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CHALLENGING THE SUNLIGHT - SKIN CANCER CONNECTION by Dr. Ro nald S. n Educatio , Un sity of Newca astle & John F. Ashto ‘Chiel Che ‘ist, Sanitar ium Re rch Labo CONNECTION In what follows it will be argued that the orthodox explanation of skin cancer and the assumptions about the dangers of sunlight which underpin it are highly misleading and may in fact be contributing unwittingly to the very behaviour responsible for the increase in melanoma. higher incidence of melanoma among indoor workers and among those of higher social class. It is also revealing that the distribution of melanomas across the body is often higher on parts of the body least exposed to sunlight. (1) Compounding the problem are a number of environmen- tal factors which may actually increase the sensitivity of our skin to sunlight. By 1964 more than 100 chemical agents, including many commonly used drugs, had been documented as increasing the sensitivity of the skin to nat- ural light. Within the class of photosensitizing drugs are found hypoglycaemic, antihypertensive, tranquilliser, broad spectrum antibiotic drugs, and even sunscreens and tanning lotions. (2) Around the same period reports of pho- toallergic reactions to artificial sweetener cyclamate was added to the list in 1967. (3) The processing and refining of our food is also thought to increase skin sensitivity and thus reduce skin tolerance to sunlight. (4) There is evidence that a deficiency of B6 in the diet, for example, increases photosensitivity to ultravi- olet light. Vitamin B6 levels in grains are considerably diminished in the milling and refining process, with white bread containing only 22% of Vitamin B6 compared with wholemeal bread (5). On the other hand it is ironic that our cereals are fortified artificially with other chemicals such as riboflavin, which is itself a potential photosensitizer. While factors such as the above increase our sensitivity to sunlight, the beneficial effect of sunlight on the regula- tion of our hormonal system in a way that helps to prevent melanoma needs to be addressed. For many years female sex hormones, for instance, have been suspected as being important in the induction of melanomas. It has been shown that there are oestrogen receptors in melanoma cells and there is evidence to suggest that oral contraceptives may increase the risk of the disease. (6) Women who take high- dose oral contraceptives or who become pregnant some- times develop patchy pigmentation around their face, as increased oestrogen levels appear to stimulate pigment syn- thesis in melanocytes. (7) It is also known that the human ovulatory cycle is regulated and normalised by natural light. (8) In regard to the rising incidence of melanoma, one hypothesis is that the healthy formation of skin pigmenta- tion is regulated in subtle ways by light entering the body through the eyes as well as the skin. Since different regions In what follows it will be argued that the orthodox explanation of skin cancer and the assumptions about the dangers of sunlight which underpin it are highly misleading and may in fact be contributing unwittingly to the very behaviour responsible for the increase in melanoma. The orthodox view of the increasing incidence of melanoma depends upon the assumption that regular expo- sure to sunlight is the main cause of skin cancer, a cause which is now all the more to be feared as the progressive depletion of the ozone layer leads in turn to an increase in the levels of ultraviolet light to which the human body is exposed. Substantial evidence has now accumulated to challenge the assumption that the increase in melanoma which has occurred since the 1960’s is a matter simply of environ- mental exposure to ultraviolet radiation. Contrary to the conventional wisdom, it would appear that the ability of the body to defend itself against melanoma depends upon suf- ficient exposure to natural sunlight, and that our ever increasing exposure to artificial light may have far more to do with the incidence of melanoma than has been supposed. Throughout the history of the human species, exposure to sunlight has figured as a common experience of everyday life. Today, however, we find in modern urbanised coun- tries that our relationship with the environment has changed markedly. By having progressively synthesized the world in which we live, our contact with the natural environment is rapidly becoming minimal. Many people now make their way to work just as the sun is rising and make their way home once the sun has set. For many peo- ple the world of artificial light has replaced the world of natural sunlight, as they spend most of their day working indoors. Interestingly, there is evidence which establishes a NEXUS - 19 MAY/JUNE 1991 *- YEAR BOOK