Workplace inhalational hazards such as dust, fumes, and organic substances can cause various nonmalignant respiratory diseases. These occupational exposures may cause airway diseases and parenchymal diseases. Occupation-related lung parenchymal diseases, such as hypersensitivity pneumonitis, obliterative bronchiolitis, and chronic beryllium disease are considered elsewhere. In this chapter, we discuss occupational asthma, byssinosis, and industrial bronchitis.
Below we describe important aspects of occupational asthma, including its epidemiology, causative agents, risk factors, pathogenetic mechanisms, clinical presentations, diagnosis, and management.
Work-related asthma is the most common occupational lung disease. There are two categories: (1) occupational, or work-related, asthma that is caused de novo by work, and (2) work-exacerbated asthma, which implies a work-related worsening in the setting of preexisting asthma.1 The prevalence of work-related asthma is difficult to determine. An international estimate attributes 15% to 20% of adult-onset asthma to workplace exposure.2 A recent systemic review indicated the overall occupational population attributable fraction was 16%, with wide 95% confidence intervals between 3.8 and 27.1%.3 The incidence of occupational asthma is 3% to 36% and varies among different industries, based on international studies in workers with different occupations4 (Table 88-1).
TABLE 88-1Incidence of Occupational Asthma in Main Occupations ||Download (.pdf) TABLE 88-1 Incidence of Occupational Asthma in Main Occupations
|Occupation/Exposed Antigen ||Number of Cases ||Incidence (%) ||Country |
|Snow crab processors ||303 ||15.6 ||Canada |
|Guar gum (natural polysaccharide) ||151 ||3.0 ||Canada |
|Painters (isocyanate) ||730 ||7.1 (all subjects were non-smokers) ||Italy |
|Poultry workers ||134 ||11.0 ||South Africa |
|Rat allergens ||113 ||4.4 ||France |
|Natural rubber latex (health care workers in general hospital) ||196 ||7.1 ||Italy |
|Florists ||128 ||14.1 ||USA |
|Supermarket bakery workers ||66 ||9.0 ||UK |
|Strawberry growing industry workers ||43 ||4.7 ||Japan |
|Oyster shucker (sea squirt) ||250–417 ||18.0–36.0 ||Japan |
Agents That Cause Occupational Asthma
Many agents cause occupational asthma. Two categories of agents can be classified based on molecular weight and differing mechanisms causing disease: high-molecular-weight (HMW) compounds (>5 to 10 kDa), and low-molecular-weight (LMW) compounds. A list of causative compounds and occupations at risk is provided in Table 88-2. The website www.occupationalasthma.com also provides up-to-date information on agents known to cause occupational asthma.
TABLE 88-2Causes of Occupational Asthma ||Download (.pdf) TABLE 88-2 Causes of Occupational Asthma
|Categories ||Occupations at Risk ||Major Putative Component |
|High-molecular-weight compounds |
|Animal products ||Animal handlers ||Pelt or urinary proteins |
| ||Veterinarians || |
|Seafoods ||Crab or prawn processors ||Water-extractable proteins |
| ||Oyster farmers || |
|Insects ||Entomologists ||Insect proteins |
| ||Grain workers || |
| ||Laboratory workers || |
| ||River workers || |
| ||Flight crews || |
|Plants ||Grain handlers ||Extractable plant ...|