In its 2006 Tanning 2006 IARC – ArtificialUVRad&SkinCancerreport, the WHO’s International Agency for Research on Cancer concluded,
Epidemiologic studies to date give no consistent evidence that use of indoor tanning facilities in general is associated with the development of melanoma or skin cancer… the available findings are therefore not conclusive…
Further, scientists cannot consistently demonstrate the UV-radiation-skin cancer hypothesis in animals. In its 2006 report IARC stated [pp. 8-9]:
The relevance of animal models for elucidating the biological mechanisms involved in the development of melanoma and BCC remains questionable, as even engineered mice with multiple deficiencies in key genes involved in cell cycle regulation and growth factor synthesis do not represent a model equivalent to the human skin. In addition, experiments on animals cannot reproduce the complex relationship existing in individuals between highly variable natural susceptibilities to UV radiation, different sun exposure behaviours, and exposure to various sources of UV radiation.