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Asbestos in Soil - Further Guidance

Australian Standard AS 4964:2004 Method for the qualitative identification of asbestos in bulk samples requires the reporting of presence or absence of asbestos at a Reporting Limit of 0.1 g/Kg. This method does not produce a quantifiable result of asbestos content and therefore, quantitative results cannot be reported.

Determining the concentration of asbestos in soil continues to provide challenges for those involved in soil remediation and site validation work. As discussed in Issue 151 of NATA News (March 2014), there is no accepted valid method in Australia for this estimation.  Consequently, NATA does not offer accreditation for this activity and has advised facilities that results for this work must be issued with a comment clearly indicating that the results are not covered by the scope of accreditation and the result should also be issued on a non-NATA endorsed report.

Facilities are reminded that inclusion of such a comment does not remove the need to ensure that the customer is aware of the limitations of the analysis undertaken and what is being reported.  This must be established during the contract review stage or when the customer first approaches the facility to request the examination of soil for asbestos in line with Clause 4.4 of ISO/IEC 17025 General Requirements for the competence of testing and calibration laboratories. 

For customers of facilities who use the National Environment Protection (Assessment of Site Contamination) Measure 1999 - updated in 2013 - (NEPM) for site assessment work, determination of the concentration of asbestos-containing material (ACM) in soil is required. This can be achieved by carrying out site based gravimetric work. Section 4.10 of the NEPM document for site based field observations provides details of the procedure for estimating the amount of visible ACM present in a volume of soil. It should be noted that results of any field or site based work is not covered by any NATA accreditation. 

It is important to remember that the procedures outlined in the NEPM only cover visible ACM. They do not cover free (or respirable) asbestos fibres which may be distributed throughout the soil. Only laboratory analysis using AS 4964 can determine the presence or absence of free asbestos fibres via the trace analytical technique outlined in the Standard. 

NATA is aware that some NATA accredited laboratories are confusing the NEPM gravimetric field observation with the NEPM prescribed analytical method (AS 4964). Laboratories should be aware that the gravimetric procedures in the NEPM are not analytical methods and are therefore inappropriate for discrete samples provided to laboratories for analysis. Additionally, the size of soil samples examined in the laboratory may not be representative of the field site and can result in an under estimation of any free asbestos present.

Analysis of soil samples using AS 4964 will  require the test report to include a description of the visible ACM such as fibrous asbestos (e.g. asbestos cement) and asbestos fines (e.g. small fibrous bundles) using stereo and polarised light microscopy. Only when examination is carried out using the trace analytical technique, can the presence or absence of free (i.e. respirable) asbestos fibres be determined at the Reporting Limit of 0.1 g/Kg or 0.01% by weight (note: that is is a requirement that trace analysis always be performed as part of the AS 4964 analysis process for non-homogeneous samples such as soil). 

Laboratories are cautioned against reporting detection limits for asbestos down to 0.001% as it is possible that free respirable asbestos fibre contamination exist in the sample at concentrations up to an order of magnitude greater than the reported detection limit.

Where results are reported for positive ACM (e.g. fibrous asbestos cement, asbestos bundles etc.) and/or positive free asbestos, it is important that the findings are clear and unambiguous.

In summary the following points are made:-

  • The gravimetric procedure described in the NEPM is designed for field evaluations for visible ACM only. It is not appropriate for examining soil samples provided to a laboratory.
  • There is no accepted valid analytical method in Australia for estimating the concentration of asbestos in soil.
  • NATA does not accredit facilities for the estimation of the concentration of ACM or free asbestos fibres in soil.
  • Stereo microscopic analysis which only examines visible ACM without conducting further trace analysis techniques cannot be used to establish whether the soil is asbestos free.
  • Examination for the presence of free asbestos fibres in soils can only be undertaken using AS 4964 trace analysis techniques which detects fibres where they exist in concentrations greater than 0.01% (i.e. 0.1 g/Kg).
  • Free asbestos fibres in soil when analysed using AS 4964 can only be reported as being present, if above the Reporting Limit of 0.1 g/Kg (i.e. 0.01%), or not present.
  • If asbestos in soil estimation is performed in accordance with NEPM 2013, any quantitative results reported must be clearly and appropriately annotated on test reports to indicate that they are not covered by the scope of NATA accreditation and have not been analysed in accordance with a valid method.
  • When reporting such results, a comment advising that such results cannot be used in place of field evaluations must be included on the report.

 

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