Q. What is asthma?
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A. Before discussing work-related asthma I will briefly
define asthma in general. Asthma is a pulmonary condition characterized
by episodic airflow obstruction that is at least partially reversible.
Obstruction to flow of air occurs in the bronchial tubes within
the lungs. In asthmatics these air passages become inflamed when
affected by various triggers; the inflammation in turn leads to
narrowing ("bronchoconstriction") and resultant respiratory
symptoms.
Asthma symptoms typically manifest as wheezing, chest
tightness, cough and shortness of breath. Wheezing is a high pitched
sound generated by air going through the constricted passages. Shortness
of breath is typically felt with exertion, but in severe cases can
be at rest.
Symptoms are highly variable, from mild and non-limiting,
to disabling and, rarely, fatal. Overall, asthma is a common condition,
affecting in some fashion an estimated 5-10% of the general population
(1, 2).
Q. What is the cause of asthma?
A. At a basic level the cause of asthma is unknown.
Given an individual's predisposition to asthma, a variety of factors
can trigger symptoms (Table 1). Perhaps the most common trigger
in adults is respiratory viral infections, including the common
cold. Less common, but very important, are allergens, substances
that when inhaled can react with the host's antibodies to generate
an "allergic" response. Allergens include various plant
pollens, animal furs, excreta from house mites, proteins in shellfish,
and some metals. Allergens play a major role in many cases of occupational
asthma.
Irritants can also trigger an asthma attack through
a non-allergic mechanism, by directly injuring cells within the
lungs. Other triggers of an asthma attack include climate changes;
exercise, particularly in cold weather; certain medications such
as aspirin; and acid-reflux from the stomach. Although everyone
is subjected to the types of triggers listed in Table 1, only the
5-10% of the population "with asthma" are prone to develop
symptoms when so exposed.
TABLE 1
Some common triggers of symptoms (the "asthma attack")
in patients with asthma
- Respiratory viral infections
- Allergies (e.g., to pollen, animal fur, grain dust, dust mites,
shell fish, diisocyanates, etc.)
- Irritants (smoke, fumes, gases, other pollutants)
- Climate changes
- Exercise (particularly in cold air)
- Sinus infections
- Drug reactions, e.g., aspirin
Stomach acid reflux
Q. What is work-related asthma?
A. There are two basic types of work-related asthma
(3).
1. Occupational asthma
The first type - also called "occupational asthma" is
when the asthma first begins on the job, and is directly related
to the job. Two types of occupational asthma are distinguished by
whether symptoms appear after a latency period, i.e., a period of
time (weeks to years) between the very first exposure and first
development of symptoms.
- With latency period. This is "allergic"
or "immunologic" asthma. With repeated exposure over time
to an "allergen", such as latex in hospital gloves, the
worker becomes "sensitized" to the allergen. The next
exposure after sensitization might lead to symptoms diagnosed as
asthma.
- Without a latency period. This is "non-allergic"
or "non-immunologic" asthma, and is better known as "irritant-induced"
asthma. It is also sometimes called reactive airways dysfunction
syndrome, or RADS. The irritant - typically a chemical fume - inflames
the airways and the worker has symptoms immediately.
In both types of "occupational asthma" symptoms
can range from mild to life-threatening, and leave the worker chronically
disabled. Generally, once a worker is "sensitized" he
or she must no longer be exposed to the allergen, as even tiny amounts
can trigger renewed symptoms.
2. Work-aggravated asthma
The second type of work-related asthma is called "work-aggravated
asthma." This is when pre-existing asthma (such as childhood
or teenage asthma) flares up because of exposure to some allergen
or irritant on the job. Distinction between true "occupational
asthma" and "work-related asthma" is often important
because workers= compensation agencies may handle them differently;
to the individual patient, though, asthma is asthma, and overall
management should be no different.
Q. How common is work-related asthma?
A. It is estimated that one out of 10 adult asthmatics
have a work-related connection, i.e., asthma either caused directly
by their occupation or with pre-existing asthma reactivated by the
job (4).
There are approximately 200 million people in the
U.S. age 18 or older (source: www.census.gov). Given a 5-10% prevalence
rate of asthma, an estimated 1-2 million U.S. adults have asthma
in some way related to work place exposures. (These are prevalence
estimates, and do not mean 1-2 million new cases each year.)
Q. What are some allergens that can cause work-related
asthma?
A. Many people mistakenly equate all asthma with "allergy",
but in fact allergy is only one of the potential triggers of an
asthma reaction (Table 1), including work-related asthma. However,
on the job, allergy is an important cause of asthma. Over 250 substances
have been identified in the workplace that can elicit an antigen-antibody
response and cause occupational asthma. These allergens are typically
categorized as high or low molecular weight compounds (1-3, 5),
but the two groups cannot be distinguished on clinical grounds.
Generally, high molecular weight compounds are mostly proteins from
animals and plants; low molecular weight compounds include numerous
chemicals. Examples of these compounds and the occupations at risk
are given in Table 3.
TABLE 3
Some Antigens Responsible for Work-related Asthma
| High MW antigens |
Occupation |
animal danders
insect scales
egg white proteins
grain dusts
wood dusts
latex health |
animal handlers
entomologists, lab workers
egg producers
farmers, grain store workers
saw mill workers, carpenters
care workers |
| Low MW antigens |
Occupation |
diisocyantes
anhydrides
metallic salts
antibiotics |
workers in printing and painting industry
workers in plastics and drug industries
tool and dye workers
pharmaceutical workers |
Low molecular weight diisocyanates are the leading
causes of occupational asthma (5); they are used in many different
manufacturing processes and their fumes can sensitize the worker.
Occupational asthma can also occur in "clean" environments,
such as in the pharmaceutical industry, where workers may develop
sensitization after repeated exposed to low molecular weight antibiotics;
an example is latex allergy.
Q. How does asthma arise from latex allergy?
A. Latex allergy is an example of occupational asthma
in a clean environment. Latex allergy in health care workers appears
to be increasing in incidence (6-9). Latex, or natural rubber, is
found in many medical products, particularly gloves. Latex allergy
is also seen in patients repeatedly exposed to health care workers=
gloves and other latex-containing products. Allergic reactions range
from contact hives (skin reaction only) to asthma and in some extreme
cases, shock (anaphylaxis). For this reason many hospitals and dental
offices have switched to non-latex gloves and other products. (Note
that latex is not just confined to gloves, but is a component of
numerous other hospital products, including intravenous lines and
ventilation bags.)
Factors predisposing to latex allergy include a history
of other allergies (such as hives or hay fever) and frequent exposure
to latex products. Sensitization to latex doesn't happen after a
single exposure; instead, the worker becomes sensitized to the latex
after repeated exposures, over time. Antibodies gradually build
up until there is sufficient amount to produce an antigen (latex)
- antibody reaction that produces bronchial inflammation and symptoms.
Asthma from latex allergy is thought to arise from repeated inhalation
of airborne latex particles that adhere to the cornstarch used to
powder gloves (10-11). (Cornstarch is placed in gloves to make them
easy to slip on and off.)
Q. What is RADS?
A. RADS, or reactive airways dysfunction syndrome,
was first described in the 1985, is now a well-recognized form of
occupational asthma. It is non-immunologic, i.e., unrelated to allergy.
The exposure is obvious and the symptoms are usually immediate,
although they may gradually worsen over the first 24 hours (see
Table 4). The inhaled irritant (e.g., fumes from a chemical spill),
causes direct irritation of the lining of the bronchial tubes, leading
to asthma symptoms. Symptoms can persist long after exposure, and
indeed become chronic and disabling.
TABLE 4
Reactive Airways Dysfunction Syndrome (RADS) (12-13)
- Exposure to a high concentration of irritant gas,
smoke, fume, or vapor
- Immediate onset of symptoms after single exposure to the irritant,
although symptoms may not peak for several hours
- Documented absence of preceding respiratory complaints
- Symptoms (cough, wheeze and/or dyspnea) persist at least 3 months
- Presence of airflow obstruction on pulmonary function testing
- Presence of non-specific bronchial hyper-responsiveness
- Other pulmonary diseases ruled out
How do I know if I have work-related asthma?
Sometimes it's obvious, sometimes very difficult to
know. While there are a variety of sophisticated tests (including
blood and breathing tests) to help physicians diagnose this condition,
perhaps the most important is the medical history. Medical history
includes information about your medical condition before the job
began and the specific relationship of your symptoms to job activities.
For example, an obvious case of occupational asthma
would be a 30-year-old woman who: a) never smoked; b) never had
asthma or respiratory symptoms before starting a new job; c) after
working on a new job for months to years, develops wheezing, cough
and shortness of breath; d) notes that her symptoms get better away
from work (weekends, or vacation), and flare again back at work;
d) works with a specific chemical that is known to cause occupational
asthma (e.g., toluene diisocyante); e) is diagnosed with asthma
by breathing tests.
A much more difficult case would be a 35-year-old
man who: a) currently smokes, and has smoked a pack a day for 15
years; b) has a history of episodes of "bronchitis" before
taking a new job in a factory at age 34; c) develops a respiratory
infection with fever, and then notes trouble breathing; d) gets
more short of breath when he returns to work after recovering from
the infection. This patient may in fact have smoking-related chronic
obstructive disease exacerbated by infection, and not work-related
asthma. Only by testing and further history could a physician make
a reasonable determination.
Q. I might have work-related asthma. What should
I do?
A. There is one cardinal rule that every worker must
remember: Your health comes first. If asthma occurs on the job,
and the job doesn't change, the asthma won=t get better. The worker
must remove himself or herself from the environment. If this is
you, I recommend seeing an asthma specialist as soon as possible.
Be prepared to give a detailed history of your symptoms and their
relationship to the job. Ideally, this information should be written
down and handed to the physician. If there is a strong suspicion
based on your history, your doctor can write a note asking for a
position change within the company (if possible), or that you stay
off work while tests are performed. Again, the diagnosis may not
be obvious, and it may take time to make a reasonable assessment.
Q. Can I get worker's compensation for work-related
asthma?
A. Every state runs a worker's compensation agency,
and work-related asthma is certainly compensable. The worker will
have to satisfy some stringent medical criteria. Usually, an exam
will be ordered with a state physician (i.e., someone other than
your treating physician).
More often than not, the employer will dispute the
diagnosis, and may ask for yet another exam with a physician they
designate. Conflicting reports are common, making it difficult for
a workers' compensation agency to decide on a case's merits. In
truth, these agencies were originally set up to compensate "injured"
workers, and this meant broken limbs and other external injuries.
It is much more difficult to adjudicate a medical diagnosis like
asthma: a) where the cause is often not obvious; b) in which symptoms
can be extremely variable, and c) that is also very common in the
general population. Given the potential for disagreement, it is
not surprising that the decision of the compensation agency is often
appealed.
If you think you have work-related asthma, by all
means get it checked out, but don't expect a speedy resolution.
And remember: your health comes first.
Q. Does cigarette smoking predispose to occupational
asthma? If I smoke will it be more difficult to prove I have occupational
asthma? Will my symptoms likely improve if I quit smoking?
A. Yes. Yes. Yes. No point in belaboring the obvious.
Q. I have asthma and am taking several medications
that control my condition. Should I still avoid a dusty environment?
A. By all means, yes. The fact that you need asthma
medications to control your condition is warning flag; any dusty
environment could trigger your symptoms. Note that the offending
work environment could be outdoors, e.g., work around diesel truck
fumes or dust in an outdoor saw mill. Or, it could be indoors in
a non-factory setting, such as a smoke-filled bar. Evaluate your
potential job environment carefully if you have asthma.
Q. Is treatment of occupational asthma different from
regular asthma?
A. Treatment of work-related asthma is no different
from asthma unrelated to the job, with one important exception:
advice about continued working. If a worker has developed an allergic
reaction to something in the environment (i.e., is "sensitized"
to it), he or she must leave that environment. The quicker they
remove themselves, the better the outcome; studies have shown that
continued exposure to the sensitizing agent is associated with further
deterioration of lung function (14-15). Masks and other devices
to minimize the exposure are of no help, and should not be relied
on. Even tiny amounts of allergen can trigger a reaction if the
worker is sensitized to it.
On the other hand, if the asthma was due to a one-time irritant
exposure, and the irritant is removed completely, than there should
be no contraindication to continued working in that environment.
Sometimes, though, other pollutants in the environment may bother
the worker more than before, even though the specific agent causing
the asthma is removed.
Although stopping exposure generally results in clinical improvement,
this is not invariable, particularly if the worker is a smoker or
has co-existing sinusitis (which can also trigger asthma exacerbations).
Even without these other conditions, the patient may continue to
manifest asthma symptoms and require medication for months or years
after leaving the job (15).
Q. I hear what you say, and I have asthma symptoms
at work, but there is no way I can quit my job. What can I take
for it?
A. If that is your situation, then you must work with
a physician to find the best strategy. Generally, this is two-fold.
First, some type of airway protection (masks, changes in ventilation
at the work site, etc.) that your doctor may be able to recommend
to your employer. Second, there are numerous asthma medications
on the market, and finding the proper regimen is often a matter
of trial and error.
If you continually function on two (out of 6) cylinders
day in and day out, you could end up a "respiratory cripple"
With attention to airway protection, and proper medication, your
physician may be able to get you up to 4 or 5 cylinders, and still
keep you on the job.
