Occupational asthma: Occ-health nurse should know causes and prevention
Aggressive approach at first sign can help ill worker, prevent asthma in others
An employee at a manufacturing worksite complains of a chronic cough that comes on at night, hours after his shift at work has ended. He says he's never been asthmatic, and the cough doesn't bother him at work, but some careful assessment is needed to determine if he does have asthma, and whether it might be job-related.
"When a patient presents with the sentinel event — the indicator that he might have asthma — it's important to be aggressive in getting help for him and in assessing the workplace," according to Michael C. Zacharisen, MD, an immunologist and associate professor of pediatrics and medicine at the Medical College of Wisconsin in Milwaukee.
An occupational health nurse should know what risks there might be at his or her worksite, and once the risks are identified, should be aware of what exposures workers might be subject to.
Ask the right questions
Asthma is considered the single most common occupational respiratory disorder in developed countries. It is preventable and controllable with proper diagnosis, treatment, and attention to prevention.
The incidence of occupational asthma varies within individual industries, according to the American College of Occupational and Environmental Medicine (ACOEM), which cites, for example, the detergent industry in which inhalation of a particular enzyme used to produce washing powders has led to the development of respiratory symptoms in approximately 25% of exposed employees. About 5% of people working with laboratory animals or with powdered natural rubber latex gloves have developed occupational asthma. Isocyanates are chemicals that are widely used in many industries, including spray painting, insulation installation, and in manufacturing plastics, rubber, and foam; these chemicals can cause asthma in up to 10% of exposed workers.
Asthma causes periodic reversible attacks of wheezing and shortness of breath, but those symptoms may not appear often, or at all, depending on the patient. Sometimes, the only symptom is a chronic cough, explains Zacharisen. An asthma attack at the workplace can be immediate upon exposure to environmental triggers, or it can be delayed by hours, making diagnosis sometimes difficult.
Asking the right questions when an employee presents with possible asthma symptoms is key to determining whether that employee — and possibly, other employees at the same site — is at risk for developing occupational asthma.
"You want to stop it right away, so you don't have an epidemic," Zacharisen says. Ask the employee:
- What is your work; specifically, what is your exposure? "With occupational asthma," says Zacharisen, "the devil is in the details."
- How you do your job, and do you wear personal protection?
- Do you have other jobs or hobbies that expose you to triggers?
- What were your previous jobs?
- Do you smoke?
- Did you have asthma as a child?
Occupational asthma is treated like regular asthma from a medical standpoint, according to Zacharisen, a fellow of the Milwaukee-based American Academy of Allergy, Asthma and Immunology, who has researched and written on occupational asthma.
But identifying occupational asthma is important, so that the occasional attack doesn't lead to progressive, chronic asthma.
The symptoms of asthma include wheezing, a tight feeling in the chest, coughing, and shortness of breath. While asthma is often associated with wheezing, one of the hallmarks of occupational asthma is a cough, particularly after leaving work or at night.
Sometimes the cough will be only slight, and may not be recognized as a sign of a bigger problem until the person experiences a severe reaction to the triggering substance.
Workers most likely to develop the disease are those with a personal or family history of allergies or asthma and frequent exposure to highly sensitizing substances. But the disease also can develop in persons with no known allergies.
Asthma a common occ-health issue
Zacharisen points out that 15% to 20% of all adult-onset asthma is job-related.
"It's not an uncommon or rare thing," he says. "When it comes to asthma, not only do the symptoms get worse at work, but they can be later onset, so knowing the pattern of asthma is important."
Early on, occupational asthma can be worse at work, and get better after work and on weekends or vacations. But over time, the asthma can become persistent, so the clearly defined times of attacks can become blurred.
"If you go way back in the history, you may be able to capture a work-related pattern," suggests Zacharisen.
A peak flow meter used to take a cross-shift measurement (one measure taken before a shift, and one taken after for comparison) can be a valuable tool in determining an occupational link.
"The primary thing, of course, is to recognize it as asthma," Zacharisen explains. "It can be easily missed, especially when it presents as a chronic cough and no wheezing. So before you can assume it's occupational asthma, you have to identify it as asthma."
When a person's airways overreact to dust, gases, fumes, or other irritants or allergens at the workplace, asthma causes the irritation to progress from airway inflammation to tightening of muscles in the airway, to swelling of the airway, to overproduction of mucus, adding up to difficulty breathing.
Occupational asthma is usually reversible, but permanent lung damage can occur if exposure to the substance that causes the disease continues — thus the urgency in determining what the triggering exposure is, and whether more than one person may be affected.
Asthma linked to allergies, irritants
Some cases of occupational asthma can be traced to an allergy, and others to one-time exposure to irritants or toxins. According to ACOEM, occupational asthma may be caused by one of three mechanisms. These include:
• Direct irritant effects — Irritants that provoke occupational asthma include hydrochloric acid, sulfur dioxide or ammonia. Workers exposed to these substances will frequently begin wheezing and experiencing other asthma symptoms immediately after exposure to the irritant substance. This is an irritant reaction rather than an allergic reaction because the immune system is not involved. Workers who already have asthma or some other respiratory disorder are particularly affected by this type of exposure.
• Allergy (long-term exposure) — Because the body's immune system needs time to develop allergic antibodies or other immune responses to a particular substance, this type of asthma generally develops only after long-term exposure (e.g., months or years) to a work-related substance. Allergic occupational asthma can occur in workers in the plastic, rubber, or resin industries following repeated exposure to small chemical molecules in the air.
• Pharmacologic mechanisms — Inhalation of some substances in aerosol form can directly lead to the accumulation of naturally occurring chemicals in the body, such as histamine or acetylcholine within the lung, that in turn lead to asthma. For example, insecticides used in agricultural work can cause a buildup of acetylcholine, which causes airway muscles to contract, constricting airways. (See table, below.)
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Prevention, treatment of asthma
When a worker develops asthma symptoms due to his or her work environment, the disease can often be reversed when the employee changes jobs, is relocated to a new area within the organization, or accommodations are made to remove exposures from the present job. Workers who suffer from asthma are protected by the Americans with Disability Act if they can still perform their jobs.
At trade and industry worksites at which there is a known risk to workers, steps can be taken to eliminate or at least reduce the number of workers who will be affected.
A change in the manufacturing process or use of modern industrial hygiene techniques, engineering controls, and changed work practices can diminish or eliminate pollutant concentration in the workplace air.
Persons at increased risk due to a family or personal history of allergy or asthma should be aware of the potential problems involved in entering trades with obvious hazards and seek advice. Periodic medical surveillance may allow early identification of affected workers before they have any permanent lung damage, according to ACOEM guidelines.
If a worker begins to have asthma symptoms due to occupational exposure, the disease usually can be reversed and permanent lung damage prevented by changing jobs. Sometimes, a transfer to a location within the same plant is helpful. Because changing jobs may cause a severe financial hardship, such a recommendation should be made only after careful medical evaluation, ACOEM suggests.
Smoking may make the disease more severe. Smoking also increases the chances of getting other complicating lung diseases, such as emphysema, chronic bronchitis, or lung cancer. Workers with occupational asthma who change their job environment and quit smoking are more likely to recover fully than a worker who changes jobs but continues to smoke.
Once the cause is identified, exposure levels should be reduced. For instance, a worker could be moved to another job within the plant. Employers might consider pre-screening potential employees with lung function tests and then continue to test for symptoms after certain periods on the job once the worker has been hired to ensure that he or she has not developed asthma. Work areas should be closely monitored so that exposure to asthma-causing substances is kept at the lowest possible levels.
[For more information, contact:
Michael C. Zacharisen, MD, FAAAAI, associate professor of pediatrics and medicine, Medical College of Wisconsin, Milwaukee. E-mail: [email protected].
American Academy of Allergy, Asthma and Immunology. Address: 555 East Wells Street, Suite 1100, Milwaukee, WI 53202. Phone: (800) 822-2762. Web site: www.aaaai.org.
American College of Occupational and Environmental Medicine. Address: 1114 N. Arlington Heights Rd., Arlington Heights, IL 60004. Phone: (847) 818-1800. Web site: www.acoem.org.]
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