State of the Art in Occupational Asthma

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In a "State of the Art" article on occupational asthma, researchers report that the illness has become one of the most common forms of occupational lung disease in industrialized countries, constituting 9 to 15 percent of all adult asthma.

Writing in the first issue for August 2005 of the American Thoracic Society's peer-reviewed American Journal of Respiratory and Critical Care Medicine, Cristina E. Mapp, M.D., of the Section on Hygiene and Occupational Medicine at the University of Ferrara in Ferrara, Italy, along with three associates, noted that the most cost-effective way to lower the rate of this type of asthma is to reduce the employee's exposure to the offending agent as early as possible to prevent sensitization.

(Sensitization occurs when repeated exposure to a noxious substance in the workplace causes the person's airway to become inflamed and narrow.)

"Briefly, occupational asthma is a disease characterized by variable airflow limitation and/or airway hyperresponsiveness due to causes and conditions attributable to a particular occupational environment and not to stimuli encountered outside the workplace," Dr. Mapp writes.

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She noted that work-aggravated asthma varies from occupational asthma because the outcome, medical management and preventive measures "differ substantially." In addition, work-aggravated asthma involves pre-existing or concurrent asthma that is exacerbated by workplace exposure.

The job fields in which workers had the greatest risk of occupational asthma were: construction; metal, rubber, and plastic work; printing; and industrial cleaning.

According to the article, the most common form of occupational asthma, which accounts for 90 percent of the cases, is immunologic in nature, induced by the immunoglobulin E (IgE) mechanism or other immune responses to particular workplace agents. Such sources include dust from woods; epoxy compounds in spray paint; animal, plant, insect and fungal allergens; cleaning agents; flour dust; and food and animal protein.

(IgE is one of five classes of antibodies produced by lymph tissue in response to the invasion of foreign substances. It is present primarily in skin and mucus membranes, and plays a role in allergic reactions.)

The less common type of occupational asthma, irritant-induced asthma, accounts for about 7 percent of all cases. Industries in which workers are exposed to irritant-induced asthma include metal refining, fertilizer manufacturing (with ammonia) and mining.

In a large population-based study in Finland (1997-2000), men had the strongest risk for occupational asthma in metal work and in forestry.

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