By Elizabeth Lesko
With warm weather and sunny days occurring with increasing frequency, I thought it might be a good time to discuss a topic that is near and dear to my research: ultraviolet radiation (UVR) and skin cancer. Throughout my tenure as a dermatology-focused graduate student I have come across a plethora of misinformation on skin cancer from sources ranging from social media to family, and even to medical professionals in the media. So, today I will endeavor to dispel a number of the most prevalent myths I’ve heard, and hopefully replace some of that misinformation with good science.
Myth #1: Sunlight is only damaging to your skin if you get a sunburn.
Fact: Any level of unprotected sun exposure can damage your skin. It’s fairly common for people to think of sunburn as the major negative consequence of a day in the sun but in truth, damage is being done to the skin long before sunburn occurs1. Erythema (redness) following sun exposure is a result of skin inflammation following UVR-induced damage. Severe or prolonged exposure can result in larger-scale cell death via apoptosis – indicated by blistering and peeling of the skin. While sunburns are the biggest lifetime risk factor for the development of the skin cancer melanoma2, lifetime non-burning sun exposure is considered a major risk factor for non-melanoma skin cancers (NMSCs) and can also contribute prematurely to signs of skin aging, such as wrinkles or dark spots.
Myth #2: UVR isn’t that harmful – after all, it’s used by dermatologists to treat skin disease!
Fact: UVR is a complete carcinogen that can be very dangerous to healthy skin, but can also be used to treat skin disease. Much like how chemotherapy and radiation therapy are used for the treatment of cancer despite their potential to damage healthy tissue, UVR can be used to treat diseases such as eczema or psoriasis3 when the physician and patient both decide that the benefits outweigh the risks. Patients undergoing this type of treatment (typically called phototherapy) will still accumulate damage over time due to the UVR, and often participate in more frequent and thorough skin cancer screenings than the general population due to the increased cancer risk. Bottom line: UVR-based phototherapy is something that should only be prescribed by a medical professional who has thoroughly weighed the risks and benefits, and is not something that should be self-administered without medical guidance.
Myth #3: Melanoma is the only skin cancer you should really be worried about.
Fact: While melanoma is generally considered the most aggressive and potentially deadly form of skin cancer, NMSCs are much more common and can prove dangerous if left unnoticed or untreated. Cutaneous squamous cell carcinoma and basal cell carcinoma (the two most common UVR-related NMSCs) are the most frequently diagnosed cancers in the United States4. Over 3 million people are diagnosed with NMSC each year in the U.S. – more than 10 times the number of people diagnosed with breast cancer, lung cancer, or prostate cancer5 – which is likely why NMSC statistics are often left out of graphics describing cancer facts and figures. NMSCs are most common on the sun-exposed face and upper torso, and typically have a low rate of metastasis, particularly due to early detection and removal by surgical excision. However, NMSC can still metastasize if ignored, and account for over 2,000 deaths annually in the U.S. So, while you shouldn’t necessarily make yourself anxious about NMSCs, it is still an excellent idea to wear your sun protection and talk to a dermatologist about any unusual spots or lesions on your skin.
Myth #4: Sunscreen contains harmful chemicals that can increase cancer risk and do more harm than not wearing sunscreen at all.
Fact: The ingredients in commercial sunscreens are all GRAS (generally recognized as safe), and some of the most common ingredients are even inert minerals. Sunscreens in general can be classified into two major categories: physical and chemical. Physical sunscreens use substances such as zinc oxide to create a coating on the skin that physically blocks the penetration of UVR by reflection or absorption, while chemical sunscreens are organic compounds that absorb UVR and release lower energy (less damaging) radiation6. The best protection against both UVA (lower energy, aging-associated UVR) and UVB (higher energy, sunburn-associated UVR) often involves combining both physical and chemical sunscreens. There is some concern that newer, man-made ingredients used in sunscreen and other cosmetics lack the data to definitively declare safety over lifetime exposure despite GRAS status. While these ingredients are still considered safe, the FDA had requested more complete data to address concerns about sunscreen safety and efficacy7. In such cases, the use of physical sunscreens containing zinc oxide or titanium oxide (naturally-occurring, largely inert, and thoroughly safety-tested minerals) may be preferable for those concerned.
Myth #5: You shouldn’t wear sunscreen because you need the UV light to create Vitamin D.
Fact: Vitamin D synthesis requires UVB exposure, but using sunscreen is not likely to prevent you from getting enough Vitamin D. The Vitamin D and sun exposure relationship has been well studied and debated, but numerous studies have suggested that typical sunscreen use (that is, how the average person applies sunscreen) does not have a significant impact on serum levels of Vitamin D over time8,9. This is likely due to the fact that some UVB radiation is able to penetrate most sunscreens and other forms of sun protection. In months where it is too cold to venture outside, increasing dietary Vitamin D is suggested to compensate for the lack of UVB exposure.
Myth #6: Commercial sunscreens are bad for the environment.
Fact: Several ingredients once used in chemical sunscreens were found to cause harm to marine life, but these ingredients are now falling out of use, or are banned in locations with fragile ecosystems. The ingredients octinoxate and oxybenzone in particular have fallen under scrutiny thanks to the penchant of these chemicals for bleaching coral reefs (due to sunscreens containing these ingredients washing off in the water)10. For the most part, everyday use of sunscreen inland will not cause environmentally harmful chemicals to find their way into marine ecosystems, but those who plan to vacation at the beach should certainly check the most recent recommendations for safe ingredients prior to swimming.
Myth #7: Sunscreen is 100% effective at blocking harmful UVR and is therefore the best form of sun protection.
Fact: While sunscreen is a great way to decrease your dose of UVR, it does not block 100% of UVR and should be used in combination with other sun protection measures. Sun protection factor (SPF) refers to how much UVB radiation is blocked by that sunscreen (93% for SPF 15, 98% for SPF 50, etc. 11), but some percentage of radiation will always be able to reach the skin. Therefore, it is a good idea to couple sunscreen use and reapplication with UV-blocking clothing and other sun protection measures such as keeping in the shade or avoiding peak sunlight hours when possible.
Myth #8: Sunglasses are just to help you see better in bright light – any old pair will do just fine.
Fact: Your eyes can be damaged by UVR just like your skin, so UVR-blocking glasses are the healthy choice. UVR exposure can increase your risk for cataracts and other ocular diseases12 and not all dark lenses are capable of blocking UVR. Sunglasses marketed as UVA/B filtering will be made of or coated with materials that block UVR, and these glasses range from very cheap drugstore sunglasses to high-end brands. Polarization can help with glare but is not a substitute for UV filtering ability, so be sure to double check the material and stay protected!
Sources:
1.Narayanan DL, Saladi RN, Fox JL. Ultraviolet radiation and skin cancer. Int J Dermatol. 2010 Sep;49(9):978-86. doi: 10.1111/j.1365-4632.2010.04474.x. PMID: 20883261.
2. Gandini S, Sera F, Cattaruzza MS, Pasquini P, Picconi O, Boyle P, Melchi CF. Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure. Eur J Cancer. 2005 Jan;41(1):45-60. doi: 10.1016/j.ejca.2004.10.016. PMID: 15617990.
3. Addison R, Weatherhead SC, Pawitri A, Smith GR, Rider A, Grantham HJ, Cockell SJ, Reynolds NJ. Therapeutic wavelengths of ultraviolet B radiation activate apoptotic, circadian rhythm, redox signalling and key canonical pathways in psoriatic epidermis. Redox Biol. 2021 Mar 10;41:101924. doi: 10.1016/j.redox.2021.101924. Epub ahead of print. PMID: 33812333.
4. Cancer.Net Editorial Board. Skin Cancer (Non-Melanoma): Statistics. Cancer.net. 2021 Feb. https://www.cancer.net/cancer-types/skin-cancer-non-melanoma/statistics
5. American Cancer Society: Cancer Facts and Figures 2020. Atlanta, Ga: American Cancer Society, 2020. https://www.cancer.org/content/dam/cancer-org/research/cancer-facts-and-statistics/annual-cancer-facts-and-figures/2020/cancer-facts-and-figures-2020.pdf
6. Gabros S, Nessel TA, Zito PM. Sunscreens And Photoprotection. 2020 Sep 29. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–. PMID: 30725849.
7. FDA News Release. FDA advances new proposed regulation to make sure that sunscreens are safe and effective. U.S. Food & Drug Administration. Feb 21, 2019. https://www.fda.gov/news-events/press-announcements/fda-advances-new-proposed-regulation-make-sure-sunscreens-are-safe-and-effective
8. Feketea GM, Bocsan IC, Tsiros G, Voila P, Stanciu LA, Zdrenghea M. Vitamin D Status in Children in Greece and Its Relationship with Sunscreen Application. Children (Basel). 2021 Feb 5;8(2):111. doi: 10.3390/children8020111. PMID: 33562659; PMCID: PMC7914486.
9. Neville JJ, Palmieri T, Young AR. Physical Determinants of Vitamin D Photosynthesis: A Review. JBMR Plus. 2021 Jan 19;5(1):e10460. doi: 10.1002/jbm4.10460. PMID: 33553995; PMCID: PMC7839826.
10. NOAA. Skincare Chemicals and Coral Reefs. National Ocean Service. 2021 Feb 26. https://oceanservice.noaa.gov/news/sunscreen-corals.html
11. Skin Cancer Foundation. Sun Protection and Vitamin D. Skin Cancer Foundation. 2018 May 14. https://www.skincancer.org/blog/sun-protection-and-vitamin-d/
12. Yam JC, Kwok AK. Ultraviolet light and ocular diseases. Int Ophthalmol. 2014 Apr;34(2):383-400. doi: 10.1007/s10792-013-9791-x. Epub 2013 May 31. PMID: 23722672.
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