Risks and Benefits of Sun Exposure

Exposing skin to sunlight presents both health risks and health benefits. Sunlight is the major source of vitamin D-producing Ultraviolet B radiation, which has a wide range of positive health effects, including possibly inhibiting the growth of some cancers. On the other hand, long-term sunlight exposure is known to be associated with the development of skin cancer, skin aging, immune suppression and eye diseases such as cataracts. Sun exposure has also been associated with the timing of melatonin synthesis and reduced risk of seasonal affective disorder. A number of public health organizations state that there needs to be a balance between having the risks of having too much and the risks of having too little sunlight. There is a general consensus that sunburn should always be avoided.

However, not all physicians agree with the assertion that there is an optimal level of sun exposure, with some arguing that it is better to minimize sun exposure at all times and to obtain vitamin D from other sources.

Serum levels of 25(OH) D3 are below the recommended levels for a large portion of the general adult population and in most minorities, indicating that Vitamin D deficiency is a common problem in the United States.
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Benefits

According to the U.S. National Institutes of Health Office of Dietary Supplements, most people in the United States can meet their vitamin D needs through exposure to sunlight, even though a large portion have serum 25(OH)D3 levels below recommendations. Ultraviolet (UV) B radiation with a wavelength of 290-315 nanometers penetrates uncovered skin and converts cutaneous 7-dehydrocholesterol to previtamin D3, which in turn becomes vitamin D3. Season, geographic latitude, time of day, cloud cover, smog, skin melanin content, and sunscreen are among the factors that affect UV radiation exposure and vitamin D synthesis. The UV energy above 42 degrees north latitude (a line approximately between the northern border of California and Boston) is insufficient for cutaneous vitamin D synthesis from November through February; in far northern latitudes, this reduced intensity lasts for up to 6 months. In the United States, latitudes below 34 degrees north (a line between Los Angeles and Columbia, South Carolina) allow for cutaneous production of vitamin D throughout the year.

Complete cloud cover reduces UV energy by 50%; shade (including that produced by severe pollution) reduces it by 60%. UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D. Sunscreens with a sun protection factor of 8 or more appear to block vitamin D-producing UV rays, although in practice people generally do not apply sufficient amounts, cover all sun-exposed skin, or reapply sunscreen regularly. Skin likely synthesizes some vitamin D even when it is protected by sunscreen as typically applied.

The factors that affect UV radiation exposure and research to date on the amount of sun exposure needed to maintain adequate vitamin D levels make it difficult to provide general guidelines. It has been suggested by some vitamin D researchers, for example, that approximately 5-30 minutes of sun exposure between 10 AM and 3 PM at least twice a week to the face, arms, legs, or back without sunscreen usually lead to sufficient vitamin D synthesis and that the moderate use of commercial tanning beds that emit 2%-6% UVB radiation is also effective. Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement.

Risks

Despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight and UV radiation from tanning beds. According to the National Toxicology Program Report on Carcinogens from the Department of Health and Human Services, broad-spectrum UV radiation is a carcinogen thought to contribute to most of the estimated 1.5 million skin cancers and the 8,000 deaths due to metastatic melanoma that occur annually in the United States Lifetime cumulative UV damage to skin is also largely responsible for some age-associated dryness and other cosmetic changes.

It is not known whether a desirable level of regular sun exposure exists that imposes no (or minimal) risk of skin cancer over time. The American Academy of Dermatology advises that photoprotective measures be taken, including the use of sunscreen, whenever one is exposed to the sun.

Is there a safe level of sun exposure?

According to a recent study submitted by the University of Ottawa to the Department of Health and Human Services in Washington, D.C., there is not enough information to determine a safe level of sun exposure at this time.

There is no consensus on which component of Ultraviolet Radiation (UVA or UVB or UVC) actually is carcinogenic, and the composition of Ultraviolet Radiation changes throughout the day: At high noon, Ultraviolet Radiation reaching ground level is 95% UVA and 5% UVB, while before 10am and after 2pm this percentage changes over time to 99% UVA and 1% UVB. This is caused by the the reflection of UVB rays back into space due to sun angle as the earth slowly rotates on its axis. The rate of change is faster the farther the position moves away from the equator (ie more north or south) 99% UVA / 1% UVB sunlight is known as “bronzing” rays, as it provides the deepest colour tanning.

On average over a day, 98.7% of the ultraviolet radiation that reaches the Earth’s surface is UVA. UVC is almost completely absorbed by the ozone layer and does not penetrate the atmosphere in any appreciable quantities. As a result, only the combination (UVA, UVB, and UVC) known as “Ultraviolet Radiation” is listed as a carcinogen, the components are only “likely to become” known carcinogens. Solar radiation, also known as “sunlight” is also listed as a carcinogen because it contains Ultraviolet Radiation. This means also that the UV Index is a measure of total Ultraviolet Radiation, and not just Vitamin D-producing UVB.

Sunlight is therefore the only listed carcinogen that is known to have health benefits, in the form of helping the human body to make Vitamin D. This makes sunlight unique on the list of known carcinogens.

Homo sapiens evolved near the equator, and human skin color is a visible indication of direct sun exposure due to the pigmentation level. With new evidence of Vitamin D receptors in all body tissues, experts advise having a balance between Vitamin D from sun exposure and Vitamin D from supplements. The only way to quantify adequate levels of Vitamin D is with a serum 25(OH) D3 test.

Sun and Cultural Aspects

Many people find direct sunlight to be too bright for comfort, especially when reading from white paper upon which the sun is directly shining. Indeed, looking directly at the sun can cause long-term vision damage. To compensate for the brightness of sunlight, many people wear sunglasses. Cars, many helmets and caps are equipped with visors to block the sun from direct vision when the sun is at a low angle.

In colder countries, many people prefer sunnier days and often avoid the shade. In hotter countries the converse is true; during the midday hours many people prefer to stay inside to remain cool. If they do go outside, they seek shade which may be provided by trees, parasols, and so on.

Sunshine is often blocked from entering buildings through the use of walls, window blinds, awnings, shutters or curtains.

Sunbathing

Sunbathing is a popular leisure activity in which a person sits or lies in direct sunshine. People often sunbathe in comfortable places where there is ample sunlight. Some common places for sunbathing include beaches, open air swimming pools, parks, gardens, and sidewalk cafés. Sunbathers typically wear limited amounts of clothing or some simply go nude. An alternative some use to sunbathing is to use a sunbed that generates ultraviolet light and can be used indoors regardless of outdoor weather conditions and amount of sun light.

For many people with pale or brownish skin, one purpose for sunbathing is to darken one’s skin color (get a sun tan) as this is considered in some cultures to be beautiful, associated with outdoor activity, vacations/holidays, and health. Some people prefer nude sunbathing so that an “all-over” or “even” tan can be obtained.

Skin tanning is achieved by an increase in the dark pigment inside skin cells called melanocytes and it is actually an automatic response mechanism of the body to sufficient exposure to ultraviolet radiation from the sun or from artificial sunlamps. Thus, the tan gradually disappears with time, when one is no longer exposed to these sources.

Sunlight

Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth’s atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.

When the direct solar radiation is not blocked by clouds, it is experienced as sunshine, a combination of bright light and radiant heat. The World Meteorological Organization uses the term “sunshine duration” to mean the cumulative time during which an area receives direct irradiance from the Sun of at least 120 watts per square meter.

Sunlight may be recorded using a sunshine recorder, pyranometer or pyrheliometer. Sunlight takes about 8.3 minutes to reach the Earth.

Direct sunlight has a luminous efficacy of about 93 lumens per watt of radiant flux, which includes infrared, visible, and ultraviolet light. Bright sunlight provides illuminance of approximately 100,000 lux or lumens per square meter at the Earth’s surface.

Sunlight is a key factor in photosynthesis, a process crucially important for life on Earth.

Life on Earth

The existence of nearly all life on Earth is fueled by light from the sun. Most autotrophs, such as plants, use the energy of sunlight, combined with minerals and air, to produce simple sugars—a process known as photosynthesis. These sugars are then used as building blocks and in other synthetic pathways which allow the organism to grow.

Heterotrophs, such as animals, use light from the sun indirectly by consuming the products of autotrophs, either directly or by consuming other heterotrophs. The sugars and other molecular components produced by the autotrophs are then broken down, releasing stored solar energy, and giving the heterotroph the energy required for survival. This process is known as respiration.

In prehistory, humans began to further extend this process by putting plant and animal materials to other uses. They used animal skins for warmth, for example, or wooden weapons to hunt. These skills allowed humans to harvest more of the sunlight than was possible through glycolysis alone, and human population began to grow.

During the Neolithic Revolution, the domestication of plants and animals further increased human access to solar energy. Fields devoted to crops were enriched by inedible plant matter, providing sugars and nutrients for future harvests. Animals which had previously only provided humans with meat and tools once they were killed were now used for labour throughout their lives, fueled by grasses inedible to humans.

The more recent discoveries of coal, petroleum and natural gas are modern extensions of this trend. These fossil fuels are the remnants of ancient plant and animal matter, formed using energy from sunlight and then trapped within the earth for millions of years. Because the stored energy in these fossil fuels has accumulated over many millions of years, they have allowed modern humans to massively increase the production and consumption of primary energy. As the amount of fossil fuel is large but finite, this cannot continue indefinitely, and various theories exist as to what will follow this stage of human civilization (e.g. alternative fuels, Malthusian catastrophe, new urbanism, peak oil).

The Sun is a Star

The Sun is the star at the center of the Solar System. The Sun has a diameter of about 1,392,000 kilometers (865,000 mi) (about 109 Earths), and by itself accounts for about 99.86% of the Solar System’s mass; the remainder consists of the planets (including Earth), asteroids, meteoroids, comets, and dust in orbit. About three-quarters of the Sun’s mass consists of hydrogen, while most of the rest is helium. Less than 2% consists of other elements, including iron, oxygen, carbon, neon, and others.

The Sun’s color is white, although from the surface of the Earth it may appear yellow because of atmospheric scattering. Its stellar classification, based on spectral class, is G2V, and is informally designated a yellow star, because the majority of its radiation is in the yellow-green portion of the visible spectrum. In this spectral class label, G2 indicates its surface temperature of approximately 5,780 K (5,510 °C.), and V (Roman five) indicates that the Sun, like most stars, is a main sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. Astronomers once regarded the Sun as a small and relatively insignificant star, it is now presumed to be brighter than 85% of the stars in the Milky Way galaxy, most of which are red dwarfs. Estimates for its magnitude are 4.8. The Sun’s hot corona continuously expands in space creating the solar wind, a hypersonic stream of charged particles that extends to the heliopause at roughly 100 AU. The bubble in the interstellar medium formed by the solar wind, the heliosphere, is the largest continuous structure in the Solar System.

The Sun is currently traveling through the Local Interstellar Cloud in the Local Bubble zone, within the inner rim of the Orion Arm of the Milky Way galaxy. Of the 50 nearest stellar systems within 17 light-years from Earth, the Sun ranks 4th in mass. The Sun orbits the center of the Milky Way at a distance of approximately 24,000–26,000 light years from the galactic center, completing one clockwise orbit, as viewed from the galactic north pole, in about 225–250 million years.

The mean distance of the Sun from the Earth is approximately 149.6 million kilometers (1 AU), though this varies as the Earth moves from perihelion in January to aphelion in July. At this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The energy of this sunlight supports almost all life on Earth via photosynthesis, and drives Earth’s climate and weather. The enormous impact of the Sun on the Earth has been recognized since pre-historic times, and the Sun has been regarded by some cultures as a deity. An accurate scientific understanding of the Sun developed slowly, and as recently as the 19th century prominent scientists had little knowledge of the Sun’s physical composition and source of energy. This understanding is still developing; there are a number of present-day anomalies in the Sun’s behavior that remain unexplained.

Sun Light Observation and Effects

Sunlight is very bright, and looking directly at the Sun with the naked eye for brief periods can be painful, but is not particularly hazardous for normal, non-dilated eyes. Looking directly at the Sun causes phosphene visual artifacts and temporary partial blindness. It also delivers about 4 milliwatts of sunlight to the retina, slightly heating it and potentially causing damage in eyes that cannot respond properly to the brightness. UV exposure gradually yellows the lens of the eye over a period of years and is thought to contribute to the formation of cataracts, but this depends on general exposure to solar UV, not on whether one looks directly at the Sun. Long-duration viewing of the direct Sun with the naked eye can begin to cause UV-induced, sunburn-like lesions on the retina after about 100 seconds, particularly under conditions where the UV light from the Sun is intense and well focused; conditions are worsened by young eyes or new lens implants (which admit more UV than aging natural eyes), Sun angles near the zenith, and observing locations at high altitude.

Viewing the Sun through light-concentrating optics such as binoculars is very hazardous without an appropriate filter that blocks UV and substantially dims the sunlight. An attenuating (ND) filter might not filter UV and so is still dangerous. Attenuating filters to view the Sun should be specifically designed for that use: some improvised filters pass UV or IR rays that can harm the eye at high brightness levels. Unfiltered binoculars can deliver over 500 times as much energy to the retina as using the naked eye, killing retinal cells almost instantly (even though the power per unit area of image on the retina is the same, the heat cannot dissipate fast enough because the image is larger). Even brief glances at the midday Sun through unfiltered binoculars can cause permanent blindness.

Partial solar eclipses are hazardous to view because the eye’s pupil is not adapted to the unusually high visual contrast: the pupil dilates according to the total amount of light in the field of view, not by the brightest object in the field. During partial eclipses most sunlight is blocked by the Moon passing in front of the Sun, but the uncovered parts of the photosphere have the same surface brightness as during a normal day. In the overall gloom, the pupil expands from ~2 mm to ~6 mm, and each retinal cell exposed to the solar image receives about ten times more light than it would looking at the non-eclipsed Sun. This can damage or kill those cells, resulting in small permanent blind spots for the viewer. The hazard is insidious for inexperienced observers and for children, because there is no perception of pain: it is not immediately obvious that one’s vision is being destroyed.

During sunrise and sunset sunlight is attenuated due to Rayleigh scattering and Mie scattering from a particularly long passage through Earth’s atmosphere, and the Sun is sometimes faint enough to be viewed comfortably with the naked eye or safely with optics (provided there is no risk of bright sunlight suddenly appearing through a break between clouds). Hazy conditions, atmospheric dust, and high humidity contribute to this atmospheric attenuation.

A rare optical phenomenon may occur shortly after sunset or before sunrise, known as a green flash. The flash is caused by light from the Sun just below the horizon being bent (usually through a temperature inversion) towards the observer. Light of shorter wavelengths (violet, blue, green) is bent more than that of longer wavelengths (yellow, orange, red) but the violet and blue light is scattered more, leaving light that is perceived as green.

Ultraviolet light from the Sun has antiseptic properties and can be used to sanitize tools and water. It also causes sunburn, and has other medical effects such as the production of vitamin D. Ultraviolet light is strongly attenuated by Earth’s ozone layer, so that the amount of UV varies greatly with latitude and has been partially responsible for many biological adaptations, including variations in human skin color in different regions of the globe.

Nature’s Healer: The Sun

The sun has always been seen as the source of life and healing. We must not forget the many benefits the sun bestows on us. It is nature’s healer.

Sunlight

Throughout history there has been no better and more common symbol of happiness and well being than the sun. The ancient Egyptians, the Aztecs, Romans and Greeks all worshipped the sun and thought of it as the source of life and health. Regardless of the historical time that comes to mind, you will find people cheered and uplifted by the life-giving rays of the sun.

Whether it was in the form of the god Helios or establishing Sun-day as the first day of the week, the sun always has played an important role in people’s lives.

The great Greek physician Hippocrates wrote extensively about the sun’s healing powers. Herodotus, the father of Heliotherapy, made frequent statements about the healing properties of the sun in his medical practice. In our own time, we see a reflection of these ancient sentiments in songs, poems and movies. And who of us could deny the feeling we have when the sun breaks through the darkened clouds: our mood lifts; our eyes turn upward; our energy and zest for life returns.

Although there have been many serious medical warnings about overexposure to the sun in recent years, we must not neglect the positive role sunlight plays in our mental and physical health. There is good news coming from scientific research telling us why we look and feel better from the sun.

The Blues

Sunlight is an important part of our daily lives. Ever notice how much time is spent at the office worrying about who gets the office with the window. And what about all that energy you feel when spring and summer come around. Everyone seems to be outdoors, planning hikes, barbecues and pool parties. You name it and it’s happening.

Tom Wehr, M.D., a research psychiatrist at the National Institutes of Health, is an expert in mood disorders and feels that our elevation in mood during the spring and summer can be directly linked to the amount of sunlight we are exposed to. “Researchers have found the exposure to natural light increases the production of serotonin, a chemical that stimulates the brain’s pleasure center, thereby perking up your mood while warding off anxiety and depression.”

In contrast, look at what happens to people in the long winter months, especially those living in the Northeast and Northwest. Over 11 million people suffer from what is called Seasonal Affective Disorder or SAD, and another 25 million suffer from a milder form of “winter blues.”

The symptoms of SAD and the “winter blues” can include fatigue, craving carbohydrates, irritability, sleeping more and a change of personality from your summer self to your winter self. It’s not exactly known what causes SAD, but according to health writer Francis FitzGerald, “SAD occurs year after year during a specific season – usually the winter – and vanishes when spring ushers in longer days and more sunshine.”

Medical Researchers think that our depressed moods during the winter may be the result of a chemical imbalance between serotonin and melatonin. With too little sunlight, melatonin makes us drowsy, and disrupts our internal clock.

Our Bodies

Besides just making us feel better and more energetic, exposure to sunlight plays an important role in helping us create vitamin D in our bodies. What makes this so important? Vitamin D has been shown to help prevent and treat serious medical conditions, including: breast cancer, osteoporosis, prostate cancer, psoriasis, acne, etc.

Though many people aren’t aware of it, most of our physiological requirements for vitamin D are provided for by casual exposure to sunlight. It is easy to see how important sunlight is for our physical and mental health.

Breast Cancer

Over 180,000 women will be diagnosed with breast cancer this year. It is a major concern for women of all ages. But there is hope. According to Judy Gaillard and Donald Smith of Sun Wellness magazine, a study by researcher Ester M. John at the Northern California Cancer Center, entitled “Vitamin D and Breast Cancer Risk…” casual exposure to sunlight, along with other factors, can help reduce the risk of breast cancer.

The scientists concluded “high exposure to sunlight was associated with a 25 percent to 65 percent reduction in breast cancer risk among women whose longest residence was in a state of high solar radiation.” A 25 percent reduction in the number of breast cancer cases would mean approximately 44,000 women would not have to suffer the trauma of this disease. Since vitamin D and sunlight exposure are life-style behaviors, this is good news for women wishing to reduce their risk of breast cancer.

Osteoporosis

Sometimes called “the silent disease,” osteoporosis is the loss of bone mass due to the malabsorption of calcium into the bone. Bone fragility results in increased risk of bone fracture in many parts of the body, including the hips, spinal vertebrae, and ribs. According to James F. Balch, M.D., author of Prescription for Nutritional Healing, fully “half of all women between the ages 45 and 75 show signs of osteoporosis.” Although osteoporosis is mostly an issue for post-menopausal women, both sexes and all age groups suffer from this disease.

“If vitamin D is absent, calcium, which is vital for normal bone growth and development, will not be absorbed from the intestinal tract and the bones become deformed,” says Zane Kime, M.D., M.S. in his book Sunlight. One of the best ways to get adequate vitamin D is moderate exposure to the sun. The World Health Organization Task-Force for Osteoporosis recently recommended sunlight as a part of the treatment and management of this disease.

Prostate Cancer

Prostate cancer is the second most common cause of death from cancer in men over age 75. In a recent study by Hanchette and Schwartz of the University of North Carolina and published in the journal Cancer, the researchers a 20 to 40 percent lower incidence of prostate cancer among men in southern climates. Because of findings like this some researcher are suggesting that vitamin D may be an effective preventive agent against prostate cancer. The importance of sunlight cannot be underestimated in maintaining prostate health. If the incidence of prostate cancer is reduced by 20 percent nearly 37,000 men would not suffer the anguish of this disease.

Athletic Achievement

Most of us believe that sunlight gives us extra pep and energy. During the summer months, we tend to sleep less, play more and just have more get up and go. To back up this idea scientifically, Bylle Dopps and Scott Hoover of Sun Wellness magazine looked at research from the Sports Medicine Department of the German National Olympic Team Training Center. The results of their research showed that routine exposure to the sun optimized performance capabilities and reduced the incidence and recovery time of athletes from minor injuries.

If simple sunlight can help world class athletes recover from the stresses of training and competition, it seems reasonable to conclude that we can all benefit from the stress busting affects of sunlight.

Conclusion

Recent scientific studies have demonstrated what humans have suspected all along: natural sunlight promotes feelings of well-being, improves immune function, promotes natural healing and optimizes athletic performance. Don’t neglect these positive benefits of sunlight. Include moderate exposure to the sun in your overall health regimen.

Beat the Heat and Sun

Everyone is at risk for heat-related illnesses when temperatures rise above 90 degrees, but the elderly and the very young are most susceptible. Heat-related illnesses can cause serious injury and even death if unattended. Signs of heat-related illnesses include the following:

* nausea
* dizziness
* flushed or pale skin
* heavy sweating
* headaches

Victims of heat-related illness should be moved to a cool place, given cool water to drink and ice packs or cool wet cloths should be applied to the skin. If a victim refuses water, vomits or loses consciousness, call 9-1-1 or your local emergency number immediately.

The American Red Cross treats severe heat like any other major emergency. “We go ‘on alert’ any time the forecast calls for high temperatures,” said Skip Batchelor, head of disaster services for the American Red Cross of Greater Chicago. “Our disaster team supports the city agencies as they open cooling centers – providing water, cots and health care if needed. During a particularly dangerous heat wave, our volunteers help officials go door-to-door, checking on elderly or sick residents who cannot leave their homes.”

Red Cross Heat Safety Tips . . .

* Dress for the heat. Wear lightweight, light-colored clothing. Light colors will reflect away some of the sun’s energy. It is also a good idea to wear hats or to use an umbrella.
* Drink water. Carry water or juice with you and drink continuously even if you do not feel thirsty. Avoid alcohol and caffeine, which dehydrate the body.
* Eat small meals and eat more often. Avoid high-protein foods, which increase metabolic heat.
* Slow down. Avoid strenuous activity. If you must do strenuous activity, do it during the coolest part of the day, which is usually in the morning between 4:00 a.m. and 7:00 a.m.
* Stay indoors when possible. Be a good neighbor. During heat waves, check in on elderly residents in your neighborhood and those who do not have air conditioning

A Few Basic Facts About The Sun and Our Skin

Here are some straight forward facts to consider on the topic of sun protection. The sun radiates two different rays that are cancer causing, UVA and UVB. The UVA ray is longer and it affects the skin much deeper than a UVB ray. The UVB ray is the one that gives you sunburn. Both can cause skin damage and skin cancer.
When you buy a sunscreen and you look for a sun proof factor (spf), you are looking for protection from the UVB ray. The thing is, most sun blocks are only keeping out the UVB. So, you can have sunscreen on, thinking you are safe, but still get skin cancer from the UVA rays.

SPF, an abbreviation for sun-protection factor, is a number such as 15, 30, or 50 that indicates how long a topical sunscreen remains effective on the skin. A user can determine the duration of effectiveness simply by multiplying the SPF by the length of time it takes for him or her to suffer a burn without sunscreen.

Basal Cell Carcinoma is a common form of skin cancer with almost 1 million cases each year in America. Treatment includes a procedure to remove the cancer, typically by cutting out the affected area or treating with a topical chemotherapy. If left untreated, the cancer will continue to grow. Individuals who have been diagnosed with basal cell carcinoma need sun protection to minimize UV exposure.

Bottom line – the sun is our friend.  We need it and it is wonderful for our spirits and our health. Enjoy it but safely and in moderation.