Approximately 9 out of 10 patients diagnosed with mesothelioma have a history of exposure to asbestos.
What is asbestos?
Asbestos is a natural rock mineral, mined or quarried and used commercially since the 18th century. It was discovered for its excellent fire retardant and insulation properties. It consists of strong pliable fibres that can be separated into thread like strands and spun or woven to produce several types of bonded material for many uses, predominantly in the building and construction industries between 1900’s – mid 1970’s.
How mesothelioma develops
As a rule most fibres and irritants that are inhaled are cleared through the natural body’s defence mechanism of coughing which forces them back up to the throat in a layer of mucus, the mucus is then either spat out, or swallowed, and makes it way out of the body naturally.
The theory is though – is that some inhaled asbestos fibres (particularly smaller strands) are not cleared from the lungs and have the ability to translocate to the lungs into other tissues such the alveolar sacs the tiny pockets where the fibres may remain indefinitely. Asbestos fibres that enter the alveoli can undergo a series of fates. I.e. some of the fibres may penetrate the alveolar wall and enter into the interstitial fluid thus posing of risk of them being cleared by the natural process of the lymphatic system and deposited in the perihilar lymph nodes. Other fibres particularly amphiboles (blue and brown asbestos fibres) may penetrate the lung parenchyma and enter the pleural or peritoneal space.
Amphibole fibres are considered to be more of a health hazard as they are less degradable than other asbestos fibres such as chrysotile fibres (white asbestos) and can stay in the lungs for much longer. Studies have concluded that smaller quantities of chrysotile fibres have been found in lung tissue than amphibole fibres and amphibole fibres cannot easily be degraded by macrophages (white blood cells that engulf and destroy foreign material). However – fibre size is believed to play a crucial role in determining the risk of a particular asbestos-related disease, and the health safety issues surrounding white asbestos still poses as a threat as medical evidence proves its significance in the development of mesothelioma.
Biopsy below shows a strand of asbestos fibre in a human lung.
Asbestos particles are capable of stimulating chronic inflammatory responses in the pleura, inducing an array of cellular responses, i.e. interfering with mesothelial cells, damaging DNA that controls cell division, thus promoting malignant cell division – resulting in asbestos-induced tumours – mesothelioma.
