How to Choose the Perfect Sun Protection Hat

Choosing a good sun hat is very important. Not only do 1/3 of all skin cancers appear on the face but the biggest cause of premature aging is cumulative damage of the sun from infancy on up. So let’s get started finding the perfect sun hat for you.

All of our hats are chosen with sun protection in mind, but not all hats are created equal.

Let’s start with 5 basic questions to narrow down your search:

1. What activity will you be doing? Will there be wind? Do you need good peripheral vision? Will it be hot?
2. Do you want maximum sun protection or is good sun protection just fine?
3. How wide of a brim is comfortable for you?
4. How important is fashion to you or is functionality all you need?
5. Is your hair short? Thinning? Bald or shaved? Do you dye your hair?

1.What activity do you plan to do? Is it gardening, sailing, hiking, travel or a round of golf? Whatever the activity, it creates conditions we need to be concerned about.

Will you be in the wind? With a wide brim hat, a chin strap is very important for keeping your sun hat in place. Remember the old sitcom The Flying Nun? A wide brim hat will pick up the wind like it has wings of its own. Additionally, a chin strap will help keep your hat in place when bending over or dropping your chin is part of your activity, like in gardening.

Peripheral vision is an important factor for both safety and playing various sports like tennis or volleyball. This will be a personal decision for you. Consider both the size of the brim and, if a neck drape is involved, how far does the drape wrap around the face. I am a beach volleyball player and for me a 3″ brim is the widest I can use and still see high flying balls as well as the other players.

Will you be doing an activity that generates body heat? You may want to wear a sun visor for total head aeration or choose a sun hat with mesh on the side of the crown or a hat that made of a fast drying fabric that allows evaporative cooling. One trick for cooling your head in a hot, dry climate is to wet the hat and then let the evaporation cool your head.

Maximum sun protection vs good sun protection?

What is a maximum sun protection hat? We feel a maximum protection hat has a UPF rating of 50 and a hat brim that is 4 inches wide or greater. But there’s more. The brim needs to be angled downward. This downward sloping brim allows you to be protected for more hours of the day.

How does this work? At high noon, when the sun’s rays are directly overhead, even a 3″ brim hat may provide maximum sun protection for your head. But when the sun is either ascending or descending the sun’s rays can sneak right under your hat and strike your face or neck. At daybreak or sunset, when the suns ray’s are virtually horizontal, a wide brim hat may provide no protection at all.

Adventure sun hatIf you plan to be spending time outdoors when the sun is close to either horizon, you may want to think about our more unique designs such as the Kalahari hat, Adventure Hat or Chic Sheik that drop a vertical protective block of fabric between you and the sun.

Good sun protection can be had with a brim less than 4 inches wide or a brim that is more horizon from the head.

How wide of a brim are you comfortable with?

We all have different feelings about this one. Some people can handle a wide brim with no problem while others find it very distracting. Bottom line is that the wider the brim of the hat the more surface area there is to block the sun. But, of almost equal importance, is the angle of the brim. A wide brim hat that comes straight out from the head is good but when the sun is not straight overhead the rays can come under the brim and strike the face and neck. A brim that is angled downward goes a long way in giving you more hours of protection. As a basic rule of thumb, for maximum sun protection choose a downward angled 4″ brim sun hat … and, if you are comfortable, choosing a brim wider than 4″ is even better. If you are not sure how wide a brim you would like you may want to consider a 3 1/2 brim.

Now, how important is fashion to you?

As you can see, some of the sun protection inventors have come up with novel hat designs to protect you from the sun but, alas they would not be called high fashion … except possibly on another planet. Most of these unique hats were designed to solve special sun protection needs such as full face protection, additional neck protection or increased ventilation.

Some of our wide brim hats are the height of fashion creating a dramatic flare or ultra feminine silhouette. As we all know, fashion is in the eyes of the beholder so look for a hat that accentuates your attributes.

5. Next, let’s take a look at your hair.

Do you have thinning hair, or are you balding or shave your head? If yes, mesh panels on the crown of the hat may provide extra air flow to keep your head cooler but it will also let UV radiation sneak through and reach your scalp. With maximum sun protection in mind, it is better to leave the mesh panels for those with thick tresses. For those of you who do have thick hair, choosing a hat with mesh panels will help your head stay cooler in the heat.

Do you have short hair? If yes, we need to be extra concerned about your neck. A sun visor or a brim less than 4″ leaves your neck open to sun damage. Typically a full brim hat will be your best choice.

Hair can get dry, cracked and brittle from too much sun. Dyed hair is especially susceptible to problems under UV radiation so, to protect your hair, I would suggest staying away from visor hats that leave your hair open to the sun light.

Just a few parting suggestions for picking the perfect hat for you:

Hat size: A hat that is too big is better than one that is too small. A tight hat may give you a headache and then you won’t want to wear it. Many of our hats are adjustable, but in all cases, please be sure to measure your head to ensure a perfect fit. For those of you with lots of little grey cells we have hats for big heads. And, for those of you with smaller heads, please know that you may request stick-on sizing tape to help you fit your hat.

Cotz sunscreenReflective rays: Even the widest brim hat will not be able to stop rays reflecting up from the ground, a near by car or any other reflective surface so wearing sunscreen is important for maximum sun protection. Rule of thumb: Sun protective fabric is always better than sunscreen in protecting you from the harmful rays of the sun but alas not always practical. On areas where you can’t cover up with fabric use sunscreen. Maximum sun protection is achieved by a combination of sun protective clothing and sunscreen.

What You Eat Can Protect Your Skin from the Sun

By now you probably think you’ve heard all of the health reasons there are for eating your vegetables. But recently, researchers from Harvard University have announced that lutein — a potent antioxidant found in such dark green, leafy vegetables as spinach and kale — may protect the skin from sun damage.

“Lutein has been widely recognized for its eye health benefits for several years. But, our data is the first of its kind to suggest that lutein may have the potential to act as a preventative agent against UVB-induced skin cancer,” said Salvador Gonzalez, M.D., Ph.D., leader of the Harvard research team. “In addition, these data suggest that lutein protects the skin against damage caused by exposure to UVB light, further validating our position that lutein is a critical component to overall skin health.”

Lutein (LOO-teen) is a yellow pigment (the yellow is covered up by chlorophyll in green leaves) found predominantly in vegetables. It is also present in the eyes and skin of the human body. In women, lutein is found in the breasts and cervix. As an antioxidant, lutein protects the eyes from the damaging effects of aging. Lutein also acts as a light filter, protecting against the sun’s harmful rays.

UVA and UVB rays are two types of harmful rays found in sunlight. UVA rays contribute to wrinkling the skin, as well as to the development of skin cancer. UVB rays are the ones that are the primary cause of sunburn and skin cancer.

Good sunscreens block both UVA and UVB rays and are critical to skin health. But, you can do even more to protect your skin and eyes when you’re outside.

Safety tips to keep top of mind:

Wear UV-blocking sunglasses. Over time, exposure to ultraviolet light can cause cataracts and increase your risk of macular degeneration, a disease that causes irreversible blindness.

If you’re a parent, protect your children’s skin. Research indicates that one or more severe, blistering sunburns in childhood or adolescence can double the risk of skin cancer later in life.

Check the expiration date on your sunscreen. Sunscreen without an expiration date has a shelf life of no more than three years.

Eat a healthy diet comprised of green leafy vegetables. Consumption of 6 milligrams of lutein per day (approximately one-third cup of cooked spinach) has been linked to a reduced risk of cataracts and age-related macular degeneration. Vitamins and dietary supplements formulated with purified lutein provide another option for adding this nutrient to a daily diet.

It’s important to note that when lutein is consumed in foods or vitamins, it deposits in various tissues in the body — the eyes, the skin, fat tissue and so on. Therefore, it may also be beneficial to apply lutein directly to the surface of your skin. Several skin care products containing lutein are now available.

Skin Damage Caused by Sunlight

Some sunlight is important because our skin uses it to produce vitamin D, which helps to build and maintain strong bones. Too much sun is harmful and can damage your skin.

The sun gives out ultraviolet (UV) radiation that is made up of three types of rays: UVA, UVB and UVC. UVC rays from the sun can’t get through the ozone layer but UVA and UVB rays can, and these rays have been linked to skin damage.

Short-term skin damage

Sun tan

A tan is actually a sign that your skin has been damaged and is trying to protect itself. UV radiation stimulates your skin to produce more pigment (colour), which protects against damage. Your tan will fade, but the damage to your skin remains.

Sunburn

Short-term overexposure to the sun can cause your skin to burn, usually making it red, hot and painful. You can soothe your burnt skin with calamine lotion or aftersun lotions. If your sunburn is severe, you may need medical treatment.

Heat exhaustion and heat stroke

This is when your body becomes overheated after overexposure to the sun or by getting sunburn. You may have symptoms including vomiting, headaches and fever. If you think you have heat stroke, get to a cool place as soon as possible and drink plenty of water. If your temperature is higher than 39ºC (you can measure your temperature using an oral thermometer), your skin has become dry and flushed or you feel very unwell, you should see a doctor immediately.

Long-term skin damage

Ageing and infection

Ageing of your skin is a result of the UVA rays penetrating it, causing wrinkles and sagging. UV rays can also cause damage to the eyes. It has been suggested that too much sun exposure may damage your immune system, increasing your risk of infection.
Skin cancer

Although the exact cause of skin cancer isn’t known, some things make it more likely. Your risk of skin cancer increases if you’re exposed to UV rays because of spending a lot of time in the sun.

Preventing sun damage

To protect your skin, you should stay out of the sun between 11am and 3pm, when the sun’s UV rays are strongest. Look for shady areas such as under trees, and use umbrellas or canopies.

Watch the UV index

The UV index describes the strength of the sun’s UV radiation. It’s usually shown as a number in a triangle on a weather map. The numbers range from one to 11+ and the higher the number, the stronger the UV radiation. If the UV index is higher than three you will need protection when you go outside.

In many countries, the UV index is reported alongside the weather forecast in newspapers, on TV and on the radio.
You can protect your skin by wearing long-sleeved tops and trousers. Choose materials that have a close weave as these block out the most UV rays. Wet clothing stretches and lets more UV radiation through to your skin.

Wearing a wide-brimmed hat can halve the amount of UV radiation reaching your face.

Sunglasses help to protect your eyes and eyelids. Wraparound sunglasses will also protect the skin around your eyes. You should choose a pair of sunglasses that has the following labels:

* 100 percent UV protection
* UV 400 – this means it protects from both UVA and UVB rays

If you’re buying a pair of sunglasses in Europe, check that they also carry the European Standard CE mark and the British Standard (BE EN 1836:1997).

Wear sunscreen

Always use “broad spectrum” sunscreen. This means that it protects your skin against UVA and UVB rays. Make sure it has a sun protection factor (SPF) of 15 or higher. The SPF tells you how good the sunscreen is at filtering out the UVB rays. There isn’t a measure of protection against UVA rays. Sunscreen can’t give you complete protection since some UV rays will always get through, but you will get more than 90 percent protection from UVB rays with SPF 15.

Re-apply sunscreen every two hours or more often if you go swimming, or sweat a lot. Water reflects the sun’s rays so you need to apply sunscreen before swimming.

Cloud doesn’t stop the sun’s UV rays getting through so you should protect yourself even if it’s cloudy. Haze (from thin clouds or mist) can even increase your UV radiation exposure because the rays are scattered.

Check moles

You should check your moles regularly for changes that may indicate skin cancer. Most changes are harmless, but you should see your GP if you notice:

* growth of an existing mole – especially over 7mm (a quarter of an inch) in diameter
* a mole with an uneven or ragged edge
* a mole of varying shades of colour
* a mole with an inflamed or red edge
* a mole that bleeds, oozes or crusts
* a mole that feels different, painful or itches

Don’t use sunbeds

Sunbeds mimic the effect of the sun and give out artificial UVA and UVB radiation. Exposure to artificial UV radiation can also damage your skin. Sunbeds have been linked to an increased risk of skin cancer as well as eye conditions.

An artificial tan from a sunbed doesn’t protect your skin against sunburn on holiday; it’s similar to using a sunscreen with SPF 2 to 3.

There are no regulations relating to the use of sunbeds, but the World Health Organization (WHO) recommends that you shouldn’t use sunbeds if you:

* are under 18
* have sunburn, burn easily or had frequent sunburn as a child
* have a lot of moles
* tend to freckle
* have pre-cancerous or cancerous skin lesions
* are wearing cosmetic products (these may make you more sensitive to UV radiation)
* are taking medication (you should seek medical advice to check whether your medication will make you particularly sensitive to UV radiation)

Winter sun

You can’t feel UV rays. The warmth you feel on your skin is actually caused by the sun’s infrared radiation. So just because you can’t feel the hot rays of the sun, it doesn’t mean you won’t get sunburnt.

The amount of UV radiation is generally lower during the winter but snow reflects most of the sun’s rays, so you can still get sunburnt. If you’re high up in the mountains, there is less atmosphere to block out the UV rays, so make sure you use sunscreen.
Protecting children from the sun

Young skin is sensitive and very easily damaged by the sun. Getting sunburnt as a child is known to increase the risk of developing skin cancer as an adult.

Keep your baby in complete shade. Pop-up shelters are a good way to protect children from the sun on the beach or in the garden. Canopies and parasols for prams and buggies protect children when you’re out and about.

Dress your child in loose-fitting clothes that cover up their arms and legs. A hat with a brim at the front and a cloth flap that covers the neck provides good sun protection. Sunglasses will help to protect your child’s eyes.

Use water-resistant sunscreen with SPF 20 or higher on all exposed areas of your child’s skin and apply generously every couple of hours. If you take your child swimming, re-apply the sunscreen after towel drying.

Fake tans

Fake tanning lotions are a popular alternative to sunbathing and sun beds. The tanning lotion reacts with your skin and produces a brown pigment. Fake tan needs to be re-applied regularly if you want to maintain the tan, because your outer skin cells are shed naturally as your skin grows.

Some fake tanning lotions contain sun protection but the SPF is usually very low, so you should also wear sunscreen with an SPF of 15 or higher when you’re out in the sun.

Although fake tanning lotions aren’t known to be dangerous, they can sometimes trigger an allergic reaction. Always test the lotion on a small area of your skin first to see if you have a reaction.

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.

SPF, UVB and UVA Protection Explained

Try this quiz:

• Is SPF 45 sunscreen three times stronger than SPF 15 sunscreen? Does it last three times longer?
• Do sunscreens provide better UVA protection than UVB protection?
• What works better, sunscreens or sunblocks?
• Do “broad-spectrum” sunscreens protect against all UV rays?

If you’re not certain of the answers, join the club. Recent research shows that people who buy sunscreens aren’t sure exactly what protection they offer, and are cloudy about the technical terms on their labels. A survey of 235 women who bought sunscreen found they did not know the difference between UVA and UVB or between SPF and UVA. They mistakenly believed that higher SPF ratings meant stronger UV protection, not longer protection, and the concept of “broad-spectrum” protection confused them further.

The U.S. Food and Drug Administration is urging sunscreen manufacturers to clarify the claims made on their products so that the public can make more informed purchases. In the meantime, we’d like to do our part. Here, from medical experts on The Skin Cancer Foundation’s Photobiology Committee, is a concise primer on the ABC’s of sunscreen protection:

UVA (ultraviolet-A): long- wave solar rays of 320-400 nanometers (billionths of a meter). Although less likely than UVB to cause sunburn, UVA penetrates the skin more deeply, and is considered the chief culprit behind wrinkling, leathering, and other aspects of “photoaging.” The latest studies show that UVA not only increases UVB ’s cancer-causing effects, but may directly cause some skin cancers, including melanomas.

UVB (ultraviolet-B): short-wave solar rays of 290-320 nanometers. More potent than UVA in producing sunburn, these rays are considered the main cause of basal and squamous cell carcinomas as well as a significant cause of melanoma.

Sunblocks and sunscreens: Sunscreens chemically absorb UV rays, sunblocks physically deflect them. Sunscreen has long blocked UVB effectively, but until recently provided less UVA protection. New ingredients such as octylcrylene and the benzophenones have improved sunscreen’s defenses against shorter UVA rays, and the revolutionary chemical avobenzone (Parsol 1789) works against all UVA wavelengths.

Sunblocks have also markedly improved. New preparations such as micronized titanium dioxide are less conspicuous on the skin and offer substantial protection against both UVA and UVB.

SPF (sun protection factor): measures the length of time a product protects against skin reddening from UVB, compared to how long the skin takes to redden without protection. If it takes 20 minutes without protection to begin reddening, using an SPF 15 sunscreen theoretically prevents reddening 15 times longer — about 5 hours. (Actually, it may take up to 24 hours after sun exposure for redness to become visible.) To maintain the SPF, reapply sunscreen every two hours and right after swimming.

The Skin Cancer Foundation recommends SPF’s of at least 15, which block 93 percent of UVB. While SPF’s higher than 30 block only 4 percent more UVB, they may be advisable for sun-sensitive individuals, skin cancer patients, and people at high risk of developing skin cancer. They also allow some margin for error if too little sunscreen is applied.

While SPF is the universal measurement of UVB protection, no comparable standard exists for UVA. Scientists worldwide are working to develop a standardized testing and certification method to measure UVA protection.

Broad-spectrum protection: The phrase indicates that a product shields against UVA as well as UVB. It does not guarantee protection against all UVA wavelengths, however. Most broad-spectrum sunscreens and sunblocks with an SPF of 15 or higher do a good job against UVB and short UVA rays; if they also contain avobenzone, zinc oxide, or titanium dioxide, they should be effective against the entire UVA spectrum.

Even with the ideal sunscreen, some UV rays can get through to your skin and cause damage. The Skin Cancer Foundation considers sunscreen one part of a comprehensive sun protection program, along with sun-protective clothing, sunglasses, shade, and sun avoidance from 10A.M. to 4 PM.

What is Sun Protection?

Sun protection is simply guarding a body from the adverse effects of sunlight. Aside from the hazards of heat, the sun poses the danger of sunburn, which can permanently damage the skin and cause skin cancer, precancerous changes in the skin, as well as premature wrinkling and signs of aging. Exposure to ultraviolet rays from the sun is a known risk factor for the development of both melanoma and non-melanoma skin cancers.

How is sunburn best prevented?

The best ways to avoid sunburn are to:

• limit time in the sun, especially between peak sunlight hours of 10 a.m. and 3 p.m.;
• wear protective clothing, including
• a broad-brimmed hat,
• a shirt with sleeves that cover the arms, and
• a long skirt or pants with long legs; and
• use a protective sunscreen to minimize the penetration of the sun’s ultraviolet (UV) rays.

What is sunscreen?

Sunscreen is any substance or material that protects the skin from UV radiation. Sunscreens are available in the forms of topical lotion, cream, ointment, gel, or spray that can be applied to the skin; a salve or stick that can be applied to the lips, nose, and eyelids; a moistener in towelettes that can be rubbed against the skin; sunglasses that protect the eyes; certain types of sun-protection clothing; and film screen that can be affixed to the windows of a car, room, or office.

What is meant by SPF?

SPF, an abbreviation for sun-protection factor, is a number such as 15, 30, or 50 that indicates the degree of sunburn protection provided by sunscreens. SPF is related to the total amount of sun exposure rather than simply the length of sun exposure. It is a common mistake to assume that the duration of effectiveness of a sunscreen can be calculated simply by multiplying the SPF by the length of time it takes for him or her to suffer a burn without sunscreen, because the amount of sun exposure a person receives is dependent upon more than just the length of time spent in the sun. The amount of sun exposure depends upon a number of factors including the length of exposure, time of day, geographic location, and weather conditions.

A common mistake is applying too little sunscreen, which can drastically reduce the effective SPF of the product. About 1 ounce (5-6 teaspoons) of sunscreen is recommended to cover the entire body. Further, sunscreen must be reapplied every two hours when staying outdoors for a prolonged period of time. Sunscreen should also be applied at least 30 minutes before going outdoors.

People with sensitive skin who burn quickly and must spend a lot of time outdoors should always apply a sunscreen with an SPF of 30 or more.

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