What is Asbestos

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Asbestos is the collective term given to a group of naturally occurring fibrous varieties of silicate minerals. Asbestos types occur within two groups of minerals: the serpentine minerals and the amphibole minerals. Although there are about a dozen asbestos minerals, only three were in widespread use in Australia. These were:

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• chrysotile, or white asbestos. This has soft, white curly fibres and was the type in most common use;
   

• amosite, or brown asbestos. This has straight, harsh grey to brown fibres and was often used in situations where additional strength was required, such as in the manufacture of asbestos-cement pressure pipes; and
   

• crocidolite, or blue asbestos. This has straight, blue fibres and the fibres tend to be very fine. Blue asbestos tends to have been used in situations in which acid resistance was particularly needed.
   

Asbestos Properties

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The properties of asbestos fibres include thermal stability and resistance, chemical resistance, high tensile strength, abrasion resistance, low electrical and thermal conductivity, low biodegradability and good sound absorption qualities.

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The presence of asbestos in commercial products varies depending upon the product’s uses. While all forms of asbestos are fibrous silicates, they differ in their chemical composition and properties, crystalline structure and fibre dimensions, and as such their commercially useful properties also vary.

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All asbestos types are excellent thermal insulators and have been widely used as fire proofing (on steel structural beams and soffits) and insulation materials (on boilers, ovens, kilns, steam pipes and hot water pipes). The amphibole group has considerable resistance to chemical corrosion and has been used in environments which are prone to attack by acids. Both chrysotile and crocidolite have high tensile strength and have been widely used in the manufacture of woven asbestos products. All the asbestos types show low electrical and thermal conductivity, low biodegradability and good sound absorption properties.

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Types of Asbestos

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There are two main types of asbestos-containing materials (ACMs):

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• bonded asbestos has been mixed with other products to form building materials commonly found in houses and home units; and
   

• friable asbestos is any asbestos material that can be crumbled or pulverized by hand pressure when dry or asbestos that is in a powder form.
   

Removal

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Removal of asbestos-containing materials should only be undertaken by licensed contractors. Each state has its own regulations and you should check with your local Council before removal commences. Essential safety precautions include wearing appropriate personal protective equipment (e.g. respirator and coveralls), barricading or enclosing work areas, notifying neighbours, air monitoring, wetting down materials, use of non-powered hand tools, wrapping waste in clearly labeled plastic and immediate transport and disposal of waste to an approved site.

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Asbestos is Commonplace

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From the early 1900s until the early 1970s, asbestos was widely used in industry. The use of asbestos cement sheets in roof pipes and wall cladding was particularly widespread, as was the use of “limpet” asbestos fibre insulation in steel framed high rise buildings. Asbestos was also used for applications such as insulation of pipes and high temperature electricity cables, in plastics, in PVC floor tiles, for reinforcement in cements, putties and mastic and in gaskets and friction materials.

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Whilst major uses of asbestos were sometimes recorded on engineering drawings, there are few records of the ad hoc use of asbestos containing products and materials. To give examples from the building industry, plumbers frequently used asbestos fibre in caulking compounds and builders often used AC sheeting as packing under squeaky floor boards.

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In short, asbestos could be almost anywhere in a building or plant constructed before the 1980s.

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General Health Risks

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Inhalation of asbestos fibres may lead to the following asbestos related diseases:

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• mesothelioma: cancer of the pleura (lining of the lung cavity) or peritoneum (lining of the abdominal cavity);
   

• asbestosis: scarring of the lung tissue;
   

• lung cancer: a cancer similar to that associated with tobacco smoking; and
   

• other cancers: cancer of the larynx, oesophagus, stomach, bowel, rectum and kidneys has been identified in heavily exposed asbestos workers.
   

Asbestos related diseases do not appear for a long time following exposure to asbestos. The term “latency period” is used to describe the period of time which passes between being exposed to airborne asbestos fibre and the disease being diagnosed. Depending upon the asbestos type and magnitude of exposure, the latency period generally ranges from between 10 and 40 years.

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Asbestosis, mesothelioma and lung cancer, the recognised diseases caused by asbestos, are all as a result of inhalation of airborne asbestos fibres. Hence for asbestos containing products to pose a health risk airborne fibres must be generated either through degradation or high energy mechanical action. The degree of asbestos fibre release, and hence inhalation exposure, is in part dependent upon the matrix material binding the asbestos and its general condition.

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Asbestos Cement Products

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Asbestos cement products were commonplace building materials prior to 1986. The material consists of asbestos fibres bound in a cement matrix and the degree of fibre release depends on the condition of the material.

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The main health risk with asbestos cement products is from maintenance or similar activity where the material is worked upon resulting in airborne dust.

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It is necessary to have in place safe systems of work when working upon asbestos cement products.

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Vinyl Floor Coverings

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With vinyl floor coverings, asbestos may be present in any of the following:

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• the vinyl body of the tile or sheet;
   

• a fibrous backing under the tile or sheet; and
   

• an adhesive used to fix the tile.

 

Asbestos contained in the vinyl body of the tile or sheet is held in a stable matrix. The very low rate of wear does not normally give rise to fibre release considered to pose a significant health risk. A health risk may arise when asbestos fibres are released due to maintenance work and possibly the use of metal brush mechanical floor scrubbers (although this is not proven) or when the flooring is friable due to age.

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Asbestos backing is sometimes used to line the back of vinyl sheeting. This product does not pose a risk to exposure from airborne fibres, so long as it is not disturbed or worked upon, i.e. abraded, scuffed or handled. Any of these actions may release the asbestos fibres into the environment.

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Asbestos backing or asbestos adhesive is normally not exposed and does not represent a significant health risk. However, when exposed these materials may liberate fibres depending upon the amount of abrasion and the age and condition of the material.

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Asbestos Millboard Insulation

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Asbestos millboard insulation can be friable. Generally this material does not pose a significant risk to health except where it has severely degraded or when it is mechanically or physically disturbed.

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Gaskets and Asbestos Pipe Lagging

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Gaskets are composed of a wide variety of materials. Asbestos may be present in some gaskets.

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Asbestos pipe lagging can be in the form of either woven rope material or formed section insulation. Where the material is in situ it does not pose a significant risk except where the materials have severely degraded.

 

The main concern with asbestos gaskets and asbestos pipe lagging is during maintenance activities where significant fibre release can result if the gaskets or rope are worked upon.

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Air-conditioning Heaterbank Millboard Insulation

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The risk from exposure to airborne asbestos fibres through the air conditioning system is minimal, so long as the material is not disturbed or damaged.

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Although not usually accessed internally for inspection because the units are sealed, it is possible that these heaterbanks may be lined with asbestos millboard. Further investigation may be warranted to confirm the presence of asbestos millboard in the ductwork.

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Asbestos Containing Electrical Backing Boards

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Asbestos-containing materials such as the asbestos impregnated resin board (ie “Zelemite” or “Ausbestos”), are generally in good condition. These products do not pose a risk to exposure from airborne fibres, so long as they are not disturbed or worked upon, i.e. cut, sawn, drilled or sanded. Any of these actions may release the asbestos fibres into the environment.

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Asbestos Impregnated Sealants (Mastics)

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Asbestos-containing materials such as asbestos impregnated sealant (i.e. mastic) are generally in good condition. This product does not pose a risk to exposure from airborne fibres, so long as they are not disturbed or worked upon, i.e. drilled, sanded or burnt. Any of these actions may release the asbestos fibres into the environment.

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Asbestos Fire Door Core Material

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Asbestos containing core materials in fire doors are usually sealed and undisturbed.

This material does not pose a risk to exposure from airborne fibres, so long as the core is not disturbed or worked upon, i.e. drilled, cut, or abraded. Any of these actions may release the asbestos fibres into the environment.

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Limpet Asbestos

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Limpet asbestos is friable (unbound) and normally has been hand applied or sprayed onto the material being insulated. Generally speaking limpet asbestos is located in areas not readily accessible to occupants of a building (e.g. ceiling cavities, roof spaces, plant rooms).

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Risk of exposure to airborne asbestos fibres is significant to maintenance personnel, and the like, whose tasks may involve accessing these areas and when safe work practices are not enforced. It is usually necessary to wear personal protective equipment, such as a respirator, prior to accessing these areas.

Under normal circumstances where the asbestos is not disturbed the risk of exposure to airborne asbestos fibres is minimal.