The main environmental risk factor that leads to melanoma is exposure to the sun’s ultraviolet (UV) rays. This means that melanoma is a highly preventable type of cancer. Other forms of artificial UV light can be just as dangerous as the UV rays of the sun, such as the light emitted by tanning beds and sun lamps.

Some risk factors may increase a person’s chances of developing melanoma. For instance, people with a large number of moles or certain types of moles, such as dysplastic nevi (nevus is the medical term for mole), are at higher risk.

Normally, these nevi have a single color – usually tan, brown or black. They are characterized by a distinct border that separates the mole from the surrounding skin. Some individuals have moles that are not uniform in color or have irregular shapes or borders. These types of moles are known as dysplastic nevi, and they are far more likely to develop a malignancy than normal moles. Dysplastic nevi can run in families. Patients with these moles have a lifetime risk of  6 to 10 percent of developing melanoma, according to the American Cancer Society (ACS).

Having fair skin, light eyes or hair color, and having many freckles may increase a person’s risk as well. Caucasians are 20 times more likely to develop melanoma than African Americans who are more protected by their skin pigment, according to the ACS. However, it should be noted that people of color can also develop melanoma. Other risk factors include:

• Family history of melanoma. Approximately 10 percent of those diagnosed with melanoma have a family history of the disease, according to the ACS. Genetic mutations are seen in as much as 40 percent of families with a high incidence of melanoma.
  
  
• Immunosuppressive therapy. People being treated with medications that may suppress the immune system, such as those who have undergone an organ transplant, are at greater risk of developing melanoma.
  
  
• Age. According to the ACS, the incidence of melanoma among 70-year-olds is twice that of 45-year-olds. However, among cancers, melanoma is one of hte more common ones that occurs under age 30.
  
  
• Smoking. Tobacco use – particularly smoking cigarettes – increases a person’s risk of developing melanoma.
  
  
• Gender. Men are more likely to develop melanoma than women (a risk of 1 in 52 versus 1 in 77), according the ACS.
  
  
• Xeroderma pigmentosum. This rare, inherited condition causes people to be less likely to repair DNA damage caused by sunlight.
  
  
• Previous melanoma. After a person has had a melanoma, the risk of developing another melanoma is increased.
  
  
• Living in a sunny or high-altitude climate. People who live in sunny climates, such as in the southern United States, and those who live at high altitudes with little or no cloud cover for protection are at an increased risk of developing melanoma.
  
  
• Exposure to carcinogens (cancer-causing substances), such as coal, tar, creosote (a wood preservative), arsenic compounds in pesticides and radium increases the risk of melanoma.