ULTRAVIOLET RADIATION AND CANCER 557 



States. Certainly it is not desirable to instill fear of exposure to sunlight 

 in a large part of the population, but certain prophylactic measures may 

 be suggested. Continuous regular exposures to artificial sources of ultra- 

 violet radiation, even in moderate doses, would seem unwise, particularly 

 when these are used during the winter months to supplement summer 

 exposure, either for cosmetic or therapeutic reasons. Probably a large 

 proportion of the white population could practice such regular exposures 

 without accident, but an unfortunate few might be expected to develop 

 cutaneous cancer. Those individuals who show changes in the skin 

 which the dermatologist recognizes grossly as "precancerous," for 

 instance, the appearance of keratoses, or those w^ho have already had 

 one cancer of the skin of the squamous-cell or basal-cell type, might well 

 be cautioned against even relatively mild continued exposure to ultra- 

 violet radiation. But they should be informed of the character of the 

 carcinogenic radiation and the facts regarding sunlight which have been 

 discussed in the previous chapter. They should know that they are 

 relatively safe in exposing themselves in the early morning or late after- 

 noon, but should avoid the midday sun. They should also be informed 

 that window glass offers good protection against carcinogenic radiation. 

 The use of sunburn preventives when going outdoors may also be recom- 

 mended, although the uncertainty of evaluating these has already been 

 discussed in the previous chapter. 



REFERENCES 



Bain, J. A., and H. P. Rusch (1943) Carcinogenesis with ultraviolet radiation of 



wave length 2800-3400 A. Cancer Research, 3: 425-430. 

 Beard, H. H., T. S. Boggess, and E. v. Haam (1936) Experimental production of 



malignant tumors in the albino rat by means of ultraviolet rays. Am. J. Cancer, 



27: 257-266. 

 Bellini, A. (1909) Dell' influenza degli agenti fisici e piu particolaramente della luce 



nella eziologia dell' epithelioma cutaneo. Giorn. ital. malattie venerei e pelle, 



50: 732. 

 Blum, H. F. (1940) Sunlight and cancer of the skin. J. Natl. Cancer Inst., 1 : 397- 



421. 

 (1943a) Wavelength dependence of tumor induction by ultraviolet radiation. 



J. Natl. Cancer Inst., 3: 533-537. 

 (1943b) Physiological and pathological effects of ultraviolet radiation. Ann. 



Rev. Physiol., V: 1-16. 

 (1944) Relationships between spontaneous tumors of the lung and cutaneous 



tumors induced with ultraviolet radiation in strain A mice. J. Natl. Cancer 



Inst., 5: 89-97. 



(1948) Sunlight as a causal factor in cancer of the skin of man. J. Natl. 



Cancer Inst., 9: 247-258. 



(1950a) Radiation: non-ionizing; photophysiology and photopathology. 



In, Medical physics, ed. O. Glasser. Year Book Publishers, Inc., Chicago. 

 Vol. II. Pp. 753-766. 



(1950b) On the mechanism of cancer induction by ultraviolet radiation. J. 



Natl. Cancer Inst., 11: 463-495. 



