The most important contributor to the incidence of skin cancer -- the most common type of cancer throughout the world -- is the powerful effect of the sun's ultraviolet (UV) light.

Overexposure to the sun permanently damages the skin and can lead to skin cancer. Due to a reduction of ozone in the earth's atmosphere, the level of UV light today is higher than it was 50 or 100 years ago and the incidence of skin cancer is on the rise.

Ozone serves as a filter to screen out and reduce the amount of UV light that we are exposed to. With less atmospheric ozone, a higher level of UV light reaches the earth's surface.

The amount of exposure and intensity of exposure one has to the sun's UV rays are influenced by both lifestyle and geographic factors. People who spend a lot of time in the sun increase their risk of developing skin cancer.

In addition, people who live or spend time at high altitudes (where the thinner air cannot filter UV as effectively as it does at sea level) or at latitudes close to the equator (where the earth is closer to the sun) may have a higher risk of developing skin cancer.

On the other hand, people who live in areas that have regular or frequent cloud cover may actually be exposed to as much as 50 percent less UV light.

Two other factors may be influential in determining a person's risk for developing skin cancer:

  • Heredity: People with a family history of skin cancer are generally at a higher risk of developing the disease. People with fair skin and a northern European heritage appear to be most susceptible.

  • Multiple or atypical nevi (moles): People whose skin has lots of moles or atypical moles may have a slightly greater chance of developing cancer.