Asbestos is a naturally occurring rock forming mineral silicate in fibrous form belonging to the serpentine and amphibole groups. It occurs naturally in large deposits on every continent in the world. There are six types of naturally occurring asbestos fibres of which only three have been used commercially in Australia. These included the serpentine: Chrysotile (white asbestos); and the amphiboles: Crocidolite (blue asbestos) and Amosite (brown or grey asbestos). The other three non-commercially used amphiboles included Tremolite, Actinolite and Anthophyllite.
Asbestos has been used in the ancient world of the Egyptians, Greeks and Romans. It is believed that as early as 4000 BC, asbestos fibres were used for wicks in lamps and candles. Between 2000-3000 BC, embalmed bodies of Egyptian pharaohs were wrapped in asbestos cloth. The Greeks and Romans documented the harmful effects of asbestos fibres on those who mined the silken material from ancient stone quarries noting a “sickness of the lungs” in slaves who wove asbestos into cloth.
The commercial use of asbestos commenced in the late 1800s in Australia in four main industries including Mining and Milling; Building & Construction (for strengthening cement and plastics, for insulation, fireproofing and sound absorption); Ship Building (eg. insulation of boilers and steampipes) and the Automotive Industry (eg. vehicle brake shoes, gaskets and clutch pads).
There were over 3000 products (Asbestos Containing Materials or ACM) manufactured with asbestos fibres. The ACM fall into two broad categories: friable and non-friable (or bonded).
‘Friable’ is ACM that can be easily reduced to powder when crushed by hand, when dry. These materials can contain higher percentages of asbestos fibres and are easily or more likely to release airborne fibres into the environment with minimal disturbance. As such, they pose a greater risk to health. Friable materials must only be handled and removed by an asbestos removalist with Class A Asbestos Removal Licence. Examples of friable asbestos-containing materials include sprayed on fire retardants, insulation (eg. millboard, pipe insulation), sound proofing, the lining on some old domestic heaters, stoves and hot water systems and associated pipe lagging, the backing of sheet vinyl and linoleum floor coverings, thermal lagging, some vermiculite.
‘Non-friable’, or bonded ACM is used to refer to ACM in which the asbestos is firmly bound in the matrix of the material. These materials are unlikely to release measurable levels of airborne asbestos fibre into the environment if they are undisturbed. Therefore, they generally pose a lower risk to health. However, activities that may abrade the ACM such as drilling, grinding have the potential to release higher concentrations of airborne asbestos fibres into the environment. The non-friable ACM are mainly made up of asbestos fibres together with a bonding compound (such as cement), and typically contain up to 15 per cent asbestos. Non-friable ACM are solid, quite rigid and the asbestos fibres are tightly bound in the material. Non-friable ACM are the most common in domestic houses. They are commonly called ‘fibro’, ‘asbestos cement’ and ‘AC sheeting’. Examples of non-friable ACM include asbestos cement products (flat, profiled and corrugated sheeting used in walls, ceilings and roofs, moulded items such as downpipes) and vinyl floor tiles.
While asbestos is a hazardous material it can only pose a risk to health if the asbestos fibres become airborne in respirable size, are inhaled and lodge deep into the lungs (in the alveoli). Inhalation is the main route of entry to the body. Respirable fibres are fibres that are more likely to reach the small airways and alveolar region of the lung and are defined as having a length of more than five microns, and an aspect ratio (length/width) greater than 3:1.
Asbestos is classified according to the Globally Harmonised System of Classification and Labelling of Chemicals (GHS) as Carcinogenicity Category 1A (May cause cancer).
There are several asbestos related diseases that may result from the exposure to asbestos which depends on factors such as fibre type; size and shape of fibres; concentration of asbestos fibres in the inhaled air and period of time over which the person was exposed. The asbestos related diseases include: