asbestos in soils - ags › content › uploads › 2017 › 07 › ags... · asbestos...
Post on 28-May-2020
1 Views
Preview:
TRANSCRIPT
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
top related