Sun Exposure and our health in 2013
As summer is approaching in North America and we all want to know should we expose our body to sun or not. This new study confuses us more about Sun Exposure…..
What is In Sun Rays?
Radiation from the Sun, which is more popularly known as sunlight, is a mixture of electromagnetic waves ranging from infrared (IR) to ultraviolet rays (UV). It of course includes visible light, which is in between IR and UV in the electromagnetic spectrum.
All electromagnetic waves (EM) travel at a speed of approximately 3.0 x 10 8 m/s in vacuum. Although space is not a perfect vacuum, as it is really composed of low-density particles, EM waves, neutrinos, and magnetic fields, it can certainly be approximated as such. Now, since the average distance between the Earth and the Sun over one Earth orbit is one AU (about 150,000,000,000 m), then it will take about 8 minutes for radiation from the Sun to get to Earth.
Actually, the Sun does not only produce IR, visible light, and UV. Fusion in the core actually gives off high energy gamma rays. However, as the gamma ray photons make their arduous journey to the surface of the Sun, they are continuously absorbed by the solar plasma and re-emitted to lower frequencies. By the time they get to the surface, their frequencies are mostly only within the IR/visible light/UV spectrum.
During solar flares, the Sun also emits X-rays. X-ray radiation from the Sun was first observed by T. Burnight during a V-2 rocket flight. This was later confirmed by Japan’s Yohkoh, a satellite launched in 1991.
Previous research -Health Effects of Overexposure to the Sun
Ozone layer depletion decreases our atmosphere’s natural protection from the sun’s harmful ultraviolet (UV) rays. This Web page provides a quick overview of the major health problems linked to overexposure to UV radiation. Understanding these risks and taking a few sensible precautions will help you enjoy the sun while lowering your chances of sun-related health problems.
Skin Cancer
Each year, more new cases of skin cancer are diagnosed in the U.S. than new cases of breast, prostate, lung, and colon cancer combined. One in five Americans will develop skin cancer in their lifetime. One American dies from skin cancer every hour. Unprotected exposure to UV radiation is the most preventable risk factor for skin cancer.
Melanoma
Melanoma, the most serious form of skin cancer, is now one of the most common cancers among adolescents and young adults ages 15-29. While melanoma accounts for about three percent of skin cancer cases, it causes more than 75 percent of skin cancer deaths. UV exposure and sunburns, particularly during childhood, are risk factors for the disease. Not all melanomas are exclusively sun-related—other possible influences include genetic factors and immune system deficiencies.
Non-melanoma Skin Cancers
Non-melanoma skin cancers are less deadly than melanomas. Nevertheless, they can spread if left untreated, causing disfigurement and more serious health problems. There are two primary types of non-melanoma skin cancers: basal cell and squamous cell carcinomas. If caught and treated early, these two cancers are rarely fatal. Between 40 and 50 percent of Americans who live to age 65 will have one of these types of skin cancer at least once.
•Basal cell carcinomas are the most common type of skin cancer tumors. They usually appear as small, fleshy bumps or nodules on the head and neck, but can occur on other skin areas. Basal cell carcinoma grows slowly, and it rarely spreads to other parts of the body. It can, however, penetrate to the bone and cause considerable damage.
•Squamous cell carcinomas are tumors that may appear as nodules or as red, scaly patches. This cancer can develop into large masses, and unlike basal cell carcinoma, it can spread to other parts of the body.
Other Skin Damage
Other UV-related skin disorders include actinic keratoses and premature aging of the skin. Actinic keratoses are skin growths that occur on body areas exposed to the sun. The face, hands, forearms, and the “V” of the neck are especially susceptible to this type of lesion. Although premalignant, actinic keratoses are a risk factor for squamous cell carcinoma. Look for raised, reddish, rough-textured growths and seek prompt medical attention if you discover them.
Chronic exposure to the sun also causes premature aging, which over time can make the skin become thick, wrinkled, and leathery. Since it occurs gradually, often manifesting itself many years after the majority of a person’s sun exposure, premature aging is often regarded as an unavoidable, normal part of growing older. However, up to 90 percent of the visible skin changes commonly attributed to aging are caused by the sun. With proper protection from UV radiation, most premature aging of the skin can be avoided.
Cataracts and Other Eye Damage
Cataracts are a form of eye damage in which a loss of transparency in the lens of the eye clouds vision. If left untreated, cataracts can lead to blindness. Research has shown that UV radiation increases the likelihood of certain cataracts. Although curable with modern eye surgery, cataracts diminish the eyesight of millions of Americans and cost billions of dollars in medical care each year.
Other kinds of eye damage include pterygium (tissue growth that can block vision), skin cancer around the eyes, and degeneration of the macula (the part of the retina where visual perception is most acute). All of these problems can be lessened with proper eye protection. Look for sunglasses, glasses or contact lenses if you wear them that offer 99 to 100 percent UV protection.
Immune Suppression
Scientists have found that overexposure to UV radiation may suppress proper functioning of the body’s immune system and the skin’s natural defenses. For example, the skin normally mounts a defense against foreign invaders such as cancers and infections. But overexposure to UV radiation can weaken the immune system, reducing the skin’s ability to protect against these invaders.
(Source- epa.gov)
New Research-Sun Exposure Benefits May Outweigh Risks Say Scientists
Scientists at the University of Edinburgh in the UK suggest that the heart-health benefits of sun exposure may outweigh the risk of developing skin cancer. In the landmark study, the researchers found that when sunlight touches our skin, a compound called nitric oxide that helps lower blood pressure, is released into our blood vessels. Richard Weller, Senior Lecturer in Dermatology, and colleagues, say the effect is such that overall, sun exposure could improve health and even prolong life, because the benefits of reducing blood pressure, cutting heart attacks and strokes, far outweigh the risk of getting skin cancer.
The proof-of-principle study is being presented this week in Edinburgh at International Investigative Dermatology 2013, the world's largest gathering of skin experts. The abstract was published online in the Journal of Investigative Dermatology on 15 April. The researchers note that rates of high blood pressure and cardiovascular disease rise in winter and are tied to geographic latitude (for instance they are higher in northern Europe than in southern Europe). Also, estimates show that in northern Europe, for every death from skin cancer, about 60 to 100 people die of stroke and heart disease linked to high blood pressure. This new study is important because until now it was thought that sunlight's only benefit to human health was production of vitamin D, which rises after exposure to the sun. Previous studies have found that while increased vitamin D levels link to lower cardiovascular disease, oral supplements do not have an effect on this. Weller and colleagues found that the body's production of nitric oxide is separate from production of vitamin D.
For their study they invited 24 volunteers to sit under sunlamps for two 20 minute sessions while they examined their blood pressure. In one session, they exposed the volunteers to both ultra-violet (UV) rays and heat from the lamps. In the other session, they only exposed them to the lamps' heat and blocked the UV rays. The results showed that the volunteers' blood pressure fell and their heart rate rose in the session where they were exposed to both UV and heat, but not when they were exposed to heat only. The reduction in blood pressure lasted for about 50 minutes. Human skin contains large stores of nitrite (NO2) and nitrate (NO3). The researchers note that while nitrate is "biologically inert", the action of sunlight can reduce it to active nitrite and nitric oxide (NO). They found that circulatory nitrate fell and nitrite rose during UV and heat exposure, but not during exposure to heat only. There was no difference in vitamin D levels.
Weller says in a statement that, “We suspect that the benefits to heart health of sunlight will outweigh the risk of skin cancer. The work we have done provides a mechanism that might account for this, and also explains why dietary vitamin D supplements alone will not be able to compensate for lack of sunlight."
He and his team now want to look at the relative risks of skin cancer and heart disease in people who have received different amounts of exposure to sunlight. "If this confirms that sunlight reduces the death rate from all causes, we will need to reconsider our advice on sun exposure," says Weller. There have also been suggestions that exposure to the sun can help prevent infectious disease. For example, in 2011, Phil Rice, a virologist at St George's Hospital, University of London, suggested that the sun's UV rays inactivate the chickenpox virus on the skin.
(Source- Journal of Investigative Dermatology)
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