By: Sarina Khanal
Sunscreen (also commonly known as sun block / sun cream), that absorbs or reflects some of the sun’s ultraviolet (UV) radiation on the skin exposed to sunlight and thus helps protect against sunburn. Sunscreens contain one or more UV filters of which there are three main types: Organic chemical compounds that absorb ultraviolet light, Inorganic particulates that reflect, scatter, and absorb UV light. Organic particulates that mostly absorb light like organic chemical compounds, but contain multiple chromophores, may reflect and scatter a fraction of light like inorganic particulates, and behave differently in formulations than organic chemical compounds.
The use of sunscreen is recommended because it prevents the squamous cell carcinoma and the basal cell carcinoma. However, the use of sunscreens is controversial for various reasons. Many do not block UVA radiation, which does not cause sunburn but can increase the rate of melanoma (another kind of skin cancer), so people using sunscreens may be getting too much UVA without realizing it. Additionally, sunscreens block UVB, and if used consistently this can cause a deficiency of vitamin D.
Most sunscreens with an SPF of 15 or higher do an excellent job of protecting against 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 sunscreen theoretically prevents reddening 15 times longer — about five hours.
Another way to look at it is in terms of percentages: SPF 15 blocks approximately 93 percent of all incoming UVB rays. SPF 30 blocks 97 percent; and SPF 50 blocks 98 percent. They may seem like negligible differences, but if you are light-sensitive, or have a history of skin cancer, those extra percentages will make a difference. And as you can see, no sunscreen can block all UV rays.
But there are problems with the SPF model: First, no sunscreen, regardless of strength, should be expected to stay effective longer than two hours without reapplication. Second, “reddening” of the skin is a reaction to UVB rays alone and tells you little about what UVA damage you may be getting. Plenty of damage can be done without the red flag of sunburn being raised.
Anyone over the age of six months should use a sunscreen daily. Even those who work inside are exposed to ultraviolet radiation for brief periods throughout the day. Also, UVA is not blocked by most windows.Children under the age of six months should not be exposed to the sun. Shade and protective clothing are the best ways to protect infants from the sun.
How much sunscreen to use depends on how much sun exposure you’re anticipating. In all cases a broad-spectrum sunscreen offering protection against both UVA and UVB rays.Many after-shave lotions and moisturizers have a sunscreen (usually SPF 15 or greater) already in them, and this is sufficient for everyday activities with a few minutes here and there in the sun. However, if you work outside or spend a lot of time outdoors, you need stronger, water-resistant, beachwear-type sunscreen that holds together on your skin. The “water resistant” and “very water resistant” types are also good for hot days or while playing sports, because they’re less likely to drip into your eyes. However, these sunscreens may not be as good for everyday wear. They are stickier, don’t go as well with makeup, and need to be reapplied every two hours.
To ensure that you get the full SPF of a sunscreen, you need to apply 1 oz – about a shot glass full. Studies show that most people apply only half to a quarter of that amount, which means the actual SPF they have on their body is lower than advertised. Sunscreens should be applied 30 minutes before sun exposure to allow the ingredients to fully bind to the skin. Reapplication of sunscreen is just as important as putting it on in the first place, so reapply the same amount every two hours. Sunscreens should be reapplied immediately after swimming, toweling off, or sweating a great deal.
Of all the threats to our oceans – chemical waste, pollution, plastic products, over fishing, ocean acidification (CO2 damage), we can add another threat we humans can take credit for – viral infections due to the sunscreens we use. Sun screen chemicals are not only bad for us, our health and genetics, but they also severally damage coral reefs. It seems that the main chemicals in sunscreen: octinoxate, oxybenzone, homosalate and a host of other chemicals activate a virus in the algae that attaches itself to coral – once the virus is activated, it destroys the host coral. Marine researchers are finding that small doses of sun screen chemicals activate the virus and the net result is dead coral – or the bleaching we see.
Sources : Wikipedia
Planet Protect Blog
http://www.skin cancer. org