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Epidemiologic Notes and Reports Asthma-Like Illness among
Crab-Processing Workers -- Alaska
At the request of the Alaska Department of Labor, the National
Institute for Occupational Safety and Health (NIOSH) is
investigating
the incidence of newly developed asthma-like symptoms (marked
dyspnea
and wheezing) among crab-processing workers in the Dutch Harbor
area
on the Aleutian island of Unalaska.
Data were collected between March 13 and May 13, 1981, when 46
crab-processing workers with marked dyspnea and wheezing visited
the
Iliuliuk Family Health Service Clinic, the sole provider of medical
care in Dutch Harbor. Of the 46, 10 were from neighboring islands
or
offshore processing ships; 3 had a history of having had similar
symptoms before.
The other 33 workers (mean age 23 years, range 18-30), who were
employed in 4 seafood-processing plants in the immediate Dutch
Harbor
area, gave no history of previously experiencing such symptoms.
The
combined employment of these 4 plants was approximately 825
crab-processing workers, giving an approximate rate for development
of
dyspnea with wheeze ("crab asthma") of 2 cases/100 workers/month
for
the crab-processing season. This is at least 80 times the monthly
incidence of new cases of asthma and 8 times the incidence of new
cases of bronchitis with wheeze reported for groups of Americans of
similar age (1).
Many workers reported that symptoms began with an upper
respiratory infection that resolved except for a residual,
nocturnal
cough that became progressively stronger until it severely
disturbed
sleep. The cough worsened on evenings after the processors had
worked
near high concentrations of steam from crab-cooking pots and
improved
when the workers had been away from the crab-processing area for 1
or
more days. After experiencing the severe cough at night for 1-4
weeks, the affected individuals became markedly short of breath and
sought medical attention.
Several conditions may predispose crab-processing workers to
have
respiratory infections: the Aleutian weather; the generally cold,
damp
working conditions; the long working hours (up to 10-16 hours/day
for
7 days each week); and the close living quarters (2-5
persons/room).
Some workers may also have been suffering from acute asthmatic
bronchitis. However, it is unlikely that the high incidence of
dyspnea with wheeze was due solely to a high rate of respiratory
infection, since few persons other than crab processors were seen
at
the clinic with asthma-like symptoms, and few were seen during the
salmon season when crab was not being processed. Furthermore, the
reported worsening of symptoms following exposure to concentrations
of
steam from the crab-cooking vats suggests that symptoms were
secondary
to an asthma-like reaction to crab constituents. The common
premonitory symptom of severe cough at night is especially
interesting
since cough may be the sole presenting symptom of asthma.
Reported by the Hazard Evaluations and Technical Assistance Br, Div
of
Surveillance, Hazard Evaluations, and Field Studies, NIOSH, CDC. Editorial Note
Editorial Note: Several studies, conducted with small groups of
workers who reported respiratory symptoms when processing Alaskan
crab
(2), have shown that some workers have positive scratch skin tests,
and/or positive radioallergosorbent tests (RAST), and/or positive
serum precipitin tests to crab constituents. Several workers have
also experienced significant decreases in pulmonary function after
bronchial challenge to nebulized juice from crab-cooking vats.
Similar asthma-like reactions among oyster shuckers in Japan
were
thought to be secondary to an allergic reaction to sea squirts on
the
clams (3), and in Britain, asthma-like reactions among prawn
processors were thought to be secondary to an allergic reaction to
prawn constituents (4). The British workers began having symptoms
about 6 weeks after they stopped hand-peeling the prawns and began
using air jets to blow meat from the tail. The air jets probably
increased the number of airborne prawn particles in the processing
area. A British health survey conducted 8 months after the air
jets
were introduced showed that 18 of 50 workers complained of
asthma-like
symptoms; 20 other workers with similar respiratory symptoms had
reportedly left the factory since the air jets were introduced.
Positive RAST to prawn constituents demonstrated the presence of
prawn-specific IGE antibodies for 50% of the symptomatic British
workers. After the concentration of airborne meat fragments was
reduced by a factor of 10 by substituting water jets for air jets,
only 3 workers continued to have symptoms.
The crab-processing industry employs approximately 4,000-5,000
people in the Alaska area during the king crab season
(September-December), and half that number during the Tanner and
Opilio crab season (March-June). Although further investigation is
needed to confirm the cause of the respiratory symptoms occurring
among crab-processing workers, modifications to the current
processing
methods, work practices, and environmental controls may be as
successful in reducing the incidence of respiratory symptoms among
crab-processing workers as were the modifications made in the
British
prawn-processing plant.
References
Dodge R, Burrows B. The prevalence and incidence of asthma and
asthma-like symptoms in a general population sample. Am Rev
Respir Dis 1980;122:567-75.
Orford R, Wilson J. Epidemiological and immunological studies
in
workers exposed to king crab. University of Washington School
of
Public Health, 1976.
Nakashima T. Studies on bronchial asthma observed in cultured
oyster workers. Hiroshima J Med Sci 1969;18:141-84.
Gaddie J, Legge J, Friend J, Reid T. Pulmonary
hypersensitivity
in prawn workers. Lancet 1980;2:1350-3.
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