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Shellfish Processing Industry in Eastern Canada

Shellfish species Processed in Eastern Canada

OCCUPATIONAL ASTHMA AND ALLERGIES

Allergy

An allergy is an “overreaction” or “hypersensitivity” by your body’s immune system to substances to which you are sensitized.  These substances are called allergens and may include pollens, dust particles, mold, food, latex rubber, insect venom, or certain medications.  A person who has an allergy will develop antibodies to the specific allergens. Each time this person comes in contact with the allergen after the first contact, certain cells in the body release chemical substances called mediators.  These mediators are the substances which cause the symptoms.

Symptoms of allergies include:

• redness
• swelling
• itching
• increased mucous production
• sneezing
• coughing
• pinkeye (conjunctivitis)
• shortness of breath
• stomach cramps
• rash
• hives

Asthma is a respiratory condition that results in breathing difficulties.  These occur when the airways constrict, become inflamed and/or swollen and fill with mucus (figure 1).

Asthma affects 8.4% of Canadians aged 12 and over according to the 2003 Health Status Indicators. The prevalence of asthma in the Canadian population has increased over the last number of years from 6.5% in 1994-1995 to 8.4% in 2003.  Women (9.6%) have a higher prevalence than men (7.1%).  The Eastern Canadian provinces have some of the highest recorded percentages, all above the national average."

Normal airways - Airways of a person without asthma	Airways of a person with asthma - redness and swelling (inflammation)	Airways of a person with asthma - tightened muscles (bronchospasm)
In people without asthma, the muscles around the airways are relaxed, allowing the airways to stay open. There is no swelling or mucus inside the airways.	In people with asthma, the inside of the airways can get red, swollen, and filled with mucus.	In people with asthma, the muscles around the airways can spasm and squeeze tighter. This leaves less room for air to pass through.

Occupational Asthma & Allergy

Asthma and allergy are considered to be occupational, or work-related, when there is an association between symptoms and work.  Occupational asthma is the only type of asthma that is preventable.  Occupational asthma is caused by inhalation of airborne dusts, gases, fumes, and vapours that workers are exposed to in the workplace.  Chemicals and organic dusts have also been implicated in the onset of rhinitis and other hypersensitivity lung disorders as well as occupational asthma.  Of all adult onset asthma, 10-15% is occupational.

Limiting exposures to sensitizers in the workplace (i.e. improving ventilation, wearing protective equipment, changing work procedures) and education are the keys to prevention.  Symptoms can sometimes disappear with early diagnosis and removal from the exposure, but many workers will not be diagnosed early enough and may fail to recover even when completely removed from the exposure.

Shellfish Occupational Asthma & Allergy

Occupational asthma due to shellfish is a specific type of work-related asthma associated with processing shellfish species.  Shellfish species include crustaceans (lobster, crab, shrimp), mollusks (clam, oyster, scallop, squid, mussel, whelk), and echinoderms (sea urchins, sea cucumber).

Shellfish occupational asthma is caused by exposure to the airborne materials that are generated during the processing of shellfish.  Processing can include cooking, steaming, washing, sawing, crushing, scrubbing, or scraping the shellfish.  During these activities, some shellfish proteins can become airborne and enter the lungs.  Some workers respond adversely to these proteins by producing antibodies resulting in sensitization which can develop after several weeks or even years of exposure.  These antibodies enter the blood stream where they react with new shellfish allergens on subsequent exposures.  This can result in the symptoms we associate with shellfish allergies (rash, runny nose, red eyes) and shellfish asthma (tightness of chest, wheezing, difficulty breathing).

General Shellfish Respiratory Risks

Crab processing is also associated with the use of chemicals that may cause respiratory symptoms in processing workers.  These chemicals include sulphites, which are applied to raw crab products destined for the Japanese market, and some cleaning chemicals.  More research is needed on the extent and context for the use of these chemicals in snow crab processing and their potential role in causing respiratory symptoms in processing workers.

A third possible contributor to respiratory problems among snow crab processing workers that has not been studied extensively is exposure to endotoxins. Endotoxins are part of the outer membrane of the cell wall of Gram-negative bacteria which live on crab.  They can produce symptoms (e.g. cough, flu-like symptoms, fever, chills).  A fourth risk is exposure to fumes from diesel and propane forklifts

Crab Asthma

Occupational asthma to snow crab is a specific type of asthma experienced by some crab processing workers that is caused by their work.  Some other names you may hear to describe occupational asthma to crab include:

• crab lung
• the lung
• crab asthma

Snow crab asthma is mediated through an allergic mechanism involving the production of specific IgE antibodies to crab meat and cooking water.  Research on other occupational allergens suggests that exposure to crab allergens is a factor in the development of the disease – the higher the exposure, the greater the risk of sensitization.

Once workers have developed occupational asthma to snow crab, the risk of long term breathing problems can persist after they are no longer exposed to crab.  This risk can increase with the length of time they remained exposed after developing the occupational disease. 

Documents

Frequently Asked Questions about Crab Asthma (PDF)

Occupational Health in Seafood Processing: Risks and Resources (PDF)

Ventilation Publications

American Conference of Governmental Industrial Hygienists: Ventilation Manual

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