According to the National Cancer Institute, more than 1 million new cases of non-melanoma skin cancer will be diagnosed in 2010 alone, with nearly 1,000 proving fatal. Skin cancer, which is characterized by the proliferated growth of skin cells, most often occurs in skin exposed to ultraviolet light from the sun. Early detection affords the best chance of survival. However, your first and best line of defense is to avoid getting too much sun. Using sunblock can help, but there are concerns about sunblock safety.
Sunblock Basics
Sunblock differs from sunscreen in that the former either absorbs or deflects UV radiation, while the latter merely filters UV rays into benign infrared wavelengths to minimize absorption. This is a significant difference in terms of skin protection, not only from cancer but also from photo-aging effects that causes premature wrinkling and abnormal pigmentation. Sunblock also contains active ingredients that block different types of UV rays, including UVA rays, which damage the collagen matrix in the uppermost layer of skin, and UVB rays, which break down DNA and promote genetic mutation within skin cells.
Types
According to the faculty of the Department of Dermatology at the University of California San Francisco, there are two types of sunblock---chemical and physical. As the term implies, chemical sunblocks contain chemical agents. Because no single chemical successfully blocks both UVA and UVB rays, several chemicals are used in combination. In contrast, physical sunblocks literally provide a barrier to deflect UV rays before they reach the skin. The two types of physical sunblocks are the mineral salts zinc oxide and titanium dioxide. These minerals are not harmful or irritating to the skin. However, some of the chemicals found in chemical sunblock formulas have raised concerns about safety.
SPF Facts
SPF stands for Sun Protection Factor, which can range from 8 to 45 or higher. Many people mistakenly think that this number represents the strength of the product. However, this number actually tells you how long you can safely expose your skin to the sun. To determine what SPF is right for your skin and the outdoor activity planned, you would use this simple formula: SPF x the number of minutes it takes to burn in the mid-day sun. So, if your skin typically starts to redden within 15 minutes of exposure, an SPF of 15 will provide protection for about 225 minutes, or 3 hours and 45 minutes. After that time, your window of safe sunbathing is closed.
Common Ingredients
Some of the most common sunblock ingredients include oxybenzone, avobenzone, octyl methoxycinnamate and padimate O. According to the Environmental Working Group, or EWG, these chemicals are of the most concern in terms of safety.
Safety Issues
According to EWG, oxybenzone is associated with skin allergies, is a potential hormone disruptor and is readily absorbed in large amounts through the skin. Avobenzone, which is also readily absorbed through the skin, has been shown to produce genetic mutations in cultured animal skin cells. Although in vitro studies show that octyl methoxycinnamate is absorbed through the skin in limited amounts, it has been found in breast milk. This chemical also produces estrogenic effects and reduces thyroid hormones. Padimate O has also been found to produce estrogenic effects and has been detected in breast milk.
Considerations
Studies on the effects of sunblock ingredients are ongoing. It should also be noted that much of the existing data is based on animal models and may not apply to humans. In addition, because the risk of skin cancer is well established, it would be prudent to protect your skin. If you're concerned about the safety of sunblock, wear adequate clothing and a hat when outdoors.
