Ultraviolet radiation skin cancer from

O Exposure to ultraviolet radiation from the sun is recognized as one of the primary triggers for skin carcinogenesis. Based on their wavelengths, UV radiation is divided into three components UVA (320 00 nm), UVB (280-320 nm), and UVC (200-280 nm).15 UVB accounts for only 5% of the solar radiation that reaches the earth, but it is the primary carcinogenic component in the UV spectrum.15 The following sequence of events describes the process in which UV radiation causes skin cancer (1) UV radiation reaches the earth, and on the skin, it reaches the cells in the epidermal layer (i.e., squamous cells, basal cells, and melanocytes),16 (2) the UV radiation (specifically... 

Several studies have linked lutein to a lower risk for eye, skin and other health disorders, probably through its antioxidant activity. Lutein is apparently metabolized to zeaxanthin, an isomer, and several other compounds which protect the macula from ultraviolet radiation. The suggestion is that lutein may play a positive role in reducing macular degeneration. Other reports have linked lutein to a reduction of risk of cancer.13 Regardless, lutein is currently being promoted as an important dietary supplement. 

Ozone exists naturally in the upper atmosphere of the earth. The ozone layer is especially important because it absorbs ultraviolet light and thus acts as a screen to prevent this radiation, which can cause skin cancer, from penetrating to the earth s surface. When an ozone molecule absorbs this energy, it splits into an oxygen molecule and an oxygen atom ... 

Light and Toxic Reactions In many individuals, exposure to ultraviolet radiation from the sun causes skin reactions such as erythema, thickening of the epidermis, and darkening of existing pigment. Exposure to ultraviolet light also increases the risk of different forms of skin cancers, especially malignant melanoma. ... 

O Exposure to ultraviolet radiation from the sun is recognized as one of the primary triggers for skin cancer development. 

Ultraviolet radiation Invisible rays that are part of the energy that comes from the sun. UV radiation can damage the skin and cause melanoma and other types of skin cancer. UV radiation that reaches the earth s surface is made up of two types of rays, called UVA and UVB rays. UVB rays are more likely than UVA rays to cause sunburn, but UVA rays pass deeper into the skin. Scientists have long thought that UVB radiation can cause melanoma and other types of skin cancer. They now think that UVA radiation also may add to skin damage that can lead to skin cancer and cause premature aging. For this reason, skin specialists recommend that people use sunscreens that reflect, absorb, or scatter both kinds of UV radiation. [NIH]... 

No doubt the greatest environmental threat to the skin is not chemical, but is rather a physical agent, sunlight most skin cancers are caused by excessive exposure to ultraviolet radiation from the sun. 

The concentration of ozone near the Earth s surface is very low, typically in the range of 15-45 pphv (parts per billion by volume). In contrast, ozone is more abundant in the Earth s stratosphere, where it is formed by the action of ultraviolet radiation on molecules of dioxygen. A distinction is sometimes made between stratospheric ozone ("good ozone") and tropospheric (low-level or surface ozone "bad ozone"). This distinction arises from the fact that stratospheric ozone reduces the amount of ultraviolet radiation that reaches the Earth, reducing the rate of skin cancer and other medical problems... 

Sunscreens absorb ultraviolet radiation before it can be absorbed in the skin. They are recommended to protect the skin from the major toxicities of sun exposure sunburn and skin cancer. Most available agents primarily absorb UVB, although newer preparations also provide protection against UVA. Physical sunscreens (which are generally opaque, hke titanium dioxide and zinc oxide) block all ultraviolet radiation. 

Relatively little of the atmosphere s mass is located above the troposphere, but the chemistry that occurs there is nonetheless crucial to maintaining life on earth. Particularly important is what takes place in the ozone layer, an atmospheric band stretching from about 20-40 km above the earth s surface. Ozone (03) is a severe pollutant at low altitudes but is critically important in the upper atmosphere because it absorbs intense ultraviolet radiation from the sun. Even though it is present in very small amounts in the stratosphere, ozone acts as a shield to prevent high-energy solar radiation from reaching the earth s surface, where it can cause such problems as eye cataracts and skin cancer. 

Over recent years, scientists have become aware of a reduction in the amount of ozone in our atmosphere and of the formation of ozone holes in the stratosphere (Figure 11.5). The reduction of ozone in our atmosphere has led to an increased risk of skin cancer as more harmful ultraviolet radiation has reached the surface of the Earth. This is a different type of problem from the greenhouse effect and associated global warming, which is caused mainly by an increase in the amount of carbon dioxide in the atmosphere. For a further discussion of the greenhouse effect and global warming see p. 212. 

Ultraviolet (UV) rays Radiation from the sun that can be useful or potentially harmful. UV rays from one part of the spectrum (UV-A) enhance plant life. UV rays from other parts of the spectrum (UV-B) can cause skin cancer or other tissue damage. The ozone layer in the atmosphere partly shields us from ultraviolet rays reaching the Earth s surface. 

Ozone is O3. The ozone layer is a region of the stratosphere that contains higher concentrations of ozone than other parts of the atmosphere. The ozone layer is important for human health because it blocks ultraviolet radiation from the sun, and this helps to protect us from skin cancer. Research in the 1970s revealed that several gases used for refrigeration and other purposes were depleting the ozone layer. Many of these ozone-destroying molecules are short alkyl halides known as chlorofluorocarbons or CFCs. 

With reduced ozone levels, more ultraviolet radiation from the Sun reaches Earth. Among humans, UV-induced skin cancer and eye damage are becoming a serious threat. The increased levels of radiation also damage phytoplankton in fresh and marine ecosystems. Since phytoplankton are the base of the aquatic food chain, this damage affects all other water species. As you learned earlier, the presence of ozone close to Earth damages crops and forests. A lack of ozone in the atmosphere, however, also reduces the yield of crops, such as barley and canola, and harms forests. 

In 1993, a scientific link was established between ozone depletion and increases in ultraviolet radiation. It was found that increased exposure to UV-B radiation causes skin cancer, the formation of cataracts, and the suppression of the human immune system. Research has shown skin cancer to be as common as all other types of cancer combined. Sunscreens can protect humans from the risk of some skin cancers. Unfortunately they do not appear to provide protection against damage to the immune system. 

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