Most of us are exposed to large amounts of UVA throughout our lifetime. UVA rays account for up to 95 percent of the UV radiation reaching the Earth's surface. Although they are less intense than UVB, UVA rays are 30 to 50 times more prevalent. They are present with relatively equal intensity during all daylight hours throughout the year, and can penetrate clouds and glass.
Studies over the past two decades, show that UVA damages skin cells called keratinocytes in the basal layer of the epidermis, where most skin cancers occur. (Basal and squamous cells are types of keratinocytes.) UVA contributes to and may even initiate the development of skin cancers. Ultraviolet (UV) radiation is part of the electromagnetic (light) spectrum that reaches the earth from the sun.
It has wavelengths shorter than visible light, making it invisible to the naked eye. Ultraviolet A (UVA) causes lasting skin damage, skin aging, and can cause skin cancer. Ultraviolet B (UVB) causes sunburns, skin damage, and can cause skin cancer. Unprotected exposure to UV Rays may lead to premature skin aging and wrinkling (photoaging). Sunburned skin doesn’t just feel awful, it can cause permanent damage over time.
SUNSCREENS & UV RADIATION...
Sunscreens are products combining several ingredients that help prevent the sun’s ultraviolet (UV) radiation from reaching the skin. Two types of ultraviolet radiation, UVA and UVB, damage the skin and increase your risk of skincancer. Sunscreens vary in their ability to protect against UVA and UVB. SPF — or Sun Protection Factor — is a measure of a sunscreen’s ability to prevent UVB from damaging the skin. Here's how it works: If it takes 20 minutes for your unprotected skin to start turning red, using an SPF 15 sunscreentheoretically prevents reddening 15 times longer – about five hours. Most sunscreens with an SPF of 15 or higher do an excellent job of protecting against UVB.
What Does Broad-Spectrum Mean? Broad-spectrum sunscreens protect the skin from both UVA and UVB rays. Beginning in December 2012, the U.S. Food and Drug Administration (FDA) began to implement new rules for “broad-spectrum” products. Under the oldrules, a product could be called “broad spectrum”, even though it would not efficiently block UVA rays from reaching the lower layers of skin.
UNDER THE NEW FDA RULES, A “BROAD SPECTRUM” PRODUCT MUST BE ABLE TO EFFECTIVELY BLOCK UVA RAYS AS WELL.