Work Related Asthma

Definition: Work-Related Asthma (WRA) is asthma worsened by or caused by inhalation exposures in the workplace.

WRA has 2 basic subgroups: (1) Occupational Asthma (OA) and (2) Work Exacerbated Asthma (WEA), previously called Work Aggravated Asthma.  OA, in turn, has 2 subgroups: (1) Immunologic (“allergic”) and (2) Non-immunologic (“irritant induced”).

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Simply put, OA is asthma caused by exposure to a specific workplace agent, and not to stimuli encountered outside the workplace; whereas WEA is increased asthma symptoms or need for asthma medication, triggered by various work-related factors in workers known to have pre-existing or concurrent asthma.

How common is OA? Though the actual rate of occurrence of occupational asthma is unknown, it is suspected to cause 2-20% of all cases of asthma in industrialized nations. Recent studies estimate the risk at 9%. It is the most common cause of non-acute occupational lung disease in the US.

What is Immunologic OA? After repeated exposures to certain substances or agents, workers may become sensitized, or highly reactive, and upon further exposure, even to very tiny amounts, develop a sudden asthmatic response. The time to become sensitized might be months or years.The exposures do not have to be large.

There are many substances that can cause OA. Thus far, over 250 potential causes have been identified. Some common agents include: wood dust, grain dust and cereals, animal dander, metals, latex, enzymes, gums, isocyanates, and dyes.

Many different workers or job types are at risk for OA, including: bakers, plastics workers, metal workers, millers, farmers, spray painters, wood workers, grain elevator workers, laboratory workers, detergent manufacturers, drug manufacturers and textile workers.

What are the symptoms of OA? The usual symptoms are the same as those for regular asthma- cough, chest tightness, shortness of breath and/or wheezing. The symptoms may get worse as the work week progresses and may get better or go away on weekends/holidays. In some cases, the asthma symptoms might not occur at work, but instead begin 6-10 hours later, making the association to work more difficult to recognize.

What is Non-immunologic OA? This is caused by an irritant, not an allergic, reaction. It does not have a latent period (extended time between exposure and disease) and requires a large and obvious exposure. This is best exemplified by Reactive Airways Dysfunction Syndrome (RADS).

In RADS, there is a single and specific exposure incident or accident, with exposure to an irritant gas, fume, smoke or vapor present in very high concentration. The asthma-like symptoms occur within 24 hours and persist for at least 3 months. There must be no previous lung problem and no other cause for the current problem.

Reported causes for RADS include: Sulfuric acid, Hydrochloric acid, Phosgene, Ammonia, Chlorine, Fire/Smoke, Sulfur Dioxide, and Bleaching Agents.

How do you diagnosis OA? Most importantly, call your health care provider if you have symptoms of asthma. Consider seeing a lung or occupational specialist. The doctor will need to take a comprehensive history, and thorough physical examination. asthma2Other tests include chest x-ray, pulmonary function (breathing) tests, complete blood count, and possibly other blood tests. You might be asked to measure and record your breathing at work and at home for several weeks or more using a peak flow meter, a simple device you blow into. The doctor might need additional tests, including immune testing or inhalation challenge tests.

How is OA treated? For Immunologic OA, the treatment generally starts with complete avoidance of further exposures. The doctor will usually begin inhaler medication, as commonly used for regular asthma. The response to treatment and prognosis depends upon many factors, including time until the diagnosis was recognized, severity of asthma, degree of lung function loss, and certain factors of the individual.

Where can I learn more?

US Dept of Labor/OSHA
American Lung Association
Tarlo SM, Balmes J, Balkissoon R, Beach J, Beckett W, Bernstein D, Blanc PD, Brooks SM, Cowl CT, Daroowalla F, Harber P, Lemiere C, Liss GM, Pacheco KA, Redlich CA, Rowe B, Heitzer J. Diagnosis and Management of Work-Related Asthma: American College of Chest Physicians Consensus Statement. Chest Sep 2008: 1-41S. DOI 10.1378/chest.08-020
CDC/NIOSH