Ozone is a form of oxygen. It is a pale blue gas that has a strong odor.
Image to left: The ozone is a protective layer of gas that surrounds the Earth. Credit: World Book illustration
Most ozone is in the air high above the Earth. This layer of ozone shields the planet from dangerous rays of the sun that can cause skin cancer. Scientists have found that areas in the ozone layer are thinning out. These areas are called ozone holes. They lie near areas above the North and South Poles.
Some ozone is also near the ground. There, it pollutes the air. It can also damage rubber and plastic and harm plants. It can cause headaches, burning eyes, and sore throats in many people.