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Understanding Tanning: Part 1

By Kellie Heywood

What do you need to know before getting that bronzed glow?


              Understanding Tanning: Part 1

Can you tan safely? This is a question that has caused some controversy not least because, according to the World Health Organization, one in every three cancers diagnosed is a skin cancer. On the other hand, some scientists have warned about health problems related to Vitamin D deficiency which can be linked to lack of sun exposure.

So what's a lover of the sun, or suntans for that matter, to do? A set of reviews looking at the science behind tanning suggests you should think seriously before setting out to get a suntan.

Seeing in ultraviolet

To understand the controversy over whether or not to tan, you need to know about what ultraviolet radiation does to the skin.

On the upside, ultraviolet radiation:

  • Causes cells called melanocytes in the skin to produce a pigment called melatonin which leads to darkening of the skin that occurs in a tan.
  • Stimulates the production of pre-vitamin D in the skin. Vitamin D is important for bone strength and Vitamin D deficiency has been linked with increased risk of some internal cancers.
  • May act on a receptor in the skin to cause an elevation in mood which may explain why some people report having a tan makes them feel better.

But, and it's a big but, ultraviolet radiation also has been found to:

  • Reduce the amount of antioxidants in the skin
  • Cause photo-ageing by damaging collagen in the skin
  • And, most seriously, ultraviolet light can cause mutations in the DNA of skin cells. Mutation of DNA can lead to cancer.

Ultraviolet light exposure has also been linked to a number of eye conditions including melanoma of the eye, cataract and pterygium (a growth of white, scar-like tissue across the cornea).

According to Dr David Fisher and his fellow authors of one of the reviews, "There are few lingering doubts from epidemiological data as well scientific information regarding the massive risk UVR (ultraviolet light) imposes on development of skin cancer."

On the right wavelength?

Not all ultraviolet radiation is the same and that's where the difference between sunbaking outside and using a tanning bed occurs.

Ultraviolet radiation is sorted into three separate ‘bands' according to wavelength:

  • UVA, 400-320 nanometres
  • UVB, 320-290 nanometres
  • UVC, 290-200 nanometres.

If you’re out in the sun, almost all UVC radiation is filtered out by the atmosphere and the UVA far outranks the UVB.(In summer UVA accounts for around 95 per cent of total ultraviolet radiation coming from the sun.) In a tanning bed, the combination of UVA, UVB and UVC depends upon the manufacture.

While both UVA and UVB radiation can produce a tanning effect, UVB is the most effective, with wavelengths of 290-300 nanometres being the optimum. Unfortunately those are the peak wavelengths at which DNA damage and Vitamin D synthesis are at their greatest too.

But can you get a guilt-free glow?

There have been some claims that by reducing exposure to UVB radiation, it is possible to get a safe tan. However, recent advances in understanding the molecular basis of tanning suggest that this is not the case. Research suggests the trigger for production of melanin is the damage of DNA in skin cells. Essentially: no damage = no melanin. No melanin = no tan.

In the words of the reviewers: "Safe tanning" with ultraviolet may be a physical impossibility.

They also point out that while UVA has a much lower tendency to cause DNA changes in the skin than UVB, there is evidence that it does cause some changes. They note that better experimental evidence is needed to determine whether damage caused by UVA causes cancer or not.

In Understanding Tanning: Part 2 we look more closely at the health claims and risks for tanning.

References:

World Health Organization (2005) Fact Sheet No 287: Sunbeds, tanning and UV exposure. Available at www.who.int/mediacentre/factsheets/fs287/en/index.html Viewed 12/03/09 (03/12/09 US)

Tran T, Schulman J, Fisher D (2008) UV and pigmentation: molecular mechanisms and social controversies. Pigment Cell Melanoma Research 21: 509-516.

Berwick, M (2008) Are tanning beds “safe”? Human studies of melanoma. Pigment Cell Melanoma Research 21: 517-519.

Bennett D (2008) Ultraviolet wavebands and melanoma initiation. Pigment Cell Melanoma Research 21: 520-524.

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