The Winston Churchill Memorial Trust of Australia
Risk Assessment of Asbestos-Contaminated Soils: An International Perspective
Benjamin Hardaker – 2008 Churchill Fellow I understand that the Churchill Trust may publish this Report, either in hard copy or on the internet, or both, and consent to such a publication. I indemnify the Churchill Trust against loss, costs or damages it may suffer arising out of any claim or proceedings made against the Trust in respect of or arising out of the publication of any report submitted to the Trust and which the Trust places on a website for access over the internet. I also warrant that my final report is original and does not infringe the copyright of any person, or contain anything which is, or the incorporation of which into the final report is, actionable for defamation, a breach of any privacy law or obligation, breach of confidence, contempt of court, passing-off or contravention of any other private right or of any law.
Signed
B. Hardaker
May 2009
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Contact Details Name
Benjamin Hardaker
Address
AECOM Australia Pty Ltd Level 11, 44 Market Street, Sydney NSW 2000
Postal Address
PO Box Q410, QVB Post Office, Sydney NSW 1230
Position
Graduate Engineer Environment, Water and Civil Infrastructure Group
Telephone
+61 2 8295 3600
Facsimile
+61 2 9262 5060
Email
[email protected]
Project description
To study how various jurisdictions assess the risk of asbestos-contaminated soils to receptors in both fragment and free asbestos fibre forms. This included studying source-pathway-receptor models, application of risk models and studying appropriate remediation techniques to reduce the risk of contracting an asbestos-related disease.
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Acknowledgements I gratefully acknowledge the Winston Churchill Memorial Trust for providing this opportunity to complete this research. This opportunity has allowed the ASBINS (ASBestos IN Soil) workgroup to create relationships with leaders in the field to better understand risk assessment of asbestos-contaminated soils. Many thanks to all ASBINS’ contacts that provided a considerable amount of time and effort to meet with me and discuss current and past research on the topic. Thank you for your hospitality while on my visit. I would also like to acknowledge the great amount of technical support my employer and colleagues at AECOM Australia have provided. ASBINS, an AECOM Australia workgroup, has sustained the energy, support and network to continue this research for the benefit of the Australian contaminated land industry.
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Executive Summary The risk that asbestos-contaminated soils pose to receptors in Australia is relatively unknown due to a lack of regulatory guidance. Risk is based upon a number of factors including the type of asbestos (serpentine or amphibole), the concentration that a receptor is exposed to, the duration of exposure, the frequency of exposure, and the time since first exposure (latency period). In comparison to countries such as the United States, United Kingdom and the Netherlands, Australia has remained idle in contaminated site clean-up of asbestos. Epidemiological studies and risk models have been completed to determine negligible risk air concentrations of asbestos to which receptors can be exposed. The problem found though is the lack of data in low concentration environments often experienced in para-occupational or non-occupational settings, resulting in the need to extrapolate a number of orders of magnitude lower than available data. This increases the uncertainty and reliability of concentrations deemed of negligible risk. Further to this challenge is the assessment of the exposure-pathway model where asbestos migrates from soil to air. Jurisdictions have developed methods that are deemed representative of conditions or scenarios where dust generation would cause receptors to be exposed to asbestos. Of great importance is their usefulness and relevance to Australian conditions, but of course, their representativeness of exposure to asbestos. While the challenge of developing a scientifically-defensible, ecologically sustainable ASBINS (ASBestos IN Soil) process that may be accepted on a national basis is daunting, the current wasteful and poorly justified practices cannot be allowed to continue. However, this is based upon social and political acceptance of there being a ‘safe’ asbestos exposure level. Research in the Netherlands suggests there is an air concentration of asbestos seen as being of negligible risk, although when compared with guidance values in the United Kingdom and United States a range of values exist. This report provides a brief summary of current risk assessment tools available, including risk models used in the United States, United Kingdom and the Netherlands. These models are used for the determination of excess lifetime cancer risks to receptors associated with asbestos exposure. It is hoped that Australia can adopt some of these principals in a regulatory form by including asbestos-specific information in the National Environmental Protection Assessment of Site Contamination Measure (NEPM), which is currently under review.
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Table of Contents CONTACT DETAILS ................................................................................................................II ACKNOWLEDGEMENTS........................................................................................................III EXECUTIVE SUMMARY .........................................................................................................IV TABLE OF CONTENTS ...........................................................................................................V PROGRAMME.........................................................................................................................VI LIST OF FIGURES ................................................................................................................VIII LIST OF TABLES..................................................................................................................VIII ACRONYMS............................................................................................................................IX 1. INTRODUCTION .................................................................................................................. 1 2. UNITED STATES OF AMERICA .......................................................................................... 2 2.1 United States Environmental Protection Agency (US EPA) Asbestos Technical Review Workgroup (TRW) Summit, Las Vegas, Nevada.............................. 3 2.2 United States Environmental Protection Agency (US EPA) Region 9 Office, San Francisco, California.................................................................................... 3 2.3 California Environmental Protection Agency (CAL EPA), Oakland, California........ 5 2.4 United States Environmental Protection Agency (US EPA) Environmental Response Team - West, Las Vegas, Nevada ............................................................... 6 2.5 United States Environmental Protection Agency (US EPA) Region 10, Seattle, Washington................................................................................................. 9 2.5.1 North Ridge Estates ........................................................................... 9 2.5.2 Region 10 Laboratory, Manchester, Seattle ...................................... 10 2.6 Massachusetts Department of Environmental Protection Agency (MassDEP), Boston, Massachusetts ............................................................................. 11 3. THE NETHERLANDS......................................................................................................... 12 3.1 Netherlands Ministry of Housing, Spatial Planning and Environment (VROM), Den Haag, Netherlands .................................................................................... 13 3.2 Netherlands Organisation for Applied Scientific Research (TNO), Utrecht, Netherlands............................................................................................... 13 3.3 Agrolab Analytical Laboratory, Deventer, Netherlands ........................................ 15 4. UNITED KINGDOM ............................................................................................................ 16 4.1 Institute of Occupational Medicine (IOM), Edinburgh, Scotland ........................... 17 4.2 Health and Safety Laboratories, Buxton, England ............................................... 17 4.3 British Occupational Hygiene Society (BOHS) Asbestos Contaminated Land Seminar, London, England ........................................................................ 19 4.3.1 Woolston Riverside........................................................................... 19 4.3.2 Electricity Supply Board (ESB) Contamination Assessment and Remediation 19 5. CONCLUSION.................................................................................................................... 21 6. RECOMMENDATIONS....................................................................................................... 24 7. REFERENCES ................................................................................................................... 25 APPENDIX A – ADDITIONAL INFORMATION OBTAINED FROM THE UNITED STATES ENVIRONMENTAL PROTECTION AGENCY .......................................................... 29 APPENDIX B – ADDITIONAL INFORMATION OBTAINED FROM THE NETHERLANDS...... 32
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Programme United States Environmental Protection Agency (US EPA) Asbestos Technical Review (TRW) Workgroup Meeting
Building D, 4220 South Maryland Parkway, Las Vegas, Nevada, United States.
United States Environmental Protection Agency, Region 9
75 Hawthorne Street, San Francisco, California, United States.
California Environmental Protection Agency (CALEPA)
1515 Clay Street, Oakland, California, United States.
AECOM Environment, Oakland
Suite 220, 300 Lakeside Drive, Oakland, California, United States.
United States Environmental Protection Agency, Environmental Response Team – West, Region 9
Building D, 4220 South Maryland Parkway, Las Vegas, Nevada, United States.
United States Environmental Suite 900, 1200 Sixth Avenue, Seattle, Protection Agency, Region 10 Washington, United States. United States Environmental 7411 Beach Drive East, Port Orchard, Seattle, Protection Agency, Region 10 Washington, United States. Laboratory Massachusetts Department of 1 Winter Street, Boston, Massachusetts, United Environmental Protection States. Agency (MassDEP) AECOM Environment, Westford
2 Technology Park Drive, Westford, Massachusetts, United States.
Netherlands Ministry of Housing, Spatial Planning and the Environment (VROM)
Rijnstraat 8, Den Haag, the Netherlands.
Netherlands Organisation for Applied Scientific Research (TNO)
Princetonlaan 6, Utrecht, the Netherlands.
Agrolab, Deventer
Handelskade 39, NL-7400 AR Deventer, The Netherlands.
Institute of Occupational Medicine (IOM)
Research Avenue North, Riccarton, Edinburgh, Scotland.
Faber Maunsell, Edinburgh
Dunedin House, 25 Ravelston Terrace, Edinburgh, Scotland.
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Health and Safety Executive Laboratories
Harpur Hill, Buxton, Derbyshire, England.
Bureau Veritas, Cranfield
Unit 5, Trent House, Cranfield Technology Park, Cranfield, England.
British Occupational Hygiene Society (BOHS) Asbestos Contaminated Land Seminar
Society for Chemical Industry, 14/15 Belgrave Square, London, England.
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List of Figures Figure 2.1
US EPA Framework for conducting risk assessment at Superfund sites.
Figure 2.2
US EPA investigation results for adult cancer risk using the IRIS risk model.
Figure 2.3 Figure 2.4
An aerial photograph of a site showing areas of focus. The general arrangement for ABS with stationary air monitors placed approximately 3.5m from ABS activities.
Figure 2.5
The fluidised bed asbestos separator developed by the US EPA.
Figure 3.1
The general Netherlands.
Figure 3.2
Results showing the relationship developed between soil and air concentrations of asbestos.
Figure 4.1
The general approach currently adopted for assessing risks at contaminated soil sites in the United Kingdom.
Figure 4.2
The laboratory based soil dustiness testing apparatus.
Figure 4.3
A view inside the rotating drum.
risk
assessment
process
used
in
the
List of Tables Table 3.1
Risk levels for concentrations of asbestos fibres >5µm in length per cubic metre of air.
Table 3.2
Potencies of various asbestos fibre types.
Table 5.1
A risk matrix of regulatory and guideline values for asbestos in soil and air.
Table 5.2
Asbestos fibre potencies suggested in each risk model.
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Acronyms ABS
Activity-based sampling
ACM
Asbestos-containing material
AS
Australian Standard
ATSDR
Agency for Toxic Substances and Disease Registry
ASBINS
ASBestos IN Soil
BOHS
British Occupational Hygiene Society
CARB
California Air Resources Board
CALEPA
California Environmental Protection Agency
CCMA
Clear Creek Management Area
EA
Environment Agency
ERT
Environmental Response Team
HEPA
High efficiency particulate air
HIL
Health-based Investigation Level
HSL
Health and Safety Laboratories
IRIS
Integrated Risk Information System
ISO
International Standards Organization
MassDEP
Massachusetts Department of Environmental Protection
MPR
Maximum permissible risk
MSDS
Methods for the determination of hazardous substances
NATA
National Association of Testing Authorities
NEPM
National Environmental Assessment) Measure
NOA
Naturally occurring asbestos
NR
Negligible risk
PCM
Phase contrast microscopy
PCMe
Phase contrast microscopy equivalent
PLM
Polarized light microscopy
PPE
Personal protective equipment
Protection
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(Contaminated
Site
SEM
Scanning electron microscopy
SOP
Standard operating procedure
TEM
Transmission electron microscopy
TNO
Netherlands Organisation for Applied Scientific Research
TRW
Technical Review Workgroup (US EPA)
UKAS
United Kingdom Accreditation Service
US EPA
United States Environmental Protection Agency
VROM
Netherlands Ministry of Housing, Spatial Planning and the Environment
WHO
World Health Organization
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1. Introduction A problem not only faced in Australia, but internationally is asbestos-contaminated soils. There is an increasing amount of information available on occupational exposure, waste management and toxicology of bonded and friable asbestos, but there is great difficulty in translating this information into forms that can be used in risk assessment. In comparison to countries such as the United States, the United Kingdom and the Netherlands, Australia has remained idle in contaminated site clean-up of asbestos for some time now. The risk that asbestos-contaminated soils pose to receptors in Australia is relatively unknown due to a lack of guidance in regulatory form. Current guidance documents (enHealth Council, 2005; ACLCA, 2002) state that a site is deemed contaminated if asbestos concentrations exceed 0.001% (w/w) in soil and 0.001 fibre/mL in air. The basis of these guidance values is unclear, with other jurisdictions providing a more science based approach to risk assessment. Various studies have been completed on health effects relating to exposure of asbestos and also in modelling asbestos migration through the source-pathway-receptor model. This report provides a brief summary of current risk assessment tools available abroad, including various risk models used for the determination of excess lifetime cancer risks to receptors resulting from para-occupational and non-occupational exposures. Risk is based upon a number of factors, including the type of asbestos (serpentine or amphibole), the concentration that a receptor is exposed to, the duration that exposure occurs for, the frequency of exposure, and the time since first exposure (latency period). Although each jurisdictions approach is specifically tailored to local conditions, Australia has the ability to adopt parts of each process for use in risk assessment here.
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2. United States of America The United States Environmental Protection Agency (US EPA) has recently released the Framework for Investigating Asbestos-Contaminated Superfund Sites1 (US EPA, 2008a). Figure 2.1 shows the general process outlining the use of activity-based sampling (ABS) in the framework to determine concentrations of asbestos in ambient air. Results obtained from ABS are then combined with values contained within the Integrated Risk Information System (IRIS)2 risk model for determination of the excess lifetime cancer risk. Generally an action level corresponding to an excess lifetime cancer risk of 10-4 is used to determine if remediation is required, although site-specific characteristics ultimately determine the appropriate risk management level.
Figure 2.1: US EPA Framework for conducting risk assessment at Superfund sites (US EPA, 2008a, p. 4).
1
http://epa.gov/superfund/health/contaminants/asbestos/pdfs/framework_asbestos_guidance.pdf
2
http://www.epa.gov/iris/subst/0371.htm 2
2.1 United States Environmental Protection Agency (US EPA) Asbestos Technical Review Workgroup (TRW) Summit, Las Vegas, Nevada A week long meeting was held by the US EPA asbestos technical review workgroup (TRW) to share experiences of Superfund sites across the United States. It also involved discussing how the US EPA was to further refine the risk assessment process contained within the framework. Areas discussed for further research at the meeting include investigating: the relationship between surface area of asbestos fibres and adverse health affects resulting from exposure; the effect of chemical composition, including surface and leachate compositions, due to the body ‘breaking down’ asbestos fibres and developing an asbestos related disease; the importance of determining the retained dose rather than exposure concentration; the use of ABS confirmation sampling when fill is imported to a site during the remediation phase. This would be conducted after remediation has taken place to confirm adequate remediation has occurred. Soil samples would still be taken before importing ‘clean’ fill onto the site; how to approach sites where ABS produces non-detect results, but stationary air monitoring upwind and/or downwind detects asbestos; possible derivation of action or screening levels for air for the excess lifetime cancer risk range of 10-4 ~10-6 based upon current or proposed site usage; and determination of uncertainty within the risk assessment phase.
2.2 United States Environmental Protection Agency (US EPA) Region 9 Office, San Francisco, California Clear Creek Management Area (CCMA)3 was a recreational area available to residents and visitors in California. Upon investigation it was found that naturally occurring asbestos (NOA) was present at the site. Initial investigations found that exposure scenarios included incidental (visitors) and continual (workers) exposures. A set of activities using ABS were developed by the US EPA to replicate activities conducted at the site with ambient air measurements taken to determine concentrations of asbestos. An action level corresponding to an excess lifetime cancer risk of 10-4 was deemed appropriate with an acceptable risk range of 1 in 10 000 to 1 in 1 000 000. Concentrations of asbestos obtained through ABS using ISO 10312 (International Standards Organization, 1995) were then combined with IRIS risk model values to determine if an excess lifetime cancer risk was present. Risk was calculated using the following equations:
3
http://epa.gov/region09/toxic/noa/clearcreek/index.html 3
ELCR EC x IUR EC
C x Texposure x Fexposure x D exposure
(after US EPA, 2008a)
A time
where: ELCR = excess lifetime cancer risk (unitless) EC = average chronic daily exposure over a 70 year lifetime (f/mL)-1 C = measured asbestos concentration (f/mL) Texposure = exposure time (hours/day) Fexposure = frequency of exposure (days/year) Dexposure =duration of exposure (years) Atime = averaging time (lifetime) IUR = IRIS inhalation unit risk (f/mL)-1 = 0.23 (f/mL)-1 for lifetime exposure
Figure 2.2: US EPA investigation results for adult cancer risk using the IRIS risk model (US EPA, 2008b, p. ES- 4).
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It was determined that for almost all activities except hiking, visiting the area five times or more per year would result in an excess lifetime cancer risk of 10-4 being exceeded. As this was out of the US EPA’s acceptable excess lifetime cancer risk range the CCMA site was closed to the general public.
2.3 California Environmental Protection Agency (CAL EPA), Oakland, California There is still great debate between professionals as to specific characteristics of asbestos fibres such as length, width and type that cause adverse health effects. It is well known that asbestos is a carcinogen, but a definitive set of characteristics remains unavailable for use in risk assessment. There is a general consensus though that the longer the fibre, the greater the potency. There are a number of uncertainties present within the derivation of the IRIS cancer risk values for specific air concentrations. These include: the use of phase contrast microscopy (PCM) to determine fibre characteristics and concentrations. It has been debated that light microscope methods do not provide the required analytical sensitivity. Transmission electron microscope (TEM) analysis is readily available in the United States, where phase contrast microscopy equivalent (PCMe) fibre counting rules are often used to correlate results with IRIS risk values as PCM was used in the IRIS values derivation; the possible over-estimation of asbestos concentrations when using indirect methods to determine concentrations within air. This includes the need to convert from the mass of asbestos contained on the filtered media to a fibre concentration within air; the need to extrapolate to low concentrations, typically a number of orders of magnitude lower than concentrations seen in occupational environments, due to a lack of data in non-occupational environments; and the reliability of exposure data obtained in occupational exposure cohorts to determine concentrations and types of asbestos. This also includes the applicability of animal exposure studies. It should be noted that the IRIS risk model does not differentiate between amphibole and serpentine fibre types. Concentrations obtained using the IRIS risk model may be further refined in the future by reanalysing filter papers used in the original derivation of the IRIS risk values. This would be completed using TEM and a statistical analysis. CALEPA uses different asbestos unit risk values, cancer endpoints and computational methods to determine excess lifetime cancer risks at sites in the state of California.
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2.4 United States Environmental Protection Agency (US EPA) Environmental Response Team - West, Las Vegas, Nevada The Environmental Response Team (ERT) helps develop sampling plans for both asbestos in soil and air. ERTs focus is on anthropogenic sites, although the US EPA has led the assessment of a number of NOA sites. At Superfund sites a site history assessment is conducted, including the study of aerial photographs, locating asbestos storage or dump locations, and whether ACMs were transported through the site (e.g. Rail cars removing tailings from a mine site). From here a sampling plan for soil is developed using the program Visual Sampling Plan4 to determine the number and location of soil samples. This program was developed by a number of US government institutions for use on contaminated sites in the United States with a soil detection limit for asbestos of 0.25% (w/w) (US EPA, 2008a; CARB, 1991). Composite samples are taken within each grid to determine areas of focus when conducting ABS to Standard Operating Procedures - Activity Based Air Sampling for Asbestos5 (US EPA, 2007). Soils are classified and the site is portioned into grided areas of similar characteristics (i.e. asbestos concentration and soil classification). An example of a site separated into portioned areas is shown in Figure 2.3, where the red areas are of high, yellow of medium, and blue of low concern.
Figure 2.3: An aerial photograph of a site showing areas of focus.
Meteorological data such as wind speed and direction is collected during sampling, but ideally will also be collected for 6~12 months prior to sampling to determine worst-case conditions. Personal sampling pumps are calibrated in the laboratory and again on-site. Depending on the required sensitivity, the amount of time required for sampling will be determined prior to sampling. The formula used for determining sampling time is:
4
http://vsp.pnl.gov/
5
http://www.ert.org/products/2084.PDF 6
V
A filter K A grid S
(after US EPA, 2007)
where: V = volume required to obtain desired analytical sensitivity (L) K = number of grid openings observed during TEM analysis (unitless) S = determined analytical sensitivity (structures/L) Afilter = area of filter media (mm2) Agrid = area of grid openings examined during TEM analysis (mm2)
It has been found that a 0.8µm pore size filter paper is sufficient for use with both amphibole and serpentine fibre types and that it provides greater flow rates than smaller pore sizes. Typically a flow rate of 3.5~10 L/min should be used to ensure an adequate sample volume is collected. Problems with increased flow rates resulting in an unrepresentative sample being obtained may include: increased backpressure across the filter; large amounts of debris on the filter; modification of asbestos structures or dislodgment from the filter; or pumps faulting. Stationary air monitors are placed upwind (one) and downwind (two) during ABS activities, shown below in Figure 2.4. Perimeter samplers and background or reference air monitors should be located well clear of ABS, with reference samplers being located well away from the site to determine background concentrations. Containment structures with a high efficiency particulate air (HEPA) filter or mist sprays may be used to suppress dust migrating off-site if the location of testing is sensitive, but must be designed to ensure that ABS sampling is not affected. Results obtained from grids where ABS has been conducted may be extrapolated to other grids where ABS is not completed to reduce sampling volumes. This can only be done when similar soil types and asbestos concentrations are present. This is highlighted in Figure 2.3 where the site is portioned into areas of focus. There are a number of analytical considerations that need to be taken into account when developing ABS plans, including: determination of the analytical sensitivity required for the site, and therefore the amount of air required to pass through the filters; and the amount of grids to be viewed during TEM analysis to ISO 10312 (International Standards Organization, 1995). 7
If a low analytical sensitivity is required, a large amount of air is required to pass through the filter or a greater number of grids must be counted. For sampling to remain feasible a higher flow rate would be desirable. To ensure a representative sample is obtained, it should be noted that higher flow rates may result in: increased debris other than asbestos obstructing the view of laboratory analysts when analysing for asbestos; the pump failing due to increased backpressure; larger batteries being required; and possible dislodgement or alteration of original forms of asbestos structures on the filter.
Figure 2.4: The general arrangement for ABS with stationary air monitors placed approximately 3.5m from ABS activities. A large amount of debris on the filter paper may require an indirect sample analysis, although direct analysis is desirable for ease of analysis. The basic assumption of both methods is that the sample is evenly distributed on the filter, with indirect analysis possibly overestimating concentrations due to changes in asbestos matrices (i.e. the 8
modification of matrices causing higher numbers of free fibres). Indirect analysis should only be used if >25% of the filter paper is covered with debris. It should be noted that unquantifiable errors may be introduced during indirect analysis due to the solution needing to be diluted for quantification. Ultimately, risk assessment at the site is dependant upon the risk assessor and the sensitivity of the site. Separate risk calculations should be completed for each ABS activity and for stationary air monitoring. These calculations are later combined to determine excess lifetime cancer risk levels. Risk ranges for the site are developed taking into account soil concentrations, soil type and proposed site usage using professional judgement. Remediation may include the use of capping layers, excavation of portions of soil deemed to produce unacceptable concentrations of asbestos in air and appropriate site management to mitigate dust generation where possible. Under the new framework Superfund sites are reviewed every 5 years to ensure the site still remains below the allowable cancer risk level and that soil disturbing activities in areas of contamination have not occurred.
2.5 United States Environmental Protection Agency (US EPA) Region 10, Seattle, Washington 2.5.1 North Ridge Estates North Ridge Estates6 is a residential subdivision developed on an ex-military recuperation barracks located in Klameth Falls, Oregon. The military base was demolished in the late 1970’s, resulting in a variety of ACMs being scattered across the site. No remedial measures were taken during the demolition phase with building footprints still visible at the site. Chrysotile was found to be the predominant asbestos type found, although amosite was also been found in small quantities. No risk assessment was conducted prior to residential redevelopment, with large scale asbestos contamination, predominantly bonded ACMs, found on and below the soil surface. Of greatest concern is the degradation of these bonded materials into more friable forms, with asbestos being released into the ambient environment over time. Preliminary investigations were conducted including intrusive soil investigations and stationary air monitoring to determine concentrations of asbestos. Soil samples were analysed using PLM, with no excessive levels of asbestos detected. Stationary air monitoring results also only detected low levels of asbestos posing relatively low risk to receptors. Preliminary risk assessment at the site was completed using the Modified Elutriator Method7 (Berman & Crump, 2000) and ABS. Results from the preliminary investigation have shown that a greater risk was present at the site than first thought. While a majority
6
http://yosemite.epa.gov/r10/cleanup.nsf/4c5259381f6b967d88256b5800611592/6d3ab7def32c248a88256d 3a007e7f53!OpenDocument 7
http://www.aeolusinc.com/Modified_Elutriator_Method.pdf 9
of contamination is in bonded forms, friable materials would pose an increased risk as they degraded over time. Of concern also were bonded materials that had weathered over time and become friable. Initial risk reduction measures included identifying and remediating areas of known amosite containing materials and ‘emu bobbing’ of visible ACM pieces as an emergency response. Approximately 60 tonnes of ACM has been removed from the site, with an estimated 1500 tonnes still remaining. The handling of chrysotile materials was seen as low risk, unless purposely broken or abraded. It has also been observed that ACMs are migrating to the surface, requiring continual passes to remove ACMs. An immediate response is not required as most materials are in a relatively bonded form, resulting in the option to conduct a more thorough risk assessment to determine appropriate remediation options for the site. Generally the site lies within the USEPAs generally accepted risk range of 10-4~10-6 at this stage, but would exceed this as ACMs degraded over time and became friable. 2.5.2 Region 10 Laboratory, Manchester, Seattle The fluidised bed asbestos separator is currently a tool under development by the US EPA. It is envisaged to be used in conjunction with ABS at Superfund sites, and is shown in Figure 2.5. It has been developed to determine approximate concentrations in air based upon soil samples obtained from the field. 15L/min of air is forced through the ~20g soil sample, capturing the lighter materials on a cassette which may then be analysed for asbestos using TEM to ISO 10312 (International Standards Organization, 1995). This method is still to be validated by the US EPA, although a standard operating procedure (SOP) is available.
Figure 2.5: The fluidised bed asbestos separator developed by the US EPA.
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2.6 Massachusetts Department of Environmental Protection Agency (MassDEP), Boston, Massachusetts Currently the Massachusetts Department of Environmental Protection (MassDEP) asbestos in soil workgroup8 is creating asbestos in soil guidelines to be included in the Massachusetts Contingency Plan (MCP). Within these guidelines are a number of options available to assess risk including ABS, Modified Elutriator Method (Berman & Crump, 2000) and determining levels at a site that are consistent with background levels. Providing options to assess risk allows contaminated land owners and/or consultants to choose appropriate assessment and remediation techniques for a given site to ensure risk is below the required excess lifetime cancer risk level. In Massachusetts there are currently no special waste facilities available for disposal of asbestos containing soil or waste. Hence, it is a very expensive exercise to remediate a site. This has led to proposed soil concentration thresholds for reuse at landfill sites as grading/shaping material (8000 mgACM/kgsoil) and daily cover (1000 mgACM/kgsoil). This is based upon testing conducted at North Point Park, Cambridge9. ABS, the MassDEP Sieve Method (MassDEP, 2007) and the Modified Elutriator Method were all used to determine these threshold values for reuse.
8
http://www.mass.gov/dep/cleanup/compliance/asbest03.htm
9
http://www.mass.gov/dep/cleanup/compliance/AIS-results-081106.pdf 11
3. The Netherlands The Netherlands are currently the only jurisdiction to implement threshold levels for asbestos in soil and air, but also to derive a relationship between soil and air concentrations. Threshold levels to which receptors can be exposed with negligible risk were determined through a study completed in the late 1980’s looking at both human and animal exposures. Current regulations (TNO, 2005) allow 100mg/kg (the sum of 1x serpentine and 10x amphibole fibre types) of asbestos in recycled waste materials and soils in the Netherlands. Figure 3.1 shows the general tiered risk assessment approach. Preliminary investigation and desktop study Exploratory survey
Soil conc. >100 mg/kg
No
Yes Detailed survey
Site-specific risk assessment
No
Air conc. >0.001 f/mL
Yes Remediation completed
No further action required
Figure 3.1: The general risk assessment process used in the Netherlands (after TNO, 2005; Swartjes et al., 2003).
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3.1 Netherlands Ministry of Housing, Spatial Planning and Environment (VROM), Den Haag, Netherlands Approximately a third of all buildings in the Netherlands contain asbestos, with an extensive inventory conducted of all government buildings. Schools may also be inventoried in the near future. All asbestos used in the Netherlands was imported, with a total ban placed on the importation and use of asbestos in 1994 (European Communities, 2007). Risk communication campaigns are currently being developed by the Netherlands government to better educate the general public on the risks associated with asbestoscontaminated soils. There is still a mixed response from the community regarding contaminated sites.
3.2 Netherlands Organisation for Applied Scientific Research (TNO), Utrecht, Netherlands The Netherlands are currently the only jurisdiction to provide in a regulatory form threshold limits for excess lifetime cancer risk levels. Epidemiological and toxicological studies were completed in the late 1980’s to determine allowable concentrations to which humans could be exposed (Montizaan & van der Heijden, 1989). Conclusions drawn from this study are outlined in Table 3.1. Table 3.1: Risk levels for concentrations of asbestos fibres >5µm in length per cubic metre of air (after Swartjes et al., 2003, p. 22). Disease
Mesothelioma
Lung Cancer 1
2
Concentration of asbestos fibres >5µm in length per cubic metre of air1
Risk Level
2
1 in 1 000 000 (10-6)
10 – 100 (amphibole) 100 – 10 000 (serpentine)
1 in 10 000 (10-4)
1 000 – 10 000 (amphibole) 10 000 – 100 000 (serpentine)
1 in 1 000 000 (10-6)
100 – 1 000
1 in 10 000 (10-4)
10 000 – 1 000 000
Analysed using scanning electron microscopy (SEM). Assuming 30% of the population are smokers.
It was found that asbestos fibres had differing potencies which depended upon the asbestos fibre type and length. A summary of potency values assigned to fibres is shown in Table 3.2. Approximately twenty contaminated sites were used to develop ASBINS regulations in the Netherlands, with a summary provided in Table B.1 of Appendix B of raw data collected at each site. This included collecting unique site characteristics such as types of ACMs, form of asbestos (bonded or friable), and included a range of levels of contamination concentrations, soil types and weather conditions. Soil concentrations were determined to Netherlands Standard NEN 5707 (TNO, 2005) where possible. Soil samples taken from 13
across the site were based upon statistical methods outlined in NEN 5707 (TNO, 2005) to determine the number and location of sampling locations. When a large range of concentrations of contamination were found at a site, the greatest contamination concentration was assumed across the entire site as a ‘worst-case’ scenario. If results were generally consistent, then a spatial average contamination concentration was used. Table 3.2: Potencies of various asbestos fibre types (Swartjes & Tromp, 2008). Fibre Type
Fibre Length
Potency
Chrysotile
>5µm
1
Chrysotile
5µm
10
Amphibole
