Occupational Asthma – Causes, Symptoms and diagnosis, treatment

Occupational Asthma


Occupational asthma is a lung disorder triggered by exposure to dust, vapors, gases, fumes or other irritants at a patient’s workplace. Breathing difficulties, such as wheezing and coughing, are typical symptoms associated with this workplace disorder.

People with traditional asthma may experience symptoms of occupational asthma after moving into a new work environment or using new materials. It may also occur in people who have no history of asthma and those who have asthma but have not experienced asthma symptoms for a number of years. Most episodes are triggered by exposure to a substance that either provokes an allergic reaction or an irritant reaction. Many agents in the workplace are potential sources of occupational asthma symptoms. Protein molecules and various chemicals are among the most common triggers.

Those with symptoms of occupational asthma should see a physician to make sure the disorder is properly diagnosed. Left untreated, occupational asthma symptoms are likely to get worse with repeated exposures, leading to long-term health problems. Many employers have shown a willingness to help employees find or create a more suitable work environment.

About occupational asthma

Occupational asthma has been a problem in workplaces for centuries. People with this condition suffer shortness of breath and other breathing difficulties when exposed to certain workplace allergens or irritants. Occupational asthma is the leading cause of work-related lung disease in developing countries. The American Academy of Allergy, Asthma and Immunology (AAAAI) estimates that up to 15 percent of asthma cases may have job-related factors.

Agents that have traditionally caused problems include flour, wood dust, smoke and grain. In the modern era, new sources of workplace asthma have arrived on the scene, including latex and various chemicals used in the manufacture of products.

Occupational asthma is divided into two groups:

  • Work-aggravated asthma. Occurs in individuals with diagnosed asthma who find that symptoms are triggered soon after beginning work in a new setting or after working with new materials.
  • New-onset asthma. Occurs in individuals who have no history of asthma, or who have not suffered symptoms for at least two years. Symptoms begin soon after starting work in a new setting or beginning work with new materials.

Episodes of occupational asthma usually strike in one of two ways:

  • Allergic reaction. This usually occurs over time, as a person is repeatedly exposed to a certain allergen and eventually becomes sensitized to it. For instance, a healthcare worker with a latex allergy may find over time that using certain latex-based surgical gloves triggers asthma symptoms. Individuals may also experience allergy symptoms, such as hives, sneezing or a runny nose, as the result of this sensitization. However, allergy symptoms do not always occur.
  • Irritant reaction. This can occur suddenly upon first exposure to an irritant. For example, a worker may experience asthma symptoms after being exposed to a vat of shellac, or exhaust billowing from a machine. In these cases, workers exhibit asthma symptoms despite not being allergic to the offending substances.

    This type of reaction is more likely to occur in those who already have asthma. Many cases of an irritant reaction occur in response to a chemical spill or other situation where an unusually large amount of the irritant is present.

Although job-site conditions are responsible for triggering the asthma symptoms, the symptoms themselves may not appear until an individual has been away from the workplace for several hours. It is not unusual for workers with occupational asthma to report symptoms on weekends and holidays, when they are away from the job site.

Workers in several job fields may be at a higher risk for developing occupational asthma. These include:

  • Plastics workers
  • Metal workers
  • Bakers
  • Millers
  • Farmers
  • Animal handlers (e.g., veterinarians, kennel workers)
  • Jockeys
  • Grain elevator workers
  • Laboratory workers
  • Printers and publishers
  • Healthcare workers
  • Automobile and gas station workers
  • Woodworkers
  • Drug manufacturers
  • Textile workers
  • Detergent manufacturers
  • Food service workers (especially those who handle, process or prepare food)

A recent study suggests that hairdressers may be at increased risk for occupational asthma as well, due to frequent exposure to bleaching agents. Airborne irritants present in hair salons can also trigger the condition in hairdressers.

Those with signs of occupational asthma are strongly urged to seek medical treatment. The longer workers are exposed to work-site triggers, the more likely they are to suffer permanent damage to their breathing capacity.

Those who exhibit symptoms of occupational asthma should also report their condition to employers and local health authorities. If one person suffers symptoms of occupational asthma, it is likely others are also at risk.

Potential causes of occupational asthma

Occupational asthma is the result of allergens and irritants that can be found in virtually any workplace. Indoor air in offices, manufacturing plants, schools, healthcare facilities and other workplaces can be contaminated with many agents that can trigger occupational asthma. Poor ventilation, water damage, closed-in working areas and heat increase the risk. These agents may be divided into categories of high-molecular and low-molecular weight substances.

High molecular weight substances are composed of heavier molecules than low molecular weight substances. Approximately half of all workers who develop occupational asthma through exposure to low molecular weight compounds never experience complete symptom resolution. The lighter weight of the molecules makes them easier to inhale deeply into the respiratory system. Some of the high molecular compounds may remain in the nasal passages and thus not create as severe a reaction in the lungs and lower airways.

High molecular weight substances include:

Animal products: dander, feathers, urine, saliva, insect proteins, bee moths, lake flies, locusts, mealworms, midges, mites, screwworms, sewer fliesAnimal handlers, laboratory workers, veterinarians
Plants: castor bean dust, exotic wood dusts, grains, flours, green coffee bean dust, gum acacia, gum arabic, latex, pollens, tragacanth, pharmaceuticals, ipecacuanha, psylliumGrain handlers, tea workers, bakers, natural oil manufacturers, tobacco and food processing plant workers, healthcare workers, printers, gum manufacturing workers, carpenters, sawmill workers and furniture makers
Enzymes: bromelain, pancreatic enzymes, papain pepsin, trypsin, fungal amylaseBakers, workers using detergent, pharmaceutical and plastic industry workers
Other: crab, prawns, sea squirtCrab and prawn processors

Low molecular weight substances include:

Toluene diisocyanate, Diphenylmethane diisocyanate, Naphthalene diisocyanate, Hexamethylene diisocyanate
Polyurethane industry workers, plastics producers, foundry workers and workers using varnish
Acid anhydrates:
Himic anhydrate, Phthalic anhydrate, tetrachlorophthalic anhydrate, Trimellitic anhydrate
Epoxy, polymer, resin and plastics workers
Metals/metallic salts:
platinum, nickel, chromium, aluminum, stainless steel, uranium hexafluoride, vanadium, cobalt
Platinum and nickel refining workers, hard metal factory workers
penicillin, methyldopa, tetracyclines, cephalosporins, sulfonamides, isoniazid, macrolide antibiotics
Pharmaceutical and healthcare industry workers
Other organic chemicals:
urea formaldehyde, dyes, formalin, azodicarbonamide, hexachloroethylene diamine, dimethyl ethanolamine, polyvinyl, chloride pyrolysates, popcorn flavoring , wood dusts
Chemical, plastic and rubber industry workers, hospital workers, laboratory workers, foam insulation manufacturing workers, food wrapping factory workers, spray painters, popcorn factory workers, carpenters, sawmill workers, furniture makers

Latex allergies are responsible for symptoms associated with many cases of occupational asthma. The problem has become a major concern in the healthcare industry. The growing popularity of latex gloves ­– which protect workers from infectious diseases such as AIDS and hepatitis B – has led to growing numbers of employees sensitized to latex proteins.

Water-damaged areas can encourage the spread of mold and dust mites. These are both common types of allergens that are frequently responsible for causing asthma symptoms in asthmatic people.

Scientific studies are examining the potential of different substances to contribute to the development of occupational asthma. Some chemicals and/or other substances may have particular qualities that cause them to be more likely to produce asthma in people. Further research into the effect on the immune system of these different substances will help to answer these questions.

Symptoms and diagnosis methods

Symptoms of occupational asthma are largely the same as those that appear during a traditional asthma attack. Spasms of the muscles lining the airways cause the airways to narrow. This results in breathing problems, such as coughing and shortness of breath, and chest tightness. For some, the only symptom is wheezing at night.

It may take months or years of exposure to an allergen or irritant before occupational asthma develops. In some cases, the condition develops 24 hours after exposure to an irritant.

Once the condition has developed, occupational asthma symptoms may occur at the workplace soon after subsequent exposures to the allergen or irritant. However, some people experience delayed symptoms as long as 24 hours after exposure to the offending agent.

Symptoms also are known to come and go for up to a week after the last exposure. This can pose difficulties in diagnosing the problem, because symptoms may occur even after a long period away from the workplace. However, others with occupational asthma report reduced levels of symptoms on weekends, holidays and other periods where they are away from work.

As occupational asthma gets worse, the patient is more likely to experience symptoms regularly both at the workplace and away from it.

It can be very difficult to diagnose the exact allergen or irritant responsible for occupational asthma symptoms. A physician is likely to do a full physical examination, and to compile a complete medical history and list of symptoms. Patients should be prepared to describe symptoms and how often they emerge. One way to keep track of symptoms is to record them in an asthma diary.

A physician will also find it helpful if the patient can give a detailed description of workplace conditions and a list of potential triggers to which the patient is exposed. This might include gases, fumes, smoke, dust, chemicals and other potential allergens.

If a physician suspects occupational asthma, the patient will be asked to undergo one or more asthma or allergy tests.

Treatment and prevention

Once an individual has been diagnosed with occupational asthma, a physician will develop an asthma action plan to help the asthmatic to monitor the condition. A typical plan will contain the following elements:

  • A list of specific symptoms that often precede an individual’s asthma attacks

  • Steps to take during an attack

  • How to recognize a serious attack, and what to do about it

  • How to recognize an emergency, and what to do about it

  • Changes in environment and behavior that can reduce the chances of an asthma flare–up

Treatment of occupational asthma is the same as for other forms of asthma. The best form of treatment is to avoid the allergen causing the symptoms. However quitting a job or transferring jobs within the same workplace is not always an option. In addition, symptoms may continue years after exposure to the allergen has been eliminated.

People can greatly reduce their risk of developing occupational asthma by not entering trades linked to the condition. This is particularly important for individuals at higher risk for developing occupational asthma, such as those with a family history of allergies or asthma.

Some research seems to indicate that adults who work in some occupational environments (e.g., farms) tend to have fewer instances of allergies and asthma. Researchers theorize that regular exposure to some types of toxins gives a person a greater chance of resisting some types of allergens. However, this theory is not yet embraced by the wider scientific community and more research is needed on the subject.

Individuals who have been diagnosed with occupational asthma can take many steps to reduce the likelihood of suffering symptoms related to their condition. These include:

  • Reducing exposure to an offending allergen or irritant. This is the best way to prevent occupational asthma symptoms. However, this can be especially challenging in jobs where the very nature of the job makes modifying work conditions impractical.

  • Working with an employer to improve work conditions. The Americans with Disabilities Act of 1990 requires that employers attempt to adapt their workplace to the special needs of employees. Many employers are willing to assist their employees in finding or creating a more suitable work environment. Employers can allow testing of workplace air quality. Some might provide protective gear, such as masks or respirators, to an employee. However, some workers may find they have no choice but to search for a new career.

  • Stop smoking. Those who smoke increase the odds that workplace irritants or allergens will trigger asthma symptoms.

  • Use a peak flow meter regularly. Patients should use a peak flow meter to check the status of their airways. Regular use of this device can help patients to detect an imminent asthma attack before it occurs.

  • Take all medications as directed. It is important to follow a physician’s or pharmacist’s directions for taking medications, even when symptoms are not apparent.  

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions regarding occupational asthma:

  1. Does my occupation put me at risk for occupational asthma?
  2. Do my symptoms indicate occupational asthma?
  3. What substances in my workplace may be triggering my asthma?
  4. What tests will you use to determine the cause of my symptoms?
  5. If my workplace is causing my symptoms, why do I experience symptoms at night and on the weekends?
  6. Is occupational asthma dangerous to my overall health?
  7. What are my treatment options? How effective will they be?
  8. How can I reduce my exposure to allergens while at the workplace?
  9. Do you suggest that I get a new job? Will my symptoms stop if I leave my current job?
  10. What affect does smoking have on my occupational asthma?
  11. My coworker was recently diagnosed with occupational asthma. Does this mean that I am at risk?
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