UV radiation and skin damage
Skin cancer in SA
UV radiation
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, overexposure 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 it does not cause sunburn. However, UVA is capable of damaging DNA indirectly by producing hydroxyl and oxygen free radicals and does not damage DNA directly like UVB and UVC. Because UVA does not cause reddening of the skin it cannot be measured in the SPF (sun protection factor) testing.
UVB radiation has been demonstrated to cause skin cancer. UVB radiation excites DNA molecules leading to DNA mutations. DNA mutations are 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 (UVC and UVB) , 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. For further information, refer to the IARC website.
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.
Skin cancer in SA
In South Australia the incidence of melanoma is steadily increasing and, in the next 5–10 years, is likely to overtake lung cancer as the fourth most common cancer in people. In 2005, 25,600 people were diagnosed with non-melanoma skin cancer (NMSC) and 728 people were diagnosed with melanoma. There were 79 deaths from melanoma alone.
The mortality associated with NMSC is low with 390 people dying in Australia in 2003; however the morbidity can be significant with facial scarring, disfigurement, infection and pain being common side effects of treatment. The estimated cost to South Australia in treating people with NMSC and melanoma is approximately $18 million per year and $2.3 million per year respectively.
This page was last modified 18-03-2008
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