Moderate exposure to Ultraviolet (UV) radiation helps the skin produce a type of vitamin D, (vitamin D3), which plays an important role - along with calcium - in bone and muscle health. However, overexposure to UV radiation can lead to the major health problems such as: (1) skin cancer (melanoma and nonmelanoma), (2) premature aging and other skin damage, (3) cataracts and other eye damage and (4) immune system suppression.

Almost all skin cancers (approximately 99% of non-melanoma skin cancers and 95% of melanoma) are caused by too much UV radiation from the sun or other sources such as solaria (solariums, sunbeds, and sun lamps). Skin cancer develops in the cells in the epidermis – the top or outer layer of the skin.

Here are some helpful resources:

• World Health Organization
• US Environmental Protection Agency
• US Food and Drug Administration

UV radiation is made up of UVA (320–400 nm) and UVB (280–320 nm). Large doses of UVA cause premature ageing and may enhance the development of skin cancers. The mechanisms of this UVA damage are not fully understood, but a popular hypothesis assumes that UVA increases oxidative stress in the cell.

UVB is responsible for sunburn – a significant risk factor for skin cancer, especially melanoma. The exact mechanism of how UVB initiates or promotes cancer is not yet known. In people suffering from Xeroderma pigmentosum (XP), a rare pigmentation disease, however, the ability to repair DNA damage caused by exposure to UV radiation is impaired. The much-increased rates of skin cancer in these patients suggest that direct UV damage of DNA may be the mechanism that links exposure to the development of cancer. It is important to note that humans do not have photoreactivating enzymes (DNA photolyase and 6-4 photolyase) that efficiently repair UV-damaged DNA to the intact form of original DNA. These enzymes are widespread in nature but are absent in humans. In humans, the nucleotide excision repair (NER) system is the sole mechanism for removing UV damage from DNA, and genetic disruption of this repair pathway leads to the photosensitive XP.

Learn More from the World Health Organication and the following publications

• World Health Organization
• A. Sancar
• S.T. Kim et al., Journal of Biological Chemistry 269, 8535-8540
• E Otoshi et al., Cancer Research 60: 1729-1735

Melanoma is a form of cancer that begins in melanocytes (cells that make the pigment melanin) and is the deadliest form of skin cancer. Often the first sign of melanoma is a change in the shape, color, size, or feel of an existing mole. However, melanoma may also appear as a new mole.

The greatest burden from melanoma falls on Australasian, North American, European, elderly and male populations. In the United States, melanoma is one of the most rapidly increasing cancers, jumping 2% per year between 2005 and 2015 in both men and women, with an estimated 151,000 cases a year by 2030 up from just over 96,000 in 2019, if current trends continue. The state-level incidence rates for UV-attributable melanoma range from 15 cases per 100,000 in Alaska to 65 cases per 100,000 in Hawaii.

Here are some helpful resources:

• US National Cancer Institute
• F. Islami et al., International Journal of Cancer, 2020
• DOI: 10.1002/ijc.32921
• C. Karimkhani et al., British Journal of Dermatology, 177(1): 134–140.

Sunscreens contain organic (chemical) and/or inorganic (mineral) UV filters that absorb, reflect or scatter UV light.

Inorganic UV filters such as zinc oxide and titanium dioxide scatter, primarily reflect the sun’s radiation that reaches the skin. However, these formulations tend to leave a white residue with a heavier feel.

Organic UV filters absorb the sun’s rays and release their excitation energy as heat and include include avobenzone, oxybenzone, octocrylene, octisalate, homosolate, padimate O, sulisobenzone, and octinoxate. These formulations tend to be easier to rub into the skin without leaving a white residue.

Everyone, except babies under age 6 months. Sunscreen use can help prevent skin cancer by protecting you from the sun’s harmful ultraviolet (UV) rays. Anyone can get skin cancer, regardless of age, gender or race. However, the risk of melanoma skin cancer increases with age and the incidence rate of melanoma skin cancer is increasing worldwide.

U.S. Food and Drug Administration (FDA), U.S. Centers for Disease Control and Prevention (CDC), U.S. Surgeon General, American Academy of Dermatology (AAD), Skin Cancer Foundation, Association of European Cancer Leagues (ECL), European Commission (EC), and health professionals worldwide emphasize the important health benefits sunscreens provide as part of a safe sun regimen to help prevent sunburn and reduce skin cancer risk.

Here are some helpful resources: 

• U.S. Food and Drug Administration
• U.S. Centers for Disease Control and Prevention
• U.S. Surgeon General
• American Academy of Dermatology
• Skin Cancer Foundation

Every day! The sun emits harmful UV rays year-round. Even on cloudy days, up to 80 percent of the sun’s harmful UV rays can penetrate your skin.

Dr. Aziz Sancar, who was one of three scientists who won the 2015 Nobel Prize in Chemistry for showing precisely how DNA is repaired after damage, showed that DNA repair activity is highest in the afternoon/evening hours and is at its lowest in the night/early morning hours. This emphasizes the importance of sunscreen use during early morning hours – not just during sun's peak hours (10:00 am to 4:00 pm) - to reduce the skin cancer risk.

Here are some helpful resources: 

• American Academy of Dermatology
• T.H. Kang et al., Proceedings of the National Academy of Sciences 106 (8) 2864-2867

https://www.cnn.com/2020/05/13/cnn-underscored/best-sunscreen-for-face/index.html