Common Skin Cancer Symptoms and Causes
Sunlight contains ultraviolet light that is harmful to human skin cells. These energetic light waves can produce mutations in the DNA of skin cells, which in turn can lead to skin cancer. In areas close to the equator, the incidence of cutaneous cancers is dramatically higher due to the increase in sun exposure.
The most obvious skin cancer warning sign is the development of a persistent bump or spot in an area of sun-damaged skin. These spots are likely to bleed with minimal trauma and produce a superficial erosion.
Ultraviolet Light and Skin Cancer
Ultraviolet rays are classified by three types: UVA, UVB, and UVC. UVC is very dangerous, but it does not reach the earth’s surface due to the ozone layer. Exposure to both UVA and UVB radiation poses potential skin cancer risks.
UVA light is the most abundant source of solar radiation. Scientists think it can penetrate the top layer of skin, potentially damaging connective tissue and causing skin cancer. An estimated 50% of UVA exposure occurs in the shade. Light skin is far more vulnerable to UVA radiation: while dark skin allows only 17.5% of UVA to penetrate, light skin allows 55% of UVA light to pass through.
Sunburns are mostly caused by UVB radiation. Because of the ozone layer, UVB light accounts for only about 5% of the light that reaches the earth’s surface. UVB light can be filtered out by glass windows and does not penetrate as far into the skin as UVA, but it can still cause some forms of skin cancer. UVB is absorbed directly by DNA. Dark skin is twice as effective as light skin at protecting against UVB penetration.
How Skin Cancer Develops
UV light causes skin cancer by damaging the skin’s cellular DNA. That damage is caused by free radicals, which are hyperactive molecules found in UV light. Free radicals cause damage to the DNA double helix, changing the way cells replicate and naturally die, which is how cancer develops. In addition to sun exposure, free radicals are also found in environmental pollutants, cigarette smoke, alcohol, and other toxins.