How does the sun and UV cause cancer?

The sun has been revered for its ability to sustain life on Earth. It provides warmth, energy, and essential vitamins for our well-being. However, despite its numerous benefits, the sun also poses a significant threat to our health in the form of ultraviolet (UV) radiation. Prolonged exposure to UV radiation from the sun or artificial sources, such as tanning beds, is a well-established risk factor for skin cancer.

Understanding UV Radiation

The UV spectrum is divided into three categories: UVA, UVB, and UVC. UVA and UVB rays are the types that reach the earth’s surface and can impact our skin, while UVC is mostly absorbed by the earth’s atmosphere. These two types, UVA and UVB, have distinct effects on our skin, but both can contribute to the development of skin cancer.

How UV Radiation Affects Skin

DNA Damage:

UV radiation is particularly harmful to our skin because it can damage the DNA in our cells. UV rays can cause mutations in our DNA by disrupting the normal structure of our genes. This genetic damage can accumulate over time and lead to uncontrolled cell growth, a hallmark of cancer.

Melanin and Sunburn:

The skin’s natural defence against UV radiation is the production of a pigment called melanin. When we expose our skin to UV rays, the specialised cells in our skin produce more melanin. Melanin is what gives our skin its colour and helps protect us from UV damage. In response to UV exposure, our skin may tan or, in some cases, burn. Sunburn is an inflammatory response to the damage caused by UVB radiation. Over time, frequent sunburns can increase the risk of skin cancer.

Formation of Skin Lesions:

The cumulative effects of UV radiation can lead to various skin lesions, including liver spots and abnormal moles. These skin changes are often precursors to skin cancer, and their presence indicates increased risk.

Types of Skin Cancer

The most common types of skin cancer are basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma. Each of these cancers is associated with different risk factors, but UV radiation plays a significant role in their development.

Basal cell carcinoma (BCC):

BCC is the most common form of skin cancer and is generally associated with chronic sun exposure. It tends to occur on sun-exposed areas of the skin, such as the face, neck, and arms. Although it rarely metastasises to other parts of the body, BCC can be locally destructive if not treated promptly.

Squamous cell carcinoma (SCC):

SCC is the second most common type of skin cancer and is also linked to UV exposure. It typically appears as scaly, red or pink patches on the skin, often on the face, ears, or hands. While SCC is less aggressive than melanoma, it can spread to other parts of the body if left untreated.

Melanoma:

Melanoma is the most dangerous form of skin cancer and can be fatal if not diagnosed and treated early. While UV exposure is a significant risk factor for melanoma, it can also occur in areas of the body that are not frequently exposed to the sun. Melanoma often arises from atypical moles or existing pigmented lesions.

How UV Radiation Triggers Skin Cancer

Mutations in DNA:

UV radiation damages the DNA within skin cells. When the body’s repair mechanisms cannot keep up with the damage, mutations accumulate. Some of these mutations can affect genes that regulate cell growth and division, leading to the development of cancerous cells.

Immunological impact:

UV radiation can also weaken the immune system’s ability to identify and destroy abnormal cells. This weakened immune system allows for potentially cancerous cells to thrive and multiply.

How to reduce your risk of skin cancer

While the link between sun and UV exposure and skin cancer is well-established, there are effective ways to reduce your risk. Here are some strategies for protecting your skin:

Sunscreen: Use a broad-spectrum sunscreen with an SPF of at least 30, even on cloudy or overcast days. Apply it generously to exposed skin, and reapply every two hours when outdoors. Sunscreen should be an integral part of your daily routine.

Protective clothing: Wear long-sleeved shirts, wide-brimmed hats, and sunglasses with UV protection. These items provide physical barriers against UV radiation.

Seek Shade: Whenever possible, stay in the shade, especially during the peak hours of UV radiation (10h00 to 16h00).

Avoid Tanning Beds: Artificial UV radiation from tanning beds is just as harmful as natural sunlight. Avoid using tanning beds to prevent skin cancer.

Self-Examinations: Regularly check your skin for any changes, including new moles, changes in existing moles, or other skin abnormalities. Early detection can improve the chances of successful treatment immensely.

Annual Skin Check: Visit a dermatologist annually for a professional skin examination, especially if you have a family history of skin cancer or other risk factors.

Conclusion

The sun, a symbol of life and warmth, can also be a potent carcinogen when its UV radiation interacts with our skin. Understanding how UV radiation causes cancer is the first step in protecting ourselves from this threat. By taking preventative measures, such as using sunscreen, wearing protective clothing, and avoiding tanning beds, we can significantly reduce our risk of developing skin cancer. Regular self-examinations and professional skin checks are essential for early detection and timely treatment.

For more information, please contact:

Dr S Ibrahim
Discipline: Oncologist
Hospital: Royal Hospital and Heart Centre
Telephone: +27 (0) 53 045 0515