Occupational Asthma

Author: V. Dimov, M.D., Allergist/Immunologist, Assistant Professor at University of Chicago
Reviewer: S. Randhawa, M.D., Allergist/Immunologist, Assistant Professor at NSU

The workplace is a significant contributor to the burden of asthma. The majority of asthma cases probably represent what is labeled "work-exacerbated asthma". However, in a significant number of subjects, asthma is actually caused by one or more agents present in the workplace; this is occupational asthma.

Occupational Asthma (click to enlarge the image).

Occupational asthma (OA)may account for 25% or more of "de novo" adult asthma.

Two types of occupational asthma are distinguished:

1. Immunologic occupational asthma with a latency period due to high-molecular-weight agents (protein from animals, plants and food) and low-molecular-weight agents (hapten - platinum, penicillin, epoxy resin). Immunologic OA constitutes 85% of cases of OA

2. Non-immunologic occupational asthma without a latency period.

OA is caused by:

1. Immunologic OA - sensitizing agents

- high-molecular-weight agent such as a protein from biological sources
- low-molecular-weight reactive chemical such as isocyanate

Animal lab workers usually need 2 two years to develop sensitization. In contrast, flour workers need a significantly longer period for sensitization.

Allergic rhinitis usually precedes OA for HMW agents but not for LMW agents (haptens).

2. Non-immunologic OA - irritants, for example, the reactive airways dysfunction syndrome (RADS)

When evaluating patients for occupational asthma, sputum eosinophil counts at 7 and 24 hours after specific inhalation challenge have a greater sensitivity and positive predictive value than exhaled nitric oxide (eNO).

Reactive Airway Disease Syndrome (RADS)

RADS is non-allergic and non-immunologic OA. RADS occurs with a single, high dose exposure and has the following features:

- no latency
- onset within 24 hours
- persists for longer than 3 months

The major causes of RADS are soluble gases and fumes which are corrosive. An example of RADS is the World Trade Center-associated cough.

Agents implicated in RADS

Toluene diisocyanate
Sulfuric acid
Chlorine dioxide
Hydrochloric acid
Phosphoric acid
Hydrogen sulfate
Anhydrous ammonia
Sulfur dioxide

Timely removal from exposure leads to the best prognosis in OA.

Work-related asthma (WRA) has 3 phenotypes:

1. sensitizer-induced occupational asthma (OA) caused by high-molecular-weight (HMW) proteins or low-molecular-weight (LMW) chemicals

2. irritant-induced asthma

3. work-exacerbated asthma

Agents associated with occupational asthma (click to enlarge the image).

Agents associated with occupational asthma

Western Red Cedar mill
Plicatic acid

Body shop and spray paint
Paints, adhesives, and plastics
Acid anhydride
Electronic soldering
Colophony, abietic acid and pimaric acid
Catalytic converters
Platinum salts

Ammonium persulfate

Printers, hairdressers
Gum acacia
Adhesives and epoxy resin
Phthalic anhydride
Trimellitic anhydride
Bathtub paint, varnish, and lacquer

Forest workers and carpenters
Wood dusts
Shellac and lacquer


Hospital workers

Related reading: One desk chair - hold the formaldehyde. If building materials had nutrition labels, you'd be scared of toxic ingredients, Google blog.

Drug industry workers
Textile industry workers
Azo dyes

In a French study, physicians were asked to report newly diagnosed cases of work-related asthma and reactive airway dysfunction syndrome (RADS). 82.3% of 559 cases reported (64% males, mean age 36 yrs) involved occupational asthma, 4.7% RADS and 12.7% atypical asthma syndromes.

The most frequently suspected agents were flour (23.3%), followed by isocyanates (16.6%), latex (7.5%), aldehydes (5.5%), and persulphates (4.1%). Occupations at risk were bakers (23.9%), healthcare workers (12%), painters (9.1%), hairdressers (5.2%), wood industry workers (4.8%) and cleaners (3.5%).

Work-related Asthma - AAAAI COLA video lecture by David Bernstein, MD, 07/2012:


Occupational asthma: Current concepts in pathogenesis, diagnosis, and management. Mark S. Dykewicz. JACI, Volume 123, Issue 3, Pages 519-528 (March 2009)
Agents causing occupational asthma. Jean-Luc Malo et al. JACI, Volume 123, Issue 3, Pages 545-550 (March 2009)

Occupational asthma in France: a 1-yr report of the Observatoire National de Asthmes Professionnels project. Eur Respir J 2002; 19:84-89.

Hairdressers Working in Hair Salons for Women are at increased risk for occupational asthma - prevalence is 9.5% http://goo.gl/fKPDq
Occupational sensitization to soy allergens in workers at a processing facility, high molecular weight allergens Gly m 5 and Gly m 6 may be the respiratory sensitizers http://goo.gl/6oXYd

Workforce occupational asthma in New Zealand. The highest risks: printer/baker/sawmill labourer/metal processing. Ann Occup Hyg. 2010.
The new guidelines for management of work-related asthma - ERJ 2012.

Work-exacerbated asthma and occupational asthma: Do they really differ? http://buff.ly/PLajpw

Published: 05/09/2010
Updated: 10/09/2012

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