Ultraviolet (UV) radiation is part of the electromagnetic spectrum emitted by the sun; it has high energy and is non-visible.
UV radiation consists of three categories, UVA, UVB and UVC.
UVC is the most dangerous but is absorbed by the Earth's atmosphere. Most of the radiation in the UVA range and approximately 5% of UVB reaches the Earth's surface. Small amounts of UVB are essential for the production of vitamin D in people. However, over-exposure may result in acute and chronic health effects including skin damage such as premature ageing, skin cancer, eye damage and suppression of the immune system.
For further information, refer to the World Health Organization.
UV radiation and skin damage
Sunburn (erythema) is the best-known acute effect of excessive UV radiation exposure. All categories of UV radiation (UVA, UVB and UVC) damage the collagen fibres of the skin which accelerates the ageing process. In addition, both UVA and UVB destroy vitamin A in skin which can cause further damage.
UVA by itself does not cause sunburn. However, UVA is capable of damaging DNA indirectly by producing hydroxyl and oxygen-free radicals; it does not damage DNA directly like UVB and UVC. UVA cannot be measured in the SPF (sun protection factor) testing because it does not cause reddening of the skin.
UVB radiation has been demonstrated to cause skin cancer. UVB radiation excites DNA molecules leading to DNA mutations commonly found in cancerous growths. The connection between UV radiation and cancer is one reason for concern about ozone depletion as the ozone layer absorbs most UV radiation (UVB and UVC) , preventing it from reaching the Earth's surface.
In 1992, both UVA and UVB were categorised as 'probably carcinogenic to humans' by the International Agency of Research on Cancer (IARC) which classifies carcinogenic agents.
The skin tans (depending on skin type) when exposed to moderate levels of radiation as a defence mechanism against UV radiation. UV radiation exposure triggers the release of the brown pigment melanin from melanocytes. This tan helps to block UV penetration and prevent damage to the vulnerable skin tissues deeper down.
In South Australia the incidence of melanoma is steadily increasing and is the 3rd most common cancer in both women and men, and most common for 15 to 44-year-olds.
Two in three Australians will be diagnosed with skin cancer by the time they are 70.
From 1998 to 2007, GP consultations to treat non-melanoma skin cancer increased by 14%, to reach 950,000 visits each year.
More information is available at Cancer Council Australia
Commercial tanning units used for cosmetic purposes are banned from 1 January 2015.