Asbestos is the name applied to six naturally occurring minerals that are mined from the earth. The different types of asbestos are:
Of these six, three are used more commonly. Chrysotile (white) is the most common, but it is not unusual to encounter, Amosite (brown / off-white), or Crocidolite (blue).
All types of asbestos tend to break into very tiny fibres. These individual fibres are so small that many must be identified using a microscope. In fact, some individual fibres may be up to 700 times smaller than a human hair. Because asbestos fibres are so small, once released into the air, they may stay suspended there for hours or even days.
Asbestos fibres are also virtually indestructible. They are resistant to chemicals and heat, and they are very stable in the environment. They do not evaporate into air or dissolve in water, and they are not broken down over time. Asbestos is probably the best insulator known to man. Because asbestos has so many useful properties, it has been used in over 3,000 different products.
Usually asbestos is mixed with other materials to actually form the products. Floor tiles, for example, may contain only a small percentage of asbestos. Depending on what the product is, the amount of asbestos in asbestos containing materials (ACM) may vary from 1%-100%.
Asbestos may be found in many different products and many different places. Examples of common uses and applications of asbestos are:
Asbestos cement
Asbestos content: 10-15% chrysotile
Flat and corrugated sheets, tiles, drainage and rainwater pipes, gutters, flues for boilers and ascots, high-pressure water pipes, steam pipes, water tanks, wall ventilators, fire surrounds.
Insulation boards (e.g. asbestolux, LDR, Marinite and Turnabestos)
Asbestos content: 20-40%
Usually amosite, but may also contain small proportion of chrysotile or crocidolite. Cladding for walls, ceilings and structural steelwork. Acoustic and thermal insulation.
Lagging (to pipes, boilers and calorifiers)
Up to 90% chrysotile, amosite or crocidolite. May be combined with magnesia for high temperature applications (boiler casings, steam pipes etc.)
Pre-formed sections and slabs or wet plastering. Note that asbestos ropes, tapes, corrugated papers, quilts, felts and blankets are also found lagging boilers etc. In the past, woven asbestos quilts filled with loose asbestos were sometimes used for insulation of hot water cylinders, calorifiers etc.
Sprayed coatings
Up to 85% crocidolite, amosite or chrysotile.
Fire protection to structural steelwork, thermal and acoustic insulation, condensation prevention.
Caulking materials (jointings and packings)
30-88% chrysotile or amosite.
Found anywhere a fireproof seal is needed e.g. ovens, sections of system built dwellings, sealing holes in service ducts, joints to soil pipes.
Asbestos yarns and ropes
65-100% chrysotile.
Mainly used to seal joints (e.g. boilers, flues, chimneys, etc.) as a rot-free fire stop (e.g. where pipes go through a wall) or between components in plant and machinery.
Asbestos cloths and textiles
65-100% chrysotile, but crocidolite was also used.
Fire blankets, fireproof clothing, oven gloves, safety curtains and blankets.
Asbestos paper
Up to 100% chrysotile.
Electrical insulation, fireproof facings, heat reflective layers to boilers and electric storage heaters.
Gaskets
Approximately 70% asbestos. Normally chrysotile, but crocidolite is also likely.
Asbestos/vinyl floor tiles
7-10% chrysotile (older types up to 20%)
Paints and surface coverings
4% chrysotile, but note that artex “AX” is now asbestos free.
The most common way for asbestos fibres to enter the body is through breathing. In fact, asbestos-containing material is not generally considered to be harmful unless it is releasing dust or fibres into the air where they can be inhaled or ingested. Many of the fibres will become trapped in the mucous membranes of the nose and throat where they can then be removed, but some may pass deep into the lungs, or, if swallowed, into the digestive tract. Once they are trapped in the body, the fibres can cause health problems.
Asbestos is most hazardous when it is friable. The term “friable” means that the asbestos is easily crumbled by hand, releasing fibres into the air. Sprayed on asbestos insulation is highly friable. Asbestos floor tile is not.
Asbestos-containing ceiling tiles, floor tiles, undamaged laboratory cabinet tops, shingles, fire doors, siding shingles, etc. will not release asbestos fibres unless they are disturbed or damaged in some way. If an asbestos ceiling tile is drilled or broken, for example, it may release fibres into the air. If it is left alone and not disturbed, it will not.
Asbestos pipe and boiler insulation does not present a hazard unless the protective canvas covering is cut or damaged in such a way that the asbestos underneath is actually exposed to the air.
Damage and deterioration will increase the friability of asbestos-containing materials. Water damage, continual vibration, aging, and physical impact such as drilling, grinding, buffing, cutting, sawing, or striking can break the materials down making fibre release more likely.
Because it is so hard to destroy asbestos fibres, the body cannot break them down or remove them once they are lodged in lung or body tissues. They remain in place where they can cause disease.
There are three primary diseases associated with asbestos exposure:
Asbestosis is a serious, chronic, non-cancerous respiratory disease. Inhaled asbestos fibres aggravate lung tissues, which cause them to scar. Symptoms of asbestosis include shortness of breath and a dry crackling sound in the lungs while inhaling. In its advanced stages, the disease may cause cardiac failure.
There is no effective treatment for asbestosis; the disease is usually disabling or fatal. The risk of asbestosis is minimal for those who do not work with asbestos; the disease is rarely caused by neighbourhood or family exposure. Those who renovate or demolish buildings that contain asbestos may be at significant risk, depending on the nature of the exposure and precautions taken.
Lung cancer causes the largest number of deaths related to asbestos exposure. The incidence of lung cancer in people who are directly involved in the mining, milling, manufacturing and use of asbestos and its products is much higher than in the general population. The most common symptoms of lung cancer are coughing and a change in breathing. Other symptoms include shortness of breath, persistent chest pains, hoarseness, and anaemia.
People who have been exposed to asbestos and are also exposed to some other carcinogen—such as cigarette smoke—have a significantly greater risk of developing lung cancer than people who have only been exposed to asbestos. One study found that asbestos workers who smoke are about 90 times more likely to develop lung cancer than people who neither smoke nor have been exposed to asbestos.
Mesothelioma is a rare form of cancer that most often occurs in the thin membrane lining of the lungs, chest, abdomen, and (rarely) heart. About 200 cases are diagnosed each year. Virtually all cases of mesothelioma are linked with asbestos exposure. Approximately 2% of all miners and textile workers who work with asbestos, and 10% of all workers who were involved in the manufacture of asbestos-containing gas masks, contract mesothelioma.
People who work in asbestos mines, asbestos mills and factories, and shipyards that use asbestos, as well as people who manufacture and install asbestos insulation, have an increased risk of mesothelioma. So do people who live with asbestos workers, near asbestos mining areas, near asbestos product factories or near shipyards where use of asbestos has produced large quantities of airborne asbestos fibres.
Evidence suggests that cancers in the oesophagus, larynx, oral cavity, stomach, colon and kidney may be caused by ingesting asbestos.
E-mail: envhealth@dover.gov.uk
