Melanoma is a type of cancer that affects the melanocyte cells of the skin, which produce pigment [1]. Over the past several decades the number of new cases of melanoma in Canada has increased [2]. In 2022, it is estimated that 9,000 Canadians will be diagnosed with the disease [1]. While non-melanoma skin cancer is much more common, melanoma accounts for the most deaths from skin cancer [3].
Exposure to solar radiation is the most important risk factor for melanoma [1]. Non-modifiable (unchangeable) risk factors for melanoma include having many or atypical moles; light-coloured skin, eyes, and/or hair; a personal and/or family history of skin cancer; and rare genetic mutations [4].
Known occupational risk factors
Possible occupational risk factors
In the ODSS, workers in construction trades, agriculture, transport equipment operating, petroleum, protective services, and healthcare were found to have higher risks of melanoma when compared to all workers in the ODSS.
There are several risk factors that may account for the increased risk of melanoma in workers in the construction trades. One possible factor is that construction occupations have one of the highest levels of sun exposure due to the high amount of outdoor work [6].
Polychlorinated biphenyls (PCBs) are known skin carcinogens that were historically used in a variety of construction materials including electrical equipment, cable insulation, and adhesives [7-8]. In Canada, the 1977 ban on PCBs allowed equipment containing PCBs to be used until the end of its service life, so construction workers may have continued to be exposed when working with older equipment [7].
Farm workers often work outdoors with prolonged exposure to solar radiation, which may contribute to their increased risk of melanoma [9]. There is also limited evidence for pesticide exposure as a potential risk factor for melanoma [10-11].
Workers in transport equipment operating occupations showed higher risks of melanoma in the ODSS. Exposure to ultraviolet (UV) radiation during flights may put aircraft operators at higher risks of developing melanoma [12-14]. Airplane windshields block most, but not all UV transmission [14]. Other transport operating occupations, such as bus, taxi, and truck drivers, may be exposed to UV radiation through vehicle windows.
Workers in petroleum industries may be exposed to solar radiation through outdoor work. They may be exposed to chemicals such as polycyclic aromatic hydrocarbons (PAHs) and benzene, but the association with melanoma is unclear [16-18]. PAHs and benzene are found in crude petroleum and petroleum by-products and workers may be exposed through inhalation or skin contact during production, drilling, and maintenance operations [10,18].
Various protective service occupations were found have higher risks of melanoma in the ODSS. Protective service workers may be exposed to solar radiation during outdoor calls and training [19]. In addition, firefighters may be exposed if PCB-containing materials or equipment are damaged during a fire [15].
It is unclear why healthcare workers have a higher risk of melanoma, although there is some evidence suggesting an association with occupational exposure to ionizing radiation [20-21]. Healthcare workers may be exposed to ionizing radiation through diagnostic and therapeutic procedures, such as medical x-rays. However, non-occupational sun exposure cannot be ruled out.
Several other occupation groups showed higher risk of melanoma, such as teaching and recreational occupations. Workers in these groups may be exposed to long periods of sun exposure from outdoor activities, such as school breaks, field trips, and outdoor sports. Sun exposure outside of work may also play a role in the higher risks observed in these groups.
Figure 1. Risk of melanoma diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 2006-2020
The hazard ratio is an estimate of the average time to diagnosis among workers in each industry/occupation group divided by that in all others during the study period. Hazard ratios above 1.00 indicate a greater risk of disease in a given group compared to all others. Estimates are adjusted for birth year and sex. The width of the 95% Confidence Interval (CI) is based on the number of cases in each group (more cases narrows the interval).
Figure 2. Risk of melanoma diagnosis among workers employed in each occupation group relative to all others, Occupational Disease Surveillance System (ODSS), 2006-2020
