Occupational Asthma


This article has been reviewed by Thanai Pongdee, MD, FAAAAI

Occupational asthma has become the most common work-related lung disease in developed countries. However, the exact number of newly diagnosed cases of asthma in adults due to occupational exposure is unknown. Up to 15% of asthma cases in the United States may be job-related.

Occupational asthma is caused by inhaling fumes, gases, dust or other potentially harmful substances while "on the job." Often, your symptoms are worse during the days or nights you work, improve when you have time off and start again when you go back to work.

You may have been healthy and this is the first time you've had asthma symptoms, or you may have had asthma as a child and it has returned. If you already have asthma, it may be worsened by being exposed to certain substances at work.

People with a family history of allergies are more likely to develop occupational asthma, particularly to some substances such as flour, animals and latex.

But even if you don't have a history, you can still develop this disease if you're exposed to conditions that induce it. Also, if you smoke, you're at a greater risk for developing asthma.

Causes
The rate of occupational asthma varies within individual industries.

Irritants in high doses that induce occupational asthma include hydrochloric acid, sulfur dioxide or ammonia, which is found in the petroleum or chemical industries. If you are exposed to any of these substances at high concentrations, you may begin wheezing and experiencing other asthma symptoms immediately after exposure. Workers who already have asthma or some other respiratory disorder may also experience an increase in their symptoms during exposure to these irritants.

Allergies play a role in many cases of occupational asthma. This type of asthma generally develops only after months or years of exposure to a work-related substance. Your 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, while bakers may develop an allergy and occupational asthma symptoms from exposure to various flours or baking enzymes.

Veterinarians, fishermen and animal handlers in laboratories can develop allergic reactions to animal proteins. Healthcare workers can develop asthma from breathing in powdered proteins from latex gloves or from mixing powdered medications. Similarly, about 5% of people working with laboratory animals or with powdered natural rubber latex gloves have developed occupational asthma.

Occupational asthma can also occur in workers after repeated exposure to small chemical molecules in the air, such as with paint hardeners or in the plastic and resin industries. For example, isocyanates are chemicals that are widely used in many industries, including: spray painting, insulation installation and in manufacturing plastics, rubber and foam. These chemicals can cause occupational asthma in up to 10% of exposed workers.

The length of time you are exposed to a substance before it triggers your asthma varies. It can be months or years before symptoms occur. On the other hand, exposure to a high concentration of irritants can cause asthma within 24 hours.

Finally, inhaling some substances in aerosol form can directly lead to the buildup of naturally occurring chemicals in your body, such as histamine or acetylcholine within your lungs, which leads to asthma. For example, insecticides, used in agricultural work, can cause a buildup of acetylcholine, which causes your airway muscles to contract and tighten.

Diagnosis and Treatment
Many people with persistent asthma symptoms caused by substances at work are incorrectly diagnosed as having bronchitis. If occupational asthma is not correctly diagnosed early, and you aren't protected or removed from the exposure, it can cause permanent changes to your lungs.

An allergist / immunologist, often referred to as an allergist, is the best qualified physician to determine if your symptoms are allergy or asthma-related. Your allergist can properly diagnose the problem and develop a treatment plan to help you feel better and live better.

Once the cause of your symptoms is identified, you and your employer can work together to assure that you avoid exposure to the substance that triggers your asthma symptoms and to high concentrations of irritants. Also, you may need to avoid or reduce your exposure to irritants that can trigger symptoms in most asthmatics, such as smoke or cold air.

In some cases, pre-treatment with specific medications to protect against asthma worsened at work may be helpful. In other situations, particularly if you are very allergic to a substance in your workplace, avoiding the substance completely may be necessary.

Healthy Tips
• Occupational asthma is caused by inhaling fumes, gases, dust or other potentially harmful substances while at work. You may find that your symptoms are worse during the days or nights you work, improve when you have time off and start again when you go back to work.
• The length of time you are exposed to a substance before it triggers your asthma varies. Asthma can be triggered within 24 hours or symptoms can occur months and years later.
• Once the cause of your symptoms is identified, develop a treatment plan with your doctor and talk to your employer to avoid exposure to that substance.
• If occupational asthma is not correctly diagnosed early, and you aren't protected or removed from the exposure, it can cause permanent changes to your lungs.

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AAAAI - American Academy of Allergy Asthma & Immunology