The ozone layer is important to humans and other living organisms because it absorbs most of the sun's harmful ultraviolet rays. Ozone is a type of oxygen molecule that has three atoms instead of the usual two. Ozone molecules are thinly spread within a belt that exists between 15 and 30 miles above the Earth's surface, in the atmospheric layer called the stratosphere. If all molecules of stratospheric ozone were settled onto the Earth's surface, they would form a layer that is only about -inch thick.
The depletion of the ozone layer, in recent years, has been linked to a number of human health problems. The most serious problem is a rise in cases of skin cancer. In fact, it is estimated that every 1 percent reduction in the ozone layer results in a 2 to 5 percent rise in the incidence of skin cancer. Other human consequences of the loss of protective ozone may include an increase in sunburns and eye cataracts, as well as the suppression of the immune system. Scientists also predict that depletion of the ozone layer could lead to the disruption of sensitive terrestrial (land) and aquatic ecosystems.
While ozone is beneficial in the stratosphere, when it is present near the ground it is a pollutant that contributes to the formation of photochemical smog and acid rain.
Sources: Engelbert, Phillis. The Complete Weather Resource, vol. 3, pp. 509, 513-16; Lean, Geoffrey, et al. WWF Atlas of the Environment, pp. 97-98; Schweitzer, Glenn E. Borrowed Earth, Borrowed Time, pp. 214, 218.