Sun protection
Sun protection encompasses various methods designed to prevent skin damage from ultraviolet radiation (UVR) emitted by the sun. This can involve both physical barriers, such as clothing and sunscreen, and chemical barriers that absorb UVR. Sunscreens, which can be applied as creams, lotions, or sprays, contain substances that either physically block UVR, like zinc oxide and titanium dioxide, or absorb it, including chemicals like oxybenzone and avobenzone. The effectiveness of sunscreens is measured by the sun protection factor (SPF), while fabrics are rated with a ultraviolet protection factor (UPF) to indicate their protective ability against UVR.
Limiting sun exposure, especially during peak hours from 10:00 A.M. to 4:00 P.M., and seeking shade are crucial strategies for skin protection. Additionally, it's important to consider that UVR can penetrate clouds, making sun protection necessary even on overcast days. As global climate change affects the ozone layer, which filters UVR, increased exposure may lead to an uptick in skin conditions, including various forms of skin cancer. Given the serious health implications associated with UVR exposure, adopting effective sun protection practices is essential for everyone, starting from a young age.
Sun protection
Definition
Sun protection refers to methods of preventing damage or injury to the skin from ultraviolet radiation (UVR) emitted by the sun. Such methods often involve physical or chemical barriers, sun exposure reduction, or both. Physical barriers act to physically block UVR and include sunscreens, fabrics, and glass. Chemical barriers act by absorbing UVR and primarily include the chemicals incorporated in some sunscreens and in certain fabrics.
Sunscreens, usually applied as creams, lotions, or sprays, are composed of chemical substances that prevent UVR penetration of the skin. Sunscreens that act as a physical barrier to UVR include zinc oxide and titanium dioxide. Sunscreens that act as a chemical barrier to UVR include para-aminobenzoic acid (PABA), cinnamates, camphor derivatives, oxybenzone, avobenzone, octocrylene, and salicylates. The effectiveness of sunscreens in protecting skin against UVR is measured by a number called the sun protection factor (SPF); a higher number indicates a greater degree of protection.
Fabrics act as physical barriers to UVR and include those that make up clothing, umbrellas, and hats (especially wide-brimmed hats to protect the face, eyes, and neck). The effectiveness of fabrics to block out UVR is indicated with a number called the ultraviolet protection factor (UPF); the higher the number, the greater the ability to protect against UVR. Fabrics that have a greater ability to block UVR are darker in color, heavy-weight, and tightly woven. Fabrics may also act as chemical barriers when they are made from fibers having such an ability or when the fabric is impregnated with a chemical sunscreen.
Limiting sun exposure, especially between 10:00 A.M. and 4:00 P.M., when the sun’s ultraviolet rays are the strongest, and seeking shade when appropriate are effective in protecting against UVR. These precautions must be observed even on cloudy days because UVR can penetrate clouds. Although a certain amount of protection is afforded by a hat or umbrella, the ground can reflect UVR. Therefore, sunscreens should also be applied.
Glass also acts as a physical barrier to block the three main types of UVR (UVA, UVB, and UVC). Some glass (such as the side and rear windows of many automobiles) block only UVB and transmit a considerable amount of UVA. Other types of glass used in automobile windshields, such as laminated glass (two pieces of glass bonded together with a plastic), are much more effective in blocking UVA and UVB. The effectiveness of glass to block UVR can also be increased by the application of UVR-blocking substances to the glass. Sunglasses, which may be made of glass, polycarbonate, or other materials, are particularly effective in protecting the eyes from UVR. Sunglasses designed with side panels or that wrap around afford better protection against UVR reaching the eyes from the sides.
Significance for Climate Change
The ozone layer is a layer of gas present in the stratosphere (the middle portion of the Earth’s atmosphere) that plays a significant role in the regulation of UVR transmission to the Earth. Of the three main types of UV radiation that reach the earth from the sun, UVC is extremely hazardous, but it is completely absorbed by the ozone layer, as is most of UVB; UVA is completely transmitted through the ozone layer.
Substances that contribute to global warming can deplete the ozone layer, thereby allowing increased amounts of dangerous UVR to reach the earth. Ozone-depleting substances include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, methyl bromide, carbon tetrachloride, and methyl chloroform. These chemical compounds are unstable in the when subjected to UVR. As these compounds undergo reactions in the stratosphere, they are broken down into halogens such as chlorine, fluorine, or bromine. These halogens play a role in converting ozone into oxygen and other related by-products, thereby depleting the ozone layer. The continued depletion of the leads to higher levels of UVB transmitted to the earth, which in turn can lead to an increase in various medical problems.
All forms of UVR are harmful to biological organisms. UVA is responsible for damaging the deeper layers of the skin and producing harmful skin effects, including accelerated skin aging, tanning, and other conditions, such as drug-induced sunlight sensitivities. UVB affects the top layer of the skin and can produce skin cancers, especially basal cell carcinoma and melanoma. Skin cancer is one of the most common forms of cancer in the United States, and more than 90 percent of the cases are due to sun exposure. Significantly, Australia has the highest incidence of skin cancer in the world; associated risk factors are the great number of fair-skinned individuals in the country and the amount of sun exposure.
UVB also causes tanning, sunburns, actinic keratosis (benign skin lesions that may develop into invasive squamous cell cancer), and formation of senile cataracts. UVB has been associated with other effects on the eyes, including the development of pterygium (benign tissue growth of the conjunctiva) and acute inflammation of the eyes, specifically the inside lining of the eyelids, cornea, and iris.
UVB has also been linked with decreased ability of the immune system to elicit a protective response. This immunosuppression has been observed in a number of rodent and human studies; in fact, rodents exposed to UVB have shown increased susceptibility to certain infectious diseases. Solar UVR and exposure to sunlamps and sunbeds were classified by the United States Department of Health and Human Services in 2000 as known human carcinogens. Therefore, as the continued depletion of the ozone layer will lead to higher levels of UVR and a concomitant increase in the various medical conditions discussed above, sun protection is essential for everyone exposed to UVR and should begin even in infancy.
Bibliography
Bellenir, Karen, ed. Health Reference Series Cancer Sourcebook. 5th ed. Detroit, Mich.: Omnigraphics, 2007.
Kroschwitz, Jacqueline I., and Arza Seidel, eds. Kirk-Othmer Encyclopedia of Chemical Technology. 5th ed. Hoboken, N.J.: Wiley-Interscience, 2004-2007.
Skin Cancer Foundation. 2007 Skin Cancer Facts. New York: Author, 2007.
"Sun Safety Tips." EPA, 5 Feb. 2024, www.epa.gov/sunsafety/sun-safety-tips. Accessed 11 Dec. 2024.
University of Bath. "Sunscreen Doesn't Protect As Well As It Could: Here Is What Is Missing." Science Daily, 12 Apr. 2022, www.sciencedaily.com/releases/2022/04/220412140903.htm. Accessed 11 Dec. 2024.
World Health Organization. Global Solar UV Index: An Educational Tool to Reduce Risks of Skin Cancer and Cataract. Geneva, Switzerland: Author, 2004.