Because it reacts strongly with other molecules, large concentrations of ozone near the ground prove toxic to living things.
At higher altitudes, where 90 percent of our planet's ozone resides, it does a remarkable job of absorbing ultraviolet radiation.
In this season of new beginnings, the hole in the ozone layer reforms, allowing lethal ultraviolet radiation to stream through Earth's atmosphere.
The hole lasts for only two months, but its timing could not be worse.
Years of study on the ground, in aircraft, and from satellites has conclusively identified the source of the chlorine: human-made chemicals called chlorofluorocarbons (CFCs) that have been used in spray cans, foam packaging, and refrigeration materials.
Ozone is a relatively simple molecule, consisting of three oxygen atoms bound together.Yet it has dramatically different effects depending upon its location.Near Earth's surface, where ozone comes into direct contact with life forms, it primarily displays a destructive side.This biologically damaging, high-energy radiation can cause skin cancer, injure eyes, harm the immune system, and upset the fragile balance of an entire ecosystem.Although, two decades ago, most scientists would have scoffed at the notion that industrial chemicals could destroy ozone high up in the atmosphere, researchers now know that chlorine creates the hole by devouring ozone molecules.Although the entire increase cannot be blamed on ozone loss and increased exposure to ultraviolet radiation, there is evidence of a relationship.Scientists estimate that for each 1 percent decline in ozone levels, humans will suffer as much as a 2 to 3 percent increase in the incidence of certain skin cancers.But in attempting to further analyze the composition of the atmosphere, researchers at the turn of the century faced a major stumbling block: virtually all gases, except for molecular nitrogen and oxygen, exist in such minute concentrations that available equipment could not detect them. During the 1880s, scientists had begun perfecting a new, highly precise method of identifying a compound by recording a special kind of chemical fingerprint—the particular pattern of wavelengths of light it emits or absorbs. By the 1950s, researchers had identified 14 atmospheric chemical constituents.Despite this progress, researchers were still missing a major piece of the atmospheric puzzle.Instead, they began with basic questions about the nature of Earth's atmosphere—its composition, density, and temperature distribution.The composition of our planet's atmosphere fascinated humans long before chemistry became a formal science. Dobson developed a spectrometer that could measure small concentrations of ozone.