Two Types of
Immunologic asthma develops after a variable period of time during
which "sensitization" to an agent present in the workplace takes place. Irritant-induced
asthma occurs without a latency period after an intense exposure to an irritating
dust, mist, vapor, or fume. The pathophysiologic mechanism underlying irritant-induced
asthma is not well understood, and it is not known why the asthmatic response persists in
Two Types of Immunologic OA
The Haz-Map database focuses on immunologic asthma and the predictable and preventable
occupational settings in which exposures occur. Immunologic asthma can be classified into
that caused by high-molecular or low-molecular weight compounds. The high-molecular-weight
compounds are animal and plant derived proteins or polysaccharides such as wheat
flour and animal dander that cause an Ig-E-dependent immune response. The low-molecular-weight
compounds are chemicals that can also initiate an immune response after repeated
inhalation. The nature of the immune response is more complex for the low-molecular-weight
chemicals than it is for the high-molecular-weight agents. "An IgE- or
mechanism has not been consistently seen with low-molecular-weight agents (isocyanates,
for example). These agents can cause sensitization through a hapten-mediated effect. The
role of lymphocytes or other immunologic mechanisms remain unclear."2
The Haz-Map database contains over 180 biological agents and chemicals that can cause
immunologic OA based on a previously published table. (Chan-Yeung & Malo
and Appendix B in Harber) In the two tables
that follow, the high-molecular-weight compounds and wood dusts are listed as
"Biological Agents," while the low-molecular-weight compounds are listed in the
"Chemicals" table. Wood dusts are biological agents or products, but
sensitization may occur through a low-molecular-weight chemical, as has been proven for
the case of Western red cedar.
Incidence and Prevalence of OA
In a study done in the West Midlands Region of the United
Kingdom, the average annual incidence of occupational asthma was found to be 43 cases per
million workers, with a range of 1833 per million for spray painters to eight per million
The prevalence of occupational asthma in adults with asthma is
estimated to be between 3% and 20%.
Prevention of Occupational Asthma
The diagnosis of occupational asthma is a sentinel event--an alert that engineering
controls or protective equipment could prevent asthma from developing in workers in the
same workplace or industry.
- Balmes JR. Occupational Lung Diseases. p.
315 in LaDou
- Malo JL, Cartier A. Occupational Asthma, p. 424 in Harber
- Gannon PF, Burge PS. The SHIELD scheme in the West Midlands Region, United
Kingdom. Br J Ind Med 1993 Sep;50(9):791-6. Read Shield
reports at the website of the Oasys research group.
- PubMed Abstracts
- See Table 2 from page 6 in Asthma
in the Workplace.
and management of work-related asthma: American College Of Chest
Physicians Consensus Statement