2. The hazards associated with asbestos
The very properties that made asbestos a valuable raw material also create problems when it is inhaled; namely the ability of the fibres to split along their length into fine fibres that can reach the furthest part of the lung, and the resistance of the fibres to the chemical attack of the lung's defences.
Figure 2 Asbestos vein in situ
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Fine fibres are more likely to be inhaled than coarse fibres because they remain suspended in the air for longer. The thin fibres that are generated when asbestos is handled can penetrate deep into the lung where they can cause disease.
Asbestos has been used since prehistoric times. One of the earliest recorded uses was as lamp wicks and funeral shrouds, and the women who wove wicks for the vestal virgins' lamps apparently wore masks to keep the dust out! However, the real hazards were first recognised by the medical profession about 1900 when the first case of lung scarring, or asbestosis, was described. This was about thirty years before the first legislation was enacted to protect asbestos workers.
In the years following the recognition of asbestosis, several other diseases, including lung cancer and a cancer of the lining of the lung or gut known as mesothelioma, have been described in association with asbestos. To combat these newly recognised risks, the law in the UK has progressively been tightened with Regulations in 1931 and 1969 and 1983 and these have been further strengthened with the introduction more stringent legislation and guidance.
The International Agency for Research on Cancer (IARC) recently reaffirmed that there is sufficient evidence for asbestos to be classified as a known human carcinogen (i.e. Group 1). All commercial forms of asbestos, including chrysotile (white asbestos), cause lung cancer and mesothelioma. The IARC also concluded that there is "sufficient" evidence that asbestos causes laryngeal cancer and, perhaps surprisingly, ovarian cancer. They also found that there was "limited" evidence that asbestos exposure causes cancers of the pharynx, stomach and gastrointestinal (GI) cancers, with the evidence for an association between asbestos exposure and GI cancer being the strongest.
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