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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.
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Below we describe important aspects of occupational asthma, including its epidemiology, causative agents, risk factors, pathogenetic mechanisms, clinical presentations, diagnosis, and management.
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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).
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Agents That Cause Occupational Asthma
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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.
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