A link between the location of skin cancer on the body and the sun's position in the sky has been found by Australian scientists. 

Australia has the highest incidence rate of non-melanoma skin cancer (NMSC) in the world. The country is at a low latitude (a short distance from the equator), which means that it receives higher UV exposure levels throughout the day than countries at higher latitudes.   

To investigate how this affects skin cancer incidence, Nathan Downs and Alfio Parisi at the University of Southern Queensland, Toowoomba, spent four years measuring UV exposure levels on a life-sized mannequin in Australia. They took measurements at 1453 body sites, improving upon previous data. When the sun was high in the sky, all parts of the mannequin received the highest irradiation levels. This is because the sunlight takes a shorter path through the atmosphere. But then the pair found that when the sun was lower in the sky, larger areas of exposed skin, such as the leg, received more low-level UV exposure.   

Downs and Parisi then compared the results with the distribution of pre-cancerous patches of skin called solar keratoses (SKs) and the two most common NMSC types, squamous cell carcinoma (SCC) and basal cell carcinoma (BCC). They found that areas with greater UV exposure, such as the nose, tended to have more BCC tumours. SKs were found to have a stronger relationship with UV exposure, being more frequent on the cheeks, top of the ears and nose. 'A more detailed collection of SKs, SCC and BCC incidence data would be of great benefit, particularly if this data could be mapped onto the body wireframe models at each of the 1453 body sites,' says Downs. 

Downs plans to investigate the effect of playing sport on UV exposure. 'At the moment I am looking at measuring UV exposures to golfers, swimmers and snorkellers with human and mannequin subjects,' he adds. 

Marko Weber, an expert in laser and optical radiation safety at Seibersdorf Laboratories, Austria, says: 'Any study that tries to improve our knowledge of skin cancer and tries to reveal the causes for its development is really important, because the incidence rate will increase in the future and could become a burden for our health systems.' 

Sylvia Pegg 

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