Occupational asthma is characterized by airway irritation, obstruction, and inflammation caused by exposure to certain substances in the workplace. The exposure triggers symptoms from your immune system or through direct irritation of the airways. With the later, symptoms begin immediately following exposure. When occupational exposure stimulates your immune system, symptoms usually develop after multiple exposures to a particular substance.
What Occupations Are at Greater Risk?
A number of occupations are at risk for occupational asthma. A few examples of the occupations and the potential irritants include:
- Dental hygienists: latex
- Bakers: flour
- Roofers, insulators and painters: isocyanates (toluene)
- Welders and metal workers: metals: metals (nickel, platinum and chromic acid)
- Plastic manufacturers: glues and resins
- Farmers and veterinarians: animal proteins
- Carpenters: wood dust
Are All Workers in these Occupations at Greater Risk?
Most people working in these fields will not develop asthma. However, risk is increased in patients who are atopic, smokers and are genetically predisposed or have a family history of asthma.
Atopy: If you are atopic, participation in any of the above occupations increases your risk of developing occupational asthma or making pre-existing asthma worse. If you are atopic, it is important to have regular medical followup.
Smoking: Smoking increases risk of developing sensitization to certain occupational exposures.
Genetics: Certain genetic markers may increase or decrease risk of occupational asthma.
What Are the Steps in the Development of Occupational Asthma?
In general, occupational asthma develops in the following steps:
- Workplace exposure to substances that may directly irritate your lungs or lead to an immune response
- Develop sensitization to the exposure
- Resulting inflammation of upper and lower airways
- Development of symptoms
- Exposure continues or stopped
- Persistence of symptoms or clinical improvement
How is Occupational Asthma Diagnosed?
Taking a thorough history is important in adult onset asthma. In every new onset adult asthmatic, occupational asthma should be considered. Your physician should ask about your current job exposures in addition to exposures in previous jobs. Development of cough, wheezing, and shortness of breath within months of starting a new job is suggestive of occupational asthma. Worsening symptoms after arriving at work and improvement on weekends or during extended periods away from work are also suggestive of occupational asthma.
Your physician will also want to confirm that you have asthma. With the appropriate history, asthma can be confirmed by documenting improvement in airflow obstruction after receiving a bronchodilator like albuterol or the development of hyperresponsiveness following bronchoprovocation testing.
After demonstrating the presence of asthma, the next step is to establishing the relationship to your work environment. This can be done in a number of ways:
- Peak Expiratory Flow Rate (PEFR): Repeated PEFRs are the most common method to determine if a particular antigen is the cause of occupational asthma. You will be asked to measure your PEFR several times per day at work and then do the same after a period of time away from work.
- Airway Inflammation: Eosinophils, a marker of airway inflammation, can be assessed in the sputum after working and after a period of time away from work.
- Spirometry: Similar to PEFR, but done by a technician using a spirometer both in and out of the workplace.
- Bronchoprovocation testing: In some cases, doctors may want to have you inhale the potential offending substance to see if you develop symptoms or hyperresponsiveness.
- Skin testing: Doctors can test to see if you are already sensitized to a certain substance with skin prick testing. While a positive test does not confirm occupational asthma, atopy is a risk factor for occupational asthma. Other allergy tests can test for the presence of specific antibodies, what your body produces when exposed to a foreign substance, to specific potential offending agents.
How is Occupational Asthma Treated?
The primary management of occupational asthma is removing the worker from further exposure after a diagnosis is made. This is especially important when the worker is sensitized to a particular substance because repeated exposures may trigger serious asthmatic reactions.
In some conditions, workers may continue with appropriate engineering controls (such as improved ventilation) to reduce or eliminate the substance, or by having the worker religiously use respiratory protective equipment. Medication treatment follows the established guidelines for asthma treatment and generally involves an inhaled steroid like Flovent or Pulmicort.
Sources:
Bernstein, IL, Bernstein DI, Chan-Yeung, M, Malo, JL. Definition and classification of asthma. In: Asthma in the workplace, 3rd ed. Bernstein, IL, Chan-Yeung, M, Malo, JL, Berstein, DI, (Eds), Francis & Taylor, New York 2006.
Dykewicz, MS. Occupational asthma: Current concepts in pathogenesis, diagnosis, and management . Journal of Allergy and Clinical Immunology. Volume 123, Issue 3, March 2009, Pages 519-528
Balmes, JR. Occupational Asthma. In Murray & Nadel's Textbook of Respiratory Medicine, 4th ed. 2005 Saunders.
