Asbestos in SoilsInnovative Laboratory Techniques to

Assist in Evaluating Risk

Dr Claire Stone

i2 Analytical Ltd

Overview

• Asbestos Analysis

– Background

• Standard Analysis Options

– Identification

– Quantification

• The next step

– Asbestos Dustiness Testing

“Assessment of respirable fibres from soils and bulks”

Background• Naturally occurring fibrous mineral silicates

• Earliest use 4,500 years ago strengthening earthenware

• Properties: sound absorption, tensile strength, its

resistance to fire, heat, electrical and chemical damage

• Kills around 5000 workers each year, more than the

number of people killed on the road

• Fibrous serpentine - Chrysotile (white)

• Amphiboles - Crocidolite (blue),

Amosite (brown), Actinolite,

Anthophyllite and Tremolite.

Background

Asbestos Analysis• Labs must be ISO 17025 for Asbestos ID

• Guidelines for ID given by Lab 30/HSG248

• Accreditation not required for Quantification

• Guidelines for quantification

– Development and validation of an analytical method to determine

the amount of asbestos in soils and loose aggregates: Addison

et al.,

– SCA Blue Book (Draft)….

Asbestos Identification Analysis

• Stage 1 – Screening and Identification

• Test must be UKAS accredited

• Sub-sample dried

• Examined under stereomicroscope

• Suspect materials/fibres/fibre bundles

removed for identification

• Identification by Polarising Light Microscopy

(PLM)

Asbestos Analysis

Asbestos Quantification

• Stage 2 – Quantification

• Also called ‘Hand Picking & Weighing’

• LOD < 0.001% (relates to sample mass and balance sensitivity)

• ‘Bulk’ ACM removed and weighed

• % Asbestos content determined using guidelines in HSG264

• Fine fraction examined and all fibres/fibre bundles removed and weighed

Asbestos Quantification

0.001 %

Asbestos Quantification

• Stage 3 – Quantification – Fibre Counting

• Soil sample is mixed with water and filtered

• Filter is used for fibre counting by Phase Contrast Optical Microscopy (PCOM)

• All fibres counted, some discrimination for ACM/Non ACM

• All fibres measured for length and diameter

• Mass of fibres calculated from known density of Chrysotile & Amphibole

What next?

Dustiness Testing

Risk Assessment

• Current techniques give you a numeric result along with a qualitative description of the asbestos fibre type and ACM type

• Only part of the picture

• Requires further information and interpretation to help define the risk this represents

• What else can be done? What is it that represents a risk?

Respirable Fibres

• Penetrate beyond the

terminal bronchioles into

the gas exchange region

of the lungs

• Represent the significant

risk to human health

• < 3µm Diameter

• > 5µm length

• aspect ratio (L:W) > 3

• Not a dust but a long thin

aerodynamic fibre

Can cause Asbestosis and

Mesothelioma with minimal exposure

What do we know?

• If the soil is wet, then there is less chance of airborne

fibres being released, but when dry, there is a significant

risk of fibres becoming airborne

• Dry soils containing 0.001% asbestos could release fibres

> current control limit of 0.1 fibres/ml

• Conditions: compressed air blown through the samples to

produce respirable dust concentrations of > 5mg/m3 Addison et.al

Analytical Options

• Activity Based Sampling

• Measuring airborne concentration of fibres during

simulated activities under controlled conditions

• Popular in US

• Pop up tents

Analytical Options

• Standard air monitoring

• Retrospective

• Calculation of potential fibres

• Use of detailed breakdown of PCM quantification data to

asses potentially respirable fibres

Fibre counting and measuring data - Chrysotile

Fibre length, μm Fibre width, μm Fibre volume, μm3

24.5 0.5 4.811

15.8 0.9 10.052

Definition: < 3µm Diameter, > 5µm length, aspect ratio (L:W) > 3

Analytical Options• Lab testing

• Various countries have looked at approaches to assessing

respirable fibres (UK, US, Australia)

• All based on agitation/disturbance of soil material under a

flow of air with filtration and fibre counting

Assessment of respirable fibres

from soils and bulks

• Adapted from EN 15051-2:2013

Principle

• Soil or bulk sample rotated in metal drum

• Constant air flow passed through equipment

• Generated dust with respirable fibres collected on a filter

• Dust on filter measured gravimetrically

Airflow

Method Principle

• Respirable fibres analysed by

standard PCOM method

(HSG 248)

• Results reported as:

– Respirable Fibre Concentration

(fibres/cm3)

– Dust Concentration (mg/m3)

– Normalised fibre concentrations at

fixed dust levels (as specified at

contract review)

Customising the process

• Moisture content

• Dry, as received or at a specified %DW

• Addition of binding agent?

• Vary Sample Preparation

• Particle size reduction/preparation

to limit fraction size

Benefits• Adds in the extra level of detail to help review risk on your

site

• Quick response

• No additional site activity or deployment of monitoring

equipment

• May provide significant cost savings over potentially

unnecessary remediation/removal techniques

Thank you