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UV Rays and Some of the UV Exposure Facts

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Most people are aware that the sun has damaging effects on their skin. Whether it is coming back from the beach with a sunburn or seeing spots on the skin appear for the first time, the sun has many effects on our health, wellbeing and appearance. The damaging impact of the sun on our skin comes from ultraviolet radiation, which is the main cause of diseases such as skin cancer and melanoma.

What is ultraviolet radiation?

Radiation is the emission of energy and comes in many forms, from high frequency x-rays to low frequency radio waves. In the case of ultraviolet radiation the main source in most people’s lives is the sun, however, it can also come from tanning beds and industrial equipment such as welding torches.

What makes ultraviolet radiation particularly dangerous to the human body is that it is a type of ionizing radiation. This means that ultraviolet rays are capable of removing an electron from an atom, which has the possibility of damaging DNA in cells and causing cancer in the skin. The good news is that UV radiation can’t penetrate deep into the body, so won’t affect deeper organs like the heart or lungs, however, it can still have a devastating effect on the skin.

Skin cancer is one of the leading causing of death in Australia, with more than 2,000 Australians dying every year from the disease. Two in three Australians will be diagnosed with skin cancer by age 70 and there are approximately 900,000 cases treated every year.

Ultraviolet radiation from the sun comes in two main forms UVA and UVB radiation, which have significantly different effects on the skin.

What is the difference between UVA and UVB radiation?

UV radiation is divided into UVA and UVB types by measuring its wavelength. The shorter the wavelength of UV radiation, the more damaging it is to the skin; however, the less able it is to penetrate the atmosphere and layers of the skin.

98.7% of the ultraviolet radiation that reaches the earth’s surface is UVA since the ozone layer absorbs most, but not all, of the UVB and UVC rays. UVC rays are the highest energy and the most dangerous type of ultraviolet radiation, but very few of these rays reach the earth’s surface as they are filtered out by the ozone in the atmosphere. This may become a concern as more ozone is lost. A small amount of UVB reaches the earth’s surface but the vast majority of rays that reach us on the surface are UVA.

What is UVA?

UVA radiation has a longer wavelength than UVB radiation, so more of it reaches the surface of the earth. Because UVA radiation has a longer wavelength, it can penetrate deeper into the skin, causing immediate tanning, skin aging, and wrinkling. UVA also contributes to skin cancer. It penetrates the skin more deeply than UVB does, weakens the skin’s immune system, and increases the risk of cancer – especially melanoma. Ordinary glass is partially transparent to UVA, but is opaque to the shorter wavelengths of UVB and UVC. For this reason, care is needed when spending long periods in the car. Tinted windows or specialized windows with "UV Blocker" will, however, block out the vast majority of UVA.

UVA is even thought to break down Vitamin D in the skin, contributing to lower than-normal Vitamin D levels in people who are overexposed to the sun. UVA causes long-term, visible damage such as wrinkles, blotchiness, sagging, and discolouration by damaging the collagen fibres present in our skin.

What is UVB?

UVB radiation has a shorter wavelength than UVA radiation so it is much less present on the surface of the earth. However, it has more energy than UVA radiation and thus has a more severe impact on the skin, even though it can’t penetrate as deeply as UVA radiation. UVB radiation penetrates only the top layer of skin and is very important for synthesising Vitamin D. Overexposure to UVB rays is responsible for causing sunburn and for many basal cell and squamous cell cancers.

UVB is almost completely filtered out by glass and, therefore, does not contribute to Vitamin D synthesis when you are indoors. At one time, scientists believed that only UVB rays were responsible for the formation of skin cancer, they have since discovered that UVA rays also contribute. It is the main cause of sunburns, skin cancer and melanoma.

Sources of UV rays

  1. Much of the damage to DNA in skin cells results from ultraviolet (UV) radiation found in sunlight and commercial tanning lamps and tanning beds. There are many other sources around, and some may even be dangerous. Artificial sources include black lights, curing lamps, germicidal lamps, mercury vapor lamps, halogen lights, high-intensity discharge lamps, fluorescent and incandescent sources, and some types of lasers. Arc-welding is another prevalent source of UV rays
  2. Tanning beds deliver high doses of UVA, which makes them especially dangerous. What’s more, even occasional exposure to intense UVA puts you at greater risk of developing skin cancer than spending long hours in the sun does. An initial high dose of UV radiation will severely damage melanocytes, but not destroy them. When these damaged cells are subjected to further intense bouts of UVA light, they have little capacity to repair their DNA. This makes them more likely to become malignant.
  3. Although UVC rays are filtered out by the atmosphere, they are found in sterilizing equipment such as pond sterilization units. They can pose an exposure risk if the lamp is switched on outside of its enclosed pond sterilization unit.

Beneficial effects of UV rays

UVB is essential for synthesising Vitamin D in the skin (this important subject will be covered in another chapter). Ultraviolet radiation can also have other medical applications, such as treating psoriasis and vitiligo. UV rays are also used to sterilize materials such as food and water.

Harmful effects of UV rays

Sunburn & Skin Cancer.
Overexposure to ultraviolet radiation can cause sunburn and some forms of skin cancer by damaging the DNA in our skin cells. The main damage caused by UV radiation is to the skin, but other parts of the body can also be affected.

Eye Damage.
High intensities of UVB light are hazardous to the eyes and exposure can cause welder’s flash (photokeratitis or arc eye) and may lead to cataracts, pterygium, and pinguecula formation; these are tissue growths that grow to cover the eye, and are probably the body’s mechanism of protecting the eye from further damage.

6 facts about UV exposure that you may not know

The following facts demonstrate how the environment or terrain affects the level of UV radiation that we are exposed to:

  1. Wet, fresh snow can reflect as much as 85% of UV radiation. This means that snow reflection can double overall UV exposure.
  2. Similarly, white water and sand can reflect the UVI by up to 50% and 20%, respectively.
  3. Every 100 meters of increase in altitude increases UVI by 100%. This is because a thinner atmosphere at higher altitudes absorbs less UV radiation.
  4. 80% of UV rays pass through a cloud. Therefore, even with cloud cover, the UVI can be very high.
  5. Concrete buildings reflect 15% of the received UV.
  6. Shade can reduce UV by 50% or more, but it may not significantly reduce UV.

In other words, cover up as much as possible and be aware of reflected UV radiation.

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