Examining the role of visible light in photocarcinogenesis – Lessons from the past

Recent publications have confirmed the ability of visible light from sunlight (in the absence of Ultraviolet A or B) to cause free radical formation in human skin, increases in metalloproteinases, induced pigmentation and even erythema from exposures within reasonable exposure periods (e.g. less than 8 h). This raises questions regarding the role of visible light on the formation of skin cancers and even the need for protection against visible light in general. Conducting such studies is a challenge, considering the doses of visible light required for observation of reactions, the difficulty in conducting animal studies with appropriate models in the current regulatory environment, and the lack of funding for basic photobiological research. A review of research from an earlier era in photobiology studies gives us some clues and suggests that there may in fact be detectable influences of visible radiation (for example on skin cancer induction) that warrant new approaches to photoprotection in this era.