What is the difference between Occupational Asthma and Asthma?

Answered by: 
Dr. B. Lauren Charous, Director of Allergy & Respiratory Care Center, Milwaukee Medical Clinic

The answer to the question, "What is the difference between occupational asthma and asthma?" rests on an understanding of what is meant by the term "occupational disease." Furthermore, legal and medical perspectives in this area are somewhat different.

From the stricter medical perspective, occupational disease is defined as any illness which is due to causes and conditions that are attributable to the work place exposure and not to those encountered outside the workplace. To prove that there is a causal relationship between the work place exposure and subsequent illness, physicians and epidemiologists assess several variables including: the nature and strength of the association between the illness and work place exposure; the temporal relationship of incidence of the illness to work place exposure; and the biologic plausibility that the disease seen in exposed workers is in fact due to work place exposure.

Asthma is a common illness characterized by respiratory symptoms such as wheezing, chest tightness or shortness of breath due to intermittent airway obstruction; evidence of bronchial irritability and hyper-responsiveness; and by underlying inflammation of the bronchial airways. In many individuals, allergy may play a major role in the pathogenesis of asthma, and in fact, a majority of individuals with asthma are allergic to such common inhalants as dog and cat dander, dust mite or cockroach. Furthermore, a majority of asthmatics demonstrate asthmatic reactions to irritant responses to a variety of "normal" stimuli such as strong odors, cold air or even stress.

Occupational asthma, then is an asthmatic condition resulting from exposure to work place inhalants. In the past, occupational asthma tended to be limited to workers exposed to certain industrial settings and chemicals such as toluene diisocyanate or red cedar dust (plicatic acid) or to animal protein exposures such as in snow crab workers. Latex- induced occupational asthma is a newly recognized entity. Because of the ubiquity of latex in the office, home and medical setting, evidence demonstrating its occupational nature has only become available in the last few years. However, there is now a convincing body of data which demonstrates that latex aeroallergen levels in quantities comparable to those known to induce asthma from other allergens result from the use of high allergen powdered latex gloves. Experiments in which sensitive workers are challenged with latex aerosols results in predictable asthmatic responses. In other studies, removal of powdered gloves lowered latex aeroallergen levels and decreased asthma in affected workers. Taken as a whole, these findings strongly support the concept that latex can induce occupational asthma.

It is important to add that the legal definition of occupational asthma under workman's compensation laws in most states and under Federal statutes is less strict. In the state of Wisconsin, for instance, a condition that is due to an appreciable period of work place exposure need be either the sole or only a material contributory causative factor. Moreover, a history of asthma prior to work place exposure does not rule out a possible claim if work place exposure is responsible for significant progression of the asthma. For instance, a lab worker who has mild asthma due to pet cat, may find that his/her work with rabbits has caused severe reactions and material worsening of asthma symptoms has recourse to workman's compensation protection.

This article originally appeared in THE ALERT, Vol. 4, No. 2