The sun is the primary source of ultra violet (UV) radiation. Artificial sources include welder's flash, sunlamps or tanning parlors, high-intensity mercury vapor lamps used for night sports, special lamps used in infant care units, xenon arc lamps, and lasers.
Ultraviolet radiation is divided into two major bands, UV-A and UV-B. UV-A is longer wavelength radiation, close to the blue in the visible spectrum, that usually causes skin tanning and browning. UV-B is more active shorter wavelength radiation that causes blistering sunburn and is associated with skin cancer.
Ultra violet B radiation values for Pretoria, Durban and Cape Town show that the levels of radiation is in the dangerous to very dangerous level for almost half the year, with summer months having the highest radiation levels.
The level of UV light now is generally speaking higher that it was 50 years ago. This is due to a reduction of ozone in the earth's atmosphere. Ozone serves as a filter to screen out and reduce the amount of UV light that we are exposed to. With less atmospheric ozone, a higher level of UV light reaches the earth's surface.
Other factors that influence the amount of UV include elevation, latitude and cloud cover. Ultra Violet light is stronger as elevation increases. The thinner atmosphere at higher altitudes cannot filter UV as effectively as it can at sea level. The rays of sunlight are also stronger near the equator. In Antarctica, Chile and New Zealand the UV levels are much higher than normal, especially in springtime due to the occurrence of the ozone hole in the southern hemisphere.
Ultra violet radiation (UVR) from the sun and sunburn can damage your skin. This damage can lead to skin cancer, premature aging of the skin later in life, immune system suppression and reduced vitamin D synthesis. Ultra violet radiation can also cause cataracts in the eye.
In plants, exposure to enhanced UV radiation can inhibit the essential process of photosynthesis. Increased UV radiation can also influence agricultural productivity and cause deterioration of synthetic materials such as plastics. Increased or excessive UV radiation could have substantial negative impacts on fish populations, and many terrestrial and marine ecosystems.
There's no doubt that the sun is very hard on your skin. In fact, excessive sun exposure is the primary cause of skin cancer. The more sun you're exposed to, the greater the risk you have of developing skin cancer. And while it's both preventable and curable, it can also be extremely serious. Serious enough to kill you.
There has been a 20-40% rise in skin cancer in the human population since the 1970's. The incidence of skin cancer has risen by much more, for example in the USA it has risen by about 90% during 1974-1990. This is due primarily to increased exposure to the sun, but also to a growing population of elderly people and better health screening. |
Skin cancer is a disease in which cancer cells are found in the outer layers of our skin. It can occur anywhere on your body, but is most common in places that have been exposed to more sunlight such as your face, neck, hands and arms.
There are several cancers that start in the skin. The most common skin cancers are basal cell cancer and squamous cell cancer. If detected and treated early, basal cell carcinomas and squamous cell carcinomas usually respond well to treatment and cause no further trouble. The appearance of these types of skin cancers can vary considerably. If you notice any skin changes, which do not disappear within a few weeks you should see a doctor. Melanoma on the other hand is a more serious type of skin cancer. Warning signs of melanoma include change in the size, shape, or colour of a mole, oozing or bleeding from a mole, or a mole that feels itchy, hard, lumpy, swollen or tender to the touch. If untreated, it can spread quickly to other parts of the body through the lymph system or through the blood.
Skin cancer does not develop immediately after exposure to solar UV-B but takes years, even decades to develop. So remember, skin cancer develops very slowly. Skin cancer that developed recently could be due to exposure in the 1960s to the 1970s. This was a period when there was no ozone depletion, yet sunbathing slowly became a popular pursuit and protective sunscreen lotions hardly existed.
Both the total amount of sun received over many years, and overexposure resulting in sunburn can cause skin cancer. The sunburn you receive this week may take 20 or more years to become skin cancer. Most people receive 80% of their lifetime exposure to the sun by 18 years of age. So it is important to protect children from sunburn.
A cataract is a cloudy or opaque area in the normally transparent lens of the eye. As the opacity thickens, it prevents light rays from passing through the lens and focussing on the retina. Symptoms include blurred vision, sensitivity to light and glare, increased nearsightedness, or distorted images. People living at high altitudes or those who spend a lot of time in the sun develop cataracts earlier than others. Excessive exposure to intense sunlight, or to an artificial source such as a welding arc or suntanning lamp, can burn the surface of the eye much like sunburn on the skin. Both UV and deep blue light may contribute to retinal aging.
Skin Cancer
Saving your skin. It's easy, it's important, and it's up to you.
The sun's ultra violet rays stimulate skin cells to produce a dark pigment called melanin. All skins have the same number of melanin-producing cells (melanocytes), but some produce more melanin than others. Fair skinned people, for example, produce less melanin than dark-skinned people. The amount of melanin which your skin produces determines the colour and the depth of tan that you may or may not acquire as the case may be. Redheads, fair skinned people and those who freckle need to take extra care in the sun.
When the sun's ultra violet rays penetrate the skin they injure living cells, making them swell and the skin burns. In an effort to prevent further injury, your skin develops a tan - but this, in fact, is its attempt to defend itself against the harshness of the sun. A tan is literally skin damage - damage that builds up, year after year, tan after tan. A tan does not protect or prevent your from getting skin cancer. Even if you do have a nice tan, your skin should not stay unprotected in direct sunlight for any length of time.
In South Africa we have a lifestyle and climate that encourage staying out in the sun for long periods of time while wearing as little as possible. This is especially true during the summer holiday season when thousands of people flock to the beaches and holiday resorts.
Major skin risk times are between the hours of 10am and 3pm. You are particularly at risk if you:
- work outdoors;
- get large and sudden doses of sun on the weekend after working indoors all week;
- have a bald head;
- have red hair, or freckle;
- is a fair skinned newcomer to the hot South African climate;
- or if you are using photosensitising drugs, that is drugs that make your skin more sensitive to light.
Babies, small children and elderly people are also highly sensitive to UV radiation.
REMEMBER: The average skin begins to suffer damage in the sun after about 10 minutes.
Whether you are a construction worker, an agriculturalist, or an outdoor sports enthusiast, you can still enjoy healthy outdoor activity, if you take a few simple steps to reduce your exposure to ultra violet radiation. The best protection against skin cancer is to minimise exposure to the cause - exposure to sun.
Wherever you are, try to take these simple precautions:
- MINIMIZE SUN EXPOSURE Avoid being in the sun, particularly midday sun, as much as possible. You'll find the shade a whole lot cooler. Reduce the time you spend in the midday sun. UV rays are strongest between 10:00 a.m. and 4:00 p.m., so plan your outdoor activities before or after these times. Keep in mind that Ultra violet radiation may be increased by reflective surfaces such as water, concrete, or sand.
- USE SUNSCREEN Whatever your skin type, maximum protection SPF 15+ sunscreen is advisable - be it when working, gardening, walking to the shops, cycling, playing sport, as well as on the beach. Sunscreen is most effective when applied liberally and left on the surface of the skin. Do NOT rub it in thoroughly. Look for a sunscreen product with both UV-B and UV-A protection and a sun protection factor (SPF) of 15 or greater. Apply sunscreen at least 20 minutes before going into the sun, and reapply generously after swimming or physical activity. Remember that perspiration will reduce the effectiveness of your sunscreen, so reapply frequently. Baby oil is not a sunscreen, and may in fact actually cause a child to sunburn faster.
- Because skin damage is cumulative, teaching sensible sun habits from a young age will reduce the risk of skin cancer later on.
- COVER UP When outdoors wear a wide brimmed hat and protective clothing such as a shirt with sleeves, a beach jacket etc. Clothing, hats, and shade provide the best protection against UV. Let kids wear a T-shirt in the swimming pool but keep in mind that a wet T-shirt is less effective at screening sun that a dry T-shirt. Protect your eyes and shade your face with UV absorbent sunglasses and a broad brimmed hat. Wear clothing to cover your arms and legs. Although knee length shorts don't protect as well as long pants, they are better that very short shorts. Remember that you don't have to be in direct sunlight to get sun damage. Sand, snow, water, buildings, concrete, all reflect ultra violet rays - this means you can get burnt, for example, sitting under a beach umbrella on a bright day.
- SEEK SHADE Ultra violet rays can pass though water and clouds, even on overcast days. On the other hand, trees, grass and earth all absorb ultra violet rays. Moving from sand at the beach to shaded, grassy areas will protect you from burning. Carry an umbrella with you to the beach or other recreation areas. Remember that your skin doesn't have to be hot to burn, so don't be fooled by cloudy or overcast weather. Encourage the use of shady areas at all times. Keep children under one year old out of the direct sun.
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Cataracts
Given the increased risk of skin cancer and some types of cataracts associated with UV exposure, you should protect your eyes, especially when exposed to excessive sunlight. If there is sufficient UV present to cause sunburn, wearing a wide brimmed hat and sunglasses are highly recommended. Just wearing a hat will reduce exposure to UV by half. Sunglasses are capable of eliminating all of the UV.
People with high UV exposure, especially those spending prolonged time in the sun during the middle of the day, or those exposed to artificial sources such as welding arcs or suntanning lamps, should consider close fitting sunglasses with lenses that absorb all UV-A and UV-B.
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