Melanoma Awareness Month is in May

Melanoma & Skin Cancer Awareness Month: UV Radiation and Sun Exposure

About Melanoma & Skin Cancer

May is Melanoma & Skin Cancer Awareness Month in the United States. This is a good time to learn more about how melanoma and other types of skin cancer develop, signs and symptoms to watch out for, and ways to reduce your skin cancer risk. Skin cancer is the most common cancer in the United States. About 1 in 5 people in the United States will develop skin cancer in their lifetime. Melanoma accounts for about one percent of skin cancers but causes most cancer deaths. 

Melanoma develops in skin cells called melanocytes. These cells produce and contain the pigment melanin. This pigment is what gives skin a tan or brown color. Melanoma is typically more dangerous than other skin cancers because it is more likely to spread to other parts of the body. Melanoma can develop anywhere on the skin, but it is most common on the chest, back, face, neck, and legs. Other common types of skin cancer include basal cell and squamous cell cancers. These cancers form in cells in the epidermis, the outermost layer of skin. 

Ultraviolet Radiation, Sun Exposure, & Prevention

Most skin cancers are caused by UV radiation from sun exposure. UV radiation is a form of invisible radiation that comes naturally from the sun’s rays. UV radiation can also be used in an artificial form in tanning beds and sunlamps, and less commonly in certain types of lights and lasers. UV rays can damage the DNA in cells, leading to cell changes, mutations, and uncontrollable cell growth. The body can repair some of this damage but not all, and damage that is not repaired builds up over time, increasing the risk of skin cancer. 

There are three different types of UV rays: Ultraviolet A (UVA), Ultraviolet B (UVB), and Ultraviolet C (UVC). UVA rays are the most prevalent UV radiation on Earth because they are not absorbed by the ozone layer. UVA rays penetrate deeply into the skin. They can cause premature aging of the skin, fine lines, and wrinkles and play a role in some skin cancers. UVA rays are consistent throughout the year and are strong even on cloudy days. Tanning beds mostly emit UVA rays. 

UVB rays are partially absorbed by the ozone layer and atmosphere but some still reach Earth’s surface. The intensity of UVB rays fluctuates over time, with the strongest UVB rays occurring from late-morning to mid-afternoon from spring to fall. However, damage can still occur from exposure year round. UVB rays penetrate the outer layers of the skin, causing damage to skin cells. UVB rays are the main case of sunburn, thickening of the skin, and most skin cancers, including melanoma. UVB rays can also damage the eyes and immune system. 

UVC rays are the strongest UV rays. However, UVC rays do not reach the Earth’s surface and are blocked by the ozone layer. UVC rays are only used in artificial sources, such as sunlamps and lasers. UVC rays penetrate the outermost layer of the skin, but they can cause severe burns and damage to the skin and eyes in just a few seconds. This damage usually resolves in about a week and typically doesn’t cause long-term damage or health risks.

You can protect yourself from UV rays and lower your risk of getting sunburns and developing skin cancer by using sunscreen. Sunscreen works by preventing UV rays from penetrating the skin in different ways. Physical sunscreens use minerals that reflect UV rays back. Chemical sunscreens use specific chemicals that absorb UV rays and undergo a chemical reaction, transforming the UV rays into heat and releasing them. Other prevention strategies include limiting time in the sun, staying in the shade, not using tanning beds or booths, wearing a sunhat and sunglasses outdoors, and covering your skin with long sleeves and pants. 

Sun Exposure & Cancer Research

It was long suspected that sun exposure was related to melanoma risk, as well as other skin cancers, and there was circumstantial evidence to support this. Higher skin cancer incidences and mortality were observed in Caucasian people in areas closer to the equator and in areas with stronger and prolonged sun exposure, like Australia and New Zealand. Skin cancer rates also increased as tanning became more popular and fashion choices changed to have more skin exposed to sunlight. Furthermore, skin cancer rates were higher in outdoor workers. However, it wasn’t until the 1980s that conclusive studies were published that linked UV radiation exposure to melanoma.

A study published in 1982 examined how sun exposure may be related to melanoma by having 113 melanoma patients fill out questionnaires. The questionnaires included questions about hair color, eye color, skin color, typical skin response to sun exposure (such as whether a person burns, tans, both, or neither), time spent in warmer climates, and history of sunburns. A computer program was used to analyze the results and estimate risk. These results were then compared to those of a control group of 113 people without melanoma with the same age and gender distribution. The study found that 56 percent of melanoma patients had a history of severe sunburns compared to just 22 percent of the control group. This was the first study to demonstrate a clear connection between sun exposure, history of sunburns, and melanoma.

As a result of increased awareness of the danger of UV radiation and legislation on indoor tanning use, melanoma and other skin cancer rates are decreasing in some groups, especially in those under 30. Melanoma death rates are also declining. This month and all year, make sure you are reducing your melanoma risk by staying in the shade, using sunscreen (SPF 30 or higher is best), and not using indoor tanning beds or booths. To learn more about sun safety, skin cancer, and sunscreen, check out MNCCTN’s previous article on sun protection and sunscreen research.