Nearly 20 million Americans suffer from asthma. Every day in America, 40,000 people miss school or work; 30,000 have an asthma attack and 5,000 visit the emergency room. About 15 million work-days are lost annually at a cost of about $3 billion in lost productivity. (AAFA) NIOSH (2004) reports that 15-23% of new-onset cases of asthma in adults are work related. Whether the cause of asthma is occupational or personal, employers bear the cost of lost work days and, likely, treatment through worker's compensation claims or employee medical benefits. Because of the significance of this problem, safety professionals are prudent to consider occupational asthma in their safety programs.
Asthma is a chronic, episodic disease of the airways, with the following features (which may not be present in every patient) (Kavuru):
Recurrent episodes of respiratory symptoms
Variable airflow obstruction that is often reversible, either spontaneously or with treatment
Presence of airway hyperreactivity
Chronic airway inflammation involving many cells and cell parts
Asthma, by its most simple definition. is a respiratory syndrome of both constriction and inflammation. Inflammation is found in all asthmatic individuals; inflammation follows exposure to stressors like allergens, viruses, irritants or exercise. Increased inflammation leads to the symptoms of shortness of breath, coughing, wheezing and chest tightness, which are the most important symptoms of asthma. (Kavuru) In the lungs, the lining of the airways swell (airways are constricted) and become inflamed; mucus clogs the airway (which can result in a productive cough); muscles tighten around the airways (broncospasm, causing further constriction). (AAFA)
In the broadest sense, asthma is divided into two types: allergic asthma and non-allergic asthma. (AAFA) In allergic asthma, a person reacts to an allergen. The most common inhalant allergens are dust mites, animal dander, mold, and cockroaches. The allergen causes a person to have an "allergy" or a hyperresponsiveness reaction to the material. Non-allergic asthma is initiated not by an allergen, but by an irritant or other factor, like exercise, cold air, high humidity, or stress.
In diagnosing asthma, the physician will take a medical history, including family history, medications, and information on work and home environments, as well as present physical complaints. Most often, a lung function test is performed. The preferred test is spirometry; a spirometer records the amount of air one can exhale three different ways (Berger):
FVC or forced vital capacity measures the maximum volume of air one can exhale after inhaling
FEV1 measures the amount of air one can exhale in the first second
MMEF or maximum midexpiratory flow rate measures one's expiration as in the middle of the test, or at 25-75% of the FVC
Asthma may be confirmed by the use of bronchodilator tests or measurements of airway responsiveness (Hendrick).
