Improving Human Health Risk Assessment in Soils using Innovative Asbestos Dustiness Testing

The uncertainty in the relationship between soil and airborne asbestos concentrations has led to increasing focus on new ways of assessing risk including fibre releasability tests. The dustiness test is used to determine the production of dust and assess the amount of respirable asbestos fibres released.

Used in conjunction with asbestos fibre identification (TM48) and quantification of soils methods (TM304), this innovative approach provides additional detailed information to better inform risk assessment and improve understanding of the soil-to-air relationship.

ALS’s accredited method is based on an adapted version of BS EN 15051-2 in which the soil sample is placed in a rotating drum where it is continuously dropped to produce dust. The dust is then passed through a set of particle size-selective filters and through a 1.2 μm nitrocellulose filter at a controlled flow rate. These filters collect the dust fractions generated, allowing the laboratory to gravimetrically quantify the amount of total dust generated and then using PLM/PCM (polarised light microscopy/phase contrast microscopy), quantify the number of respirable fibres released.
Each fibre is measured (both length and width) with the aspect ratio calculated to ensure it meets the criteria for respirable status.

Soils can be analysed to determine site-specific or worst-case conditions:

• As-received
• Dried
• At a specific moisture content

The following information is reported:

• Discrimination of respirable fibres: chrysotile, amphiboles and non-asbestos fibres
• Respirable fibres counted
• Respirable fibre concentration (f/ml)
• Dust concentration (mg/m³)

Dust concentration is determined by measuring the amount of dust collected on the filter over a set time period. The respirable fibre count and discrimination is determined by counting fibres collected on a 1.2 μm nitrocellulose filter, following the fibre counting method outlined in HSG 248. The respirable fibre concentration is calculated from the fibre count.

Table 1 Sampling and Analysis Requirements

A minimum of 200g of soil is required for analysis at each moisture level. A 1 litre tub is recommended. The sample container should be secured, double-bagged and clearly labelled as potentially containing asbestos.  

_References

• _{Addition, J, Davies LST, Robertson, A, Wiley, RJ (1988). The release of dispersed asbestos fibres from soil. IOM Historical Research Report TM/88/14.}
• _{BS EN 15051-2:2013 +1:2016 Measurement of the dustiness of bulk materials; Part 2: Rotating drum method.}
• _{HSG248 – Asbestos: The analyst’s guide for sampling, analysis and clearance procedures (second edition) 2021.}
• _{Nathanail. C P., Jones, A., Ogden R., and Robertson A. (2014) Asbestos in soil and made ground: a guide to understanding and managing risks. C733, CIRIA. London.}

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