What Is Occupational Asthma? What Causes Occupational Asthma?

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Main Category: Respiratory / Asthma
Also Included In: Allergy
Article Date: 25 Jun 2010 - 0:00 PDT

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Occupational asthma is asthma that is caused by types of working practices or the presence of irritants, fumes or gases at work. If the individual already has asthma, but it gets worse in the workplace, this may also be classed as occupational asthma. The sufferer has the same symptoms as in non-occupational asthma - the inside walls of an person's airways are swollen or inflamed. This swelling or inflammation makes the airways extremely sensitive to irritations and increases their susceptibility to an allergic reaction, which may result in wheezing, chest tightness, and other asthma signs and symptoms.

Treatment for occupational asthma can be effective if diagnosed early enough. However, if the person has been exposed to the irritant for a long time, his/her asthma may become chronic (long-term, irreversible).

Treatment for occupational asthma is basically the same as for asthma that is not work-related. However, an individual with occupational asthma may have the option of avoiding the irritant, by either changing jobs or working with his/her employer for better working conditions.

Many irritants in the workplace can trigger occupational asthma. The most common one being wood dust, grain dust, animal dander, fungi, diisocyanates and other chemicals.

Diisocyanates are manufactured for reaction with polyols in the production of polyurethanes. Polyurethanes are widely used in high resiliency flexible foam seating, rigid foam insulation panels, microcellular foam seals and gaskets, durable elastomeric wheels and tires, automotive suspension bushings, electrical potting compounds, high performance adhesives and sealants, Spandex fibers, seals, gaskets, carpet underlay, and hard plastic parts.

According to the World Health Organization, between 2% to 20% of all asthma rates in industrialized nations are cases of occupational asthma.

The USA Department of Labor says "An estimated 11 million workers in a wide range of industries and occupations are exposed to at least one of the numerous agents known to be associated with occupational asthma".

According to the American Journal of Respiratory and Critical Care Medicine (Vol 167. pp. 450-471, 2003)

Occupational asthma is a disease characterized by variable airflow limitation and/or airway hyper-responsiveness due to causes and conditions attributable to a particular occupational environment and not stimuli encountered outside the workplace.

What are the signs and symptoms of occupational asthma?

A symptom is something the patient senses and describes, while a sign is something other people, such as the doctor notice. For example, drowsiness may be a symptom while dilated pupils may be a sign.

Signs and symptoms of occupational asthma are basically the same as other types, and may include wheezing, coughing, difficulty breathing, and a blocked/stuffy nose. How occupational asthma may affect people depends on many factors, including the person, age, type of irritant, and whether they already had asthma.

People with occupational asthma may find that their symptoms get worse as the working week progresses - on Monday it is not too bad, but by Friday it is worse (if they do not work weekends). The same may be noticed during vacations, with symptoms going away, and then coming back when they return to work.

In some cases asthma symptoms may continue even after there is no exposure to the irritant, especially if there has been long-term exposure to it.

What are the risk factors for occupational asthma?

A risk factor is something which increases the likelihood of developing a condition or disease. For example, obesity significantly raises the risk of developing diabetes type 2. Therefore, obesity is a risk factor for diabetes type 2.

Occupations - certain occupations are linked to a higher risk of developing occupational asthma, and they include:

• Bakers - flour dust and enzymes containing additives such as amylase are the second most common cause of occupational asthma in the UK. (Source: Health Safety Executive, UK)
• Detergent manufacturers
• Drug manufacturers
• Farmers and agricultural workers - grain dust rises from harvesting, moving and processing cereal crops. Grain dust causes occupational asthma. Along with farm workers, others at risk include those moving cereals, e.g. dockworkers, millers and workers in maltings; also maintenance engineers. (Source: Health Safety Executive, UK)
• Grain elevator workers
• Laboratory workers
• Metal workers
• Millers
• Plastics workers
• Woodworkers - hardwood, softwood and wood composite dusts arise in wood machining and sanding are common causes. (Source: Health Safety Executive, UK)
• Vehicle spary painters - isocyanate (typically in 2-pack paints) is the most common cause of occupational asthma. (Source: Health Safety Executive, UK)
• Solderers - rosin based solder flux fume is caused when soldering. This fume is a top cause of occupational asthma. It affects workers in the electronics and assembly industries.

Genetics (family history) - people with a family history of asthma - at least one close relative who has/had asthma - have a higher risk of developing occupational asthma, especially if they work in one of the occupations mentioned above.

Existing asthma - people who already have asthma and work in places where known irritants exist, are at risk of developing worsening and chronic (long-term) symptoms.

Existing allergies - people who have an existing allergy have a higher risk of developing occupational asthma.

What are the causes of occupational asthma?

Why some people develop asthma when exposed to a known irritant while others don't is still a bit of an enigma. Most likely the cause is a combination of the individual's genetic make up with environmental factors.

What are environmental triggers? Imagine your body is a series of buttons, and some of those buttons result in asthma if somebody comes and presses them enough times and in the right sequences. The buttons would be your genetic susceptibility, while the individual pressing them would be the environmental factors.

Asthma symptoms will appear when the lungs become inflamed (irritated). Several reactions occur which restrict the airways when there is inflammation. These reactions, plus the inflammation make breathing more difficult. Some people's airways become constricted when exposed to certain triggers and the muscles around their airways tighten, the airways swell up (inflammation), and the production of mucus increases significantly.

An irritant can cause either an allergic response, or it can be simply irritate the lungs (not an allergic response. Occupational asthma may be caused by animal products, such as fur, scales, urine, feces or saliva, certain chemicals, some plants, fumes and some enzymes.

Diagnosing occupational asthma

Diagnosis of occupational asthma is much the same as for other asthmas. However, the doctor will also try to determine whether symptoms are work-related, and if so, what the irritant might be.

Click here for more information on Diagnosing Asthma.

What are the treatment options for occupational asthma?

If the patient's asthma is caused by exposure to a workplace irritant, the best thing to do is avoid it. However, the patient may have become sensitive to the substance and will have symptoms even after being exposed to extremely small amounts. If the substance is used somewhere in the workplace, avoiding it may be extremely difficult.

In some cases the individual may eventually decide to change jobs and work somewhere else.

For more information on "Treatment Options for Asthma", click here.

What are the possible complications of occupational asthma?

Complications are more likely if the patient receives no treatment and does not do anything about exposure to the workplace substance that is causing his/her problem. If exposure continues for long enough, there is a higher chance of developing chronic (long-term) symptoms.

According to the HSE (Health Safety Executive, a UK government agency):

Simple changes in your workplace can make it a safer place for you and those working around you. Everybody has a role to play - employers, employees, government, industry and unions.

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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