What is asbestos

there are several forms of mineral silicates that form the group called asbestos. these minerals are made into an abundance of products from insulation or building material to fire blankets. Even cigarette filters contained asbestos prior to 1956.

 there are 3 main types of asbestos that are were used in New Zealand

  • Chrysotile (white asbestos) (CAS No:12001-29-5), found in serpentine rocks. The chemical composition of chrysotile asbestos is {Mg3(Si2O5)(OH)4}n.

  • Amosite (brown asbestos) (CAS No:12171-73-5), a trade name used for a specific amphibole mineral found in South Africa. The chemical composition of amosite asbestos is {(Mg,Fe)7Si8O22(OH)2}n.

  • Crocidolite (blue asbestos) (CAS No: 12001-28-4), an amphibole mineral from Africa and Australia. The chemical composition of crocidolite asbestos is Na2Fe3+Si8O22(OH)2.


Loose fibre broken down from the mined rock material is used in the manufacture of a variety of products. Asbestos is often mixed with another material and is rarely encountered in its raw form, making identification based on visual examination unreliable.

Asbestos has been incorporated in many materials for the construction, cladding, and thermal or acoustic insulation of offices, factories, and houses and a wide range of products including:

  • Heat-resistant textiles;

  • Decorative coatings;

  • Asbestos cement pipes and sheets;

  • Thermal insulation for pipes and boilers;

  • Brake and clutch friction linings;

  • Gaskets;

  • Floor tiles; and Packing materials. 


Its properties of heat resistance and mechanical strength have been exploited in these applications. Substitutes have been found for many of the above applications. It is not always practical to remove asbestos from buildings, plant, and equipment, but this is the long-term goal.

Health Aspects

Exposure to asbestos fibres will occur when materials containing asbestos are sanded, sawn, drilled, or handled during maintenance or removal tasks. Most of the larger fibres are deposited in the nose and major airways and are cleared by normal physiological processes. Smaller fibres may be deposited in the airspaces deep in the lung or migrate to other parts of the body.

Three main diseases have been associated with the inhalation of asbestos fibre:

  • Asbestos

  • Lung Cancer

  • Mesothelioma

The development of scar tissue (fibrosis) may occur after exposure to asbestos ends or may continue after exposure has ceased. Inhalation of high concentrations of all forms of asbestos may result in asbestosis, a progressive fibrosis of lung tissue. Forms of cancers associated with the inhalation of asbestos are lung cancer and mesothelioma. In addition, recent studies have identified that cancers of the larynx, oropharynx, gastrointestinal tract and kidneys can also be caused by exposure to asbestos.

Generally, fibres below 0.3 micrometres in diameter and greater than 0.5 micrometres in length1 are potentially carcinogenic, and the risk of cancer increases as fibre size decreases. It is important to remember that the risk of cancer also increases with the dose, and there is no safe lower limit for exposure.

There is a long delay between exposure and the development of mesothelioma or lung cancer. In the majority of cases this ranges from 15 to 50 years.