Tips to Remember:
Occupational asthma is generally defined as a
lung disorder caused by inhaling fumes, gases, dust or other potentially
harmful substances while "on the job." With occupational asthma, symptoms of
asthma may develop for the first time in a previously healthy worker, or
childhood asthma that had previously cleared may recur due to this exposure.
In another form of work-related asthma, pre-existing asthma may be
aggravated by exposures within the work place.
Symptoms of asthma include wheezing,
shortness of breath, chest tightness, difficulty exercising and cough. Other
associated symptoms may include runny nose, nasal congestion and eye
irritation. The cause may be allergic or non-allergic in nature, and the
disease may last for a lengthy period in some workers, even if they are no
longer exposed to the agents that caused their symptoms. Commonly, symptoms
worsen through the work week, improve on the weekend and recur when the
worker returns to the job. Less frequently, an accident at work involving a
high exposure to irritating fumes or dusts may cause asthma.
In many cases, a previous personal or family
history of allergies will make a person more likely to develop occupational
asthma. However, many individuals who have no such history still will
develop this disease if exposed to conditions that trigger it. Workers who
smoke are at greater risk for developing asthma following some occupational
exposures. The length of occupational exposure that triggers asthma varies,
and can range from months to years before symptoms occur. An accidental
irritant exposure can cause asthma within 24 hours.
Many workers with persistent asthma symptoms
caused by substances in the workplace are incorrectly diagnosed as having
bronchitis. If occupational asthma is not correctly diagnosed early, and the
worker protected or removed from the exposure, permanent lung changes may
occur and asthma symptoms may persist even without exposure.
Occupational asthma has become the most prevalent work-related lung disease
in developed countries. However, the exact proportion of newly diagnosed
cases of asthma in adults due to occupational exposure is unknown. Up to 15%
of asthma cases in the United States may have job-related factors.
The incidence of occupational asthma varies
within individual industries. For example, in the detergent industry,
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
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, which is
found in the petroleum or chemical industries. 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, since it does not
involve the immune system. Workers who already have asthma or some other
respiratory disorder are particularly affected by this type of exposure.
- Allergy (long-term exposure)-Allergies play a role in many
cases of occupational asthma. This type of asthma generally develops only
after long-term exposure (e.g., months or years) to a work-related
substance. This is because the body's immune system needs time to develop
allergic antibodies or other immune responses to a particular substance.
For example, workers in the washing powder industry may develop an allergy
to the enzymes of the bacteria Bacillus Subtilis, and food
processing workers may develop an allergy and occupational asthma symptoms
from exposure to castor beans, green coffee beans and papain. Allergic
occupational asthma can occur in workers in the plastic, rubber or resin
industries following repeated exposure to small chemical molecules in the
air. Veterinarians, fishermen and animal handlers in laboratories can
develop allergic reactions to animal proteins, and health care workers can
develop asthma from breathing in powdered proteins from latex gloves or
from mixing powdered medications.
- 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, which in turn lead to asthma. For example, insecticides,
used in agricultural work, can cause a buildup of acetylcholine, which
causes airway muscles to contract, thereby constricting airways.
See the accompanying table for common
occupational substances that may cause asthma to develop or trigger
temporary aggravation of asthma that is already present.
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.
Individuals with occupational asthma should
see their allergist/immunologist for an evaluation. In some cases,
pre-treatment with specific medications to counteract the effects of
workplace substances may be helpful. In other situations, complete avoidance
may be necessary.
|Common substances that
cause occupational asthma
||Workers at risk
||Shellac and lacquer handlers
||Users of plastics, epoxy resins
||Animal handlers, veterinarians
||Janitors, cleaning staff
||Pharmaceutical workers, health care professionals
||Detergent workers, pharmaceutical workers, bakers
||Carpet makers, pharmaceutical workers
||Spray painters, insulation installers, plastics, foam
and rubber industry workers
||Health care professionals
||Seafood processing workers
||Forest workers, carpenters, cabinetmakers
Your allergist/immunologist can provide
you with more information on occupational asthma.
Tips to Remember are created by the
Public Education Committee of the American Academy of Allergy, Asthma and
Immunology. This brochure was updated in 2003.
The content of this brochure is for
informational purposes only. It is not intended to replace evaluation by a
physician. If you have questions or medical concerns, please contact your
American Academy of Allergy,
Asthma and Immunology
555 East Wells Street
Milwaukee, WI 53202-3823
Physician Referral and
AAAAI Web site