Asthma is a serious lung disease that affects about 10 million Americans. Symptoms include reversible wheezing, cough, tightness of the chest, and lung spasms. This condition is reversible when treated with bronchodilators. Unless carefully controlled by medication, severe asthma attacks can potentially be fatal.
In certain individuals, the immune system reacts and develops antibodies to a foreign substance. In some instances, the foreign substance alters body proteins to which the immune system then reacts. Once this sensitization occurs (after weeks or even years), subsequent exposures to this sensitizer (or allergen) can result in the development of asthmatic symptoms. Common sensitizers include mold spores, pollen, animal dander, and dust mites. Asthmatics can also react to cold air, exercise, cigarette smoke, breathing restrictions (e.g. wearing a respirator), dust, and other nonspecific mild irritants. Asthma is diagnosed by observing an individual’s reaction to methacholine, a chemical that does not cause asthma.
In recent years, asthma has also begun to be recognized as a serious occupational disease. Classic occupational asthma involves exposure to a sensitizing agent for a period ranging from weeks to years before the development of asthma symptoms. Once sensitization occurs, exposure to even trace amounts can result in an asthma attack, usually within minutes of exposure. The susceptibility to asthma attacks can persist for years and even decades. The only solution to asthma caused by a specific sensitizer is complete removal from exposure, which can demand a possible change of career.
A second type of occupational asthma involves the development of asthma symptoms due to high exposure to irritants. Affected individuals have the classic asthma symptoms, including methacholine reactivity and reversibility with bronchodilators, but do not develop the antibodies found in normal allergic reactions. This type of irritant-induced occupational asthma has also been called hyperreactive airways disease. Like classic asthma, it differs from bronchitis-type irritant reactions since it results from exposure to very low concentrations after the initial exposure(s), and responds to bronchodilators.
Common occupational sensitizers in the arts include nickel, epoxy resins, fiber-reactive dyes, formaldehyde, chromates and dichromates, platinum and gold salts, Western red cedar and many tropical woods, plexiglas dust, rosin and rosin-soldering fumes, and isocyanates (particularly TDI and MDI). People with pre-existing asthma can find that the work environment can exacerbate their asthma, sometimes through higher exposures to materials the individual is already sensitized to (e.g. molds in pottery), or by exposure to non-specific dust and irritants (e.g. chalk dust or kiln gases in the classroom).
By contrast, bronchitis and other respiratory responses to irritants usually involve exposure to higher concentrations of chemicals. These types of reactions can usually be prevented by engineering controls such as ventilation to lower the exposure levels. Thus, it is crucial to properly diagnose whether a respiratory problem is asthma or irritation because the solutions can be very different. Diagnosis of asthma usually involves a careful history and reversibility of symptoms when treated with bronchodilators. Nonreactivity to methacholine usually eliminates asthma as a diagnosis.