The effect of smoking on cancer risk and ultraviolet wavelengths on melanoma risk William B. Grant, Sunlight, Nutrition, and Health Research Center (SUNARC) 30 September 2008 The study of variation of cancer incidence by socioeconomic group in England by Shack et al.  presents some interesting results; however, the interpretation of the findings overlooks two important factors: the role of smoking in risk for some types of cancer and the different roles of solar ultraviolet-B (UVB) and UVA in the etiology of melanoma and non-melanoma skin cancer (NMSC). This letter presents results in the relevant journal literature regarding these oversights.As mentioned in , those with lower socioeconomic status (SES) have higher rates of smoking. Thus, the effect of smoking on the cancers discussed should be evaluated to determine whether smoking rates, rather than SES per se might explain the findings. Lower SES is associated with increased risk of cervical cancer in . Smoking is an important risk factor for cervical cancer [2-4], as are emissions from wood and other solid fuels used in indoor cooking . Compounds in tobacco smoke synergistically increase the risk of cervical cancer in conjunction with human papillomavirus. One proposed mechanism is diminution of the major antigen-presenting cells in cervical epithelium . On the other hand, smoking reduces the risk of melanoma. The first report of an inverse relation between smoking and risk of melanoma was by Freedman et al. . The next report was from Sweden . In a meta-analysis of second cancer after diagnosis of skin cancer or melanoma, it was found that melanoma was inversely related to lung cancer incidence rate in the various populations considered . This work was extended with the finding that a linear regression analysis of lung cancer and melanoma incidence rates in 13 studies, the correlation coefficient, r, was -0.96 . The mechanism proposed is increased skin aging and elastosis from smoking; areas of the body receiving chronic rather than sporadic UV irradiance in Sweden develop melanoma later in life . Thus, the reduced risk of melanoma with lower SES in England may, in large part, be due to higher rates of smoking in the lower SES groups.As for other risk factors for melanoma, travel to sunny locations is an important factor [12,13]. However, using sunbeds may not be contributing significantly to melanoma rates in England. In my reading of , the authors of did not mention sunbed use. The IARC meta-analysis found that ever sunbed use was linked to a 15% (95% confidence interval, 0-30%) increased risk of melanoma . However, two of the studies included were from the UK with no correction for skin type; many in the UK have Fitzgerald type 1 skin (freckles, does not tan, burns easily) and should never use sunbeds. When those two studies were removed from the analysis, the increased risk of melanoma was no longer significant . Thus, it is unlikely that sunbed use contributed to the factor-of-two difference in melanoma incidence rate observed between lowest and highest SES.The authors do not understand that it is not UVB but UVA which is the primary spectral band of risk for melanoma. This point has been adequately discussed in the literature [16-18]. Further substantiation comes from the variation of melanoma and NMSC incidence and mortality rates in Western Europe: NMSC rates are highest in southern Europe while melanoma rates are highest in northern Europe . The important risk factor for NMSC is integrated lifetime UVB irradiance. For melanoma, darker skin pigmentation is protective. In Spain, melanoma mortality rates are inversely correlated with NMSC mortality rates for females . Use of sunscreen can increase the risk of melanoma . Readers with Fitzgerald skin type 2 or higher should not be afraid of obtaining vitamin D from solar UVB for reduced risk of many types of cancer [20,22,23] as well as other diseases including infectious diseases, autoimmune diseases and heart disease [24-30].References Shack L, Jordan C, Thomson CS, Mak V, Moller H. Variation in incidence of breast, lung and cervical cancer and malignant melanoma of skin by socioeconomic group in England. BMC Cancer 2008, 8:271. Plummer M, Herrero R, Franceschi S, Meijer CJ, Snijders P, Bosch FX, et al. Smoking and cervical cancer: pooled analysis of the IARC multi-centric case--control study. Cancer Causes Control. 2003;14:805-814. Gunnell AS, Tran TN, Torrång A, Dickman PW, Sparén P, Palmgren J, et al. Synergy between cigarette smoking and human papillomavirus type 16 in cervical cancer in situ development. Cancer Epidemiol Biomarkers Prev. 2006;15:2141-2147.  Tsai HT, Tsai YM, Yang SF, Wu KY, Chuang HY, Wu TN, et al. Lifetime cigarette smoke and second-hand smoke and cervical intraepithelial neoplasm--a community-based case-control study. Gynecol Oncol. 2007;105:181-188.  Velema JP, Ferrera A, Figueroa M, Bulnes R, Toro LA, de Barahona O, Claros JM, Melchers WJ. Burning wood in the kitchen increases the risk of cervical neoplasia in HPV-infected women in Honduras. Int J Cancer. 2002;97:536-541. Barton SE, Hollingworth A, Maddox PH, Edwards R, Cuzick J, McCance DJ, Jenkins D, Singer A. Possible cofactors in the etiology of cervical intraepithelial neoplasia. An immunopathologic study. J Reprod Med. 1989;34:613-616. Freedman DM, Sigurdson A, Doody MM, Rao RS, Linet MS. Risk of melanoma in relation to smoking, alcohol intake, and other factors in a large occupational cohort. Cancer Causes Control. 2003;14:847-857. Odenbro A, Gillgren P, Bellocco R, Boffetta P, Håkansson N, Adami J. The risk for cutaneous malignant melanoma, melanoma in situ and intraocular malignant melanoma in relation to tobacco use and body mass index. Br J Dermatol. 2007;156:99-105.  Grant WB. A meta-analysis of second cancers after a diagnosis of nonmelanoma skin cancer: additional evidence that solar ultraviolet-B irradiance reduces the risk of internal cancers. J Steroid Biochem Mol Biol. 2007;103:668-674.  Grant WB. Skin aging from ultraviolet irradiance and smoking reduces risk of melanoma: epidemiological evidence, Anticancer Res. 2008;28(6),in press Dal H, Boldemann C, Lindelöf B. Does relative melanoma distribution by body site 1960-2004 reflect changes in intermittent exposure and intentional tanning in the Swedish population? Eur J Dermatol. 2007;17:428-434.  Bentham G, Aase A. Incidence of malignant melanoma of the skin in Norway, 1955-1989: associations with solar ultraviolet radiation, income and holidays abroad. Int J Epidemiol. 1996;25:1132-1138. 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Health Research Forum Occasional Report #3. http://www.healthresearchforum.org.uk/sunlight.html, firstname.lastname@example.org Competing interests DisclosureI receive funding from the UV Foundation (McLean, VA), the Vitamin D Society (Canada), and the European Sunlight Association (Brussels).