Article Contaminated Land Laboratories

Asbestos in Soil

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The AGS is active in establishing industry guidance for asbestos in soils. The CLWG and LPWG have formed a small sub-group to discuss what guidance and advice should be provided for our Members, and to contribute to the work that is currently being undertaken by other groups and associations on this issue. This article is intended to give Members an awareness of the present situation; what has happened, what is being done and what may be happening in the future.  It has been suggested that many of our members, while insured for investigating and providing advice on contaminants, have specific exclusions to their professional indemnity policies in regard to claims relating to asbestos, and this may possibly have indirectly led to a lack of training and awareness about the risks of asbestos in soils.

Attempts by government agencies and independent organisations to define “safe” or “minimal risk” threshold concentration values, either for fibres in soil or for fibres in air, have been thwarted by the scientific evidence that death can be caused by a single fibre.

The current legal rule in relation to Mesothelioma is that any “material increase in risk” is sufficient for legal liability. In a recent appeal court ruling the exposure was judged to be just 18% higher than background levels.

The UK, in 1931, was the first country to establish laws regulating exposure to asbestos, primarily to protect the health of factory workers.

Currenty UK Statute is dominated by the Control of Asbestos Regulations (CAR) 2006 which were implemented under the provisions of the 1974 Heath and Safety at Work Act and bring together the three previous sets of Regulations covering the prohibition of asbestos, the control of asbestos at work and asbestos licensing.  However, while these regulations are relevant for asbestos in soil, they do not define limits or best practice and there is currently no specific published guidance from either the HSE or the Environment Agency.

The British Occupational Hygiene Society (BOHS)  have a series of asbestos-related proficiency qualifications that cover the identification, sampling and management of Asbestos in Buildings.
The development of specific training and qualifications for the contaminated land industry is being actively considered by various bodies and will need to include consideration of the following issues

  • background of asbestos; including health effects
  • recognition of debris in soil that may contain asbestos
  • procedures to be followed when soil that may contain asbestos is identified
  • safe packaging, labelling and handling of soil samples that may contain asbestos
  • the nature of operations that could result in exposure to asbestos
  • proper use, handling and disposal of personal protective equipment (PPE)
  • personnel decontamination
  • equipment cleaning

All personnel either organising fieldwork or inspecting and/or handling suspected asbestos-contaminated soil or being exposed to soil-disturbing activities at sites where there is a risk of asbestos-contaminated soil being encountered must be able to demonstrate an appropriate level of awareness of the risks associated with asbestos-contaminated soil.

The first step is to identify the potential for asbestos at a site by studying the site history and to exercise an appropriate level of caution. Asbestos may be expected within the demolition rubble from former buildings, in association with buried heating pipework and ducts, or simply within fly-tipped materials.  Asbestos Containing Materials (ACM) have been in use since 1834 but were most widely used between the 1950’s and the 1980’s.  The use of ACMs was not banned until 1999.

The potential for fibre release from ACM in damp soil may be limited, but if the site is dry and dusty, fibres may readily become airborne.

In addition to artificially damping down dust down drilling or trial pitting activities, the following PPE can be considered:

  • Boots that can be easily washed down.
  • Disposable overalls(type 5) fitted with a hood
  • High efficiency disposable particulate air respirator (FFP3)
  • Disposable Gloves
  • Goggles

Any suspect fibrous material or any cement / board type products which have evidence of fibres within them should be considered to potentially contain asbestos and samples must be taken for subsequent laboratory confirmation. All samples should be double-bagged with both the sample container and outer bag labelled as potentially containing asbestos so that the laboratory can take all the necessary precautions to prevent exposure to their staff.

Asbestos may occur as:

  • Sprayed coatings and wrapped lagging used for thermal & fire protection,
  • Insulating boards, wallboards and ceiling tiles used for fire protection, thermal and acoustic insulation
  • Profiled and flat roofing sheets, partitioning boards and decking tiles
  • Bitumen products, mastic pads, roofing felts gutter linings
  • Ropes and yarns
  • Cloth mats, fire blankets
  • Millboard and paper, general heat insulation
  • Flooring, thermoplastic, PVC floor tiles, mastics, sealants etc
  • Textured coatings e.g. artex
  • Bakelite

Unless a formal screening is requested by the person commissioning the laboratory testing, the laboratory will simple carry out a visual check.  There is an issue here in that a large proportion of soil samples are put through laboratories without any formal screening and it has been conjectured that significant percentages of made ground samples are passing through both geotechnical and analytical laboratories with undetected asbestos.

Most labs provide a tiered approach involving screening, identification and quantification:

  • Basic screening: examined under an optical microscope with magnification of x2 to x5
  • Detailed screening: ditto with magnification of x10 to x40
  • Identification: Polarised Light or Phase Contrast Microscopy (PLM or PCOM)
  • Quantification: Gravimetric (typical LoD 0.1%) *
  • Quantification:  Sedimentation and Fibre Counting (typical LoD 0.001%)

*The Gravimetric quantification method is currently being phased out.
Current UK workplace regulations for asbestos in air have a single Control Limit (max. concentration of fibres in the air averaged over a 4 hr period) for all types of asbestos of 0.1 fibres per cm3 (100 000 f/m3).  The World Health Organisation indicate that 1000 f/m3 is associated with a 10-6 to 10-5 risk of lung cancer in a population where 30% are smokers and 10-5 to 10-4 risk of Mesothelioma.

ICRCL Guidance Note 64/85 “Asbestos on Contaminated Sites” (1990) is still the most current guidance for asbestos in soil and suggest asbestos fibres should be  <0.001% w/w.

Waste Soil containing >0.1% w/w asbestos is classified as hazardous waste.

The key issue in assessing risks from asbestos in soil relates to modelling the exposure. It is not possible to use the CLEA model to calculate exposure and no reliable quantitative relationships between factors which affect asbestos fibre concentration in air and asbestos concentrations in soil are known.

There is some consensus between the UK (ICRCL), Dutch and Australian Guidance on the use of a threshold of 0.001% as a threshold for asbestos in soil. The Dutch Guidelines consider the risk from Chrysotile to be ten times less than Amphibole asbestos but the HSE, WHO, the Australian DoH and the USEPA have chosen not to distinguish between different asbestos fibre types.

For bound asbestos there is recognition that the potential generation of asbestos fibres is much lower and hence Dutch and Australian guidance use a threshold ten times higher than that for friable asbestos.

The USEPA use a method based on direct measurement during vigorous activity to assess the soil by measuring ambient air concentrations. A measurement approach is also used in the Dutch guidance.

New Guidance
It is believed that the Environment Agency and the HSE have in recent years collaborated to prepare new draft guidance for asbestos in soils in the form of a document entitled ‘A Study to Derive Soil Guideline Values for Asbestos in Soil’.

It was rumoured that this draft guidance recommended use of a strategy based on the Dutch approach for the assessment of soil contamination with asbestos.  However, the EA have seemed reluctant to publish this document, and despite a recent Freedom of Information request by the EIC it is now not expected to emerge, being instead superceded by a forthcoming update to the HSE document HSG248 (2005) ‘Asbestos: The analysts’ guide for sampling, analysis and clearance procedures’. Public consultation on this HSE document is awaited.


The AGS are supporting a current EIC incentive to develop best practice industry guidance with input from the EA / HSE / HSL/ BOHS and CL:Aire.  A CIRIA project has also been launched with similar goals so we may at present end up with two (or more!) pieces of industry guidance.     For the immediate future there is planned to be a workshop organised by CL:Aire in association with EIC & BOHS  at the Manchester Conference centre on the 1st November 2011.