Skin Cancer Causes and Risk Factors

Eighty to eighty-five percent of non-melanoma skin cancers are basal cell carcinomas and the remaining percentage are squamous cell carcinomas, with the latter being the more invasive of the two and underlying most of the deaths attributable to these tumors. (J Invest Dermatol 1994, 102:6S-9S).

A paper presented in the journal Clinical and Experimental Dermatology reported on five cases of non-melanoma skin cancer occurring in welders, an occupation in which there is potential for intense exposure to non-solar ultraviolet irradiation. (Clin Exp Dermatol. 2000 Jan;25(1):28-9).

A Canadian study found elevated risks for squamous cell carcinomas in people exposed to insecticides, herbicides, fungicides and seed treatments as well petroleum products, grease, and several other exposures.

Elevated risks of basal cell carcinomas were seen in people exposed to fibreglass dust and dry cleaning. Also, prior non-diagnostic X-ray treatment for skin conditions increased risk of both cancers. (Cancer Epidemiol Biomarkers Prev 1996, 5:419-424).

Several studies have shown an association between cumulative ultraviolet exposure and risk of basal cell carcinoma, although the magnitude of risk conferred has been small.

Other studies have failed to find a significant association between estimated cumulative sun exposure in adulthood and the presence of basal cell carcinoma.

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Other non-ultraviolet environmental exposures that have been associated with increased risk of basal cell carcinoma include ionising radiation, high dietary energy (especially fat), low intake of vitamins, and various chemicals and dust. Exposure to arsenic predisposes to multiple basal cell carcinomas. (BMJ. 2003 October 4; 327(7418): 794–798).

Analysis of the major occupational groups showed that, in the context of basal cell carcinoma, professionals and technicians have an increased risk of developing this type of cancer. When all occupations and both basal cell carcinoma and squamous cell carcinomas were analysed jointly, miners and quarrymen, secondary education teachers and masons registered excess risk.

Separate analysis of the results by type showed a higher risk of basal cell carcinoma for railway engine drivers and firemen, farmers and salesmen, in addition to the above three occupations.

The occupations that registered a higher risk of squamous cell carcinomas (though not of basal cell carcinoma) were those involving direct contact with livestock, and the groups encompassing other construction workers and stationary engine and related equipment operators. (BMC Public Health 2007, 7:180doi:10.1186/1471-2458-7-180).

It has also been reported that 2% of such tumours could be associated with exposure to radon in the UK. (Health Phys 2003, 85:733-739).

The results of our study show a strong association between the occupation of miner and both types of non-melanoma skin cancer, with the strength of association for basal cell carcinomas being double that for squamous cell carcinomas.

The explanation for this result might partly lie in the above-mentioned exposure to radon in the case of basal cell carcinomas; and possibly lie in exposure to arsenic in the case of squamous cell carcinomas. (BMC Public Health 2007, 7:180doi:10.1186/1471-2458-7-180).

Overall, an increased risk of both basal cell carcinomas and squamous cell carcinomas was found in relation to therapeutic ionizing radiation and were most pronounced for those irradiated for acne exposure.

For squamous cell carcinomas, an association with radiotherapy was observed only among those whose skin was likely to sunburn with sun exposure. (Arch Dermatol. 2000 Aug;136(8):1007-11).

In our study, farmers/animal husbandry workers were observed to register an increased risk of developing both basal cell carcinomas and squamous cell carcinomas, despite our efforts to adjust for exposure to solar radiation.

It is well known, however, that farmers suffer from multiple exposures, ranging from pesticides to hazardous air pollutants, due to their use of different types of machinery and plants.

Among workers in direct contact with livestock, risk is apparently higher for squamous cell carcinomas. Although there is a slight possibility of false diagnoses of squamous cell carcinomas in the case of viral warts, such a problem would seem unlikely, in view of the fact that the cases were reviewed by a panel of pathologists who verified the diagnoses. (BMC Public Health 2007, 7:180doi:10.1186/1471-2458-7-180).

In Conclusion: This study shows the association between non-melanoma skin cancer and certain occupations. For non-melanoma skin cancer as a whole, miners and quarrymen, secondary education teachers, and masons register excess risk, regardless of exposure to solar radiation and phenotype (such as skin, hair or eye color).

Basal cell carcinomas prove more frequent among railway engine drivers and firemen, farmers and salesmen, in addition to the above-mentioned 3 occupations.

The occupations that register a higher risk of squamous cell carcinomas (though not of basal cell carcinomas) are those involving direct contact with livestock, other construction workers not elsewhere classified and stationary engine and related equipment operators not elsewhere classified.

Exposure to hazardous air pollutants, arsenic, ionizing radiations and burns might well explain a good part of the associations observed in this study. (BMC Public Health 2007, 7:180doi:10.1186/1471-2458-7-180).

Berta Suárez, Gonzalo López-Abente, Carmen Martínez, Carmen Navarro, Maria José Tormo, Stefano Rosso, Simon Schraub, Lorenzo Gafà, Hélène Sancho-Garnier, Janine Wechsler and Roberto Zanetti. Occupation and skin cancer: the results of the HELIOS-I multicenter case-control study. BMC Public Health 2007, 7:180doi:10.1186/1471-2458-7-180. This is an Open Access article distributed under the terms of the
Creative Commons Attribution License.