Work-related Asthma

Background

• Work-related asthma is defined as asthma that is exacerbated or induced by workplace inhalation exposures.
• Types of work-related asthma include occupational asthma (asthma induced by work), which includes
  • Sensitizer-induced asthma which is defined as asthma due to sensitization with immunologic response, typically with latency period following exposure to causal agent
  • Non-sensitizer-induced asthma (irritant-induced asthma) includes reactive airways dysfunction syndrome (RADS) and is defined as new-onset asthma within 24 hours of a single, high-level exposure, as well as asthma that develops after repeated exposures to lower levels of irritants.
  • Work-exacerbated asthma is defined as worsening of preexisting asthma due to occupational causes or conditions.
• Among persons with adult-onset asthma, 5%-25% of cases are reported to be work-related.
• Risk factors for work-related asthma include atopy, smoking, female sex, eosinophilic bronchitis, work-related rhinitis, and preexisting asymptomatic airways hyperresponsiveness (AHR).
• Occupational asthma causes include high molecular weight (> 10 kilodalton [kDa]) proteins and low molecular weight (< 2 kDa) chemicals.

Evaluation

• Work-related asthma typically presents with cough, shortness of breath, wheezing, and chest tightness.
• Obtain thorough history, including symptom onset, periods of improvement, previous atopic symptoms, and thorough occupational history.
  • Ask about temporal onset of asthma and atopic symptoms and relationship to work, including new employment or changes at work.
  • Confirm latency of symptom onset after exposure.
    • Sensitizer-induced asthma has a wide variable latency period of several weeks to many years of ongoing exposure before the start of symptoms (depending on type and level of exposure).
    • Irritant-induced asthma typically has no latency period, but may take days to months to manifest.
    • Symptom onset ≤ 24 hours following single high-level exposure may indicate reactive airways dysfunction syndrome.
  • Ask about improvement in symptoms while away from work or during holidays, and/or worsening of respiratory symptoms after return to work.
  • Ask about enhanced sensitivity or response to odors or irritants.
  • If patient has clinical features of occupational rhinitis or rhinoconjunctivitis, monitor for development of signs and symptoms of occupational asthma.
  • Obtain occupational history, including job duties, exposures, industry, and use of protective devices or equipment, and obtain material data safety sheets for any known hazardous materials.
• Work-related asthma should be investigated in patients who develop new or worsening asthma symptoms at work or shortly after leaving work.
  • Asthma should be confirmed using objective measures including spirometry alone or with bronchodilator to detect reversible airflow obstruction.
  • Temporal link between symptoms and workplace is typically obtained by detailed occupational history.
• Other testing that can help confirm diagnosis if unclear based on combination of signs, symptoms, and occupational history includes peak expiratory flow rate monitoring at and away from work and specific IgE antibody or skin prick test.
• Consider referral to a specialist in occupational lung diseases if diagnosis remains uncertain.

Management

• Removal from or reduction of exposure is the primary approach for improvement or resolution of the disease.
• Avoid use of powdered natural rubber latex gloves and minimize skin exposure to asthma-inducing agents.
• Anti-asthma medications should not be considered acceptable alternatives to environmental intervention (Strong recommendation), but consider when complete exposure avoidance is not possible or symptoms are mild enough to be controlled by therapy in combination with exposure reduction.
• When used as adjunct therapy, adjust pharmacologic treatment of work-related asthma to level of asthma control (Strong recommendation) as indicated by general asthma recommendations and follow published clinical guidelines for pharmacologic management of adults with asthma.
• Benefits of immunotherapy are limited by lack of standardization for occupational allergens and potential adverse reactions.
• Nonpharmacologic management, such as respiratory protective equipment, can reduce or mitigate exposures but does not offer complete protection and can be considered as an interim measure while workplace implementation of measures to control of exposures are employed.