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What is asbestos? -

Asbestos is a naturally occurring mineral fiber that occurs in rock and soil. Pictured is tremolite, one variety of the mineral.

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Types of asbestos -

There are six main types of asbestos: crocidolite, tremolite, amosite, anthophyllite, chrysotile, and actinolite. These six types fall into two categories: amphibole and serpentine. 

Image: United States Geological Survey

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Asbestos cancer hazard -

All six asbestos mineral types are known to be human carcinogens. In other words, asbestos can cause cancer. 

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Why is asbestos dangerous? -

Inhalation or ingestion of asbestos fibers can lead to several dangerous lung conditions, including mesothelioma, asbestosis, and lung cancer.

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Asbestos can cause various types of cancer -

Over time, if asbestos exposure is repeated, fibers build up and can damage the lung tissue and lining. 

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A hazardous material -

The first medical article on the hazards of asbestos dust appeared in the British Medical Journal in 1924.

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Dangers not fully understood -

In response, the British government introduced regulations to control dangerous dust emissions in UK asbestos factories. But the danger of working with asbestos was still not fully understood. The sign in this image urges workers to wear asbestos gloves. 

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Asbestos dangers reassessed -

It was only with the discovery in the 1960s that mesothelioma was an asbestos-related disease and that workers other than those employed in the dustiest parts of asbestos factories were at risk, were the nature and scale of the hazard reassessed. But by then it was too late for thousands of employees, many of whom had handled the material over decades.  

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Use of asbestos -

Use of asbestos dates back millennia. Archeologists uncovered asbestos fibers in debris dating back to the Stone Age, some 750,000 years ago. It's known that embalmed bodies of Egyptian pharaohs were wrapped in asbestos cloth to protect the bodies from deterioration. In Finland, earthenware pots and utensils dating back to 2500 BCE were found to be strengthened by anthophyllite (pictured). And the Romans used asbestos' long hair-like fibers as wicks in lamps and candles. 

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"Sickness of the lungs" -

But even in antiquity, the harmful effects of asbestos had been identified. The Greek geographer Strabo noted a "sickness of the lungs" in slaves who wove asbestos into cloth. And it was the Roman author Pliny the Elder (pictured) who wrote of the "disease of slaves" when referencing miners forced to extract the mineral from deep underground. 

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Heat-resistant qualities -

Asbestos' resistance to heat was known to the ancient Egyptians. By the Middle Ages it was being used for a number of practical purposes. King Charlemagne, for example, is said to have had a tablecloth made of asbestos to prevent it from burning during the accidental fires that frequently occurred during feasts and celebrations. 

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Asbestos use in combat -

During the First Crusade, knights used a catapult, called a trebuchet, to hurl flaming bags of pitch and tar wrapped in fire-resistant asbestos bags over city walls during their sieges.

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"Fabric which would not burn" -

In 1280, Marco Polo described clothing worn by Mongolians as woven from a "fabric which would not burn." Curiously, he later visited an asbestos mine in China. 

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Mining on an industrial scale -

Chrysotile asbestos was being mined in Russia as early as the 17th century. Mining on an industrial scale, however, only began in the mid-19th century. Pictured is an engraving depicting the United Asbestos Co's Harefield Mills, near London. 

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Asbestos uses multiply -

By the end of the 19th century, applications of asbestos had multiplied considerably. Here, a textile factory in Normandy, France, uses asbestos in spinning and manufacturing yarn.   

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Asbestos products -

This American advertisement for asbestos roofing publicizes the product as "a substantial and reliable material, which can be safely used." 

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A replacement for glass -

During the Second World War, asbestos was used as a replacement for glass to lessen the risk of injury from flying shards during enemy bombing raids. Here, glass panels on the roof of Waterloo Station in London are replaced by asbestos sheets. 

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Asbestos fire suit -

Asbestos' heat-resistant qualities made it an ideal material for use in heavy industry—steel manufacturing, for example—where protective fire-proof suits were required. 

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Multiuse material -

Throughout the 20th century, asbestos could be found in a huge variety of industrial products, anything from table mats (pictured) to flat and corrugated sheeting, cement pipes, insulation, floor tiles, adhesives, roofing, automobile brake pads, textiles, and textured paints.  

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Mining operations -

Still ignorant of the health hazards associated with asbestos, companies around the world were establishing mining operations to extract the valuable mineral. One of the largest of these was the Thetford asbestos mines in Canada. 

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"Asbestos Capital of the World" -

The area around the city of Thetford Mines was once one of the most productive mining areas for asbestos in the world. Located at Saint-Joseph-de-Coleraine, Québec, seven mines employed 4,000 people and exported asbestos to areas such as southeast Asia, the Middle East, and South and Central America. In 2012, Canada shut down all of its asbestos mines. 

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What is asbestosis? -

As previously mentioned, the first diagnosis of asbestosis was made in the UK in 1924. It was during the mid-1930s that physicians began to notice that some patients who had asbestosis—fibrotic scarring of lungs resulting from prolonged exposure to asbestos dust—were also victims of lung cancer. This post-mortem image of a whole lung section clearly shows the effects of inhalation of asbestos fibers and subsequent mesothelioma.  

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Mesothelioma research -

The term mesothelioma was first used in medical literature in 1931. It's association with asbestos was first noted sometime in the 1940s.

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Millions at risk -

Asbestosis and mesothelioma both have long incubation periods. It can be many years from initial exposure before the diseases manifest themselves. The US-based Agency for Toxic Substances & Disease Registry detailed exposure between 1940 and 1979. Its records showed about 27 million workers were exposed to aerosolized asbestos products. According to the agency, about 1.3 million construction and industry workers in America remain at risk.

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What is mesothelioma? -

Mesothelioma is a rare cancer that affects the lining of the lungs (pleura) and the lining surrounding the lower digestive tract (peritoneum). It is almost exclusively related to asbestos exposure and by the time it's diagnosed, it is almost always fatal. Pictured is an asbestos fiber in the lung.  

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High-profile victim -

A high-profile victim of mesothelioma was Hollywood movie actor Steve McQueen. His condition was diagnosed in 1979, many years after he was exposed to asbestos during his time in the Marines in the 1940s. He died aged 50 on November 7, 1980.  

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Exposure risk -

According to Cancer Council, cancer risk from asbestos varies, depending on the following factors: length of time you are exposed to airborne asbestos fibers, amount of asbestos fibers in the air breathed, frequency of exposure to asbestos fibers, time since exposure occurred, age at which exposure occurred, and type and size of asbestos fibers.  

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Calls for a total ban -

Currently worldwide, 66 countries and territories (including all those in the European Union) have banned the use of asbestos.

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Strictly regulated -

Those still working with the material are protected from exposure to asbestos as a result of very strict regulations and enforcement.

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Still a killer -

Sadly, legislation cannot undo the damage that was done to those who previously worked in asbestos-related jobs. Indeed, according to the UK's Health and Safety Executive, asbestos still kills around 5,000 workers each year—more than the number of people killed on British roads. And despite the evidence that it can kill, the United States has yet to ban asbestos, although the material is recognized as a health hazard and is also highly regulated.

Sources: (Mesothelioma Center) (National Center for Biotechnology Information) (Environmental Chemistry) (Science Direct) (The Agency for Toxic Substances & Disease Registry) (Cancer Council) (International Ban Asbestos Secretariat) (Health and Safety Executive) (Asbestos)

See also: Surprising things that can cause cancer

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