Asthma

Background

What is Asthma?

Asthma is an inflammatory disease of the respiratory system. It is the most common chronic respiratory condition in Canada, affecting roughly 6% of the general population. Asthma is also the most common work-related respiratory condition with an estimated 15% of cases of adult asthma arising due to workplace exposures. There are numerous occupational risk factors for this condition and workers across many occupations and industries are at risk. 

 

Risk Factors
    • Isocyanates
    • Dusts (metal, wood, flour, animal, etc.)
    • Latex
    • Chemical irritants
    • Cleaning products
    • Metalworking fluids
    • Exhaust fumes
Key Findings

The greatest risks of asthma were observed among workers employed in the product fabricating, assembling, and repairing, food and beverage, and construction sectors.

Product Fabricating, Assembling, and Repairing

Painters and decorators showed an elevated risk of asthma. This group includes workers in the automobile industry who spray paint cars. Exposure to isocyanates is a well-established risk factor for asthma among automotive painters. In contrast, painters in construction showed a decreased risk of asthma. Construction painters typically work with water-based paints. This sector also includes cabinet and wood furniture makers, who showed increased risks of asthma. Exposure to wood dust, a well-established risk factor for asthma, is a common exposure for these workers.

    • Painters and decorators (not in construction): 1.6 times the risk
    • Painters and paperhangers (construction): 0.8 times the risk
    • Cabinet and wood furniture makers: 1.3 times the risk
Construction

Within the construction sector, concrete finishers showed an increased risk of asthma. These workers may be exposed to inorganic dusts, such as silica, which may act as respiratory irritants and induce asthma.

    • Concrete finishers and related workers: 1.9 times the risk
 
Food and Beverage

ODSS results indicate that bakers and confectionary makers are at an increased risk of asthma, likely due to exposure to flour dust.

    • Bakers and confectionary makers: 1.6 times the risk
Relative Risk by Industry and Occupation

Figure 1. Risk of asthma diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 1999-2016

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 asthma diagnosis among workers employed in each occupation group relative to all others, Occupational Disease Surveillance System (ODSS), 1999-2016 

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 Asthma: 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 91 7,334 0.74 (0.60, 0.91)
2/3 Forestry, Fishing and Trapping 12 1,295 0.62 (0.35, 1.09)
4 Mines, Quarries and Oil Wells 35 2,843 0.86 (0.62, 1.20)
5 Manufacturing 1,726 105,201 0.99 (0.94, 1.04)
6 Construction 596 46,501 0.87 (0.80, 0.95)
7 Transportation, Communication and Other Utilities 742 44,310 1.04 (0.96, 1.12)
8 Trade 1,770 101,827 0.97 (0.92, 1.02)
9 Finance, Insurance and Real Estate 87 4,976 0.95 (0.77, 1.18)
10 Community, Business and Personal Service 3,410 163,064 1.02 (0.98, 1.07)
11 Public Administration and Defense 792 43,588 0.97 (0.90, 1.04)
         
* SIC: Standard Industrial Classification (1970)    
† Hazard ratio in each group relative to all others    

 

 

Table 2. Surveillance of Asthma: 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 230 11,286 1.04 (0.91, 1.19)
21 Natural sciences, engineering and mathematics 109 7,012 0.95 (0.79, 1.15)
23 Social sciences and related fields 235 9,842 1.09 (0.96, 1.24)
25 Religion <5 37
27 Teaching and related 390 16,336 1.08 (0.97, 1.19)
31 Medicine and health 811 38,351 0.91 (0.84, 0.98)
33 Artistic, literary, recreational and related 115 4,921 1.27 (1.05, 1.52)
41 Clerical and related 962 44,187 1.13 (1.06, 1.21)
51 Sales 827 45,289 0.95 (0.88, 1.02)
61 Service 1,693 88,268 1.01 (0.96, 1.07)
71 Farming, horticultural and animal husbandry 145 11,255 0.79 (0.67, 0.93)
73 Fishing, hunting, trapping and related <5 100
75 Forestry and logging 6 1,103 0.37 (0.17, 0.83)
77 Mining and quarrying, including oil and gas field 22 1,755 0.91 (0.60, 1.39)
81 Processing (mineral, metal, chemical) 205 13,002 0.97 (0.85, 1.12)
82 Processing (food, wood, textile) 370 19,362 1.09 (0.99, 1.21)
83 Machining and related 410 28,820 0.97 (0.87, 1.07)
85 Product fabricating, assembling and repairing 817 52,735 1.00 (0.93, 1.07)
87 Construction trades 549 45,567 0.86 (0.79, 0.94)
91 Transport equipment operating 539 37,171 0.99 (0.91, 1.08)
93 Materials handling and related, not elsewhere classified 391 23,400 1.09 (0.98, 1.20)
95 Other crafts and equipment operating 52 3,403 0.96 (0.73, 1.26)
99 Other occupations not elsewhere classified 535 33,715 1.00 (0.91, 1.09)
         
* CCDO: Canadian Classification Dictionary of Occupations (1971)  
† Hazard ratio 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.