What is asbestos?

Asbestos is a term applied to a family of mineral rocks which are mined and then crushed to produce raw fibres. When combined with other materials these fibres add strength and heat resistance, but unfortunately, the inhalation of these fibres will adversely affect human health, and if the exposure is prolonged, this contact is potentially fatal. The importation and manufacture of all asbestos products has been illegal in the UK since 1999.

In the electron microscope image of anthophyllite asbestos fibres given below (Figure 1), the light disc indicates the approximate diameter of a human hair.

scanning electron microscope image of anthophyllite asbestos

Figure 1: Scanning electron microscope image of anthophyllite asbestos – base image courtesy of The United States Geological Survey

Common types of asbestos

There are many types of asbestos. However, the three main types of asbestos are:

amosite (brown asbestos, fibre type: amphibole);
chrysotile (white asbestos, fibre type: serpentine); and
crocidolite (blue asbestos, fibre type: amphibole).

Figure 2 shows electron microscope image of these asbestos fibres, along with their basic characteristics:

Amosite brown asbestos	Crocidolite blue asbestos	Chrysotile white asbestos

Amphibole Sharp, needle like Stiff Elastic Splits along length Barbed Very hazardous		Serpentine Curly Long Flexible Inelastic Less hazardous
Figure 2: Scanning electron microscope images of asbestos by type – base images courtesy of The United States Geological Survey

Of these, the blue and the brown fibres are the most dangerous because their barbs can become ensnared in the tissue of the lungs. The white fibres are less dangerous due to the absence of any barbs.

As the fibres are resistant to the body’s chemical dissolving mechanisms, once they are embedded in the lung tissue they cannot be removed.

Most asbestos is of low risk and can be safely managed until such time as a building is refurbished or demolished.

However, if the material is one of the higher risk types (loose insulation, sprayed insulation, asbestos insulating board, etc.), then consideration must be given to removal or encapsulation.

History

Modern mining of asbestos and its use began in the 1890s, although its properties where known to and used by both the ancient Greeks and the Romans.

By the 1920s, companies like Turner & Newell, and Cape Asbestos where adding asbestos fibres to cement and other materials to produce a range of inexpensive building products which went on to be used extensively from the 1950s through to the 1980s.

As the health implications of asbestos usage began to outweigh the advantages, the UK importation and manufacture of asbestos products were progressively banned. Starting with crocidolite (blue) and amosite (brown) in 1985, finishing with chrysotile (white) in November 1999.