What is Asbestos?

Asbestos is the collective term given to a group of naturally occurring fibrous or "asbestiform" varieties of a number of silicate minerals. Asbestos types occur within two groups of minerals: the serpentine minerals and the amphibole minerals.

Chrysotile (white asbestos), which accounts for approximately 95% of the world production of asbestos, is the only member of the serpentine group of minerals.

Crocidolite (blue asbestos), amosite (brown asbestos), anthophyllite, tremolite and actinolite are all members of the amphibole group.

Of the six types of asbestos, only chrysotile, amosite, crocidolite and to a lesser extent anthophyllite are mined for commercial use. Tremolite and actinolite have not been mined commercially although can be found as impurities in other commercially available mineral products.

Properties of Asbestos

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

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.

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 as such have been used in environments which are prone to attack by acids. Both chrysotile and crocidolite have high tensile strength, and as such 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.

Asbestos Products

Commercially manufactured asbestos containing materials can be broadly divided into the following categories:

• Thermal insulation (eg. pipe and boiler insulation)
  
• Fire-proofing materials (eg. sprayed insulation, fire door insulation)
  
• Asbestos cement/fibrocement products (eg. roof and wall claddings)
  
• Decorative and acoustic applications
  
• Electrical switchboards, insulators and fittings
  
• Vinyl floor coverings
  
• Asbestos felts and paper-like products
  
• Friction materials (eg. brake linings)
  
• Paints, coatings, sealants and adhesives
  
• Packings and gaskets
  
• Textiles (eg. woven cloths, blankets)
  
• Miscellaneous and unusual products (eg. asbestos socks, phone boxes)
  
• Asbestos has been used extensively in over 3000 commercially manufactured products.

Assessing the Risk

Hazard: Any situation with a potential for harm to life, health or property

Risk: the probability that a hazard may be realised and an individual may suffer an injury as a result of a hazard.

All asbestos containing materials are therefore considered to be a hazard, although the risk presented by the materials can vary significantly.

All forms of asbestos containing materials can be broadly divided into two groups; "friable" and "non-friable". Friability relates to the potential for the material to release asbestos fibres. A friable asbestos containing material is defined as "any material that contains asbestos that can be crumbled, pulverised or reduced to powder by hand pressure when dry." Friable asbestos containing materials include sprayed asbestos insulation, pipe and boiler insulation and non-bonded asbestos fabric. A non-friable asbestos containing material is defined as "being difficult to damage by hand". Non-friable asbestos containing materials include asbestos cement sheet products, vinyl floor tiles, electrical switchboards etc.

In general, friable asbestos containing material represent the greatest risk. The type and percentage of the asbestos, and the friability of an asbestos containing material can however vary substantially. As such there is also a large variation in the exposure risks associated with the presence of asbestos containing materials within buildings and the handling/removal of various asbestos containing materials.

Analysis of Asbestos Containing Materials

Confirmation of the asbestos content and type within a suspect material should only be performed through analysis by appropriately trained and qualified personnel.Asbestos analysis is usually performed by polarised light microscopy, which is fast and inexpensive to perform. Confirmation analysis may also be performed by x-ray diffraction, transmission electron microscopy or scanning electron microscopy.

An important part of the risk assessment associated with asbestos containing materials is the determination of airborne fibre levels. Airborne asbestos fibre monitoring is performed by a technique known as the Membrane Filter Method. A sample of air is collected onto a membrane filter, with subsequent analysis by Phase Contrast Microscopy.

Alpha Environmental are accredited by the National Association of Testing Authorities, Australia for the analysis of asbestos in bulk samples and the analysis of airborne asbestos fibre.

Health Effects

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

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.

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 described 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.

One Fibre Theory

A misconceived theory that only one inhaled asbestos fibre can cause mesothelioma. This theory was propagated by an American newspaper in 1964 following diagnosis of non-occupational mesothelioma in women and children.

This theory is not recognised by the scientific/medical community for the following reasons:

• the majority of people living in urban area, not occupationally exposed to asbestos, have large numbers of asbestos fibres in their lungs (typically millions).
• most cases of mesothelioma can be related back to at least moderate asbestos exposures. eg. housewives washing their husbands asbestos contaminated overalls, spouses and children living in the same house as an asbestos worker, living close to an asbestos factory or shipyard.
• even "minor" exposures to asbestos will result in the inhalation of relatively large numbers of asbestos fibre.