Work-related asthma includes occupational asthma, and asthma that is exacerbated by work. Occupational asthma is asthma that is caused by or worsened by exposure in the workplace. Symptoms are caused by repeated exposures to specific triggers at work over months or years, which lead to disease pathology. International estimates indicate that 15% of adult-onset asthma may be due to hazardous occupational exposures (Hoy et al. 2017).
Occupational asthma tends to be more severe, have higher medication use, reduced asthma control, more rapid decline in lung function and greater socio-economic impact than non-work related asthma (Hoy et al. 2017).
Occupational asthma can be subdivided into sensitiser-induced and irritant-induced subtypes. Approximately 90% of cases are classified as sensitiser-induced occupational asthma. Sensitisers are agents that induce an immunological response after repeated exposures. A range of workplace exposures can act as sensitisers. Irritant-induced occupational asthma is non-immune, resulting from exposure of the airways to irritant substances.
Sensitisers can be subdivided into 2 types:
- High molecular weight – includes proteins, with the most common being wheat flour, animal antigens and wood dust. Typically stimulate allergic immune responses, with activation of Type-2 and eosinophilic airway inflammation. For more on pathophysiology click here
- Low molecular weight – includes chemicals, such as diisocyanates and wood dust. The immune response is less understood but can contribute to eosinophilic or neutrophilic airway inflammation.