Idiopathic Pulmonary Fibrosis (IPF)

Background

What is idiopathic pulmonary fibrosis (IPF)?

Idiopathic Pulmonary Fibrosis (IPF) is a respiratory disease involving scarring of the lungs resulting in reduced lung capacity. The term idiopathic is used to describe conditions of an unknown cause, but family history and smoking are both thought to be risk factors for IPF. This disease is the most common fibrotic lung disease and is similar to silicosis and asbestosis. IPF has poor five-year survival and treatment options are limited.

Possible occupational risk factors
    • Metal dust
    • Wood dust
    • Animal dust from livestock farming

Because there is not yet a comprehensive understanding of the causes of IPF, the ODSS project sought to understand what occupations and industries were at an increased risk of this disease as an important step toward prevention. Metal and wood dusts are important possible occupational risk factors for IPF.

Key Findings

The greatest risks of IPF were observed among workers employed in the mining, forestry and papermaking, transportation, and food and beverage sectors.

Mining

The mining industry overall is at 2 times the risk of IPF. Groups within this industry with elevated risks include the gold quartz and uranium mining sectors, as well as drilling and blasting occupations and cutting and loading occupations. These occupations and industries would likely have significant dust exposure, including metals, silica, and diesel engine exhaust.

    • Gold quartz mines: 3 times the risk
    • Uranium mines: 3 times the risk
    • Drilling and blasting occupations: 2 times the risk
Forestry

Workers within the logging and pulp and papermaking industries are at increased risks of IPF. These workers are likely exposed to high levels of wood dust, which is a possible risk factor for IPF.

    • Logging: 1.5 times the risk
    • Occupations in elemental work, pulp and papermaking: 3 times the risk
Transportation

While the overall transportation sector did not show an increased risk of IPF, an increased risk was seen for bus drivers. Bus drivers are regularly exposed to exhaust fumes, however, this is not a recognized risk factor for this disease. This finding was unexpected and could be related to non-occupational exposures.

    • Bus drivers: 1.5 times the risk
Food and Beverage

Cooks and chefs were at an increased risk of IPF and could be exposed to organic dusts and cooking fumes. Organic dusts such as flour and confectionary materials are known risk factors for other respiratory conditions, but it is not known whether they pose a risk for IPF.

    • Chefs and cooks: 1.5 times the risk
Relative Risk by Industry and Occupation

Figure 1. Risk of idiopathic pulmonary fibrosis diagnosis among workers employed in each industry group relative to all others, Occupational Disease Surveillance System (ODSS), 2006-2016

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 idiopathic pulmonary fibrosis diagnosis among workers employed in each occupation group relative to all others, Occupational Disease Surveillance System (ODSS), 2006-2016 

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 Interstitial Pulmonary Fibrosis: 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 27 26,863 0.89 (0.61, 1.30)
2/3 Forestry, Fishing and Trapping 22 7,367 1.59 (1.05, 2.43)
4 Mines, Quarries and Oil Wells 76 16,712 1.91 (1.52, 2.4)
5 Manufacturing 986 539,988 1.03 (0.95, 1.11)
6 Construction 270 168,536 1.05 (0.92, 1.19)
7 Transportation, Communication and Other Utilities 268 158,987 1.03 (0.91, 1.17)
8 Trade 404 346,116 0.92 (0.83, 1.03)
9 Finance, Insurance and Real Estate 35 18,349 1.06 (0.76, 1.48)
10 Community, Business and Personal Service 572 467,639 0.92 (0.83, 1.01)
11 Public Administration and Defense 286 151,044 1.09 (0.96, 1.23)
         
* SIC: Standard Industrial Classification (1970)    
† Hazard ratio in each group relative to all others    

 

Table 2. Surveillance of Interstitial Pulmonary Fibrosis: 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 30 26,042 0.76 (0.53, 1.08)
21 Natural sciences, engineering and mathematics 26 22,086 0.77 (0.53, 1.14)
23 Social sciences and related fields 30 24,474 1.28 (0.89, 1.84)
25 Religion 0 105
27 Teaching and related 46 40,862 0.74 (0.55, 0.99)
31 Medicine and health 146 105,955 1.03 (0.86, 1.22)
33 Artistic, literary, recreational and related 11 12,410 0.94 (0.52, 1.71)
41 Clerical and related 210 156,416 0.94 (0.81, 1.08)
51 Sales 134 120,077 1.02 (0.86, 1.22)
61 Service 420 286,423 1.02 (0.92, 1.14)
71 Farming, horticultural and animal husbandry 38 39,527 0.87 (0.63, 1.19)
73 Fishing, hunting, trapping and related <5 443
75 Forestry and logging 15 7,263 1.20 (0.72, 2.00)
77 Mining and quarrying, including oil and gas field 44 9,268 2.07 (1.53, 2.78)
81 Processing (mineral, metal, chemical) 125 64,553 1.27 (1.06, 1.52)
82 Processing (food, wood, textile) 121 78,550 1.06 (0.88, 1.27)
83 Machining and related 295 154,998 1.07 (0.95, 1.21)
85 Product fabricating, assembling and repairing 437 265,589 0.89 (0.80, 0.98)
87 Construction trades 313 173,264 1.04 (0.92, 1.17)
91 Transport equipment operating 252 137,515 1.04 (0.92, 1.19)
93 Materials handling and related, not elsewhere classified 211 123,252 1.20 (1.04, 1.38)
95 Other crafts and equipment operating 52 22,246 1.24 (0.94, 1.63)
99 Other occupations not elsewhere classified 264 173,286 1.09 (0.96, 1.24)
         
* 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.