Occupational asthma is generally defined as a lung disorder caused by inhaling fumes, gases, dust or other potentially harmful substances while “on the job.” With occupational asthma, symptoms of asthma may develop for the first time in a previously healthy worker, or childhood asthma that had previously cleared may recur due to this exposure. In another form of work-related asthma, pre-existing asthma may be aggravated by exposures within the work place.
Occupational asthma may be caused by one of three mechanisms. These include:
- Direct irritant effects – Irritants that provoke occupational asthma include hydrochloric acid, sulfur dioxide or ammonia, which is found in the petroleum or chemical industries. Workers exposed to these substances will frequently begin wheezing and experiencing other asthma symptoms immediately after exposure to the irritant substance. This is an irritant reaction rather than an allergic reaction, since it does not involve the immune system. Workers who already have asthma or some other respiratory disorder are particularly affected by this type of exposure.
- Allergy(long-term exposure) – Allergies play a role in many cases of occupational asthma. This type of asthma generally develops only after long-term exposure (e.g., months or years) to a work-related substance. This is because the body’s immune system needs time to develop allergic antibodies or other immune responses to a particular substance. For example, workers in the washing powder industry may develop an allergy to the enzymes of the bacteria Bacillus Subtilis, and food processing workers may develop an allergy and occupational asthma symptoms from exposure to castor beans, green coffee beans and papain. Allergic occupational asthma can occur in workers in the plastic, rubber or resin industries following repeated exposure to small chemical molecules in the air. Veterinarians, fishermen and animal handlers in laboratories can develop allergic reactions to animal proteins, and health care workers can develop asthma from breathing in powdered proteins from latex gloves or from mixing powdered medications.
- Pharmacologic mechanisms – Inhalation of some substances in aerosol form can directly lead to the accumulation of naturally occurring chemicals in the body, such as histamine or acetylcholine within the lung, which in turn lead to asthma. For example, insecticides, used in agricultural work, can cause a buildup of acetylcholine, which causes airway muscles to contract, thereby constricting airways.
Individuals with occupational asthma should see our allergist for an evaluation. In some cases, pre-treatment with specific medications to counteract the effects of workplace substances may be helpful. In other situations, complete avoidance may be necessary.
