did you know ?

Ozone pollution near the ground is one of the most widespread air quality problems in the United States.

Learn More

Explore the links below to learn more about ozone, including what experts are doing to prevent problems with ozone — and what you can do to protect yourself.

Read About It Read About It

Health and Environmental Effects of Ozone Layer Depletion (U.S. Environmental Protection Agency) - Describes ozone depletion effects on human health, plants, marine ecosystems, and biogeochemical cycles.

Ozone (Tox Town - National Library of Medicine) - Information about exposure and health effects of ozone.

Ozone (Medline Plus - National Library of Medicine) - Resources about both kinds of ozone; topics include prevention/screening, organizations, glossaries, and research.

Ozone - Good Up High, Bad Nearby (PDF, 1.23 MB)(U.S. Environmental Protection Agency) - Online brochure about ground level ozone and the ozone layer, related health effects, and actions you can take.

Ozone Trends (U.S. Environmental Protection Agency) - Online data of national, regional, and local trends in ozone levels.

Ozone's Split Personality (Johns Hopkins University Ecohealth) - Description of the two ozones: ground level ozone and the ozone layer.

Ozone, Air Quality, and Asthma (KidsHealth from Nemours) - Information about air pollutants such as ground level ozone, and their health effects, including asthma.

State of the Air 2013 - Ozone Pollution (American Lung Association) - FAQs about ozone pollution, including general information, sources of the problem, and associated health risks.

Games and Activities Games and Activities

Lung Attack - test (Pima County, Department of Environmental Quality) - Interactive presentation of how lungs work and how types of air pollution, including ozone, big particles, and small particles, can affect them.

Ozone Science Crossword Puzzle (U.S. Environmental Protection Agency) - Online crossword puzzle about the ozone layer and ozone depletion.

Smog City 2 (U.S. Environmental Protection Agency) - Interactive air pollution simulator website; how individual choices, environmental factors, and different types of land use can affect air pollution.

Videos Videos

Robot ZERO's Ozone Adventure (National Library of Medicine) - Well-intentioned, but misguided outer space robot ZERO comes to Earth to help humans by spraying them with ozone. There, ZERO meets a scientist who explains ZERO’s mistake by helping him understand the difference between atmospheric and ground-level ozone.

For Teachers For Teachers

Air Pollution: What's the Solution? (U.S. Environmental Protection Agency) - A teacher's guide to teaching air pollution that includes curriculum standards, assessments, and lesson rubrics.

Air Pollution: What's the Solution? Weather's Role - Ozone (U.S. Environmental Protection Agency) - Activity to discover if weather conditions affect the formation of ground level ozone.