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of the light spectrum are involved in maintaining a delicate balance between these two pathways, artificial indoor light with its distorted spectral composition and monotony com- pared to daylight, tends to stress the feedback and comple- mentary mechanisms between the two systems, thus dis- rupting the production of adequate levels of protective melanin in the skin. As we increase our exposure to artifi- cial light, we may thus be undermining the body’s own defense mechanisms which would otherwise protect us against everyday exposure to the harmful rays of the sun. An illustration of the importance of sufficient exposure to sunlight relates to changes which occur in the surface fat layer of the skin. This layer offers the first protection against ultraviolet light. Earlier studies showed that ultra- violet radiation seemed to increase the cholesterol content of the skin, and it was suggested that the increased choles- terol may actually predispose the skin to tumour. (9) Subsequent and more detailed studies have shown, howev- er, that the higher the cholesterol level of the skin, the greater was its resistance to the harmful effects of ultravi- olet radiation. (10). Again the optic light connection is of relevance here. Lipid metabolism and blood cholesterol levels are regulated by light affecting the optic pathway to the pineal system, and again different spectral bands such as those manifest in artificial light appear to affect the eye and skin intake systems in ways which degrade the body’s protective mechanisms against melanoma. Vitamin D synthesis is another case in point. Recent research has demonstrated that the prohormone Vitamin D levels are regulated conjointly by the pineal gland and exposure of the skin to sunshine, thus emphasising the sub- tle interconnection between the optic and skin stimulation by light. (11) This is especially significant as evidence accumulates suggesting that Vitamin D inhibits melanoma and other cancers. (12) Using unnatural fat sources, such as polyunsaturated margarines to manipulate dietary fat can also affect the balance of the mechanisms which regulate the optimum fat composition of the skin. The possibility that the manipulation of dietary fat is an important factor in the aetiology of melanoma has also been mooted. (13). The artificial colours with which we have painted and decorated our environment have served to ensure that for large periods of time the nature of the light entering our eyes is vastly different from the light reflected from the natural outdoors of meadow, forest and field. In addition the use of glass, sometimes plastic coated or tinted, means, for example, that the sunlight entering our building or vehi- cle is filtered or refined by the removal of certain wave- lengths of sunlight by the glass itself. This diminished sun- light is usually supplemented by artificial lighting from incandescent or fluorescent lights. It is clear then that apart from the progressively rarer occasions when we step outdoors, we are continuously bathing in artificial light. Yet, dare we step outside? Health departments warn us constantly through the media to beware of the skin cancer demon called sunlight. We are urged to protect ourselves from direct sunlight by using sunscreens. We do this winningly, but we fail to recognise that when we coat our skin with sunscreens or tanning oils, and even wear sunglasses, the sunlight light reaching the covered areas of skin and our eyes has been modified or refined by the absorption of certain wavelength compo- nents. Exposure to natural sunlight has again been reduced NEXUS - 20 or transformed into exposure to artificial light. This bizarre situation has arisen because little attention has been paid by health educators to the accumulating lit- erature which points to the fact that the substitution of arti- ficial light for natural sunlight is an important etiological factor in understanding the melanoma enigma. Lest the dis- cussion be misunderstood, let us make plain that the rec- ommendation is not that we should all run off to the beach at the first blush of summer sun. On the contrary, the point is that regular daily exposure, not excessive exposure and sporadic, to sunlight is an important measure in the pre- vention of melanoma. It needs also to be recognized that some of the very chemical substances upon which we have come to rely to make us healthy may inadvertantly be con- tributing to our ill health. 1. Giles, G., Dwyer, T., and Coates, M. et. al. “Trends in Skin Cancer in Australia an Overview of the Available Data” in the “The Ozone Layer and Health”, op.cit., pp.143-147; see also Cox, B., and Coombs, B. “Trends in Melanoma of the Skin in New Zealand”, ibid., pp.137-140. 2. Lee, J.A.H., and Strickland, D. “Malignant Melanoma: Social Status and Outdoor Work”, British J Cancer, Vol.41, 1980, pp.757- 763; see also “The Aetiology of Melanoma”, Editorial, The Lancet, January 31, 1981, pp.253-255. 3. Young, S.W. “A List of Photosensitizing Agents of Interest to the Dermatologist”, Bull. Assoc. Milit. Derm., Vol.13, Mar '64, pp.33-35 4, Epstein, J.H. “Phototoxicity and Photoallergy: Clinical Syndromes”, in Sunlight and Man, Fitzpatric, T.B., et.al. editors, Tokyo, University of Tokyo Press, 1974, pp.459-469 5. Driskell, J.A. “Vitamin B6”, in Handbook of Vitamins, Machlin, LJ. editor, New York, Marcel Dekker Inc., 1984, p.385. 6. Lee, J.A.H., and Storer, B.E. “Excess of Malignant Melanomas in Women in the British Isles”, The Lancet, December 20/27, 1980, pp.1337-1339; see also Beral, V., Ramcharan, S., and Faris, R. “Malignant Melanoma and Oral Contraceptive Use Among Women in California”, British J. Cancer, Vol.36, 1977, pp.804-809 7. Annon. “Possible Oestrogen Use Against Melanoma”, Laboratory News, Sydney, August 1989, p.12. 9. Baumann, C.A., and Rusch, H.P. “Effect of Diet on Tumors Induced by Ultraviolet Light”, American J. Cancer, Vol.35, 1939, pp.213, 220. 10. Mackie, B.S., Johnson, A.R., and Mackie, L.E. et.al. “Dietary Polyunsaturated Fats and Malignant Melanoma”, Medical J. Australia, February 23, 1980, pp.159-163. 11. Stumpf, W.E. “The Endocrinology of Sunlight and Darkness. Complementary roles of Vitamin D and Pineal Hormones”, Naturwissenschaften, vol.75, #.5, 1988, p.247. 12. Colston, k., Colston, M.J. and Feldman, D. “1,25- Dihydroxyvitamin D3 and Malignant Melanoma: The Presence of Receptors and Inhibition of Cell Growth Growth in Culture”, Endocrinology, Vol.108, No.3, 1981, pp.1083-1086; see also Garland, C., and Shekelle, R.B. et.al. “Dietary Vitamin D and Calcium and Risk of Colorectal Cancer: A 19 Year Prospective Study in Men”, The Lancet, Feb. 9, 1985, pp.307-309. 13. Chedekel, M.R. and Zeise, L. “Sunlight, Melanogenesis and Radicals in the Skin”, Lipids, Vol.23, No.6, 1988, p.590. References 8. Luce, G.G. Body Time, Melbourne, Sun Books, 1972, pp.241-242. YEAR BOOK - MAY/JUNE 1991