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Talking Point: WSP's Zoë Cooper and Neil Housley on asbestos testing

James Clay and Stephanie Mailer’s Talking Point 'Asbestos testing and treatment in soils: A work in progress' raised important issues associated with contaminated land projects on sites containing significant levels of asbestos.

These include the variety of testing methods, the potential for variability in data and the lack of clarity for asbestos content in soils and use post-remediation. This may stem from parties including consultants, laboratories and regulatory bodies – Health and Safety Executive (HSE), local authorities, the Environment Agency – that approach the area from slightly differing perspectives.

A problem with the analysis of asbestos content in soil is the difficulty in obtaining a sample that is representative of the site. The size and nature of many asbestos containing materials (ACMs) and their distribution in the soil result in a lack of homogeneity and, potentially, a large variation in results. Laboratory testing is ultimately dependent on the quality and nature of the samples submitted and design of the site investigation. It is obvious, regardless of the parameter under investigation, that results obtained even from the most sensitive analytical method, for example, that of the United Kingdom Accreditation Service (UKAS), will not be relevant unless sampling is representative.

Dependent on the size of the sample and that used in the test, the laboratory may be required to sub-sample further. This increases the potential for a single piece of ACM being excluded from the portion analysed. An understanding between those involved in sampling and laboratory testing is therefore preferential.

Clay and Mailer’s article demonstrated the disparity in results obtained from a number of analytical methods. This included semi-quantitative judgment via microscopy, HSG 248 (HSE-published guidance) bulk identification and weighing of associated products, and water-based drop tests.

All analytical methodologies have their applications and limitations. In particular, the semi-quantitative test, whereby the analyst estimates the amount of asbestos in a material, is believed to be overly reliant on the analyst’s judgment and can, therefore, be inconsistent. This is one reason why many methodologies for the determination of asbestos content fail to meet UKAS-accredited standards to ISO 17025 for laboratory testing.

This lack of standardised methodologies is of concern, should a number of laboratories be used during a long-term project where data consistency is important to avoid step changes in results obtained, particularly when remediation is involved. This could all change should a procedure be developed that is accepted as best practise.

It was inaccurately stated in the article that there are no available methods for the determination of asbestos content that carry the assurance that accreditation provides.

A review of accredited laboratories for asbestos content in soil analysis on the UKAS’ testing website (www.ukas.org) returns two integrated service providers in the UK that have a laboratory function. These both appear to be tests developed in-house that fulfil the accreditation criteria – technically fit for purpose, reproducible and robust, performed by trained staff and supported by efficient quality management systems.

It is worth stating that asbestos sits outside the Environment Agency’s Monitoring Certification Scheme performance standard, which is limited to chemical analysis parameters in soils. Many environmental laboratories will also not proceed with chemical analysis upon discovery of asbestos in soil samples.

Regardless of the method employed, it is vital that principles behind asbestos analysis are understood to prevent data being misinterpreted. This may require collaboration from those involved in laboratory analysis, health, control of asbestos and waste disposal. This suggests a holistic approach from an integrated provider of sampling, analysis and consultancy.

Zoë Cooper is business development manager and Neil Housley is quality manager with WSP Environmental Laboratories and Neil Housley is quality manager with WSP Environmental Laboratories

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