i

Determination of typical background concentrations

of asbestos in near-surface soils of selected public

open space areas of England and Wales to define

representative concentrations in areas not expected

to be subject to significant contamination

Chris Collins1, Mark Craggs2, Nicola Harries3, David Wood4, Gary Burdett5

1.Soil Research Centre, University of Reading, Reading, RG6 6DW

2.QUEST,Quaternary Scientific, University of Reading, RG6 6AB

3.CL:AIRE, 32 Bloomsbury Street, London, WC1B 3QJ

4. REC, Osprey House, Pacific Quay, Broadway, Manchester M50 2UE

5. Health & Safety Laboratory (HSL), Buxton, Derbyshire, SK17 9JN, UK

ii

Summary

A survey of the background asbestos concentrations in the near-surface soils of public open

space across England and Wales was undertaken. Samples (272) were taken from urban

(82), peri-urban (96) and rural locations (94). The sampling distribution was based on a 40 x

40 km grid across England and Wales which provided 111 sampling squares from which the

three sample categories were taken. Samples of near-surface soil were taken from a 20 m x

20 m square in an open location away from buildings, roads and tree cover. The sampling

protocol was based on previous national studies and reviewed by the Project Steering Group

(PSG). No alterations were found necessary following audits in the field.

Samples were quantitatively analysed according to a current UKAS accredited methodology

and in line with the draft Standing Committee of Analysts “Blue Book” method, “The

Quantification of Asbestos in Soil and Associated Materials (v.11)”. The detection limit of

this method is ~0.001% by weight for asbestos fibres and asbestos-containing materials. An

extension of the Blue Book method was adopted to achieve an Limit of Detection (LOD) to

0.0001%. All 272 samples were analysed. This method, based on stereo and polarised light

microscopy, was independently cross-checked by an analytical Transmission Electron

Microscopy (TEM) method using 16 blind samples. A number of asbestos-containing quality

assurance samples which had been spiked with a known amount of asbestos were also

analysed.

Only two samples from 272 field samples gave positive results (i.e. <1% of samples); both of

these were < 0.0002% by weight.

iii

Members of the Project Steering Group (PSG)

David Middleton – Defra

Richard Clark & Andrew Williams – Welsh Government

Stephen Forster – Chair of the Joint Industry Working Group (JIWG) on Asbestos in Soil and

Construction & Demolition Materials

Simon Cole – SoBRA

Nicola Harries – CL:AIRE

Chris Collins & Mark Craggs – University of Reading

Garry Burdett – Health & Safety Laboratory

David Wood – REC Ltd

iv

Table of Contents Summary .................................................................................................................................... ii

List of Tables ............................................................................................................................. vi

List of Figures........................................................................................................................... vii

Project aims and objectives ....................................................................................................... 1

Introduction ................................................................................................................................ 3

Methods ..................................................................................................................................... 4

Sampling strategy .................................................................................................................. 4

Sampling protocol .................................................................................................................. 8

Soil analytical process ........................................................................................................... 8

Asbestos analysis by electron microscopy .............................................................................. 11

Quality assurance .................................................................................................................... 12

Auditing ................................................................................................................................ 12

Asbestos analysis ................................................................................................................ 12

Results of the examination of the known QA samples .................................................... 13

Results from the blind analysis of the unidentified QA samples...................................... 14

Outcome of QA ................................................................................................................. 15

Results ..................................................................................................................................... 16

Sampling .............................................................................................................................. 16

Soil concentrations............................................................................................................... 20

Asbestos analysis of environmental samples ..................................................................... 21

Using conventional microscopy and stratified approach ................................................. 21

Comparison of field samples between REC and HSL ..................................................... 21

Discussion ................................................................................................................................ 23

References ............................................................................................................................... 24

Appendices .............................................................................................................................. 25

Appendix 1. Standard Operating Procedure for SP1014 Sampling.................................... 26

Appendix 2. Sample Survey Recording sheet ..................................................................... 35

Appendix 3. Site audit reports ............................................................................................. 37

v

Appendix 4 – Audits of Asbestos Analysis .......................................................................... 56

Appendix 5 - Abbreviated Method Statement for Quantification of Asbestos in Soils by REC

Ltd ........................................................................................................................................ 67

vi

List of Tables

Table 1. Sampling categories as defined by the UK Census data .......................................... 6

Table 2. Results from the ‘known’ and ‘blind’ QA analysis of prepared spiked samples (weight

% of asbestos) undertaken by Health & Safety Laboratories ................................................. 14

Table 3. Final list of samples ................................................................................................... 20

Table 4. Comparison of field samples HSL and REC Ltd ....................................................... 22

vii

List of Figures

Figure 1. Selected sampling locations based on 40 km grid across England and Wales ........ 5

Figure 2. Sampling locations with 40 km grid overlaid over population data. .......................... 7

Figure 3. Soil analysis process flowsheet ............................................................................... 10

Figure 4. Example site and sample description sheet. ........................................................... 18

Figure 5. Final sample numbers and locations ....................................................................... 19

Figure 6. Asbestos concentrations results as presented by REC Ltd after light microscopy

analysis. ................................................................................................................................... 20

1

Project aims and objectives

Aim

To provide an estimate of the range of typical background concentrations of dispersed

asbestos fibres in soil across England and Wales that are primarily a result of atmospheric

dispersion and deposition of fibres from the historic import of asbestos and the manufacture

and use of asbestos-containing products.

It was not the aim of this project to establish the range of asbestos fibre or asbestos-

containing material in soil concentrations resulting from localised occurrence of asbestos in

the ground as a result of the disposal of waste or by other mechanisms such as demolition of

buildings that may have incorporated asbestos-containing materials. The survey specifically

avoided land areas where elevated concentrations of asbestos were known or strongly

suspected (for example former asbestos manufacturing facilities or manufacturing facilities

that extensively used asbestos, and areas of naturally occurring asbestos).

Objectives

• Design a survey and sampling approach which were capable of obtaining a dataset

that is amenable to relevant, robust statistical analysis and provide a reliable dataset

that can withstand public scrutiny.

• Target surface soils in publicly accessible areas e.g. open spaces or land where

access can be provided by Defra, Welsh Government or local authorities that are not

likely to have been subject to the addition of former building materials or any other

potentially asbestos containing materials.

• The survey should be capable as a minimum of distinguishing between urban and

rural soils, but should aim to provide as much land-use discretisation as is practicable

such that robust correlations can be made.

• The survey should avoid spatial biasing where practicable.

• The survey should anonymise samples and sample locations in the final report, but

sample locations should be suitably recorded so that they can be used in the data

interpretation to ascertain spatial and land-use correlations where appropriate.

2

Scope

The survey should avoid areas of naturally occurring asbestos, areas affected by major

asbestos industries (for example the former Cape and Turner Brothers factories), areas

where asbestos waste has been placed in the ground, brownfield sites, and made ground

comprising building demolition rubble. For rural areas locations should avoid land which

may contain asbestos – this might include agricultural land in and around farmsteads and

rural commercial properties, as well as former farm tip sites and old quarry holes.

The soil sampling protocol should provide representative samples of soil for subsequent

analysis. The protocol should focus on the assumption that asbestos might be present as

dispersed free fibres in soil, but should also be capable of accounting for fragments of

asbestos-containing material (ACM) if observed. The protocol should also provide sufficient

qualitative information on the sampling location to aid subsequent interpretation of the

analytical results.

The survey and sampling designs will be agreed with the PSG. Existing guidance on soil

surveys and sampling techniques should be referenced, and consideration should also be

given to the preliminary thoughts of the PSG as provided.

3

Introduction

To inform scientifically robust risk-based decisions to protect employees and the public from

asbestos in soil, it is essential to develop a scientifically defensible and pragmatic risk

management system when dealing with asbestos in soil. In ensuring that risk assessment

outputs are pragmatic, knowledge of background concentrations are required to inform

decision making within the Part 2A statutory guidance and planning decisions. The concept

for this is similar to that already published for other soil contaminants as part of the revised

Soil Guideline Values programme in 2009.

This research sampled across England and Wales to define typical background

concentrations in areas not expected to be subject to asbestos contamination (for example

small grassed areas in residential estates or playing fields rather than roadside verges).

Prior to this survey, there has not been any investigation to ascertain background

concentrations of asbestos in soil, however the British Geological Survey had carried out a

survey for Defra on determining normal background concentrations of a number of other

common contaminants [1]. In addition Defra and the Welsh Government have previously

carried out soil and herbage surveys [2] for a range of contaminants. This current research

project drew on these two projects when planning its approach and sampling protocols.

4

Methods

Sampling strategy

To provide a national sample distribution a 40 km grid covering England and Wales1 was

created using ArcGIS v10.2.2 Grid Index Features tool, this grid produced 133 sampling

squares. The Create Fishnet tool was then applied to produce centre points on the newly

created grid (Figure 1). A selection was performed to remove squares mainly comprising sea

which left 111 squares to be potentially sampled. Middle Layer Super Output Area (MSOA)

census data for England and Wales [3], were downloaded and three classifications were

assigned to the MSOA landuse categories: urban, peri-urban and rural (Table 1 and Figure

2).

The intention was to take one sub-sample from each of the land use categories (urban, peri-

urban and rural) from each sampling area; potentially providing 333 samples.

The Local Authorities (LAs) in England and Wales in whose area the land within which each

grid square centre was located were first contacted and suitable sampling locations selected

and agreed. A specific land use category was then assigned, i.e. urban, peri-urban or rural.

The nearest locations for the remaining sample categories were then chosen using Google

EarthTM. Duplicate samples were taken at 5.6 % of the plotted sites to determine within-site

variability.

This sampling strategy was reviewed by the Project Steering Group (PSG) and accepted

after several iterations. Prior to the actual sampling exercise being undertaken, University of

Reading (UoR) contacted each of the to arrange for the sampling of soil in their respective

area.

1 England and Wales boundaries downloaded from (http://census.edina.ac.uk/

5

Figure 1. Selected sampling locations based on 40 km grid across England and Wales

6

Table 1. Sampling categories as defined by the UK Census data [4]

MSOA categories Project categories

England Urban minor conurbation

Urban

England Urban major conurbation

England Urban city and town

Wales Urban city and town

England Urban city and town in a sparse setting

Peri-urban

Wales Urban city and town in a sparse setting

England Rural town and fringe

England Rural town and fringe in a sparse setting

Wales Rural town and fringe

Wales Rural town and fringe in a sparse setting

England Rural village and dispersed in a sparse setting

Rural

England Rural village and dispersed

Wales Rural village and dispersed

Wales Rural village and dispersed in a sparse setting

7

Figure 2. Sampling locations with 40 km grid overlaid over population data.

8

Sampling protocol

The collection of soil samples followed the protocol adapted from Defra and BGS when

undertaking the herbage and soil survey for England and Wales [2] and the GBASE surveys

[1] respectively. Five samples were taken from the corners and central location within a 20m

x 20m square avoiding areas beneath mature trees. A smaller square of greater than 10m x

10m was permitted if space was restricted, however any reduction was noted on the site

sampling sheet (Figure 4). At each site a location reading was taken by a hand held GPS

(+/- 10 m) and site details logged in accordance with sample sheet and photographed

(Plates 1a-d). Careful notes were also made of buildings that were close by and the fabric

materials they were made of. The surface herbage was removed with hand tools and a 5 cm

depth of soil taken using a stainless steel spade and/or trowel. Vegetation removal focused

on above-ground vegetation clearance to facilitate the soil sampling; the removal of soil was

avoided except when tightly-bound by dense root mats. For example, it was deemed

acceptable to remove the top 1cm beneath grass turf as this soil typically came away with

the turf when raised. The five samples were bulked to form one sample (2 kg +/- 10g, scale

precision 0.1g); this was coned and quartered with approximately a 1 kg sample being

retained for analysis by REC Ltd and a further 1 kg of material being retained for storage at

UoR. There was no further processing of the sample.

After sampling at each site, all tools and trays were cleaned with disposable wipes and

stored in clean bags to prevent cross contamination. All samples were systematically

anonymised and labels were only traceable to sites by UoR staff. Sample anonymisation

was based on 256 bit AES encryption with a password 64 hex characters in length. Any

images produced as part of the sampling process had their metadata stripped thereby

removing any embedded location data in the image file. Sampling data was stored at UoR

and could only be accessed by one staff member.

As with the sampling strategy the sampling protocol was critically reviewed over several

iterations by the PSG. The detailed Standard Operating Procedure (SOP) for the sampling

procedure is elaborated in Appendix 1.

Soil analytical process

REC Ltd performed quantitative stratified light microscopy analysis according to their current

UKAS accredited methodology and is broadly in line with the Blue Book method, “The

Quantification of Asbestos in Soil and Associated Materials (draft v.11)”. One variation

9

was performed whereby, even if no fibres were detected at the first stage of the analysis,

suspensions were prepared and a total of 10 aliquots were taken for filtration and

microscopic analysis. The objective here was to lower the limit of detection and hence the

reporting limit to 0.0001% and to improve the uncertainty of measurement.

The analytical approach followed a 3-stage process of visual inspection, microscopic and

gravimetric evaluation and microscopic evaluation of an aqueous suspension. This standard

analytical methodology generates three natural cut-off points for analysis at the three stages,

with Stage 3 normally offering a reporting limit of 0.001%.

The analysis consisted of the following stages which are carried out after drying as

described in the flow chart below (Figure 3).

Stage 1 – No samples were stopped at Stage 1

Stage 2 – Gross contamination (>0.1%)

Stage 3 – Result <0.1% - 0.001%

Stage 4 – Result or >0.0001% (0.001% and above UKAS accredited)

10

Figure 3. Soil analysis process flowsheet

Stage 1 Visual analysis performed on 1 kg soil plus microscopic

analysis of subsample for fibres and small ACM pieces

Stage 2 >20 g subsample analysed under microscope,

fibre clumps and ACM’s removed, identified and

weighed with material removed at Stage 1

If no asbestos detected

or suspected fines only

are found in the sample,

analysis proceeds

directly to Stage 3

If fibre clumps and/or

pieces of suspected

ACMs are found

analysis proceeds to

Stage 2

<0.1% proceeds to

Stage 3

Stage 3 Suspension in 300 ml water, 1ml aliquot filtered taken and 200

graticules counted.

Stage 4 Further 9 x 1 ml aliquots filtered of the suspension taken

and 200 graticules per aliquot counted

<0.001% proceeds to

Stage 4

11

Asbestos analysis by transmission electron microscopy

The Health and Safety Laboratory (HSL) analysed 19 samples in total for this project; three

samples as a laboratory comparison between REC Ltd and HSL which included standards

and blanks; 16 field samples were sent to HSL by REC Ltd. The field samples consisted of

12 selected samples one from each category (urban, peri-urban, rural) in the north, east,

south and west of the sample grid, two random field samples and two field samples where

asbestos had been detected by REC Ltd. All samples had been anonymised by the

University of Reading and were blind analyses.

The duplicate samples were analysed using HSL’s UKAS accredited method for asbestos in

soil, which is based on the International Standard method ISO13794 [5]. This method uses

analytical Transmission Electron Microscopy (TEM) to quantitatively identify asbestos fibres

in a known area of the filter. However, as most of the TEM analysis was carried out in the

latter stages of the project, it was decided to change from the original planned stratified

method of analysis (based on analysis at two magnifications) to a more sensitive method

which used a single magnification of x 5,600 to search a larger area (0.96 mm2 ) of the filter

for both >5 µm long fibres and any visible fibres. The high contrast and high definition CCD

camera images allow both shorter and thinner fibres to be detected. To further optimise the

analytical sensitivity most of the filters analysed were prepared by HSL from soil sub-

samples sent to HSL.

Any fibres (particles with an aspect ratio of >3:1 and with parallel or stepped sides) or

bundles of fibres found were analysed using a combination of energy dispersive x-ray

analysis and selective area electron diffraction to identify whether they were asbestos and, if

so, which type. Any asbestos fibres/bundles identified were counted and then sized at higher

magnifications and their volume and mass calculated. Results were calculated and reported

in terms of the asbestos weight % and the number of asbestos fibres/g of soil. Any >5 µm

long fibres with widths >0.2 µm are likely to be counted by the regulatory method for air

sampling (HSG 248) based on phase contrast microscopy (PCM) and were reported as PCM

equivalent fibres (PCME).

12

Quality assurance

Auditing

Both internal and external audits were undertaken of the field sampling methodology and the

analysis of soils for asbestos. For the field sampling, the site preparation and soil collection

were assessed using the procedures outlined in Appendix 1, Section 8. Three audits were

undertaken by two external assessors (Appendix 3). The soil analysis was audited against

the method statement (see Appendix 5 for the abbreviated method statement). Two audits

were undertaken, one internal and one external (Appendix 4). No additional auditing of the

TEM analysis was carried out due to the low number of samples analysed. The audit

procedure was designed to provide confidence that field and laboratory procedures

developed were being undertaken to a high standard.

Asbestos analysis

To assess the REC Ltd laboratory performance, a number of “spiked” soil samples

containing known added amounts of asbestos were distributed for analysis. The first round

of assessment involved sending two samples directly to REC Ltd for analysis (LCSA 1,

DLSA 5). Each of these samples contained a known amount of amosite fibre which had

been prepared and analysed previously by HSL and were identifiable as non-routine QA

samples.

Three further QA samples were prepared by mixing either an asbestos-containing material

or asbestos fibres into 500 g of a loam soil. One sample (1 DLS) contained two small pieces

(each less than the size of a fingernail) of dry asbestos cement containing chrysotile (AIMS

52 sample 2) weighing 0.3350g. The calculated amount of asbestos was based on the

asbestos cement containing 10% of asbestos by weight. These pieces were considered

large enough to identify during the stage 1 visual examination of the 1 litre sample when

spread out on a tray followed by asbestos identification analysis. The second sample (2

DLS) had 12.75mg of ultrasonically dispersed chrysotile fibre in water added. The chrysotile

was visible to the eye when added to the soil before mixing in a figure of eight mixer but this

would have been further dispersed and coated with soil particles during the mixing process.

The third sample (3 DLS) had no additional asbestos added and was used to check that the

loam soil used for the preparation of the QA samples was not already contaminated with

asbestos.

13

These three QA samples were sent to University of Reading where they were mixed with a

further 500g of soil from known blank field samples and repackaged and given anonymised

numbers so they were indistinguishable from the other study samples (1- 3 DLS). These

three samples were therefore “blind” analysis QA samples. These three samples were

analysed “blind” by both REC Ltd and HSL using their standard analytical protocols for this

study.

Results of the examination of the known QA samples

The first two known QA samples prepared by HSL were correctly reported by REC Ltd as

containing amosite asbestos (LCSA1 & DLSA5), but the mass percentage in each was

underestimated (see Table 2). Subsequent investigations showed that this was partly due to

the method used in stages 1 & 2 (Figure 3) to report the weight percentage which was based

on picking out fibres from the soil substrate and weighing them on a balance. This gave rise

to two issues – when picking out fibres and suspect pieces of ACM, whilst this is the

established first stage of the procedure employed by REC Ltd, it is only likely to give

accurate results if the majority of the asbestos is easily seen and/or present in easily

identifiable pieces, and if enough of it can be separated from the soil matrix to give good

precision and accuracy when weighed. As only fibres of amosite were added to the two

known QA samples, any fibre picking would only remove any of the larger fibre bundles and

clumps of fibres and give an underestimate of the total mass of asbestos present. This would

particularly be an issue when the asbestos had been relatively well dispersed in the soil

matrix and was mainly present as individual fibres, as it was in these two samples.

It was also noted at the limit of detection (LOD) for stages 1 & 2 (i.e. 0.001%) meant that the

balance used for the weighing was at the limit of its resolution and had limited precision.

However, the visual examination in stages 1 & 2 (fibre picking and stereo-microscopy) both

found the presence of finely-divided amosite fibres and REC Ltd reported it correctly as

being <0.001% (Note samples DLSA5 had been examined previously and two small fibre

bundles would have been extracted for identification).

14

Table 2. Results from the ‘known’ and ‘blind’ QA analysis of prepared spiked samples (weight % of asbestos) undertaken by

REC Ltd

HSL

sample # Anonymised Sample from

UoR

Type and amount of asbestos

(%) added by

HSL

Type and amount of asbestos

(%) reported stages 1

& 2

Type and amount of asbestos

(%) reported

stages 3 & 4

HSL TEM analysis

No of fibres

counted

Amount of

asbestos reported

(%)

Concentration (x106 fibres/g) of

bulk material

LCSA1* (100g sample in a bottle)

Known QA sample

Amosite fibres (0.001)

Amosite (<0.001)

Amosite (0.0003)

Not analysed

Not analysed

Not analysed

DLSA5* (36 g sample in a Petri dish)

Known QA sample

Amosite fibres (0.01)

Amosite (<0.001)

Amosite (0.0007)

Not analysed

Not analysed

Not analysed

DLS 1 S138

Blind sample

2 pieces of chrysotile asbestos cement (0.003)

Chrysotile (0.003)

Chrysotile 0.011

0 ND <0.0666

DLS 2 S258 Blind sample

Finely dispersed chrysotile fibres (0.0013)

Not detected (<0.0001)

Not detected (<0.0001)

0 ND <0.1106**

DLS 3 S259 Blind sample

Blank Not detected (<0.0001)

Not detected (<0.0001)

Not analysed

Not analysed

Not analysed

*These samples were prepared by HSL and sent directly to REC Ltd ** Note: Five >5 µm long chrysotile fibres with widths <0.2 µm were found in this sample with a calculated mass of 0.0000021% and a fibre concentration of 0.186 x 106 f/g

Results from the blind analysis of the unidentified QA samples

Blind analysis of these three QA samples by REC Ltd found the asbestos cement fragments

(DLS 1), but did not detect the finely dispersed chrysotile (DLS 2), and confirmed that

asbestos was not detected in the blank sample of soil (DLS 3) (Table 2.).

The TEM analysis of sample DLS 2 subsequently undertaken by HSL found that chrysotile

asbestos was present (Table 2.). However, all of the chrysotile fibres analysed had

diameters of <0.2 µm and would be too thin to be visible by light microscopy analysis. The

fineness of the fibres in this sample explained the negative result for sample DLS 2 by REC

15

Ltd. The mass of chrysotile calculated by the TEM analysis was 0.0003% well below the

actual mass percent added 0.0013%.

The sample supplied for TEM preparation was only 0.1% of the sample, so the mixing of the

small amount of chrysotile into this soil would have to be very good and the sub-sampling

representative of the original sample, both of which are challenging. The non-detect TEM

result for sample DLS 1 is explained by there only being two pieces of asbestos cement

added, which were found and extracted from the sample during stage 1 of the analysis

conducted by REC Ltd. No asbestos was added to DSL 3 which was the soil used for DLS 1

& 2 which confirmed that there was no detectable asbestos present.

Outcome of QA

All of the QA analysis was in some way challenging with small amounts of asbestos added

at or below 0.01% and generally were closer to the limit of detection for most routine soil

analyses (0.001%). The four stage REC Ltd analysis correctly identified the presence of

asbestos except in one very challenging sample where the chrysotile fibres appeared to be

too thin to be seen by light microscopy. The estimation of mass did not have good precision

but due to the low amounts added this is to be expected. What was shown was that the

overall method using visual assessment of the whole 1 kg sample to microscopic

examination of filtered aliquots is needed to identify the different forms of ACMs and

asbestos fibres that may be present.

The QA results give a reasonable degree of confidence that the REC Ltd analysis would

have had a good chance of detecting asbestos being present in the survey samples, if

present in concentrations of >0.0001%, unless the fibres were outside the size criteria for the

assessment of airborne risk.

16

Results

Sampling

Of the 333 sites scoped by the initial sampling strategy, 288 were identified as suitable

following further assessment. The reduction in the final number of sampling locations is

attributed to the fact that not all of the three categories of land use were present in each grid

square.

Once sites were identified, sampling proceeded without significant difficulties. The protocol

worked well and the recording of site characteristics was relatively straightforward (Plates

1a-d, Figure 4). The proportions of rural (35.3%), peri-urban (34.6%) and urban locations

(30.1%) were well-balanced to ensure no bias in the data. There was also good coverage

across the whole sample area with only 1 grid square un-sampled. In those squares where

all three samples categories were not taken this was often because a category was not

present, e.g. urban locations on the England-Scotland border.

17

(a) (b)

(c) (d)

Plate 1 a-d sampling photos relating to site described in Figure 4.

18

Figure 4. Example site and sample description sheet.

19

Figure 5. Final sample numbers and locations

NS

NS Natural

As

Not Sampled (due to geology)

Not Sampled (No central sampling location generated, generally greater proportion of ocean relative to land.

x/y

Done

x/y LA contacted, ‘x’ sites out of ‘y’ total sites identified and permission to sample/access available.

Sampled locations ‘x’ sites out of ‘y’ total sites within grid.

0/3 LA contacted, meaningful discussion has taken place but nothing yet identified.

x/y

Done Indicates partial grid completion (at least 1 site will l not be sampled)

Key

20

Table 3. Final list of samples

Country Urban Peri-urban

Rural

England 76 82 80

Wales 6 14 14

Total 82 96 94

Grand total 272

Soil concentrations

Samples were typically analysed by REC Ltd in batches of 20 with results usually returned

within 4 weeks in a standardised format indicating the concentrations at the different

analytical stages (Figure 3 and 6).

Figure 6. Asbestos concentrations results as presented by REC Ltd after light microscopy analysis.

21

Asbestos analysis of environmental samples

Using conventional microscopy and stratified approach

Asbestos was detected in two samples of the 272 analysed, i.e. less than 1% of the total of

all samples submitted to REC Ltd for analysis. These were from a peri-urban site

(<0.0001%, S137) and an urban site (0.0002%, S161).

Comparison of field samples between REC and HSL

To validate the results from the stratified light microscopy (REC Ltd) with the TEM (HSL) 16

samples were used for duplicate analysis (Table 4.). No asbestos was detected in any of the

samples by HSL including the two positive detects (S137, S161) reported by REC discussed

above. Both of these samples were later sent to HSL for further checking and analysis and

prolonged searching using stages 1 an 2, did not detect any further asbestos fibres in these

samples.

It appears that the non-detect by TEM was a consequence of the low concentrations of

asbestos in these samples and their non-homogeneous nature (e.g. one sample had a

single bundle picked out in stage 1), whereby any sub-sample was more likely to be free of

asbestos.

22

Table 4. Comparison of field samples HSL and REC Ltd

HSL analysis

Asbestos structures > 5 µm long (PCME) REC Ltd Analysis

Client sample No.

Analytical sensitivity

(x106 structures/g) of bulk material

No of fibres

counted

mass %

Maximum possible concentration

(x106 structures/g) of bulk material

mass %

Maximum possibile

concentration (%)

S041 0.037 0 ND <0.111 ND <0.0001

S084 0.022 0 ND <0.0663 ND <0.0001

S092 0.022 0 ND <0.0665 ND <0.0001

S098 0.022 0 ND <0.0661 ND <0.0001

S100 0.037 0 ND <0.112 ND <0.0001

S119 0.037 0 ND <0.112 ND <0.0001

S130 0.037 0 ND <0.112 ND <0.0001

S146 0.037 0 ND <0.111 ND <0.0001

S147 0.037 0 ND <0.11 ND <0.0001

S076 0.022 0 ND <0.0665 ND <0.0001

S173 0.022 0 ND <0.0668 ND <0.0001

S066 0.019 0 ND <0.058 ND <0.0001

S137 0.022 0 ND <0.0666 <0.0001 NA

S161 0.111 0 ND <0.333 0.0002 NA

S088 0.019 0 ND <0.058 ND <0.0001

S089 0.039 0 ND <0.117 ND <0.0001

23

Discussion

The sampling of near-surface soils across England and Wales was successfully completed

with 94% of the original targeted samples collected. There were two reasons for samples not

to be taken from a grid location; i) the particular category was not present e.g. no urban

sample on the England-Scotland border, or ii) lack of cooperation from the landowner.

Two samples from 272 gave positive results, i.e. <1%; these were at low concentrations

<0.0001 and 0.0002% and close to the expected detection limit. In both positive cases loose

fibres of amosite were observed. This number of samples where asbestos was positively

detected is too small to enable a discussion of any trends in the data, or to estimate a

‘background concentration’ for England and Wales.

The results do give confidence, however, that ‘background concentrations’ of asbestos in

near-surface soils following the removal of surface vegetation in public open spaces across

the spectrum of land uses are generally likely to be very low and unlikely to be detected by

the standard analytical methodology. This also gives a degree of confidence that significant

potential health risks arising from ‘background concentrations’ of asbestos in near-surface

soils in public open spaces unlikely to be of concern.

The very small number of positive detects (<1% of the total samples analysed and reported

in this survey) will give added weight that asbestos found in near-surface soils is likely to be

due to local contamination sources (e.g. demolition, waste disposal and fly-tipping) and that

the extent of these sources can be mapped by soil sampling surveys. It is not evident from

this survey that historic diffuse airborne fibre release has resulted in widespread detectable

quantities of asbestos in near-surface soil across England and Wales.

The main aim of the study was met because the soil concentrations were measured at less

than 0.0001% by light microscopy. If consideration is given to the TEM results produced by

HSL, this concentration could be even lower as shown in Table 4 where the maximum

possible concentration detectable (limit of quantification) is shown for the 16 duplicate QA

samples to be in the range of <0.58 to <0.11 x106 structures/g of bulk material.

24

References

1. Ander, E.L., et al., Methodology for the determination of normal background concentrations of contaminants in English soil. Science of The Total Environment, 2013. 454-455: p. 604-618.

2. Agency, E., Volume 1. Introduction and Summary. UK Soil and Herbage Pollutant Survey. 2007: Environment Agency.

3. Pateman, T. Rural and urban areas: comparing lives using rural/urban classifications. Regional Trends, 20101. 43.

4. Statistics, O.o.N., Middle Super Output Area Mid-Year Population Estimates. 2014. 5. 13794, I., Ambient air - Determination of asbestos fibres - indirect transfer

transmission electron microscopy method, I.S. Organisation, Editor. 1999 Geneva. Switzerland.

25

Appendices

26

Appendix 1. Standard Operating Procedure for SP1014 Sampling

1 Scope and Application

The purpose of this standard operating procedure (SOP) is to describe the procedures for

the collection of representative surface soil samples. The sampling depths required for

SP1014 are easily reached without the use of drill rigs, direct push or other mechanised

equipment. Analysis of soil samples for asbestos will be used to produce summary statistics

(such as 5th and 95th percentile, median and mean). These are standard (typically

applicable) operating procedures which may be varied or changed as required, dependent

upon site conditions, equipment limitations or limitations imposed by the procedure. In all

instances, the actual procedures used to collect samples will be documented and described

in an appropriate site report.

2 Method Summary

Soil samples may be collected using a variety of methods and equipment depending on the

depth of the desired sample, the type of sample required and the soil type. As we are

focusing on near surface sampling and are not required to sample undisturbed soil samples

(i.e. samples generated by soil coring) the use of spades, trowels and scoops is sufficient.

These collection methods will generate disturbed samples however, as the 5 samples from

each site are bulked into a single unit.

3 Sample Containers, Handling and Storage

For each sampling site, 2 kg (400 g from each corner and centre of a 20 m x 20 m sampling

grid) of soil will be placed into an appropriately sized plastic containers clearly marked with

sample identification information. Half will be sent for analysis and half stored for a period of

at least 1 year.

4 Interferences and Potential Problems

There are two primary potential problems associated with soil sampling. These are cross

contamination of samples and improper sample collection.

a) Cross contamination problems can be eliminated or minimised through the use of

dedicated sampling equipment. If this is not possible or practical, then

decontamination of sampling equipment is necessary. In addition clean and

potentially dirty areas need to be kept separate in the collection vehicle. The latter

27

will contain all collected samples, sampling equipment and used clothing and barrier

protection.

b) Improper sample collection can involve using contaminated equipment, failure to

adhere to sampling grid or sampling at an incorrect depth, or failure to identify

asbestos samples where present, resulting in variable, non-representative results.

This is addressed in detail below Section 8.

5 Asbestos Risks

5.1 Human Health

Asbestos fibres do not dissolve in water or evaporate; they are resistant to heat, fire

chemical and biological degradation and are mechanically strong. The globally harmonised

system of classification and labelling for chemicals indicates asbestos is a category 1A

carcinogen. All types of asbestos fibres are known to cause serious health hazards in

humans.

The specific risks from asbestos relate to the potential release of respirable fibres into the

atmosphere when disturbed. Outdoors, asbestos fibres or dust, once exposed, may be

released into the atmosphere by the wind, by construction activities or by the movement of

vehicles or construction plant and will undergo significant dilution at increasing distance from

the source. Even low concentrations of asbestos fibres in air can present a potential risk to

health if exposure to those concentrations is prolonged. Potential risk to health is a function

of concentration and exposure duration.

Some asbestos-containing materials (ACMs) are more inclined to release fibres than others;

for example, asbestos fibres bound in thermoplastics, resins or cement release fewer fibres

than loose, friable insulation. It is of some note that ACMs installed in buildings, which are

normally dry, tend to release more fibres when disturbed than the equivalent ACMs when

encountered in soil, where they tend to be wet.

5.2 Exposure Limits (air)

In the UK an unacceptable risk to human health from the inhalation of asbestos fibres is

reported by the Health and Safety Executive (HSE). As a consequence of this the following

regulations apply. These set out legal duties and it is important to comply with any

requirements derived from the regulations. The regulations provide minimum standards for

protecting employees from the risks associated with asbestos.

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There are two main limits set out in regulation 2 of the Control of Asbestos Regulations

2012. The first relates to the concentration of asbestos fibres in any localised atmosphere

(control limit) and the second relates to sporadic and low intensity exposure. The latter is

sometimes referred to as the short-term exposure limit (STEL).

The control limit refers a concentration of asbestos in the atmosphere when measured in

accordance with the 1997 WHO recommended method, or by a method giving equivalent

results to that method approved by the Executive, of 0.1 fibres per cubic centimetre of air

averaged over a continuous period of 4 hours.

For the purposes of regulation 2, for exposure to be sporadic and of low intensity, the

concentration of asbestos in the atmosphere should not exceed or be liable to exceed 0.6

fibres per cubic centimetre (f/cm3) in the air measured over a ten-minute period. Any

exposure which exceeds or is liable to exceed this is not sporadic and of low intensity. Note

that this approved concentration for sporadic and low intensity exposure is not the same as

the ‘control limit’ defined in regulation 2 of the Control of Asbestos Regulations 2012.

It is relatively easy to release asbestos fibres when working with asbestos coatings,

asbestos insulation, and asbestos insulating board (AIB). In most cases, only those with a

licence should carry out work with these materials. However, licensing does not apply to

short-duration work on insulation and AIB where the risk assessment shows work carried out

will only produce sporadic and low intensity exposure and will not exceed the STEL.

Licensing does not apply to sampling ACMs in buildings or in soil unless the control limit is

likely to be exceeded.

It should be noted that the Health Protection Agency (HPA) have suggested that where

possible, aim to reduce levels of exposure to as low as reasonably practicable (ALARP).

There are no safe exposures and the hazardous waste threshold of asbestos (≥0.1% wt/wt)

cannot be used as a minimal threshold for human health risk assessment purposes.

5.3 Moisture Content and Drying

Studies have demonstrated that the addition of 10% of water to soil decreases the risk of the

potential release of asbestos fibres to air by a factor between 2 and 10. Most soil is damp

when in-situ and poses little risk of fibre release, but once excavated or exposed it may

become dry very quickly. Locations commonly identified on sites having this potential are

excavations or intrusive hole locations, spoil, areas where any hard surfacing is removed,

vehicle routes passing between soft ground and hard standing, open skips and

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mudded/soiled boots and clothing. If the site presents dry, well-drained by coarse-grained

granular soil or fill at the surface, the fibres tend to become airborne more readily. The

presence of any airborne dust is a sign of potential immediate hazard.

6 Safety Equipment (PPE & RPE)

It is unlikely that asbestos in the form of dry, loose friable ACMs will be encountered during

sampling, since the sampling strategy has been designed to specifically avoid known areas

of asbestos contamination. If it is encountered, however, then appropriate steps will be

taken to ensure compliance with the Control of Asbestos Regulations (2012). The following

suggestions are taken from em6 asbestos essentials (HSE, 2012):

Overalls

• Disposable Category 3 Type 5/6 (BS EN ISO 13982-1) ideally blue in colour are

suitable.

• Wear one size too big to prevent ripping at the seams.

• Seal loose cuffs with tape if necessary.

• Wear overall legs over footwear.

• Wear hood over RPE straps.

• Dispose of used overall as asbestos waste.

Gloves

• Single use disposable gloves. If latex gloves are required use only ‘low protein

powder-free’ versions.

• Dispose of used gloves as asbestos waste.

Footwear

• Boots are preferable to disposable overshoes which cause a slipping risk.

• Avoid laced boots, these are difficult to clean properly. Keep trousers inside boots to

reduce soil contact.

Respiratory protective equipment (RPE)

• Use suitable RPE with an Assigned Protection Factor of 20 or more.

➢ A disposable respirator to standards EN149 (type FFP3) or EN1827 (type

FMP3);

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• Face fit testing will be undertaken

• Disposal of RPE is also required.

• Removal of facial hair (no beard/stubble) is important to ensure a good seal of the

mask to the face.

• RPE should only be used for a continuous period of 1 hour after which the wearer

should take a break.

Personal decontamination equipment

• Disposable ‘wet wipes’

• Bucket, clean water and rags.

7 Equipment

Soil sampling equipment includes the following:

• Maps/plot plan

• Safety equipment as specified in 6.

• Global positioning system (GPS) to locate sampling points

• Tape measure

• Survey stakes or flags to map sampling area

• Digital camera

• Appropriate size sample containers

• Ziplock plastic bags (to contain asbestos fragments if encountered)

• Logbook

• Field data sheets and sample labels

• Equipment decontamination supplies/equipment

• Spade and Shovel

• Spatula

• Scoop

• Plastic or metal spoons

• Trowel(s)

• Tool for removing surface herbage (similar to a sod cutter)*

• Water storage tank (5 L)

• Water Spray Bottle

• Portable scales (capable of weighing up to 5 kg +/- )

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* The Statement of Requirement for the England and Wales Soil Background Project states:

‘Vegetation removal should focus on above ground vegetation clearance to facilitate the soil

sampling and the removal of soil should be avoided except when tightly bound by dense root

mats. For example it is acceptable to remove the top 1 cm beneath grass turf.’

8 Procedures

8.1 Preparation

a) Prepare a suitable and sufficient Health and Safety Risk Assessment (see attached

document this will be updated on site).

b) Determine the extent of the sampling effort, the sampling methods to be employed

and the types and amounts of equipment and supplies required.

c) Obtain necessary sampling equipment, and ensure that it is in working order.

d) Prepare schedules and coordinate with staff, client and regulatory agencies to ensure

site access and agreement to sample.

e) Perform a general site survey prior to site entry in accordance with the investigation

Health and Safety Risk Assessment.

f) Perform a site walkover and take images of the site location and record site

properties. Enter these on the sample collection sheet.

g) Use stakes, flagging, or buoys to identify and mark all sampling locations within the

grid. The proposed locations may be adjusted based on site access, property

boundaries, and surface obstructions.

8.2 When asbestos is encountered

Adequate information, instruction and training of persons who may be exposed to asbestos

during the course of their work is required by Regulation 10 of the Control of Asbestos

Regulations 2012.

As this soil sampling exercise could potentially involve encountering asbestos in the ground,

it will only be undertaken by Mark Craggs or Daniel Young, both of whom have received

asbestos awareness training to enable them to avoid being exposed to asebstos during their

work. Other support staff on site will not come into contact with the soil samples.

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While unlikely, when encountering substantial bulk asbestos in the ground, e.g. lagging,

significant loose fibres, sprayed thermal/plumbing/chemical/electrical insulation, there will be

no attempt to sample such materials. The Local Authority (LA) will be contacted if these

materials are encountered.

If visible but small fragments of ACM are present these will be sampled and placed in a

secure container and, in addition to normal labelling, labelled (standard asbestos ‘a’ label) as

suspected of containing asbestos material including whether or not it is discernible or

suspected ACM. Double bag any non-soil associated asbestos fragments and adequately

label again. Other samples from the five selected within the quadrat will be sampled using

the standard procedure, i.e. bulked before cone and quartering.

Risk, in any event, will be controlled and reduced to ALARP by:

a) The material is in the ground

b) It will be dampened down to prevent suspension of fibres

c) Sampling is outdoors therefore they is rapid dilution of sample concentrations if fibres become suspended

d) Minimal disturbance techniques will be employed

e) PPE/RPE are commensurate with the potential risk

CAR 2012 requires that in the event of an accident, incident or emergency an employer

must, amongst other things, take immediate steps to: 1) Mitigate the effects of the event 2)

Restore the situation to normal, and 3) Inform any person who may be affected.

8.3 Sample Collection

For each of the 5 sampling locations (each grid corner and centre) the following should be

performed:

1. Put on new protective gloves

2. Collect and weigh an appropriate container and enter onto the site collection sheet.

3. Start a central sampling point (middle) and verify using GPS.

4. Dampen down the soil with water spray.

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5. Carefully remove the top layer of herbage with a pre-cleaned spade or sod cutter ensuring excess soil is not removed.

6. N.B. If fragments are visible go to fit the disposable respirator provided and dampen soil and fragments liberally then place the fragments in a separate Ziplock bag and the soil sample in its own container with full details of sample location.

7. If soil looks dry dampen down again.

8. Using a pre-cleaned scoop, spoon or trowel sample c. 400 g of soil to a depth of 5 cm and place in a pile onto a large plastic sheet

9. Repeat this process for the 4 corners of the quadrat adding the 4 sets of 800 g soil to the central pile.

10. You now have c.2 kg of soil in a pile. Dampen pile, repeat as necessary to reduce potential fibre release.

11. Perform a soil texture analysis using your fingers (keep your gloves on), note down texture/colour/organic matter and horizon(s) sampled.

12. Go around the pile twice moving soil from the edges of the pile to the top to ensure good homogenisation of sample.

13. Split the pile into 4 equal parts (1 kg each).

14. Place two opposite quarters into a sample container (i.e. two samples one for

analysis, one for storage)

15. One of the non-discarded corners will make up the 1 kg sample to be picked up by SAL the other will be the stored sample.

16. Seal the container, weigh and place in crate within van in the designated ‘dirty’ area.

17. Complete the sample collection sheet.

18. Get work partner to confirm all details on the collection sheet.

19. Take a photo of sample collection sheet.

20. Clean sampling equipment

21. Place all used gloves, wipes, overalls and potentially other contaminated materials in disposal bags.

22. Remove mud from boots, wash hands.

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8.4 Waste Disposal

Gloves are changed after each sample and are disposed of separately to waste suspected

of asbestos contamination. The same applies for any other non-contaminated waste

generated during sampling.

PPE suspected of being contaminated by asbestos or other contaminants will be disposed of

after site sampling is completed. Contaminated gear will be double bagged and taken back

to the University of Reading where it will be disposed of as asbestos waste. Any other items

used to clean contaminated sampling kit will be disposed of in the same manner.

9 Quality Assurance/Quality Control

There are no specific quality assurance (QA) activities which apply to the implementation of

these procedures. However, the following QA procedures apply:

a) All data must be documented on field data sheets or within site logbooks.

b) All instrumentation must be operated in accordance with operating instructions as

supplied by the manufacturer, unless otherwise specified in the work plan.

Equipment checkout and calibration activities must occur prior to

sampling/operation, and they should be documented.

c) Random auditing during the sample collection process may take place to ensure

adherence to this SOP by steering group members.

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Appendix 2. Sample Survey Recording sheet

Sample identifier Date

Photograph file numbers of site surroundings

GPS reading

Notes on surrounding land

-land use

-proximity to roads/rail networks

-proximity to

residential/commercial/industrial areas

-description of any man made constructions on site

-any large flora (if this means moving sampling gird).

Ground conditions

Notes on any sampling modifications

Asbestos fragments present Yes/No

If yes

Description

Photograph file no.

Weight of sample (g)

Bagging

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details

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Appendix 3. Site audit reports

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Appendix 4 – Audits of Asbestos Analysis

Audit of asbestos in soil analysis at REC Ltd 8/12/2015 for the soils project

Main findings

1. The operational procedures need to be tweaked and updated to more accurately

reflect the procedure observed/audited for soil analysis and to remove some

processes that were not being used (e.g. sieves and pestle and mortar).

2. Overall the basics were good. Some further improvements to the method used could

be introduced to reduce the potential for cross-contamination between samples and

to ensure that the soil samples are fully dry before weighing.

3. More systematic examination of the tray sample could be undertaken if there was a

larger tray (or less sample) as this relies on visual analysis of a thin layer of soil. The

same applied for the stereo- microscopy examination in the Petri dish – i.e. a more

systematic technique for moving of a sub-samples from one side of the dish to the

other, to observe a relative thin layer of soil would optimise the likelihood of visual

detection of the asbestos if present.

4. The analyst correctly identified the asbestos types in the bulk sample they were

asked to examine during the visit.

Purpose and scope

The purpose of the audit was to check and assess the procedures used for the analysis of

asbestos in soils by REC Ltd (Manchester). All the soil samples from the project go through

this laboratory for the determination of the asbestos content. The procedures used were

observed and commented on in respect of systematic and random variations, and the

methodology set out in the operating procedures and how well they were followed. A test

sample was also used to assess the ability to identify the asbestos types present.

As a single analyst does all the samples for this project (another analyst is currently on

maternity leave) it was not relevant to look at any intra-laboratory (between analyst)

variations during this audit.

Description of analytical process used

The following current operational procedures (By Resource and Environmental Consultants

Ltd REC):

57

• Sample receipt, preparation and initial weighing (v 1.7 06/17/14);

• Quantification procedures:

o Stage 1 initial bulk analysis(V1.5 06/17/14);

o stage 2: Handpick and weigh of ACMS -coarse fraction ( V1.8 27/jul/2015);

o Stage 3 fibre counting and sizing by PCM-fine fraction (V1.7 29/Mar/2015).

Method of Auditing

The four OP’s above were used as the basis of the audit. A number of soil samples from

Reading had been received last Friday and the analysis of one of these samples was

observed and followed through the various stages.

A bulk test sample (a former AIMS PT) sample was also brought to site by the auditor for the

analyst to identify the asbestos types present.

Observations

Sample receipt, preparation and initial weighing (v 1.7 06/17/14)

1 The procedure is for samples between 0.25 to 1.5 Kg and gives a minimum drying

time of 12 hours at 40 oC (+ 5 oC) . – The procedure does not say, that the samples

should be dried completely before analysis. The samples are in a plastic tub and

covered with a permeable membrane in a drying cabinet and it is unlikely that 1 Kg of

material would be dry in 12 hours. This was recognised by the analyst who generally

leaves samples in for several days (Friday to Tuesday) in this case. However, no

data was available to assess when a constant weight was achieved using this drying

method. The drying time would also vary with soil types – (with clay soils taking

longer to dry) and the original soil moisture content. Weighing checks were good and

used calibration weights and balances which were maintained and checked by a

UKAS accredited service.

1a It was suggested that some experimental data be collected by reweighing the same

sample after a 24 drying period using the OP conditions for a number of days until an

approximate constant weight was achieved, to give a more accurate estimate of the

required drying time required.

1b A recommended minimum drying time should be specified based on the maximum

weight of soil received ~1.5 kg so that all the samples are likely to be dried to a near

constant weight , even though moisture content and soil type will differ between

samples.

58

1c As the current samples are weighed before and after drying – It might be helpful to

look at the past data to work out the moisture content removed from the samples, to

give further information on the typical moisture content of the soils received.

2 The OP uses a relatively low drying temperature (40 oC) to reduce the liberation of

VOCs. This is clearly a possibility at some brownfield sites where chemical

contamination is likely and use of an unventilated drying cabinet has to take this

approach – however, this will give prolonged drying times for the soils held a plastic

tub.

3 The procedure calls for brushing to be used to ensure the transfer of residual

materials. For a heavily contaminated sample, there is a possibility that some

asbestos will be transferred by the brush to a following sample, unless a new brush

or cleaning procedure is used.

3a Suggest the use of the brush could be avoided as only a small % of the sample may

not be transferred e.g. <0.01% and this is an acceptable weighing error – or that the

tub can be reweighed after transfer and this weight is deducted from the (container +

content after drying) weight to get an accurate dry weight of soil examined.

Stage 1 initial bulk analysis (V1.5 06/17/14);

4 This is broadly similar to the HSG 248 appendix 2 method for bulk analysis of a small

sample and has not been fully adapted to the needs of soil sample analysis and

could really be renamed as stage 2 to better follow the procedure used by the

analyst.

The first part of the procedures is used to examine the visible pieces of suspect

ACMs and to identify the type of asbestos present. This analysis was not observes

on the potential ACMs pieces extracted from the sample but a Bulk test sample was

given to the analyst to replicate the identification analysis.

The second part of the procedure is to search the soil sub-samples in the Petri

dishes produced by the coning and quartering technique and extracting small

bundles and pieces for identification of asbestos. None were found but the ID method

is the same as for the larger visible pieces above.

Stage 2: Handpick and weigh of ACMS -coarse fraction ( V1.8 27/jul/2015);

5 The soil samples are transferred into a shallow Teflon coated baking tray (~30 x 20

cm) where the material is examined and handpicked by eye in a HEPA filtered

59

cabinet. Small lumps were squeezed to assess if they were soil or solid (stones,

wood ACMs etc.) and places in two Petri dishes - one dish for Non-ACM solids and

one for potential ACMs. This was very much a hands-on examination lasting about 5

minutes. Coning and quartering then took place to produce a sub-sample in two

further Petri dishes. Materials placed in the potential ACM category Petri dish were

examined first by stereo microscopy, to assess whether they were ACMs.

5a The amount/depth of soil in the tray made is difficult to do a systematic assessment

of the soil by moving small sub-samples from one side of the tray to the other, so it

could be spread out in a thin layer for easier observation. The analyst can only see

the surface of the soil sample and needed more room to spread the sample out. This

could be more easily and reliably performed using a bigger tray (~ 40 x 30 cm) and a

scraper to spread the sub-sample. A tray with higher sides would also help to make

the coning and quartering a bit easier to do.

5b The coning and quartering was carried out in accordance with BSI methods.

5c Observation of potential visible ACMs was carried out in the stereo microscope. Here

experience is essential. No attempt to wash the soil from the lumps was made and it

should be considered whether some further cleaning (as necessary) may be put into

the OP. If the material examined was thought to be an ACM the stage 1 procedure

would be initiated after this stage to confirm that it was an ACM and identify the

asbestos type/s present.

5d No coarse fraction ACMs were found so it was not possible to observe weighing of

suspected ACMs or the use of the quantification worksheet to calculate the mass of

asbestos present.

Stage 3 fibre counting and sizing by PCM-fine fraction (V1.7 29/Mar/2015).

6 The Petri dish was further sub-sampled to weigh out ~ 1 g of soil into a smaller tared

Petri dish, the amount of soil added was recorded and then transferred into a 1 litre

conical flask – using a brush to wipe out the dish. 300 ml of water was added to the

flask. The flask was swirled for 20 seconds and a 1 ml aliquot withdrawn after 10 s

settling time and filtered onto a pre-wetted 0.8 um MCE filter and backing pad

support held in an air monitoring cowl. The liquid was drawn through the filter using a

syringe at the bottom of the pipe connection. The filter is then dried and mounted for

PCM analysis and quantification.

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6a The final transfer to the conical flask involved the use of the brush and cross-

contamination is a possibility if brush is reused. The need to use a brush could be

avoided if the soil was weighed out directly into the flask which the water was added.

6b The re-use of the same filter holder was also a potential source of cross-

contamination and cleaning procedures need to be added and verified if non-

disposable equipment is used.

6c The filtration of a 1 ml aliquot is difficult to get a more even deposit and recommend

that a 5 ml aliquot of water should be added first to the funnel, before pipetting the 1

ml aliquot gently onto the surface – moving the pipette tip across the surface.

6d There was insufficient time to fully clear the filter so a previous sample filter (already

mounted and cleared) was chosen at random and examined. The filter was a good

mount but the deposit was slightly uneven across the slide (clusters of larger

particles) but there were no visible countable fibres and hardly any objects with a

>3:1 aspect ratio. A recount/quantification was not carried out as the original result

was BLQ and the auditors own observations showed that there was likely to be no

significant difference if a re-count/ quantification was performed.

6e Minor difference between the OP and the actual actions observed were noted (e.g.

use of 0.8 µm pore size filter and a longer drying time for the filter should be

specified).

Identification of asbestos in a bulk ACM sample

The analyst correctly identified the asbestos types in the bulk sample they were

asked to examine during the visit.

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Appendix 5 - Abbreviated Method Statement for Quantification of Asbestos in Soils by

REC Ltd

Sample Receipt, Preparation and Initial Weighing

Samples received for quantification of asbestos in soils were supplied in 1 l plastic tubs

clearly marked with a unique designation applied by the University of Reading. These

contained approximately 1 kg of soil. This allowed examination and any sub sampling

required to be conducted inside a HEPA equipped asbestos analysis cabinet. Sample

transport was arranged by in-house vehicles from Reading to the laboratory in

Manchester.

The sample weight was recorded as received.

The sample was then dried for a minimum of 48 hours in an oven operated at 40 +/- 5

0C. The mass of the sample was then determined and the dry weight calculated from a

knowledge of the mass of the empty container. The % moisture was then noted for

each sample.

Stage 1/2 – Initial Bulk Analysis

Stage 1 analysis identified whether suspected asbestos-containing materials (ACMs)

or fibres were present within the sample and then allowed identification of the type of

asbestos present.

Inside the HEPA-equipped cabinet the entire dried sample was transferred to a tray to

allow visual examination for the presence of any suspected ACMs or clumps of fibres.

Any such materials observed by the naked eye were removed and transferred to a

labelled container for further examination and weighing after removal of as much

extraneous material such as soil as possible.

A sub sample was then prepared by the coning and quartering technique. This aliquot

was transferred to two petri dishes to allow low power microscopic examination. This

examination step allowed detection of smaller pieces of ACMs or fibre clumps or

suspected asbestos fibres. These materials were removed for analysis and weighing.

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Suspected asbestos fibres were identified using polarised light microscopy (PLM) in

accordance with the procedures defined in HSE publication HSG 248 “Asbestos: The

analyst’s guide for sampling, analysis and clearance procedures”. This process was

accredited by UKAS to the ISO 17025:2005 Standard and all staff held the P401

qualification and many years’ experience.

Materials identified at this stage as asbestos-containing were weighed, and where the

product type was identified the tables contained within HSE publication HSG 264

”Asbestos: The survey Guide” were used to estimate the asbestos content of the

whole.

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Stage 3 – Fibre Counting and Sizing by Phase Contrast Microscopy (PCM) (Fine

Fraction)

Normally, only where Stage 1 analysis identifies loose asbestos fibres in the sample

would this third stage of analysis be performed. For the purposes of this work however

all samples were analysed using this third stage in the process.

A representative 1 g sub sample was taken from one of the petri dish sub-samples and

mixed in 300 ml of distilled water and agitated for 20 s. The solution was left to stand

for a further 10s before a 1ml aliquot was extracted from 1 cm below the surface using

a pipette. The aliquot was then deposited evenly onto a pre-wetted 25 mm 1.2 micron

nitro cellulose membrane gridded filter. Residual water was pulled through the filter

using a vacuum syringe and the filter was then dried on a hotplate or placed in an oven

at 40 +/- 5 0C for a minimum of 15 minutes and then mounted onto a slide. The

acetone/triacetin method was used to clear the filter in preparation for fibre

counting/sizing.

Each slide was examined by Phase Contrast Microscopy (PCM). Two hundred

graticule areas were examined and any fibres observed were counted. The number of

fields examined and fibres observed were counted using tally counters. The

dimensions of the counted fibres were also measured and recorded using a

quantification worksheet. The length of fibres was measured to the nearest 5 µm and

the width was measured to the nearest 0.5 µm.

Where prepared slides were found to be occluded and uncountable the solution would

be diluted by taking a 10 ml aliquot after shaking from the original suspension and

making up to 100 ml. This diluted sample would then be processed as the original and

the reported results would be corrected for the dilution. The solution would be diluted

further as necessary.

Stage 4 - further analysis

The above process represents the accredited method in place at REC Ltd, and was

validated to a reporting limit of 0.001% by analysis of replicate spikes in a number of

soils and hence obtaining data for the precision and bias of the method at that level. To

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improve the limit of detection and robustness of the method the decision was taken

prior to commencing this work to measure a further 9 x 1 ml aliquots of suspension as

per Stage 3. Note that the extension of the measurement to include ten separate

aliquots does not form part of the laboratory’s scope of accreditation. The summation

of the ten individual results and the associated improvement in statistical robustness

allows a reduction in reporting limit to 0.0001%. Note that this implies detection of, say,

three 5 micron length fibres on each of the ten filters on average to obtain this limit.

Quality Assurance and Control

The core of the work performed here is using the REC Ltd accredited method. As such

it is subject to a number of both internal and external quality assurance and control

measures.

These include,

Participation in the HSL’s “Asbestos in materials scheme” (AIMS), “Regular inter-

laboratory counting exchanges” (RICE) and “Asbestos in soils scheme” (AISS)

proficiency testing schemes. Individual’s performance in the AIMS and RICE schemes

are tracked based upon their performance scores issued by HSL. The analysts who

performed this work have maintained a classification of ‘0’ in the AIMS scheme and

have a majority of ‘A’ ratings for samples in the RICE scheme, with no worse than ‘B’

results whilst these samples have been analysed.

Routine analysis of in-house QC samples for identification, counting and soil analysis :-

as for the external scheme, the staff involved in this work maintained excellent

performance for the duration of this project.

Routine witness auditing of all staff performing the methods by the quality manager.

Audit findings, if any, result in corrective actions. There were no significant findings

during the performance of this work.

71

In addition to this an external witnessing audit was conducted by Dr. Garry Burdett of

the Health and Safety Laboratory, Buxton, Derbyshire. There were no significant

findings in his report.

Routine monitoring of the environment in which these tests are performed for

background fibre counts.

The results obtained for the AISS scheme by the team in Manchester for the duration

of the project are listed in the table below. Note that one sample is submitted for

identification only and the other for both identification and quantification.

Round

Number

Sample

Number

Identification REC

Result (%)

Organiser

Spike

Value (%)

All labs range No. Labs

reporting

6 11 Crocidolite

12 Amosite 0.018 0.02 0.014-1.5 19

7 13 Amosite

14 Tremolite 0.043 0.05 0.0-0.44 28

8 15 Chrysotile

16 Crocidolite 0.059 0.03 0.016 -0.082 20

9 17 ** Non detect

18 Anthophylite 0.039 0.03 <0.0001 – 1.28 37