What is naturally occurring asbestos (NOA)?
In most workplaces, the asbestos that is encountered and poses a risk to health and safety will be found in manufactured products. However, some workplaces may have to deal with asbestos in its natural state.
The health risks associated with the inhalation of airborne asbestos fibres are well established. Asbestos minerals encountered in exploration and mining operations must be managed carefully.
Employers or person conducting a business or undertaking have a duty to ensure that workers’ exposure to airborne asbestos fibres is as low as reasonably practicable. This can be achieved using appropriate recognition, evaluation and control strategies.
Exposure to NOA
Asbestos only forms under rare geological circumstances, and the regions with potential for asbestiform minerals can be defined on geological maps.
If present, asbestos usually forms thin isolated veins. The probability of intersecting isolated veins of asbestos during drilling is very low.
In open pit operations, where large surfaces may be uncovered, the probability of exposure (and detection) is much greater.The probability of exposure in underground workings is between these extremes, with small veins occasionally found.
Find out more about the workplace exposure standards for airborne contaminants.
Potential hazard
Asbestos represents a hazard only if fibres of a respirable size (< 5 μm) become airborne and are inhaled.
Undisturbed asbestos does not spontaneously emit fibres. The potential for an asbestos mineral to release respirable fibres depends on its physical characteristics and the degree of handling and processing.
The danger from exposure is not immediately obvious because harmful fibres are too small to be seen with the naked eye, and there is often a long latency period between exposure and onset of disease.
The risk of asbestos-related disease depends upon:
- concentration of respirable fibres in the air
- duration of exposure
- type of fibre (amphibole asbestos or chrysotile)
- morphology of fibres (size and shape).
What can be done to manage the hazard?
- Identify and quarantine workplaces contaminated by asbestos (designated areas).
- Maintain a register that records all known locations of asbestos at the site.
- Regularly inspect rock surfaces to ensure minimal disturbance of suspected fibrous minerals.
- Emphasise good housekeeping and apply stringent dust control techniques.
- Do not rely solely on the use of personal protective equipment.
- Follow procedures for the secure disposal of any asbestos-bearing waste material.
- Involve and educate the workforce in appropriate work practices.
- Conduct regular audits and air monitoring.
What can be done to reduce the risks?
- Adopt administrative procedures to control people entering or leaving designated areas.
- Use sealed mining equipment.
- Wet surfaces to reduce dust levels.
- Suppress, contain and extract dust in processing operations where practicable.
- Use wet drilling or other approved in-hole dust suppression.
- Seal asbestos in situ using appropriate sealants or bonding agents.
- Prevent the spread of contamination by using washdown facilities.
- Provide information, training and supervision of all employees potentially at risk.
- Use respiratory protection where indicated.
Requirements to manage NOA
Due to the difficulties in fully describing the location and extent of a NOA deposit in an asbestos register, there is no requirement for NOA be listed in an asbestos register. However, any NOA identified or assumed at a workplace must be included on the asbestos management plan for the workplace or be the subject of a new asbestos management plan. This is to ensure steps are put in place, as with all other asbestos encountered in workplaces, to ensure that risks of exposure from NOA are assessed and managed.