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Asbestos: Health Effects

The Nature of Asbestos Fibres

Asbestos fibres are chemically inert but never-the-less can result in very serious illness by exposure through inhalation.  One of the keys to the destructive element of asbestos fibres is the size and shape of the fibres as they are released into the air.  They are less than 1 micron in diameter but have a length of between 5 - 30 microns.  These are inhaled deeply into the lung's alveolar region.  Our lungs are designed to remove particulate with cilia and mucous.  But in this deeper region it is past the area where the cilia and mucous do their work.  The body's last resort is to engulf the intruders with something called macrophages whose task is to surround, encapsulate and digest these particles with reactive chemicals and digestive enzymes.  In the photo below you can see how the macrophages have tried to surround the asbestos "spears" but the ends of the fibre remain exposed on each end of the macrophage.


 Photograph taken at Darrell Jackson’s laboratory, University of Montana


From Asbestos to Cancer:  Theory of Development

The fibres are resistant to the attack of the macrophages because asbestos fibres are inorganic and thus cannot be digested.  With the ends of the asbestos fibre exposed on each end of the macrophage, the chemicals and enzymes tend to leak out into the surrounding lung tissue.  Even though the exact mechanism which leads to lung cancer from the presence of asbestos fibres, it is believed that the chronic inflammation from the byproducts of the leaking macrophage stimulates tissue repair eventually resulting in the formation of a cancerous growth. 

The Three Main Killers

Lung Cancer

In the Alberta Asbestos Abatement Manual, July 2009, pages 18 - 19 it states, "Lung cancer [from asbestos exposure] takes approximately 15 to 25 years to develop, depending on the frequency and duration of exposure.  Exposure to asbestos fibres for 4 to 6 months may be sufficient to cause lung cancer.  The combination of smoking and occupational asbestos exposure is extremely hazardous."  A chart shown on page 19 of the manual shows the results of a study of asbestos-related disease, produced by Dr. Irving J. Selikoff delineating the increased risk of lung cancer from exposure to asbestos and smoking combined.  A person who smokes and is exposed to asbestos has a 70% increased chance of developing lung cancer






 In the Alberta Asbestos Abatement Manual, July 2009, page 18 it states, "Asbestosis is a condition associated with exposure to high concentrations of airborne asbestos.  It is an irreversible, fatal disease.  The lungs build up scar tissue around the fibres in an attempt tp remove them.  This causes lung tissues to stiffen and leads to symptoms of coughing, difficulty in breathing, weight loss and eventual death.  The disease is similar to silicosis and 'black lung', disease associated with work in mines".

"Once established, asbestosis is an untreatable condition.  While elimination of further exposure to asbestos will not stop or reverse the disease, it will help to slow down the rate at which the disease progresses.  Early symptoms of the disease - shortness of breath, often accompanied by a dry cough - usually develop 10 to 20 years after initial exposure"