Laryngeal Cancer

Background

Laryngeal cancer is a relatively rare cancer, and the Canadian Cancer Society estimates there will be 1150 new cases in 2020 [1]. It is more common in men than in women. Smoking and drinking alcohol are the most important non-occupational risk factors for laryngeal cancer.

 

Known occupational risk factors
    • Asbestos [2]
    • Strong inorganic acid mists (e.g. sulfuric acid) [2]
Possible occupational risk factors
    • Second-hand smoking [2]
    • Rubber production industry [2]
    • Sulfur mustard (mustard gas) [2]
    • Polycyclic aromatic hydrocarbons (PAHs) [3]
    • Engine exhaust [3]
    • Textile dust [3]
Key Findings

The greatest risks of laryngeal cancer were observed for construction trades occupations including among excavators, graders, and pavers, and glaziers. Construction trades workers may be exposed to asbestos, but non-occupational risk factors may also contribute to their risk of laryngeal cancer. Metal processing occupations and mining industries also had relatively high risks.

 

Construction

Workers in the construction industry overall, as well as some specific trades, have an increased risk of laryngeal cancer. Construction workers may be exposed to many different known and suspected carcinogens including asbestos, which is a known risk factor for laryngeal cancer, and engine exhaust. Occupational differences in use of cigarettes and alcohol may contribute to the increased risk of laryngeal cancer among construction workers. Construction workers may also be exposed to second-hand smoke in the workplace, which is a possible risk factor for laryngeal cancer.

    • Excavating, grading, paving and related: 1.91 times the risk
    • Other construction trades occupations: 1.21 times the risk
      • Glaziers: 1.71 times the risk
      • Roofing, waterproofing and related occupations: 1.65 times the risk
      • Occupations in labouring and other elemental work, other construction trades: 1.42 times the risk
      • Structural metal erectors: 1.36 times the risk
    • Construction industry: 1.19 times the risk
 
Mining and metal processing

An excess risk of laryngeal cancer was observed among mining industry workers, but work-related risk factors for this group are unclear. Some miners may have exposure to asbestos, but too few cases were observed among asbestos miners to explore the association specifically. Workers in the metal mining industry may be exposed to engine exhaust, which is a possible risk factor for laryngeal cancer. Smoking and alcohol may be important non-occupational risk factors for this group. Workers in primary metal industries may be exposed to acid mists [4].

    • Metal processing and related occupations: 1.66 times the risk
    • Mining and quarrying, including oil and gas field occupations: 1.28 times the risk
    • Mines, quarries and oil wells: 1.43 times the risk
      • Metal mines: 1.28 times the risk
    • Primary metal industries: 1.26 times the risk
 
Other findings

Janitors and cleaners are exposed to dust and various chemical solvents, and possibly asbestos, which may increase the risk of laryngeal cancer. Many vehicles have asbestos-containing materials that can result in exposure when they are repaired.

 

    • Janitors and cleaners: 1.30 times the risk
    • Industrial, farm and construction machinery mechanics and repairers: 1.26 times the risk
Relative Risk by Industry and Occupation

Figure 1. Risk of laryngeal 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 laryngeal 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 Laryngeal 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 38 35,014 1.21
(0.88-1.66)
2/3 Forestry, Fishing and
Trapping		 28 10,699 1.55
(1.07-2.25)
4 Mines, Quarries and
Oil Wells		 71 23,200 1.43
(1.13-1.81)
5 Manufacturing 949 693,585 1.01
(0.93-1.09)
6 Construction 332 210,974 1.19
(1.06-1.34)
7 Transportation, Communication
and Other Utilities		 313 197,212 1.24
(1.10-1.39)
8 Trade 373 429,290 1.00
(0.90-1.12)
9 Finance, Insurance and
Real Estate		 43 23,988 1.46
(1.08-1.98)
10 Community, Business and
Personal Service		 368 599,658 0.92
(0.82-1.03)
11 Public Administration and
Defense		 240 190,897 1.01
(0.88-1.15)
         
* SIC: Standard Industrial Classification (1970)
† Hazard rate in each group relative to all others

 

Table 2. Surveillance of Laryngeal 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		 19 31,004 0.77
(0.49-1.21)
21 Natural sciences, engineering
and mathematics		 26 26,349 0.87
(0.59-1.29)
23 Social sciences and
related fields		 18 30,715 1.66
(1.04-2.64)
25 Religion 0 128 —
27 Teaching and related 12 48,491 0.47
(0.27-0.84)
31 Medicine and health 40 135,372 0.74
(0.54-1.02)
33 Artistic, literary,
recreational and related		 6 14,996 0.65
(0.29-1.44)
41 Clerical and related 137 197,348 0.88
(0.74-1.04)
51 Sales 67 148,140 0.78
(0.61-0.99)
61 Service 315 370,912 1.01
(0.90-1.14)
71 Farming, horticultural
and animal husbandry		 47 50,150 1.02
(0.76-1.36)
73 Fishing, hunting,
trapping and related		 <5 558 —
75 Forestry and logging 22 10,684 1.27
(0.84-1.94)
77 Mining and quarrying,
including oil and gas field		 35 13,036 1.28
(0.92-1.79)
81 Processing
(mineral, metal, chemical)		 126 79,239 1.36
(1.13-1.62)
82 Processing
(food, wood, textile)		 80 99,250 0.78
(0.62-0.97)
83 Machining and related 295 189,415 1.08
(0.96-1.23)
85 Product fabricating,
assembling and repairing		 458 328,320 1.04
(0.94-1.15)
87 Construction trades 377 215,593 1.16
(1.04-1.30)
91 Transport equipment
operating		 343 168,109 1.52
(1.35-1.70)
93 Materials handling and related,
not elsewhere classified		 205 153,057 1.23
(1.07-1.42)
95 Other crafts and
equipment operating		 46 28,305 1.19
(0.89-1.59)
99 Other occupations not elsewhere classified 255 215,261 1.04
(0.92-1.19)
         
* 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. Brenner DR, Weir HK, Demers AA, Ellison LF, Louzado C, Shaw A, Turner D, Woods RR, Smith LM. Projected estimates of cancer in Canada in 2020. Can Med Assoc J. 2020;192(9):E199–205.
  2. International Agency for Research on Cancer (IARC). List of Classifications by cancer sites with sufficient or limited evidence in humans, IARC Monographs Volumes 1-127 (2020).
  3. Paget-Bailly S, Cyr D, Luce D. Occupational exposures and cancer of the larynx—systematic review and meta-analysis. J Occup Environ Med. 2012;54(1):71–84.
  4. International Agency for Research on Cancer (IARC). Occupational exposures to mists and vapours from strong inorganic acids; and other industrial chemicals. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans Vol. 54 (1992).