The major cause of melanoma and keratinocyte cancers (KC) is exposure to UV radiation. The International Agency for Research on Cancer (IARC) has classified solar and UV radiation as carcinogenic to humans .
Excessive UV radiation damages DNA in skin cells producing genetic mutations that can lead to skin cancer. Sunlight is the main source of UV radiation and solariums are a source of artificial UV radiation. Solar radiation causes cutaneous malignant melanoma, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) of the skin.
Different patterns of sun exposure are associated with different types of skin cancer. Melanomas can arise in different ways, depending on a person’s genes. Some melanomas develop after chronic sun exposure, mostly on sun exposed areas of the body, whereas other melanomas can develop after modest amounts of sun exposure on less exposed areas of the body in people with genetic susceptibility to melanoma .
Sun exposure during childhood and adolescence has been shown to greatly impact an individual’s lifetime risk of developing skin cancer. Sun exposure in childhood has also been associated with melanoma . Intense sun exposure in the first 10 years of life has been shown to nearly double the lifetime risk of melanoma . In relation to KC, childhood and adolescent (intermittent and non-occupational) sun exposure increases the risk of BCC, while cumulative sun exposure, including occupational exposure, increases SCC risk. In Australia, both BCC and SCC rates are around three times higher in latitudes closer to the equator, where UV radiation is higher.
People who work outdoors are exposed to five to ten times more UV than indoor workers . It is estimated that around 200 melanomas and 34,000 KCs per year are due to occupational exposure in Australia . Systematic reviews conclude that outdoor work constitutes an independent and robust risk factor for the development of cutaneous SCC and BCC.
In 2009, IARC added UV emitting tanning beds to its highest cancer risk category, labelling them as "carcinogenic to humans" after deeming them to be more dangerous than previously suggested. By January 2016, all state and territories (except Northern Territory where no commercial solariums operate) introduced a complete ban of commercial solariums.
Impact of climate change
The ozone layer acts as a barrier to UV radiation; its depletion over the 20th century has resulted in higher radiation levels reaching the earth’s surface. International measures to protect the ozone layer are showing signs of impact, but improvements have not yet returned ozone to pre-1970s levels.
The CSIRO and the Bureau of Meteorology have projected that mean temperatures within Australia will rise by 0.6 to 1.5°C by 2030 compared with the climate of 1980 to 1999. Warmer temperatures may result in Australians increasing their sun exposure and wearing less covering clothing, thereby increasing their risk of skin cancer. However, very high temperatures may in contrast prompt behaviours to avoid sun exposure, and therefore "there is considerable uncertainty in modelling future human behaviour in response to climate change".
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