Table 6. Environmental Exposures Other Than Sunlight Associated with Melanomaa continued...
Occupational exposure for airline flight personnel, particularly pilots and flight attendants, appears to be particularly significant.[20,25,26,27,28,29,30,31,32] Since the risk of internal cancers is not consistently elevated in these very large cohort studies, most investigators think that the excess melanoma cancers observed are caused by lifestyle factors such as excessive intermittent sun exposure (i.e., UV radiation that does not penetrate beyond the surface of the skin) rather than cosmic (i.e., ionizing) radiation, which would be expected to increase the risk of radiation-related solid tumors.
Other occupational exposures have been variously and inconsistently associated with melanoma risk. If these reports are genuine, these exposures are likely to account for only a small fraction of cases.[33,34,35]
Arsenic exposure (both from drinking water and from exposure to combustion products) has been consistently associated with nonmelanoma skin cancer and has more recently been linked to melanoma.[34,36,37,38] Heavy metals bind to melanin, and occupational studies show that printers and lithographers have increased melanoma risk.[34,40,41,42,43] Further clarification of the occupational exposures associated with the development of melanoma in people employed in the printing/lithography trade has been difficult because of the small numbers of workers; the exposure of workers to numerous chemicals, solvents, pigments, and dyes; the extended latency of disease presentation; and changing work practices and environments over the past 50 years. Five studies have shown increased risk of melanoma among electronics workers.[24,43,44,45,46] However, more persuasive evidence of metal-related melanoma risk has been documented in the long-term follow-up of individuals with metal-on-metal hip replacements.[47,48,49]
Pigmentary characteristics are important determinants of melanoma susceptibility. There is an inverse correlation between melanoma risk and skin color that goes from lightest skin to darkest skin. Darker-skinned ethnic groups (blacks, darker Hispanics, Asians) have a very low risk of melanoma; however, individuals in these groups develop melanoma on less-pigmented acral surfaces (palms, soles, nail beds). Among relatively light-skinned individuals, skin color is modified by genetics and behavior. MC1R is one of the major genes controlling pigmentation (see below); other pigmentation genes are under investigation.