Lung Cancer

Background

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
    • Dusts and fibres (e.g. asbestos, crystalline silica) [3]
    • Combustion products (e.g. diesel engine exhaust, secondhand smoke, soot) [4–6]
    • Metals and their compounds (e.g. arsenic, beryllium, cadmium, chromium VI, nickel, welding fumes) [5,7]
    • Ionizing radiation (e.g. radon, x-radiation, gamma-radiation) [8]
    • Occupational exposures in painting, iron and steel founding, coke production, rubber manufacturing, and aluminum production [9]
 
Possible occupational risk factors
    • Acid mist [9]
    • Benzene [10]
    • Bitumen [11]
    • Polycyclic aromatic hydrocarbons (PAHs) [12]
    • Wood dust [13]
Key Findings

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.

 
Mining

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.

    • Mines, quarries and oil wells: 1.40 times the risk
      • Quarries and sand pits: 1.71 times the risk
      • Metal mines: 1.39 times the risk
        • Uranium mines: 2.04 times the risk
        • Gold quartz mines: 1.46 times the risk
      • Non-metal mines: 1.33 times the risk
        • Asbestos mines: 4.93 times the risk
    • Mining and quarrying occupations: 1.43 times the risk
      • Rock and soil-drilling: 1.70 times the risk
      • Cutting, handling and loading occupations: 1.57 times the risk

 

 

Construction

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 [9].

    • Construction trades occupations: 1.08 times the risk
      • Excavating, grading, paving & related: 1.37 times the risk
      • Other construction trades: 1.09 times the risk
        • Painters and paperhangers: 1.39 times the risk
        • Insulators: 2.35 times the risk
        • Structural metal erectors: 1.37 times the risk
        • Glaziers: 1.28 times the risk
        • Roofing, waterproofing and related occupations: 1.25 times the risk
        • Plasterers and related occupations: 1.20 times the risk

 

Primary Metal Industries and Metal Manufacturing

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. Boiler makers may be exposed to asbestos and moulding, coremaking and metal casting may involve exposure to crystalline silica.

    • Primary Metal Industries: 1.14 times the risk
      • Iron foundries: 1.43 times the risk
      • Aluminum rolling, casting and extruding: 1.30 times the risk
      • Smelting and refining: 1.24 times the risk
    • Metal processing occupations: 1.25 times the risk
      • Metal heat treating occupations: 1.79 times the risk
      • Metal processing and related occupations (foremen): 1.56 times the risk
      • Moulding, coremaking and metal casting occupations: 1.46 times the risk
    • Metal shaping occupations: 1.17 times the risk
      • Forging occupations: 1.45 times the risk
      • Boilermakers, platers and structural metal workers: 1.42 times the risk
      • Metalworking-machine operators: 1.18 times the risk

 

Transportation sector

Workers employed in the transportation sector may be exposed to elevated levels of diesel engine exhaust through work in or around diesel-powered equipment.

    • Transportation industry: 1.22 times the risk
      • Taxicab operations: 1.61 times the risk
      • Truck transport: 1.50 times the risk
      • Railway transport operating occupations: 1.14 times the risk

 

Logging and Wood Processing

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.

    • Logging industry: 1.28 times the risk
      • Log hoisting, sorting, moving and related occupations: 1.50 times the risk
      • Timber cutting and related occupations: 1.21 times the risk
    • Wood manufacturing industries: 1.10 times the risk
      • Sawmills, planning mills and shingle mills: 1.30 times the risk
      • Labouring and other elemental work in wood processing: 1.28 times the risk

 

 

Bartending and Food Service

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 [2,14]. Differences in occupational rates of smoking may also contribute to the excess risks observed for these groups.

    • Bartenders: 1.71 times the risk
    • Waiters, hostesses and stewards, food and beverage: 1.10 times the risk
Relative Risk by Industry and Occupation

Figure 1. Risk of lung cancer diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 1983-2016

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), 1983-2016 

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).

Table of Results

Table 1. Surveillance of Lung Cancer: Number of cases, workers employed, and hazard ratios in each industry (SIC)

SIC Code * Industry Group Number of cases  Number of workers employed Hazard Ratio (95% CI) †
1 Agriculture 370 35,010 0.91 (0.82-1.01)
2/3 Forestry, Fishing and
Trapping		 249 10,696 1.25 (1.10-1.42)
4 Mines, Quarries and
Oil Wells		 780 23,173 1.40 (1.31-1.51)
5 Manufacturing 12,453 693,490 1.04 (1.02-1.07)
6 Construction 3,568 210,957 1.13 (1.09-1.17)
7 Transportation, Communication
and Other Utilities		 3,483 197,194 1.13 (1.09-1.17)
8 Trade 5,306 429,234 1.03 (1.00-1.06)
9 Finance, Insurance and
Real Estate		 466 23,989 1.05 (0.96-1.15)
10 Community, Business and
Personal Service		 7,160 599,548 0.91 (0.89-0.94)
11 Public Administration and
Defense		 3,259 190,864 0.99 (0.95-1.03)
         
         
* SIC: Standard Industrial Classification (1970)    
† Hazard rate in each group relative to all others    

 

Table 2. Surveillance of Lung Cancer: Number of cases, workers employed, and hazard ratios in each occupation (CCDO) group

CCDO Code * Occupation Group Number of cases  Number of workers employed Hazard Ratio (95% CI) †
11 Managerial, administrative
and related		 344 30,994 0.81 (0.73-0.90)
21 Natural sciences, engineering
and mathematics		 278 26,342 0.75 (0.67-0.84)
23 Social sciences and
related fields		 250 30,713 0.95 (0.84-1.08)
25 Religion 0 128 –
27 Teaching and related 328 48,476 0.51 (0.46-0.57)
31 Medicine and health 1,441 135,341 0.83 (0.79-0.88)
33 Artistic, literary,
recreational and related		 130 14,992 0.98 (0.83-1.17)
41 Clerical and related 2,777 197,315 1.04 (1.00-1.09)
51 Sales 1,499 148,113 0.97 (0.93-1.03)
61 Service 5,289 370,848 0.99 (0.96-1.02)
71 Farming, horticultural
and animal husbandry		 546 50,146 0.95 (0.87-1.03)
73 Fishing, hunting,
trapping and related		 11 558 1.03 (0.57-1.86)
75 Forestry and logging 215 10,680 1.15 (1.01-1.32)
77 Mining and quarrying,
including oil and gas field		 432 13,028 1.43 (1.30-1.58)
81 Processing
(mineral, metal, chemical)		 1,406 79,219 1.22 (1.15-1.28)
82 Processing
(food, wood, textile)		 1,404 99,236 0.99 (0.94-1.04)
83 Machining and related 3,569 189,401 1.12 (1.09-1.16)
85 Product fabricating,
assembling and repairing 		 5,714 328,270 1.02 (0.99-1.05)
87 Construction trades 3,980 215,564 1.08 (1.05-1.12)
91 Transport equipment
operating		 3,632 168,082 1.38 (1.33-1.42)
93 Materials handling and related,
not elsewhere classified		 2,488 153,025 1.16 (1.11-1.21)
95 Other crafts and
equipment operating		 556 28,299 1.10 (1.01-1.19)
99 Other occupations not elsewhere classified 3,364 215,227 1.12 (1.08-1.16)
         
         
* CCDO: Canadian Classification Dictionary of Occupations (1971)  
† Hazard rate in each group relative to all others    

Please note that ODSS results shown here may differ from those previously published or presented. This may occur due to changes in case definitions, methodological approaches, and the ongoing nature of the surveillance cohort.

 

References
  1. Canadian Cancer Statistics 2019. Canadian Cancer Society. Toronto, Ontario; 2019.
  2. Burden of Occupational Cancer in Canada: Major workplace carcinogens and prevention of exposure. Toronto, Ontario; 2019.
  3. International Agency for Research on Cancer (IARC). Arsenic, Metals, Fibres and Dusts: Nickel and Nickel Compounds. IARC Monogr Eval Carcinog Risks to Humans [Internet]. 2012;100C:169–218.
  4. IARC Working Group. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans- Personal habits and indoor combustions. Vol. 100E. Lyon, France: International Agency for Research on Cancer (IARC); 2012. 319–331 p. 
  5. IARC Working Group. A Review of Human Carcinogens- Arsenic, metals, fibres, and dusts. Vol. 100C. Lyon, France: International Agency for Research on Cancer (IARC); 2012. 407–443 p.
  6. IARC Working Group. Diesel and Gasoline Engine Exhausts and Some Nitroarenes . Vol. 105. Lyon, France: International Agency for Research on Cancer (IARC); 2014. 9–699 p.
  7. IARC Working Group. A Review of Human Carcinogens- Welding, molybdenum trioxide, and indium tin oxide. Vol. 118. Lyon, France: International Agency for Research on Cancer (IARC); 2018.
  8. IARC Working Group. A Review of Human Carcinogens- Radiation. Vol. 100D. Lyon, France: International Agency for Research on Cancer (IARC); 2012.
  9. IARC Working Group. A Review of Human Carcinogens- Chemical agents and related occupations. Vol. 100F. Lyon, France: International Agency for Research on Cancer (IARC); 2012.
  10. IARC Working Group. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans- Benzene. Vol. 120. Lyon, France: International Agency for Research on Cancer (IARC); 2018.
  11. IARC Working Group. IARC Monographs on the evaluation of carcinogenic risks to humans- Bitumens and Bitumen emissions, and some N-and S-Heterocyclic Polycyclic aromatic Hydrocarbons. Vol. 103. Lyon, France: International Agency for Research on Cancer (IARC); 2011.
  12. IARC Working Group. List of Classifications by cancer sites with sufficient or limited evidence in humans, Volumes 1 to 113. Lyon, France: International Agency for Research on Cancer (IARC).
  13. Alonso-Sardón M, Chamorro AJ, Hernández-García I, Iglesias-De-sena H, Martín-Rodero H, Herrera C, et al. Association between occupational exposure to wood dust and cancer: A systematic review and meta-analysis. PLoS One. 2015;10(7):1–16.
  14. Ferguson R. Ontario to ban smoking on restaurant patios, sports fields | The Star. The Star. 2014 Nov 7 [cited 2020 Aug 20].