Measuring Fibre Release:

Post-development Risk Assessment and Evaluation

(Construction-phase risks may differ)

Dr Richard OgdenLand Quality Management Ltd

LQM and asbestos• Renowned knowledge of contaminated land

assessment, management and remediation• Track record of using detailed risk assessments to

avoid unnecessary remediation– saving public and private sector large sums of money

• Several projects relating to asbestos-containing soils (under planning and Part 2A)

• Authors (together with asbestos-specialists from IOM) of the recent Ciria C733

Cards on the table….• Are SUBSTANTIAL concentrations of airborne fibres

released from UK soils and made ground?– We don’t know

• Do asbestos-containing soils pose a MATERIAL risk in the UK?– We don’t know

• Do small amounts of asbestos (particularly chrysotile) in soils justify the current REMEDIATION costs?– We don’t know

Where is the uncertainty?• Mainly, in exposure estimation

– Under what, if any, conditions are airborne fibres released from ACS in the UK?

• Weather conditions, depths, activities• Desiccation on hard surfaces

– What, if any, is the relationship between soil and airborne fibre concentrations?

• How does it vary for different soils and made ground types?– How much ACS be ‘tracked back’ into homes and offices?– How quickly will ACMs release free fibres into soils? Does AC in soil

pose any risk?

• Internationally recognised problem

Can airborne fibres be released from soils?

Theoretically, yes!• Addison et al. (1988) proved that

airborne fibres can be released– vigorous disturbance– dry soils (<10% moisture)– Asbestos fibres not ACM

• We know that surface soils can dry out– Especially where soil/mud

desiccates on roads, paths and patios etc.

• QED airborne fibres could be released

But there is ‘no’ proof!• Only ~48 measurements in 3

types of soil• Very little real-world data

– ‘Lot’s’ of Airborne fibres rarely detected at construction sites

• How often do surface soils really dry out?

• What is the effect of vegetation/turf?

• QED would any exposure ever really be significant?

Current science

only gets us

so far…

Are airborne fibres ever released from soil/made ground?

YES!

But what about Domestic gardens? School playing fields? Public parks? Etc….

Very little data to prove that potential exposures can or cannot be significant

Existing air monitoring data• Most current measurements (in the UK and elsewhere) are

made during construction activities• Are they representative of post development conditions?

– Health and safety provisions eg damping down in dry weather ( exposures)

– Large disturbance of soil ( exposures)– Fibre types not determined– Soil concentrations not well understood– Measurements below LoD required by CAR (0.1 or 0.01 f/ml) usually

assumed to be zero/acceptable/safe.• But long-term exposures at, or below, these levels could pose

unacceptable risks (especially for amphiboles)

Dutch dataset:Lab vs field measurement?

Average airborne asbestos concentrations from several comparable measurements (symbols) in fibres/m3air and 95% confidence intervals (hyphens), from worst case simulation experiments (), from field measurements with friable () and bound () asbestos, as a function of asbestos concentration in

soil. Straight lines represent the 95% intervals of all data. (After Swartjes & Tromp, 2008)

“measurement conditions were frequently not well defined and the soil was often (made)

damp, on account of which relatively ‘favourable’ conditions (suppression of fibre

emission) prevailed.” Swartz et al (2003)

International questions (and possible solutions)

• These uncertainties are widely acknowledged• Even in countries with published frameworks/ policy on

asbestos-containing soils, including:– Netherlands, Australia and USA

• Solutions and approaches:– Ongoing research– Development of novel soil sampling and testing methods that

better represent potential fibre release rather than asbestos concentration

– Flexible policy frameworks– Sharing of information

Is ABS a gold standard?

Photos: www.epa.gov

Activity-based sampling USEPA’s preferred method

at “superfund” sites Measures actual airborne

fibre concentrations under “reasonable worst case conditions”

Discriminate fibre types? Compatible with CAR2012?

“prevent the exposure to asbestos of any employee … so far as is reasonably practicable; ”

Only possible at existing property or post-development Applicability under

planning?

Estimate fibre release in the lab?• The uncertainty in the relationship between soil and airborne

concentrations has led to interest in novel “fibre release potential” tests

• More useful data for risk assessment than asbestos in soil concentrations

• Usually involve:– Mechanical disturbance of dry soil/made ground samples– Airborne fibres collected on filter– Asbestos fibres counted (and identified) oftn expressed relative to dust

concentrations (ie f/ml per mg m3 dust)

USEPA: Fluidised bed asbestos segragator

• Air elutriation separates fibres from soil, fibres collected on filter and analysed by electron microscopy

• Approximately linear relationship between the concentration of asbestos in soil (%) and the mean concentration estimated by FBAS/TEM (asbestos structures per gram of test material)

• LoD 0.002-0.005%• Components are easy to decontaminate or

disposable• Development ongoing

Januch et al (2013) Anal. Methods (5) 1658

UK: HSL’s “dustiness test” Based on BS EN15051:2006 Sample placed in rotating

drum. Air from the drum passes through a filter which is analysed for asbestos fibres

Results expressed as f/ml per mg/m3 dust

Has been used in conjunction with real-time dust measurements to estimate airborne fibre emissions during soil remediation involving mechanical screeningImages from Hardaker (2009) “Risk Assessment of Asbestos-Contaminated

Soils: An International Perspective” http://www.churchilltrust.com.au

Australia: Asbestos in soil to air assessment method

• On-site testing analysis by optical microscopy

• ASSAM prototype developed to complement conventional sampling in – delineating free asbestos

contamination– Determine if an exposure

pathway exists and trigger further assessment

– Validate remedial works

Presented by Benjamin Hardaker (AECOM) at CleanUp 2013 http://www.cleanupconference.com/

Ongoing UK initiatives:

Including those by JIWG and SoBRA

Based on presentation from Simon Cole at Ciria “Risk Assessment and Management of Asbestos in Soil” Conference, Manchester January 2015

EIC-CL:AIRE Joint Industry Working Group (JIWG)

• Survey of background in surface soils– Industry & Defra funding– Urban, semi-rural and rural soils in England & Wales– Analysis by specially validated PCM method to

0.0001% w/w; replicate SEM analysis on a selection of samples

• Standardised “Blue book” method for quantification of asbestos in soils– Publication shortly

EIC-CL:AIRE Joint Industry Working Group (JIWG)

• Occupational risk assessment:– Re-write Managing Asbestos (L143) to apply to ACS– Risk scoring algorithm to assist with CAR risk

assessments relating to ACS• But also risk ranking public and environmental exposures• Similar framework to algorithms in HSG227 & 264 for

surveying and sampling buildings• Excel based

SoBRA support for JIWG• Focus on soil-air relationship• Including:

– Review RIVM empirical data– Open-access database for field measurements of

fibre and dust• Soil and dust/fibre measurement protocols

– CAR-compliant Activity-Based Sampling protocol• SoBRA outputs will be freely available

Conclusions• Lab studies suggest that asbestos-containing soils could pose

unacceptable risks (particularly for amphiboles)– significant uncertainties in current exposure estimation methods– Precautionary approaches = unnecessary remedial costs?

• Internationally recognised issue• Better knowledge of the Soil-air relationship is needed

– ABS is not always possible (particularly for redevelopment)– International efforts to develop more informative soil tests to indicate

the potential for fibre release are ongoing– Could radically simplify risk assessment and remedial costs at most

sites (ie lower risk with asbestos cement/chrysotile present)

Thank You!