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Is the summer sun your frind or foe?
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With the temperatures having already reached the 80s and 90s, the past few days in DC, my mind drifts to the pleasures of refreshing dips in the ocean and, of course, catching a few rays of sunshine with each passing longer day. Through the years, there have been some interesting studies on how people react to sunlight, as opposed to rainy, overcast type days. These studies have proven that the sun is a key factor in determining our moods,energy levels and basic outlook on life. There is one well-known syndrome called Seasonal Affective Disorder (SAD), which shows that a lack of adequate light during winter has been linked to a high rate of depression. Additional studies have shown that the lack of sun impacts our productivity. In an environment, such as D.C., where people working in buildings with large windows, are as much as 60% less likely to become ill than those who are forced to spend time in sunlight.
Despite the many benefits of the sun, too much of it can become a silent killer.Skin cancer, even though not the number one killer of adults in America, is the most common form of all cancers. Over the last two decades the rise in skin cancer has been attributed to an increase in UV Radiation infiltrating earth's protective ozone layer. Called a "Silent Killer", Ultraviolet (UV) Radiation is defined as the process at which energy is admitted as particles or waves. The sun emits radiation at different wavelengths, called visible light. Just like a rainbow and the spectrum of colors, Ultraviolet light is part of the electromagnetic spectrum and is comprised of three categories:
1.) UV-C wavelengths: not harmful to humans, since its rays are blocked from reaching the earth's surface by ozone in the stratosphere. The stratosphere is one of five layers to the atmosphere and is some 10-30 miles above the earth's surface.
2.) UV-B wavelengths: partially absorbed by the ozone layer; however, long term exposure can induce skin cancer and is known to be the most destructive form of UV radiation.
3.) UV-A wavelengths: partially absorbed by the ozone, it is the most commonly encountered type of UV light. Exposure has a initial tanning effect, but long-term results can become a toughening of the skin, suppression of the immune system and cataract formation.
With the above forms of UV light having been studied and understood to be harmful to one's skin if over-exposed, the Environmental Protection Agency (EPA), in conjunction with the National Weather Service (NWS), began testing and experimental Ultraviolet Index for 58 U.S. cities on June 28,1994. In April of 1995, the NWS removed the experimental label and made the index a daily product for the the sole purpose of guiding and protecting people from the sun's potential danger. For those who spend a considerable amount of time outdoors, the UV Index is a forecast of the next day's ultraviolet intensity when the sun is at its highest point in the sky. The UV scale ranges from 0 to 10+, with the highest numbers accounting for the greatest amount of skin damage. In helping the public to reduce the risk of developing skin cancer and other sun-related illnesses, the UV Index can be broken down into the following:
1.) #0-2: Minimal Risk of danger from the sun's UV rays. Most people can stay in the sun for up to one hour, during the time the sun is the strongest (10am to 4pm), without burning.
2.) #3-4: Low risk of harm from unprotected sun exposure. Use a sunscreen with a number of at least 15. A simple way to tell how much UV exposure you are receiving is to look for your shadow. If you're shadow is taller than you are, your exposure is likely to be low. If your shadow is shorter;however, you are more than likely of being exposed to high levels of UV Radiation.
3.) #5-6: Moderate Risk of harm. Fair-skinned people might burn in less than 15 minutes. Use lip balm or lip cream containing a sunscreen.
4.) #7-9: High Risk of receiving a burn within 10-15minutes. Typically, if you have red or blond hair, blue eyes and light milky skin,your chances of burning are extremely high. It would be helpful to wear long-sleeved shirts and trousers made from tightly woven fabrics. Even if you have dark hair, eyes and skin, you are still apt to burn.
5.) #10+: Very High Risk Anyone can burn within 5 minutes. If you must be outdoors, keep your head protected, wear sunglasses that block 99 to 100% of all UV rays and apply sunscreen every two hours. In addition, drink as much water as possible, since dehydration can occur rapidly.
The amount of UV radiation needed to actually damage one's skin is dependent on several factors, but in general, the darker someone's skin is naturally, the longer it takes to cause the skin to redden. A few elements affecting the amount of sun one may receive would be:
1.) Altitude - The higher one is from the earth's surface, the depth of the atmosphere and amount of ozone available to absorb the sun's rays is reduced
2.) Time of Year - During winter, sunlight is shortened by as much as four hours due to the earth's tilt and position of the earth in relation to the sun.
3.) Ozone - Absorbs UV radiation, the more abundant the ozone, the less radiation penetrates our skin
4.) Clouds - Comprised of millions of water droplets, which absorb and scatter UV radiation, depending upon a cloud's thickness
5.) Ground reflection - When UV light reaches the earth's surface, most natural surfaces, such as soil, grass and water, will reflect less than 10% of the UV rays; however, a fresh snow pack and sand reflects 25-80%. This would help to increase your chance of burning.
So how is the UV Index calculated? It is a somewhat complex tabulation that is computed by using the forecasted ozone data, cloud coverage and elevation for the 58 designated cities. Done in a three-step process, the calculation starts with the measurement of ozone for the entire globe. This information is obtained via satellites operated by NOAA. Once gathered, a computer model determines the amount of UV radiation reaching the ground in wavelengths of 280 to 400 nanometers for that particular day, time of year and latitude. The reason for the particular 280-400 range, is because those are the wavelengths that the harmful UV-B and UV-A rays fall under. This information is then weighted according to how human skin responds to those different wavelengths. Once a number is calculated, it is then adjusted for the effects of elevation and clouds ( UV radiation will increase approximately 6% for every 3000 feet above sea level). Clear skies allow 100% of the UV radiation to reach the ground; whereas scattered clouds ( mostly sunny skies) transmit 89%, broken clouds ( partly sunny skies) 73% and overcast conditions 31%. Lastly, once adjusted for elevation and clouds, this value is then divided by 25 and rounded to the nearest whole number! To see the list of 58 cities that give a daily forecast go to:
http://www.cpc.noaa.gov/products/stratosphere/uv_index/uv_current.shtml
It seems reasonable that avoiding the midday sun when possible would be highly advantageous , but each year warnings about skin cancer are hardly heeded. The result, nearly a million cases of skin cancer diagnosed every year! Most cases will deal with Basel cell or squamous cell carcinoma, slow-growing lesions that rarely spread to other organs, but the rate at which melanoma (deadliest skin cancer) is rising is very alarming. In a period of two years between 1995 and 1997, there was a 12% rise in melanoma cases reported throughout the United States. To put it in perspective, in the 1930's the odds of developing malignant cancer were 1 in 1,500,but today the odds are 1 in 87. Even though these statistics are staggering, people still want to worship the sun; hence the catch phrase "I'm working on my tan". Hopefully; however, with the addition of a UV Index, will all be better prepared to deal with all that Mother Nature has to offer during the summer months.
Photo Credit above: NOAA Space Weather Prediction Center (www.swpc.noaa.gov/
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