Vol. 15 •Issue 5 • Page 18
Allergy and Asthma
Showing Asthma Who’s Boss
Work-related respiratory problems affect thousands of U.S. workers.
From the time she was 4 years old, Carol McConnell, DVM, had big dreams of becoming a veterinarian. After eight years of veterinary school and three years in practice, however, her career came to a screeching halt.
“Some people think it’s a joke when I tell them that I’m a veterinarian who can’t practice because I’m allergic to animals,” said Dr. McConnell, 42, of Brea, Calif.
Although she didn’t have asthma before she began practicing veterinary medicine, Dr. McConnell developed it due to long-term exposure to animals. It wasn’t until a friend heard her wheezing from across the room that she admitted the severity of her problem.
“I was in denial because this was my chosen profession and something I loved, but I wasn’t healthy,” Dr. McConnell said. “I had to make a choice, and that was to remove myself from the environment.”
Dr. McConnell isn’t alone. Occupational factors may account for up to 15 percent of asthma cases in the U.S.
About 11 million workers are exposed to at least one of more than 300 agents that can cause an immunologic response similar to an allergic reaction, according to the Occupational Safety and Health Administration. Some of the most common allergens include plant and animal proteins, insects, and molds.
“You need to suspect the possibility of occupational asthma in anyone who develops symptoms while they’re working,” said Susan Tarlo, MB, BS, FRCP, a professor in the departments of medicine and public health sciences at the University of Toronto. “You have to rule out the coincidental onset of asthma and confirm an objective association with work in order to diagnose occupational asthma.”
Skin tests with animal or food extracts can help determine the exposure that has caused an allergic response. If skin tests aren’t helpful or can’t be performed, a physician can compare changes in pulmonary function during periods at work and away from work. If needed, the physician can perform a challenge test by deliberately exposing someone to an agent in the laboratory and measuring pulmonary function changes.
So, who’s at risk for occupational asthma? Let’s take a look at some professions that may leave employees breathless.
Food and agriculture
The butcher and baker may have more things to worry about these days than playing with the candlestick maker.
Exposure to carmine, a natural coloring agent for food and cosmetics, has been shown to trigger asthma in butchers.1 Usually, carmine is used as a dye for sausages. In butchers presenting with occupational asthma, skin tests and challenge tests have returned positive for carmine. It’s now considered to be an etiologic agent for butcher’s asthma.
Inhalation of garlic dust, spices, and aromatic herbs used to treat meats also can trigger respiratory problems in butchers.
Bakers, on the other hand, can be allergic to wheat, rye, barley, milk, or egg protein, Dr. Tarlo said. A study out of London found that up to 9 percent of bakers, 4 percent of bakery managers, and 3 percent of bakery assistants may have asthma symptoms caused by working in supermarket bakeries.2
Researchers examined 239 employees from 20 supermarket bakeries. They collected data from questionnaires about respiratory problems such as chest tightness, difficulty breathing, sneezing, and running or itchiness of the nose and eyes.
After using skin testing to identify allergies associated with baking, the researchers determined 15 percent of the employees reported work-related asthma symptoms. Twenty-six percent had eye or nose problems related to the work environment.
Down on the farm
Asthma also has been studied in farmers. One group of reports looked at chronic cough in dairy and poultry farming.3
Among 265 dairy farmers and 149 controls studied, asthma prevalence didn’t differ significantly. However, the dairy farmers more commonly reported chronic cough, phlegm, and bronchitis than the controls.4
In a study of poultry farmers, researchers evaluated 343 farmers for acute and chronic respiratory symptoms and lung function changes. Poultry farmers exposed to their environment for more than 10 years displayed higher incidences of chronic cough than farmers with less time in the field.5 Another study of 57 women who process poultry had similar results with the highest prevalence for chronic cough (49.1 percent), dyspnea (43.9 percent), and rhinitis (38.6 percent).6
Farmers also can develop asthma from exposure to cow dander and plants, Dr. Tarlo added.
Industry and construction
In industrial and construction workers, chemical exposure can cause an immune response. For example, some people working with isocyanates, which are the raw materials in polyurethane products, can form IgE antibodies against them, thus developing asthma when exposed.
Isocyanates are considered to be one of the most common causes of occupational asthma, affecting chemical workers, auto workers, and spray painters, among others, said David Bernstein, MD, FAAAAI, professor of medicine in the immunology and allergy division at the University of Cincinnati.
“Isocyanates have received a lot of attention over the years,” Dr. Bernstein said. “In early studies, it was shown that up to 5 percent of workers regularly exposed to isocyanates can develop occupational asthma.”
Acid anhydride compounds, chemicals used in the production of resins, adhesives, and fire retardants, are a close second. The National Institute of Occupational Safety and Health estimates 140,000 U.S. workers are exposed to acid anhydride compounds. NIOSH indicates up to 20 percent of these workers may have allergic asthma.
In construction workers, dust from cement production contains crystalline silica (also found in the granite, glass, and mining industries). Inhalation of this dust is shown to cause chronic cough and decreased lung function.7 Chronic cough also appeared in workers involved with surface and underground construction due to exposures to dust, oil mist, and nitrogen dioxide.3
Industrial and construction workers can be at higher risk for reactive airways dysfunction syndrome, a form of occupational asthma induced by exposure to an irritant.
“If there’s a fire or a spill of acid at work with exposure to a lot of irritant gas or smoke, that can cause airway inflammation and induce an asthma syndrome that can persist for weeks, months, or years,” Dr. Tarlo said.
In high-risk environments, workers exposed to these chemicals and materials should be examined annually for potential development of occupational asthma. Surveillance usually should be more frequent during the first two years of employment.
“Peak flow meters are the most cost-effective way to help diagnose occupational asthma,” said Lary Ciesemier, DO, FAAAAI, an osteopathic allergist and immunologist at Kirksville Allergy and Asthma in Missouri.
Peak flow studies should be performed before the work shift begins, during the shift, and at the end of the day. “Typically, people with occupational asthma will feel great on the weekend, but on Monday they’ll start having symptoms, and as the week goes on you’ll see a trend as to how their peak flow gradually decreases,” Dr. Ciesemier said.
Working with asthma
Workers diagnosed with occupational asthma should avoid exposure to the offending allergen. In the best scenario, if someone works for a big company, they may be able to move to a different area to avoid exposure. Often, however, a diagnosis of occupational asthma entails changing companies or being retrained for other work.
“I went back to school to get an MBA, which enabled me to work in my profession but from the business and management side of it,” Dr. McConnell said. “But I do miss working with the animals tremendously.” She’s the manager of veterinary education for Veterinary Pet Insurance, a company that provides medical insurance for animals.
“Exposure control is the most important step,” Dr. Bernstein said. “The best thing is to reassign or find a new job for the patient where they have no exposure to the causative agent and can work safely.”
Some studies have looked at allergen vaccines or allergy immunotherapy to desensitize workers, which would allow them to tolerate exposure in the work environment, but more studies need to be done, Dr. Bernstein said. For example, there are effective cat allergen vaccines for asthma triggered by domestic cat exposure, and these could be applied to the treatment of veterinary workers.
In the meantime, educating workers is crucial. If workers have symptoms at work such as chest tightness, wheeze, or chronic cough, they should be aware of the risks of developing asthma. There have been some moves to educate workers more through unions in occupations where asthma is a risk.
“If workers can go to their doctors and let them know what their risk is, it’s helpful because there are hundreds of different things that can cause occupational asthma, and not every doctor will know them all,” Dr. Tarlo said.
Debra Yemenijian is associate editor of ADVANCE. She can be reached at [email protected].
For a list of references, please call Debra Yemenijian at (610) 278-1400, ext. 1153, or visit www.advanceweb.com/respmanager.