What is it?
Occupational asthma is asthma that's caused or worsened by breathing in a workplace irritant, such as chemical fumes, gases or dust. Like other types of asthma, occupational asthma can cause symptoms, such as chest tightness, wheezing and shortness of breath.
When diagnosed and treated early, occupational asthma may be reversible. Long-term exposure to irritants can cause worsening symptoms and lifetime asthma. Treatment for occupational asthma is similar to treatment for other types of asthma, and it generally includes taking medications to reduce symptoms. But the only sure way eliminate your symptoms and prevent lung damage due to occupational asthma is to avoid whatever's triggering it.
Occupational asthma symptoms are similar to those caused by other types of asthma. Signs and symptoms may include:
- Shortness of breath
- Chest tightness
Other possible accompanying signs and symptoms may include:
- Runny nose
- Nasal congestion
- Eye irritation
Occupational asthma symptoms vary from person to person and depend on the substance you're exposed to, how long and how often you're exposed, your body's individual reaction, and other factors. Your symptoms may vary and can include symptoms that:
- Get worse as the workweek progresses, go away during weekends and vacations, and recur when you return to work.
- Occur both at work and away from work.
- Start right after exposure to an irritant at work.
- Start after months or even years of regular exposure to an irritant.
- Continue after exposure is stopped. The longer you're exposed to the asthma-causing substance, the more likely you'll have long-lasting or permanent asthma symptoms.
It's not clear why some people develop occupational asthma from exposure to something at work and others don't. It likely has to do with inherited traits (genetics) and exposure to environmental substances over time.
Asthma symptoms start when your lungs become irritated (inflamed). Inflammation causes several reactions that restrict the airways, making breathing difficult. After you're exposed to something that triggers an asthma attack, your airways become constricted:
- Muscles around your airways tighten.
- The airways themselves become swollen.
- You begin to produce too much mucous, which clogs your airways.
With occupational asthma, lung inflammation may be triggered by one of two processes:
- An allergic response. Asthma can occur when the body develops an allergy from continued exposure to a substance. Your body starts to identify the substance as a threat and activates your immune system to react. This is called sensitization. You don't have symptoms at first because the sensitization process can take months or even years to occur. Symptoms start when your immune system begins to produce specific antibodies against the irritating substance. This, in turn, triggers the release of chemicals, such as histamine, which inflame the lungs and cause asthma symptoms.
- Irritant-induced asthma. After breathing in a certain workplace irritant one or more times, you may develop asthma symptoms caused by direct irritation of your lungs rather than an allergic reaction. With a condition called reactive airways dysfunction syndrome (RADS), inhaled chemicals make the bronchial tubes more sensitive to irritants. Some irritants that can cause this type of reaction include sulfur dioxide, chlorine, hydrochloric acid and environmental smoke.
More than 300 workplace substances have been identified as possible causes of occupational asthma. These substances include:
- Animal substances, such as proteins found in dander, hair, scales, fur, saliva and body wastes.
- Chemicals, such as anhydrides, diisocyanates and acids used to make paints, varnishes, adhesives, laminates and soldering resin. Other examples include chemicals used to make insulation, packaging materials, and foam mattresses and upholstery.
- Enzymes used in detergents, flour conditioners, some pharmaceuticals and meat tenderizers.
- Metals, particularly platinum, chromium and nickel sulfate.
- Plant substances, including proteins found in natural rubber latex, flour, cereals, cotton, flax, hemp, rye, wheat and papain, a digestive enzyme derived from papaya.
- Respiratory irritants, such as chlorine gas, sulfur dioxide and smoke.
You're at increased risk of developing occupational asthma if:
- You have existing allergies or asthma. Although this can increase your risk, many people who have allergies or asthma do jobs that expose them to lung irritants and never have symptoms.
- Allergies or asthma run in your family. You are more likely to develop asthma if your parents have allergies or asthma.
- You work around known asthma triggers. Some substances are known to be lung irritants and asthma triggers. A number of workplace substances are known to cause occupational asthma.
The longer you're exposed to a substance that causes occupational asthma, the worse your symptoms will become — and the longer it will take for them to improve once you end your exposure to the irritant. In some cases, exposure to airborne asthma triggers can cause permanent lung changes and lifetime asthma symptoms.
Diagnosing occupational asthma is similar to diagnosing other types of asthma. But with occupational asthma, your doctor will also try to identify whether a workplace irritant is causing your symptoms, and if so, what it may be. Your doctor will ask you a number of questions about your symptoms, your job and how they may be related. You'll need to provide a detailed description of working conditions at your present and previous jobs, and any possible asthma triggers you may have been exposed to.
An asthma diagnosis needs to be confirmed by tests that may include a lung (pulmonary) function test and an allergy skin prick test. Your doctor will want to make sure your symptoms aren't caused by another condition, such bronchitis. He or she may order blood tests, X-rays or other tests to rule out a cause other than occupational asthma.
Testing your lung function
Your doctor may ask you to perform lung (pulmonary) function tests. These include:
- Spirometry. This noninvasive test, which measures how well you breathe, is the preferred test for diagnosing asthma. During this 10- to 15-minute test, you take deep breaths and forcefully exhale into a hose connected to a machine called a spirometer. If certain key measurements are below normal for a person your age and sex, your airways may be blocked by inflammation (obstructed). This is a key sign of asthma. Your doctor may ask you to inhale a bronchodilator drug used in asthma treatment to open obstructed air passages. Then you retake the spirometry test. If your measurements improve significantly, it's likely that you have asthma.
- Peak flow measurement. To determine if you have occupational asthma, your doctor may ask you to carry a peak flow meter, a small, hand-held device that measures how fast you can force air out of your lungs. The slower you can exhale, the worse your asthma. You'll likely be asked to use your peak flow meter at selected intervals during working and nonworking hours. If your breathing improves significantly when you're away from work, you may have occupational asthma.
- Nitric oxide test. This test is used to see how much nitric oxide gas is in your breath. High levels of nitric oxide can be a sign of asthma.
Tests for specific lung irritants
In an effort to identify what is causing your symptoms, your doctor may do tests to see whether you have a reaction to specific substances. These include:
- Allergy skin tests. During a skin test, your skin is pricked with purified allergy extracts and observed for signs of an allergic reaction. These tests can't be used to diagnose chemical sensitivities, but may be useful to evaluate sensitivity to animal dander, mold, dust mites and latex.
- Challenge test. During a challenge test you inhale an aerosol containing a small amount of a suspect chemical to see if it triggers a reaction. Your lung function is tested before and after the aerosol is given to see whether it affects your ability to breathe.