In Canada, lung cancer is the leading cause of cancer mortality in men and women [1]. Lung cancer is primarily caused by smoking, and prevention efforts have largely focused on tobacco control. However, the Burden of Occupational Cancer Project found that approximately 15% of lung cancers are caused by workplace exposures [2]. Workers in many occupations are exposed to known lung carcinogens. Asbestos, crystalline silica, diesel engine exhaust, and welding fumes are the four most important lung occupational carcinogens in Canada [2].
Known occupational risk factors
Possible occupational risk factors
The greatest risks of lung cancer are observed among workers employed in mining, construction, and transportation occupations. Occupational variation in smoking may also explain some differences in observed lung cancer risk.
Workers in mining and quarrying are exposed to a number of lung carcinogens including crystalline silica, radon, asbestos, and diesel engine exhaust. Workers in most mine types and jobs appeared to have increased risk of lung cancer.
Construction workers are involved in a wide variety of jobs and work settings with potential exposure to a wide range of lung carcinogens including diesel engine exhaust, crystalline silica dust, and asbestos-containing materials including insulation. In addition, painters, who may be exposed to chemicals in paints, solvents and adhesives are at increased risk [8].
Workers in these industries are exposed to aluminum, arsenic, beryllium, cadmium, chromium, nickel compounds, silica dust, and PAHs. IARC has also classified iron and steel founding as having an increased risk of lung cancer. Boilermakers may be exposed to asbestos and moulding, coremaking and metal casting may involve exposure to crystalline silica.
Workers employed in the transportation sector may be exposed to elevated levels of diesel engine exhaust through work in or around diesel-powered equipment.
Workers in these occupations may be exposed to exhaust from diesel-powered equipment, as well as wood dusts, arsenic-containing insecticides, and other wood preservatives.
Workers in these occupations were exposed to high levels of second-hand tobacco smoke in the workplace until smoking was banned in bars and restaurants in Ontario in 2006 and patios in 2015 [2,12]. Differences in occupational rates of smoking may also contribute to the excess risks observed for these groups.
Historically, lung cancer rates have been higher in men than women. However, this gap has decreased over time as smoking rates have declined faster among men than women, contributing to a faster decline in lung cancer incidence rates among men than women [13-15]. Although occupational exposure is a significant contributor to lung cancer burden, little research has focused on gender or sex differences in occupational lung cancer [16,17]. Here we highlight elevated risks of lung cancer among female workers in select occupations.
Female workers in machining and related occupations showed a greater increase in lung cancer risk than male workers. While those employed in this area may include workers who shape various types of materials, those performing metal machining or related metal work may be exposed to dusts and fumes containing metals and their compounds [17,18]. Some examples of carcinogenic exposures among these workers include welding fumes, nickel compounds, cadmium, and chromium VI [3,6,8].
Although both male and female workers in construction trades occupations overall are at an increased risk of lung cancer compared to workers in other occupations, this is more pronounced among female workers in certain construction trades. Construction workers have the potential to be exposed to a variety of lung carcinogens such as silica, asbestos, and diesel engine exhaust [3,5].
Although an increased risk of lung cancer is well documented among mining workers, previous studies have often included only limited information on female mining workers [16]. Based on ODSS results, female workers in mining occupations face a disproportionately elevated risk of lung cancer. Workers in mining occupations are exposed to numerous lung carcinogens including crystalline silica, radon, asbestos, and diesel engine exhaust [3,5].
Female workers were at an increased risk for lung cancer in transportation-related occupations, where exposure to diesel engine exhaust is common [5].
Lung cancer risks were elevated in female service workers but reduced in male workers across many service jobs. Other studies have found mixed results for risk of lung cancer in these workers due to the diversity of tasks in the service industry [19]. Some service workers in restaurant settings may have been exposed to second-hand smoke, especially prior to bans on smoking in restaurants and patios [20]. Some research indicates that polycyclic aromatic hydrocarbons (PAHs, found in cooking fumes) may increase lung cancer risk [8,11]. There may also be other exposures unaccounted for in these workers.
There are several of factors that could cause female workers to experience different hazards or different levels of exposure than male workers. For example, gender roles may influence the specific tasks male and female workers perform within a given occupation, leading to differences in exposure [21-23]. Personal protective equipment is often not designed with female-specific fit in mind, and may not have the same effectiveness on female bodies as male bodies [16,24]. Female workers may also find it more physically demanding to use protective equipment [16]. Part-time workers, who are more likely to be women, may receive less training on how to properly use protective equipment [16]. Further research is also needed to understand how sex-related factors such as height, reach and strength might impact exposure and the effectiveness of control strategies other than personal protective equipment [16,22].
Biological factors, such as hormonal and metabolic differences between male and female workers, may impact the effect of occupational exposures. Based on some studies of sex differences in smoking-related lung cancer risk, it is possible that female workers may be more susceptible to the carcinogenic effects of some occupational exposures than male workers [25,26].
Cancer risk may also be affected by behavioural differences. Smoking is more common among workers in manual and industrial occupations compared to other workers and this difference may be greater among females than males [27,28]. It is possible that other behavioural differences such as physical activity and dietary patterns may also contribute to observed sex differences in lung cancer risk.
Figure 1. Risk of lung cancer diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 1983-2020
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 lung cancer diagnosis among workers employed in each occupation group relative to all others, Occupational Disease Surveillance System (ODSS), 1983-2020
