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A Hole in the Sky: Ozone Depletion - Consequences Of Ozone Depletion

cancer skin radiation percent

Ironically, destruction of the ozone layer at the upper levels could increase the amount of ozone at the Earth's surface. In addition, the decline in stratospheric ozone is thought to increase hydrogen peroxide in the stratosphere, FIGURE 3.2
Altitude profile and distribution of ozone
contributing to acid rain. The ozone layer acts as a protective shield against UV radiation. As ozone diminishes in the upper atmosphere, the Earth could receive more UV radiation. Increased radiation, especially of the frequency known as ultraviolet-B, the most damaging wavelength, promotes skin cancers and cataracts, suppresses the human immune system, and produces wrinkled, leather-like skin. It also reduces crop yields and fish populations, damages some materials such as plastics, and intensifies smog creation.

Threats to Human Health

The skin is the largest organ in the human body. It covers and protects the organs inside the body. Globally, the incidence of skin cancer is rising. There are two types of skin cancer: melanoma and nonmelanoma.

The American Cancer Society reported in 2004 that more than 1 million cases of nonmelanoma skin cancer are diagnosed in the United States each year and estimated that between 1,000 and 2,000 people would die from the disease. The incidence of cancer is closely tied to cumulative exposure to UV radiation. Each 1 percent drop in ozone is projected to result in a 4 to 6 percent increase in these types of skin cancer.

Melanoma skin cancer is less common, but far more deadly, accounting for just 4 percent of skin cancer cases but a staggering 79 percent of skin cancer deaths, according to the American Cancer Society in 2004. Melanoma is more likely to metastasize (spread to other parts of the body, particularly major organs such as the lungs, liver, and brain).

FIGURE 3.3
Trends in size of ozone hole over Antarctica, 1980–2005

In June 2003 the American Cancer Society predicted that in 2004 there would be 55,100 new cases of melanoma in the United States and that 7,910 Americans would die from the disease. The Environmental Protection Agency (EPA) estimates that ozone depletion will result in an additional 31,000 to 126,000 cases and 7,000 to 30,000 fatalities among white Americans born before 2075. Melanoma appears to be associated with acute radiation exposure, such as severe sunburns, which are more likely to occur when the ozone hole is larger.

The EPA estimates that, among Americans born before 2075, depletion of the ozone layer could be responsible for 555,000 to 2.8 million additional cases of cataracts. Cataracts cause clouding of the eye's lens, which results in blurred vision and—if left untreated—blindness. It is also expected that victims will be stricken at younger and younger ages.

Some medical researchers theorize that UV radiation also depresses the human immune system, lowering the body's resistance to tumors and infectious diseases.

Damage to Plant and Animal Ecosystems

Terrestrial and aquatic ecosystems are also affected by the depletion of the ozone layer. UV radiation alters photosynthesis, plant yield, and growth in plant species. Phytoplankton (one-celled organisms found in the ocean) are the backbone of the marine food web. Studies have found that a 25 percent reduction in ozone would decrease their productivity by about 35 percent. Fish species that live solely on phytoplankton would likely disappear. As ecosystems are altered, important fish species will become vulnerable. These fish are a vital component in feeding the increasing human population. In addition, scientists have identified the rise in UV radiation caused by the thinning of the ozone layer as the culprit behind the decline in the number of frogs and other amphibians.

Deterioration of Materials

Increased UV radiation also affects synthetic materials. Plastics are especially vulnerable, tending to weaken, become brittle and discolored, and break.

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