occupational asthma

Occupational Asthma 

Definition

Occupational asthma is a form of lung disease in which the breathing passages shrink, swell, or become inflamed or congested as a result of exposure to irritants in the workplace.

Description

As many as 15% of all cases of asthma may be related to on-the-job exposure to:

• animal hair
• dander
• dust composed of bacteria, protein, or organic matter like cereal, grains, cotton, and flax
• fumes created by metal soldering
• insulation and packaging materials
• mites and other insects
• paints

Hundreds of different types of jobs involve exposure to substances that could trigger occupational asthma, but only a small fraction of people who do such work develop this disorder. Occupational asthma is most apt to affect workers who have personal or family histories of allergies or asthma, or who are often required to handle or breathe dust or fumes created by especially irritating material.

Causes and symptoms

Although occupational asthma is not new, today, more than 240 causes of occupational asthma have been identified. It was probably first recorded in 1713 when one of the fathers of occupational health, Bernadina Ramazzini said bakers and textile workers had problems with coughing shortness of breath, hoarseness and asthma. Even short-term exposure to low levels of one or more irritating substances can cause a very sensitive person to develop symptoms of occupational asthma. A person who has occupational asthma has one or more symptoms, including coughing, shortness of breath, tightness in the chest, and wheezing. Symptoms may appear less than 24 hours after the person is first exposed to the irritant or develop two or three years later.

At first, symptoms appear while the person is at work or several hours after the end of the workday. Symptoms disappear or diminish when the person spends time away from the workplace and return or intensify when exposure is renewed.

As the condition becomes more advanced, symptoms sometimes occur even when the person is not in the workplace. Symptoms may also develop in response to minor sources of lung irritation.

Diagnosis

An allergist, occupational medicine specialist, or a doctor who treats lung disease performs a thorough physical examination and takes a medical history that explores:

• the kind of work the patient has done
• the types of exposures the patient may have experienced
• what symptoms the patient has had
• when, how often, and how severely symptoms have occurred

Performed before and after work, pulmonary function tests can show how job-related exposures affect the airway. Laboratory analysis of blood and sputum may confirm a diagnosis of workplace asthma. To pinpoint the cause more precisely, the doctor may ask the patient to inhale specific substances and monitor the body's response to them. This is called a challenge test.

Treatment

The most effective treatment for occupational asthma is to reduce or eliminate exposure to symptom-producing substances.

Medication may be prescribed for workers who can not prevent occasional exposure. Leukotriene modifiers (montelukast and zafirlukast) are new drugs that help manage asthma. They work by counteracting leukotrienes, which are substances released by white blood cells in the lung that cause the air passages to constrict and promote mucus secretion. Leukotriene modifiers also fight off some forms of rhinitis, an added bonus for people with asthma. Medication, physical therapy, and breathing aids may be needed to relieve symptoms of advanced occupational asthma involving airway damage.

A patient who has occupational asthma should learn what causes symptoms and how to control them, and what to do when an asthma attack occurs.

Because asthma symptoms and the substances that provoke them can change, a patient who has occupational asthma should be closely monitored by a family physician, allergist, or doctor who specializes in occupational medicine or lung disease.

Prognosis

Occupational can be reversible. However, continued exposure to the symptom-producing substance can cause permanent lung damage. Follow-up studies of people with occupational asthma show that some cannot be protected from the exposure or are forced to change jobs, lose their jobs, or have worse prospects for future jobs based on their allergies and asthma.

In time, occupational asthma can cause asthma-like symptoms to occur when the patient is exposed to tobacco smoke, household dust, and other ordinary irritants.

Smoking aggravates symptoms of occupational asthma. Patients who eliminate workplace exposure and stop smoking are more apt to recover fully than those who change jobs but continue to smoke.

Prevention

Industries and environments where employees have a heightened exposure to substances known to cause occupational asthma can take measures to diminish or eliminate the amount of pollution in the atmosphere or decrease the number of exposed workers.

Regular medical screening of workers in these environments may enable doctors to diagnose occupational asthma before permanent lung damage takes place.

Resources

Periodicals

"Allergic to Work? Occupational Asthma Accounts for Up to 18 Million Lost Working Days a Year and Affects Thousand of Workers." The Safety & Health Practitioner September 2004: 38-41.

Solomon, Gina, Elizabeth H. Humphreys, and Mark D. Miller. "Asthma and the Environment: Connecting the Dots: What Role Do Environmental Exposures Play in the Rising Prevalence and Severity of Asthma?" Contemporary Peditatrics August 2004: 73-81.

"What's New in: Asthma and Allergic Rhinitis." Pulse September 20, 2004: 50.

Organizations

American College of Allergy, Asthma and Immunology. 85 West Algonquin Road, Suite 550, Arlington Heights, IL 60005. (847) 427-1200.

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occupational asthma,

an abnormal condition of the respiratory system resulting from exposure in the workplace to allergenic or other irritating substances. The condition is most common among people working with detergents, Western red cedar, cotton, flax, hemp, grain, flour, and stone. See also asthma, byssinosis, occupational lung disease.

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asthma [az´mah]

a condition marked by recurrent attacks of dyspnea, with airway inflammation and wheezing due to spasmodic constriction of the bronchi; it is also known as bronchial asthma. Attacks vary greatly from occasional periods of wheezing and slight dyspnea to severe attacks that almost cause suffocation. An acute attack that lasts for several days is called status asthmaticus; this is a medical emergency that can be fatal. adj., adj asthmat´ic.

Causes. Asthma can be classified into three types according to causative factors. Allergic or atopic asthma (sometimes called extrinsic asthma) is due to an allergy to antigens; usually the offending allergens are suspended in the air in the form of pollen, dust, smoke, automobile exhaust, or animal dander. More than half of the cases of asthma in children and young adults are of this type. Intrinsic asthma is usually secondary to chronic or recurrent infections of the bronchi, sinuses, or tonsils and adenoids. There is evidence that this type develops from a hypersensitivity to the bacteria or, more commonly, viruses causing the infection. Attacks can be precipitated by infections, emotional factors, and exposure to nonspecific irritants. The third type of asthma, mixed, is due to a combination of extrinsic and intrinsic factors.

There is an inherited tendency toward the development of extrinsic asthma. It is related to a hypersensitivity reaction of the immune response. The patient often gives a family medical history that includes allergies of one kind or another and a personal history of allergic disorders. Secondary factors affecting the severity of an attack or triggering its onset include events that produce emotional stress, environmental changes in humidity and temperature, and exposure to noxious fumes or other airborne allergens.

Symptoms. Typically, an attack of asthma is characterized by dyspnea and a wheezing type of respiration. The patient usually assumes a classic sitting position, leaning forward so as to use all the accessory muscles of respiration. The skin is usually pale and moist with perspiration, but in a severe attack there may be cyanosis of the lips and nailbeds. In the early stages of the attack coughing may be dry; but as the attack progresses the cough becomes more productive of a thick, tenacious, mucoid sputum.

 An asthma attack with respiratory distress. From Frazier et al., 2000.

Treatment. The treatment of extrinsic asthma begins with attempts to determine the allergens causing the attacks. The cooperation of the patient is needed to relate onset of attacks with specific environmental substances and emotional factors that trigger or intensify symptoms. The patient with nonallergic asthma should avoid infections, nonspecific irritants, such as cigarette smoke, and other factors that provoke attacks.

Drugs given for the treatment of asthma are primarily used for the relief of symptoms. There is no cure for asthma but the disease can be controlled with an individualized regimen of drug therapy coupled with rest, relaxation, and avoidance of causative factors. Bronchodilators such as epinephrine and aminophylline may be used to enlarge the bronchioles, thus relieving respiratory embarrassment. Other drugs that thin the secretions and help in their ejection (expectorants) may also be prescribed.

The patient with status asthmaticus is very seriously ill and must receive special attention and medication to avoid excessive strain on the heart and severe respiratory difficulties that can be fatal.

Patient Care. Because asthma is a chronic condition with an irregular pattern of remissions and exacerbations, education of the patient is essential to successful treatment. The plan of care must be highly individualized to meet the needs of the patient and must be designed to encourage active participation in the prescribed program and in self care. Most patients welcome the opportunity to learn more about their disorder and ways in which they can exert some control over the environmental and emotional events that are likely to precipitate an attack.

Exercises that improve posture are helpful in maintaining good air exchange. Special deep breathing exercises can be taught to the patient so that elasticity and full expansion of lung and bronchial tissues are maintained. (See also lung and chronic obstructive pulmonary disease.) Some asthmatic patients have developed a protective breathing pattern that is shallow and ineffective because of a fear that deep breathing will bring on an attack of coughing and wheezing. They will need help in breaking this pattern and learning to breathe deeply and fully expand the bronchi and lungs.

The patient should be encouraged to drink large quantities of fluids unless otherwise contraindicated. The extra fluids are needed to replace those lost during respiratory distress. The increased intake of fluids also can help thin the bronchial secretions so that they are more easily removed by coughing and deep breathing.

The patient should be warned of the hazards of extremes in eating, exercise, and emotional events such as prolonged laughing or crying. The key words are modification and moderation to avoid overtaxing and overstimulating the body systems. Relaxation techniques can be very helpful, especially if the patient can find a method that effectively reduces tension.

Asthmatic patients fare better if they feel that they do have some control over their disease and are not necessarily helpless victims of a debilitating incurable illness. There is no cure for asthma but there are ways in which one can adjust to the illness and minimize its effects.

allergic asthma (atopic asthma) that due to an atopic allergy; see asthma.

bronchial asthma asthma.

cardiac asthma a term applied to breathing difficulties due to pulmonary edema in heart disease, such as left ventricular failure.

extrinsic asthma

asthma caused by some factor in the environment, usually atopic in nature.

atopic asthma.

intrinsic asthma that due to a chronic or recurrent infection; see asthma.

occupational asthma extrinsic asthma due to an allergen present in the workplace.

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occupational asthma

Clinical immunology A clinical complex that causes predominantly pulmonary Sx in previously healthy persons exposed to a noxious fumes or gases in the workplace; OA affect ± 3% of Americans, many of whom function adequately, despite Sx. See Hypersensitivity pneumonitis, Monday morning sickness, Sick building syndrome.