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Epidemiology and Pathophysiology of Work-related Asthma

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Epidemiology

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Work-related asthma is the most common occupational lung disease and is likely underrecognized in the clinical setting. A thorough occupational history is critical for identifying patients.

  • Approximately 17% of all adult-onset asthma cases are related to occupational exposures.
  • Median prevalence of work-exacerbated asthma among adults with asthma is 22%, but some studies have suggested up to 58%.
  • Patients with work-related asthma are more likely to experience asthma attacks, emergency room visits, and worsening of their asthma symptoms compared with other adult asthma patients.
  • Women and men with asthma are equally likely to have work-related asthma.
  • Workers who are black, American Indian/Alaska Native, of multiple races, or of Puerto Rican ethnicity have a higher prevalence of work-related asthma.

Pathophysiology

The signs and symptoms of work-related asthma are generally the same as those of non-work-related asthma. Work-related asthma is defined by worsening from exposure to workplace sensitizers, irritants, or physical conditions. Regardless of the asthma trigger type, the response is characterized by inflammation, edema, bronchoconstriction, and buildup of mucus in the airways. This leads to coughing, wheezing, chest tightness, and shortness of breath.

Sensitizers

Particularly for high-molecular weight triggers, the inflammatory process activates nitric oxide synthase in the epithelial cellspdf iconexternal icon, resulting in release of nitric oxide. Sensitizers are agents that initiate an allergic (immunologic) response. There is typically a latency period of at least a few months between first exposure and becoming sensitized. Sensitizers are divided into high-molecular weight and low-molecular weight agents:

  • High-molecular-weight agents: (e.g., cereals, coffee beans, enzymes, flour, grain dust, plant proteins, seafood, latex, wood dust) stimulate the production of specific immunoglobulin E (IgE) antibodies. During re-exposure, the agent cross-links specific antibodies on mast cells and activates them to release inflammatory mediators leading to asthma symptoms.
  • Low-molecular-weight agents: (e.g., acrylates, anhydrides, diisocyanates, dyes, formaldehyde, glutaraldehyde, metals, persulfates) are incomplete antigens, called haptens, that combine with a protein to produce a sensitizing agent.

Irritants

  • Induce a non-allergic response and include gases, fumes, vapors, and aerosols.
  • Non-allergen-induced asthma pathophysiology is less understood.

Physical Conditions

    • Exposure to cold air and physical exertion.
    • Cooling or warming of the airway is thought to lead to bronchoconstriction.