Good Ozone, Bad Ozone

Ozone is the Jekyll and Hyde of the atmosphere. It is a good thing when found in large concentrations high off the ground. When it’s around people, it can sicken and kill.

Ozone is a form of oxygen: a highly poisonous, pale blue gas with a strong odor. Its name is derived from a Greek word meaning “to smell.” Commercial uses include purifying water, sterilizing air, and bleaching certain foods.

Ground-level ozone is the most widespread air pollutant. Created by nitrogen oxides and organic gases emitted by motor vehicles and industry, it is a health hazard and may cause serious damage to crops.

About 90 percent of the world’s ozone is in the stratosphere, roughly seven miles (11 kilometers) above the Earth’s surface. A naturally occurring gas there, it filters the sun’s UV radiation, which, in excess, causes sunburns and skin cancer, reduces crop yields, and interferes with the marine food chain.

Years ago scientists discovered that stratospheric ozone is being eaten away by human activity. Materials used in refrigerants, insulating foams, and solvents release chlorofluorocarbons (CFCs), which eventually find their way into the upper air and eat away at the ozone layer. The 1980s discovery of the “ozone hole” over the Antarctic led to international agreements to reduce and eventually ban the production of CFCs.

Photo: A huge ozone hole spreads over Antarctica in this September 8, 2000, NASA satellite image. The hole appears as a giant blue blob that spreads over about 11 million square miles (28 million square kilometers).

Source: National Geographic