HEALTH AT WORK

Industrial Health

Occupational Asthma: Causes, Symptoms and Prevention at Work

Health at Work · Health at Work

Occupational asthma is one of the most common work-related lung diseases in the world, yet it remains widely underdiagnosed and underreported. Unlike asthma triggered by general environmental factors, occupational asthma is directly caused or made significantly worse by substances encountered in the workplace. For many workers, a diagnosis comes only after years of repeated exposure — by which point permanent lung damage may already have occurred. Employers and occupational health professionals have a critical responsibility to act early, before breathing becomes a lifelong struggle.

What Causes Occupational Asthma and Who Is Most at Risk?

Occupational asthma is triggered by inhaling workplace substances known as respiratory sensitisers or irritants. Sensitisers — such as isocyanates in spray paints, flour dust in bakeries, latex proteins in healthcare, and wood dust in carpentry — cause the immune system to overreact, producing airway inflammation even at very low subsequent exposures. Irritant-induced asthma, sometimes called Reactive Airways Dysfunction Syndrome (RADS), results from a single high-level exposure to a corrosive gas, fume or vapour. Industries with the highest risk include baking and food processing, automotive painting, healthcare, woodworking, hairdressing, cleaning, agriculture and chemical manufacturing. Workers who smoke are at considerably higher risk of developing sensitisation and experiencing more severe symptoms.

Recognising the Symptoms: What Workers and Managers Should Watch For

The hallmark of occupational asthma is that symptoms typically improve on days off or during holidays and worsen on return to work. Key warning signs include persistent coughing — especially at night or in the early morning — wheezing, chest tightness and shortness of breath. Workers may initially attribute these symptoms to a common cold or seasonal allergy, delaying proper diagnosis. Any employee who reports recurrent respiratory symptoms that follow a clear work-related pattern must be referred promptly for medical assessment, including lung function testing and, where appropriate, specific inhalation challenge tests. Early diagnosis is essential: continued exposure after sensitisation dramatically increases the risk of permanent airway damage and disability.

Effective Prevention Strategies for Employers

Prevention of occupational asthma follows the well-established hierarchy of controls. Elimination or substitution of the causative substance is always the most effective approach — for example, replacing isocyanate-based paints with water-borne alternatives where technically feasible. Where substitution is not possible, engineering controls such as local exhaust ventilation (LEV) should be installed and regularly maintained to capture airborne substances at their source before workers can inhale them. Enclosing processes and limiting the number of workers exposed also reduces collective risk. Administrative controls — including job rotation, clear exposure limits and health surveillance programmes — form the next layer of protection. Where residual risk remains, appropriate respiratory protective equipment (RPE) must be provided, properly fitted and used consistently. Critically, RPE should never be the sole or primary control measure.

Health Surveillance and Supporting Affected Workers

Employers with workers exposed to known respiratory sensitisers are legally and ethically obliged to implement structured health surveillance. This involves regular questionnaire screening, lung function (spirometry) testing and review by an occupational health professional. When a case of occupational asthma is confirmed, the worker must be removed from further exposure to the causative agent, as ongoing exposure will worsen their condition regardless of the PPE used. Redeployment to a role with no exposure to the trigger substance is essential. Psychological support should also be offered, as a change in job role can be distressing, particularly for skilled tradespeople. A well-structured return-to-work plan, developed collaboratively between the employer, worker and occupational health team, helps ensure the best possible outcome for everyone involved.