Asthma Subgroups: Occupational Asthma
Subgroups. Occupational asthma is one of the oldest known subgroups of asthma, having been first introduced to the medical profession in 1700 by Bernardino Ramazzini (1633-1714). It is now further divided into two distinct subgroups called sensitizer and irritant-induced asthma.3,4
SENSITIZER ASTHMA. This accounts for about 90% of occupational asthma.5 It occurs as a result of chronic (day after day) exposure to minute levels of substances in the air at your work.6
It’s estimated that over 400 substances can easily become aerosolized at work and cause occupational asthma. These causative agents are called sensitizers. You may be inhaling them without even being aware of it. For this reason, the association between workplace and asthma often goes unnoticed.4
Your immune system gradually recognizes the sensitizer as harmful. This makes you sensitized to the sensitizer.4 The mechanisms involved here are similar to what I described in my post “Allergic Asthma".
The sensitizer then acts as an asthma trigger, and subsequent exposures to it cause asthma symptoms, such as coughing, chest tightness, and shortness of breath. While these symptoms are similar to those experienced with other subgroups of asthma, they are generally only experienced while working, or shortly after work. Symptoms tend to go away on weekends, during vacations, or when employment ceases..4
There are many occupations where you might be exposed to aerosolized agents that might contribute to asthma. Here’s a sample:
- Pastry workers and those who work in flour mills may inhale cereals and flour.
- Laboratory workers and farmers may inhale dander from mice, rats, and cows.
- Insulation installers and spray painters may inhale chemicals.
- Welders may inhale metals.
- Sawmill workers, carpenters, etc, may inhale wood dust.
- Healthcare workers may be exposed to latex on latex gloves.4
The best treatment is avoiding the sensitizer and working with your doctor on creating an asthma management regimen that works best for you.7
For instance, if you develop an allergy to latex, avoidance of latex products (such as latex gloves) is all that is necessary to avoid asthma symptoms. Many hospitals today accomplish this by using products that are latex-free.
About 80% of cases involve a diagnosis of new-onset asthma. The other 20% already had a diagnosis of asthma, such as childhood-onset, that may have been in remission prior to the work exposure.4
Of the 20% who already had a diagnosis of asthma, some experts do not include them under the definition of occupational asthma. Rather, they are categorized as having Work-Exacerbated Asthma. This essentially means their asthma is triggered by sensitizers but was not caused by them. This occurs in about 25% of people with a diagnosis of asthma.9
Sensitizer asthma tends to be less severe and easier to control than irritant-induced asthma.
IRRITANT INDUCED ASTHMA. It was first described by industrial workers and combatants during WWI.8 It’s when acute (right now) exposure to substances in the air at your workplace cause airway changes that cause you to develop asthma and asthma symptoms. This accounts for about 10% of occupational asthma.6
This is usually caused by inhaling large doses of fumes, gasses, or vavors (chemicals) as might occur when there is a chemical spill or a fire. It’s usually a one time, accidental occurrence. A good example is lack of airway protection (masks) by firefighters when the World Trade Center collapsed on September 11, 2001.7,8
This massive exposure irritates cells lining airways in a way that causes them to become inflamed and hypersensitive without your immune system developing a sensitivity to the causative agent. This means that it is nonallergic or intrinsic.7
Initial exposure may result in burning of the eyes, nose and throat, and may also include coughing, chest tightness and shortness of breath within minutes or hours after exposure. Most victims seek medical help for their symptoms within 24 hours after exposure.6
Damage caused by this irritation results in persistent airway inflammation, and this makes airways hypersensitive to certain asthma triggers, such as strong smells, strong emotions, cigarette smoke, wood smoke, etc..6,7
Early recognition and diagnosis is key to good asthma control. Treatment includes traditional asthma medicines, such as bronchodilators to open airways and inhaled corticosteroids to reduce inflammation and control and prevent asthma symptoms. Although the reason is unknown, some cases will resolve within 12 weeks. About 25% have a resolution of airway hyperresponsiveness within two years.6
This irritation may also result in airway remodeling that makes airway walls abnormally thick and airways narrow. This is most likely to occur when asthma is not diagnosed and treated aggressively. In 1985, this form of asthma was formally recognized and referred to as Reactive Airway Dysfunction Syndrome (RADS).9
Tracking programs. Many people with occupational asthma are unaware of it. For this reason, many states, such as Michigan, have state tracking programs that pretty much do what Ramazzini did so many years ago: spend time with workers and talk to them about any substances they might be exposed to and any symptoms they might experience. In Michigan, the most reported workplace irritants are chemicals in cleaning agents and poor quality air in welding offices.1
Looking to the future. The ideas of Ramazzini weren’t accepted by the medical community until the 19th century. Since then, knowledge and awareness of occupational asthma has grown exponentially. Researchers continue their quest to learn more, and the ultimate goal is to both preventing new cases, and finding new options for treating current cases.
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