LETTERS
Robyn M Lucas1
National Centre for Epidemiology and Population Health, The Australian National University, Canberra, ACT 0200, Australia
We thank Dr Hallberg for his comments on our paper "Is the current public health message on UV exposure correct?" We are aware of the research on EMF and melanoma; however, the weight of evidence supports a primary role for excessive UVR exposure in the causation of skin cancers.1 Clearly other factors are important, including skin pigmentation and genetic susceptibility, for example defects in DNA repair seen in people with xeroderma pigmentosa.2 Ecological studies support an hypothesis of a role for EMF in melanoma with hypothesized biological plausibility for a causative association via impaired cell repair and apoptosis if individual-level studies support that hypothesis, UVR exposure remains of primary importance as the cause of the cell damage that requires repair.
We agree that the finding that some skin cancer incidence rates are beginning to plateau in younger age cohorts correlates with an environmental change some years ago. Since most evidence supports the importance of episodic excessive sun exposure in childhood for the later development of melanoma3 (commonly diagnosed at 4050 years), then an environmental change occurring not 50 years ago, but more like 30 years ago, could be driving the incidence rate plateau. This would be consistent with the initial concerns about ozone depletion and a resulting increased risk of skin cancers starting in the early 1970s.4 Sun awareness and protection messages developed soon after this, particularly in those same countries in which plateauing melanoma incidence rates are now being observed.
Further evidence for sun exposure playing a role in melanoma comes from the consideration of changing incidence rates for cutaneous malignant melanoma, on sun-exposed compared to non-sun-exposed sites.5 Individual-level work on the role of EMF will be required to clarify its role in the causation of skin cancers, particularly cutaneous malignant melanoma. 
References
1. Armstrong BK, Kricker A. The epidemiology of UV-induced skin cancer. J Photochem Photobiol B 2001;63:8-18.
2. de Gruijl FR, et al. UV-induced DNA damage, repair, mutations and oncogenic pathways in skin cancer. J Photochem Photobiol B 2001; 63:19-27.
3. Elwood JM, Jopson J. Melanoma and sun exposure: an overview of published studies. Int J Cancer 1997;73:198-203.
4. Lucas RM, McMichael AJ. Stratospheric ozone depletion: successful responses to a global environmental insult. In: Ebi KL, Smith J et al., eds. Integration of public health with adaptation to climate change: lessons learned and new directions. London, Francis and Taylor, 2006.
5. Bulliard JL, et al. Trends by anatomic site in the incidence of cutaneous malignant melanoma in Canada, 1969-93. Cancer Causes Control 1999;10:407-16.
1 Correspondence to Robyn M Lucas (e-mail: robyn.lucas@anu.edu.au).