Work-related Asthma

Pathophysiology

The symptoms and signs of work-related asthma are generally the same as those of non-work-related asthma. Work-related asthma is defined by causation or worsening from exposure to occupational environmental 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, leading 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 cells, 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.