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Frequently Asked Questions About Asbestos Investigation, Risk, Removal, and Remediation

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What are the technical specifications required by EPA for asbestos landfills?


The regulatory responsibilities of asbestos are handled at the federal, state and local level. Laws and regulations concerning exposure to asbestos are dictated by the federal government; however, the proper disposal of asbestos-containing wastes and soils (into state or municipal landfills) is the responsibility of state and local governments. These governments are responsible for asbestos inspection and assessment activities, as well as the abatement of asbestos-containing materials. In this regard, in order to obtain technical specifications, one must evaluate individual state or local policies (which vary among states) that operate within federal law and regulation (http://www.fedcenter.gov/resources/facilitytour/landfills/asbestos/).

As an example, the solid waste regulations of Colorado landfills require landfill operators to handle asbestos wastes in a specific manner. Friable¹ asbestos waste and non-friable² asbestos waste damaged to the point of being friable must be properly packaged before being sent to the landfill. It must be tightly sealed, while wet, in at least two 6-mil, leak-tight polyethylene bags or in a wrapping or other container deemed equivalent by the Hazardous Materials and Waste Management Division. (www.cdphe.state.co.us/hm/asbestos.pdf ). The outermost layer of the packaging must be labeled with a waste shipment manifest label that gives the name and address of the generator of the waste (U.S.DOT).

This example illustrates that the disposal specifications are based on the policies of the State of Colorado; however, when the asbestos is being transported it is done so under the jurisdiction of the U.S. Department of Transportation in accordance with the National Emission Standards for Hazardous Air Pollutants program (NESHAP) and the Clean Air Act.

The role of U.S. federal agencies with regards to asbestos management (including laws and regulations) are as follows:

  1. U.S. Environmental Protection Agency (U.S. EPA) (EPA publications http://www.epa.gov/asbestos/pubs/help.html):
  2. ¹Friable - any material containing more than 1 percent asbestos as determined using the method specified in appendix E, subpart E, 40 CFR part 763, section 1, Polarized Light Microscopy, that, when dry, can be crumbled, pulverized, or reduced to powder by hand pressure. If the asbestos content is less than 10 percent as determined by a method other than point counting by polarized light microscopy (PLM), verify the asbestos content by point counting using PLM.

    ²Nonfriable - any material containing more than 1 percent asbestos as determined using the method specified in appendix E, subpart E, 40 CFR part 763, section 1, Polarized Light Microscopy that, when dry, cannot be crumbled, pulverized, or reduced to powder by hand pressure.

    1. Solid waste under the Resource Conservation and Recovery Act (RCRA)
      1. http://www.epa.gov/lawsregs/laws/rcra.html
      2. http://www.epa.gov/region6/6pd/rcra_c/pd-i/mgmt_inf.htm
    2. Hazardous substance under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA).
      1. http://www.epa.gov/oem/content/hazsubs/cercsubs.htm
      2. Hazardous wastes is defined as a solid waste (or combination of solid wastes) which, because of its quantity, concentration, or physical, chemical, or infectious characteristics, may:
        1. Cause or contribute to an increase in mortality or an increase in serious irreversible, or incapacitating illness
        2. Pose a substantial present or potential hazard to human health or the environment when improperly treated, stored, transported, disposed of, or otherwise managed.
    3. Building material under the Toxic Substance Control Act 40 CFR 763 (TSCA)
      1. http://www.epa.gov/asbestos/pubs/asbreg.html
      2. Handling and disposal labeling requirements
    4. Limits effluent discharges for asbestos fibers in water under the Clean Water Act
      1. http://www.epa.gov/compliance/assistance/bystatute/cwa/
    5. Airborne contaminant under the National Emission Standards for Hazardous Air Pollutants program (NESHAP) in accordance with the Clean Air Act.
      1. http://www.epa.gov/ttn/atw/asbes/asbespg.html
      2. 40 CFR 61 Subpart M National Emission Standard for Asbestos
      3. NESHAP requires notification of asbestos abatement activities and requires abatement contractors to follow certain procedures related to removing and packing asbestos for disposal. This also requires specific work practices to be implemented to prevent releases of asbestos to the air.
      4. iv. NESHAP (1990) for asbestos requires that all asbestos waste transport be documented by a waste shipment record (WSR). The WSR must be signed by the asbestos waste generator (the facility owner), asbestos abatement contractor, transporter, and final disposal site operator. The asbestos abatement contractor must send a copy of the WSR back to the asbestos waste generator within 35 days.
      5. v. Guidelines for Asbestos NESHAP Landfill Recordkeeping Inspections
        1. http://www.google.com/url?url=http://nepis.epa.gov/Exe/ZyPURL.cgi%3FDockey%3D900L1N00.txt&rct=j&sa=X&ei=XlBhTMr-FYP-8Aakh6T8CQ&ved=0CBgQzgQoADAA&q=EPA+for+asbestos+landfills&usg=AFQjCNGix2fSIto8XcejJ0Tj2T8kM_mY_g

  3. Work-related settings is regulated by the Occupational Safety and Health Administration (OSHA)
    1. http://www.osha.gov/SLTC/asbestos/construction.html
    2. 29 CFR 1910.1001 OSHA General Industry Asbestos Standar
    3. 29 CFR 1910.134 OSHA Respiratory Protection Standard
    4. 29 CFR 1926.1101 OSHA Construction Asbestos Standard

  4. Consumer products is regulated by the Consumer Product Safety Commission.
    1. http://www.cpsc.gov/cpscpub/pubs/453.html

  5. Transportation of asbestos (designated as a hazardous material for transportation) is regulated by the U.S. Department of transportation (DOT). The DOT has
    1. http://www.dot.gov/
    2. http://www.phmsa.dot.gov/hazmat/regs
    3. Requirements for shipping documents, packaging, labeling, and vehicle placarding. Asbestos must be loaded, handled and unloaded in a manner that will minimize occupational exposure to airborne asbestos fibers released during transit.
    4. Requires that transporters carry identification papers for all quantities of asbestos greater than 1 pound. The state police enforce this requirement.
    5. Regulates transportation of asbestos waste under title 49, section 173.1090.

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Frequently Asked Questions for Asbestos/Vermiculite Site Investigations and Cleanups


  1. Recommended asbestos sampling analytical procedures seem a bit complex and fluid. Can the TRW provide an example Scope of Work for asbestos sampling analyses in different media, including an identification of data deliverables and data validation requirements?

    1. The analytical SOW is in development by Analytical Subcommittee.

  2. How is data validation routinely performed by asbestos laboratories?

    1. In development by Analytical Subcommittee as part of the analytical SOW

  3. Can the TRW identify nationwide commercial laboratories that are familiar with and have followed analytical recommendations in the Framework for Investigating Asbestos-Contaminated Sites (“Framework”)?

    1. Not needed. The SOW will be administered by the CLP program.

  4. When conducting air sampling, under what conditions/scenarios might it be acceptable to not use ISO 10312 sampling analyses given the high cost associated with this analytical procedure and the current practice of only using PCMe results to estimate risk?

    1. In development by Risk Subcommittee.

  5. Can the TRW provide a one page listing (a “cheat sheet” so to speak) of the analytical procedures recommended for each media? …..including any modifications?

    1. See attached appendix for air methods.

  6. CARB 435 seems to be the recommended analytical procedure for soils. However, the Framework isn’t clear on the need to do a field of view vs. point count measurement. What is best?

    1. Field of view is to be used with point counting to look for any fibers in the field that do not fall on a point to be counted. When this occurs, these are typically reported as trace.

  7. Although it acknowledges the need for flexibility, the SOP for activity based sampling (ABS) presents rather rigid sampling procedures for individual scenarios (e.g. raking, gardening, weed wacking for 15 minutes in quarter circles, ) . Is it acceptable for OSCs/RPMs to develop more realistic sampling scenarios at sites after consulting with regional risk assessors/toxicologists?

    1. The Risk Subcommittee is developing case studies which provide real world ABS scenarios and risk calculations.

  8. Can site examples be presented showing ABS air values resulting from specific asbestos soil values?

    1. Examples are available online for several sites:

  9. Are there any site examples where > 1% asbestos values in soil resulted in unusually low ABS results? If so, what are the reasons for this?

    1. There are data showing that when ACM (>1%) is present air levels can be quite low. See ATSDR’s reports on Illinois Beach State Park and Quincy Mine or EPA’s report on North Ridge Estates. http://www.atsdr.cdc.gov/HAC/PHA/index.asp. Also, high soil moisture (>10%) may reduce the release of asbestos fibers to air following a disturbance. ABS results for yards where soil moisture ranged from 18-45% showed PCMe fiber concentrations of 0.004-0.008structures/cc. Because high soil moisture may adversely impact RME estimates of fiber releasability for a given disturbance activity, the Committee generally recommends ABS events be conducted when soil moisture is no greater than 10%.

  10. When conducting ABS, what other information or measurements should be collected (e.g. soil moisture, soil type, last rainfall, vegetative cover, etc)?

    1. See ERT SOP #2084 for ABS (http://www.ert.org/products/2084.PDF) . Additional suggested meteorological station specifications can be found in Table 2, Appendix A or ERT SOP #2129 for Met One Remote Meteorological Station (http://www.ert.org/products/2129.PDF).

  11. Is there a recommended number of asbestos soil samples to collect per lot size? Are grab samples or composite samples (or both) recommended?

    1. Composite samples are appropriate for characterizing study areas. Visual Sampling Plan (VSP) software may be used to grid the site and determine the number and location of samples with the appropriate confidence intervals to meet site-specific data quality objectives (DQOs) (U.S. EPA 2002: Guidance for Quality Assurance Project Plans. EPA QA/G-5 EPA/240/R-02/009). VSP is not necessarily applicable to small sites.

  12. Generally, what are the recommended ambient air and ABS sensitivity limits for asbestos analyses? Is it best to develop preliminary action levels before sampling to potentially enable higher sensitivity limits thus saving analytical costs?

    1. Detection limits for personal monitors are typically 0.003 f/cc PCME (for 2 hour sampling ABS scenarios) and 0.0003 f/cc PCME for stationary monitors. These levels were chosen because the risk values associated with these ABS exposures are typically within EPA’s risk range of 10-4 to 10-6. Under ISO counting rules, this detection limit for personal monitors is equivalent to an analytical sensitivity of 0.001 PCME structures/cc.

  13. Should we be using 0.45 or 0.8 micron filters for air sampling? Polycarbonate or mixed cellulose ester filters?

    1. Currently when sampling for asbestos the 0.8 µm pore size filters are used instead of the 0.45 µm filters because backpressure develops in outdoor dusty environments leading to filter failure. MCE filters are preferred for environmental sampling.

  14. If we learn that specific samples need to be analyzed by the indirect method, is it useful to pay for this analytical cost (usually more expensive than direct) if the results will not be used in a risk assessment?

    1. The consensus of the TRW from the San Francisco meeting is that indirect samples may be appropriate for risk assessment for amphibole fibers because there is less variability between the direct and indirect methods for amphibole.

  15. What significance should project managers place on fluidized bed or RAFS sample results if utilized at their sites?

    1. Until these methods have been validated, the results qualitative only (though they may be used to screen in).

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Risk Assessment and Risk Communication

  1. The Framework (section 5.8) makes several references to the residential baseline scenario for setting air action levels. Would this scenario (exposure 24 hours a day, 350 days a year, age 0-30 years exposure) ever be pertinent for ambient air given time spent indoors and away from one’s home?

    1. The Risk Subcommittee is developing case studies which provide real world ABS scenarios and risk calculations.

  2. Can/should indirect analytical air results be used for risk assessments?

    1. The consensus of the TRW from the San Francisco meeting is that indirect samples may be appropriate for risk assessment for amphibole fibers because there is less variability between the direct and indirect methods for amphibole.

  3. The Framework provides useful risk calculations especially for intermittent exposure scenarios. However, examples of action levels calculated for intermittent exposures would also prove helpful

    1. The Risk Subcommittee is developing case studies.

  4. Depending on the EPA region, OSCs often rely on ATSDR for assistance in making risk management decisions. Is ATSDR also following recommendations in the Framework especially as it pertains to risk calculations and use of PCMe results for determining health risks?

    1. It depends on how complicated the site is (and what the community wants). ATSDR is not strictly following it but recommending it to our health assessors to follow. If they need to deviate from it they are usually referred to one of the ATSDR TRW members (Mark Johnson, Jill Dyken, or John Wheeler) for support.

  5. Project managers are often faced with questions from an educated public about health risks presented by airborne asbestos exposure. Specifically, they question what seems to be EPA’s policy to evaluate the carcinogenic risk presented by PCMe fibers alone. Residents ask about the health threat from shorter fibers and the non-carcinogenic risk from asbestos. How can we best respond?

    1. PCMe is an index of exposure representing a subset of what is typically a complex mixture of fibers. By using PCMe results, the fiber distributions from the site and from the historical chrysotile filters on which the IRIS unit risk is based can be compared. The toxicological significance of exposure to other fibers cannot be quantified using the information currently available on IRIS

    2. What should we be saying to the public about the potential differences in toxicity among asbestos types? What is the Agency’s policy regarding this issue?

      1. The Risk Subcommittee is developing case studies which provide information on this.

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Risk Management and Cleanup

  1. In settings where human contact is common, does the TRW believe there is a minimum asbestos percentage value in soils where some type of corrective action may be warranted even if a risk assessment performed on ABS results indicates that risks are acceptable (e.g. due to high moisture content, good vegetative cover, etc).

    1. This would be generally be 1% asbestos in soil.

  2. Asbestos pipe, panels, concrete or other non-friable asbestos containing material can often be strewn about at asbestos sites. If this material is the only potential exposure source, and access to the site is infrequent, a project manager may determine that corrective action is unwarranted. However, weathering of the material leading to potential fiber releases has occasionally been cited as a cause for concern. Is research information available identifying how weathering might lead to fiber release from non-friable ACM?

    1. The relationship between the concentration of asbestos in a source material (such as soil or ACM in soil) and the concentration of fibers in air that results when the source is disturbed is very complex and depends on a broad range of variables. No method has been found to predict the concentration of asbestos in air reliably as it relates to a measured concentration of asbestos in the source material. Experience has shown that small concentration of asbestos in soil may, when disturbed, produce a substantial airborne exposure.

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Site Investigative Approach

  1. Can the TRW provide any suggestions or examples on when it might be warranted to conduct indoor dust or air sampling at sites based on residential yard soil results?

    1. The primary factors that would seem to pose the greatest potential for impacting the indoor of homes would be 1) close proximity of residences to the exfoliation facility, resulting in airborne deposition of asbestos fibers into the home or 2) presence of waste material, known to have high concentrations of Libby amphiboles, on the exterior of the residential property resulting in the potential for physical tracking of fibers into the home. In the past, EPA has focused on properties that had the highest concentrations of asbestos in surface material, the highest frequency of positive detections, and those closest to the exfoliation facility.

  2. At former vermiculite exfoliation sites, it is likely that stack emissions (presumably containing asbestos) occurred during the period of operation. Some discussion has ensued about the advisability of conducting soil or microvac sampling in areas that might have received fallout from these past emissions. Can the TRW provide any guidance in this area including how and if modeling might be used to identify past fallout areas?

    1. There is some data suggesting that dispersion modeling is not useful for asbestos particle migration.

  3. The Framework calls for each ABS scenario being performed in an area a minimum of three times to identify trends. This recommendation may be prohibitively expensive especially for Removal Programs. Would it be reasonable to conduct one ABS scenario during worst-case or near-worst case conditions (e.g. low soil moisture, no rainfall for a week, little wind)?

    1. If you find yourself reducing the size of a decision unit down to a single, discrete sample (e.g., making remedial decisions for individual sample points) then adequate thought has probably not be given to the objectives of the site investigation.
      An important goal of the site investigations is to estimate the representative, mean concentration of a targeted chemical for the designated volume of decision unit (DU) soil as a whole. Think of evaluating an entire decision area by the raking-screening protocol as an exercise in (multi)incremental sampling. By raking the entirety of the decision area one is effectively averaging the areas with very high contamination with the moderate and very low contamination areas to end up with an area–weighted sample that automatically provides the mean concentration of asbestos in air related to that activity. This is the easiest and most straightforward method. As an alternative, a representative sample (or samples) is collected from the DU and submitted for analysis. The data generated may then used to make a decision for the entire volume of soil represented by the DU. Smaller-scale variability of asbestos concentrations within a targeted DU volume of soil does not normally need to be determined or evaluated, at least at the initial phase of an investigation when a screening risk level is not exceeded. If a greater resolution of contaminant concentration variability within the soil is in fact needed to address the objectives of the site investigation then by definition, the DU is too large and the area should be re-divided into smaller decision units. Establishing decision units early in the site investigation process helps to ensure that the objectives of a site investigation are clearly thought out and defined at the beginning of the process, well before screening or site specific ABS samples are actually collected. This aids in the preparation of an effective sampling and analysis plan and helps ensure that the data collected will be adequate to meet the objectives of the investigation.

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  1. Some EPA staff have expressed concerns about airborne asbestos exposure while conducting ABS and other investigative work at sites. If concerned, what precautionary measures might OSCs or RPMS take? Is there a medical procedure (e.g. chest x-ray) that might be of some value?

    1. Any EPA employee or contractor at the site must be properly trained and equipped to be at a (possibly) uncontrolled site. Medical surveillance is an aspect of the former and personal protective equipment for the latter. The Emergency Responder Health and Safety Manual provides guidance on this (see www.epaosc.org). Consult with your regional Health and Safety Officer for further information on procedures related to developing Health and Safety Plans for ABS at vermiculite ore exfoliation sites.

  2. The Framework’s discussion of land use considerations (Appendix D) seems to be weighted toward the Remedial Program’s greater flexibility in considering future land use when making cleanup decisions. Removal Programs are more likely to only consider current use or, possibly, known future land use. Is the Framework suggesting that OSCs can/should give greater weight to future land use considerations at asbestos sites?

    1. For asbestos sites, the future land use considerations are listed in the Framework (www.epa.gov/superfund/health/contaminants/asbestos/pdfs/framework_asbestos_guidance.pdf); however, additional consideration must be given to how the asbestos material could change in the future. The appropriate type, size, shape and number of decision units (DUs) for a given project is site-specific and must take into consideration the historical, current and future use of the site and the specific type of environmental hazards posed by the targeted contaminants. Investigation objectives can change as a project proceeds and, in some cases, additional or alternate DUs may need to be established to assist in response actions or long-term management of sites. For example, DUs established for site characterization purposes may need to be refined for the remedial phase of the project to isolate high-priority areas and optimize resources available for cleanup.

Additional Technical Support: The Technical Review Workgroup (TRW) Asbestos Committee is available to provide technical support for questions concerning the assessment, removal or remediation of asbestos contamination at hazardous waste sites. Questions may be directed to the TRW Asbestos Committee’s Technical Support Hotline in either of the following ways:

  • Send a question via e-mail to asbestoshelp@epa.gov
  • Call the toll-free TRW Hotline at 1-866-282-8622. If a hotline staff member is not available to speak with you, you may leave a message on the hotline voicemail system.

Hotline requests are received and logged by staff members. Technical experts will respond to the call within 24 hours. In some instances, further research may be required to respond to the request. The requester will be notified of all progress. Hotline requests that require significant research are referred to the TRW Asbestos Committee for review and consideration. Should hotline questions require discussion during a TRW Asbestos Committee teleconference, the requesters are notified and may be encouraged to participate in the teleconference. The written response summarizing the TRW Asbestos Committee's review and recommendations will be provided after the teleconference. If a legal concern for confidentiality exists, requests for assistance should be submitted to the TRW Asbestos Committee through regional legal counsel.

Table 4-2. Comparison of Applicable Methods for Measuring Asbestos in Air
NIOSH 7400a NIOSH 7402b YAMATEe AHERAd ISO 10312e
Analytical Technique PCM TEM TEM TEM TEM
Method of Preparation Direct preparation of MCE filter Direct preparation of MCE filter Direct preparation of polycarbonate filter Direct preparation of MCE or polycarbonate filter Direct preparation of MCE or polycarbonate filter
Magnification 400 – 450x 10,000x 20,000x 15,000 – 20,000x Total 20,000x PCMef 10,000x
Estimated Limit of Detection 7 Fibers/mm² One confirmed asbestos fiber above 95% of expected mean blank value. Not specified 0.005 structures/cc Not specified
Mineralogy Determined (Yes/No) No Yes Yes Yes Yes
Maximum Number of Structures/Fibers Counted 100 Fibers Light loadingg Moderate loadingh Heavy loadingi Minimum of 100 fibrous structures or 10 grid openings, whichever is first 50 structures 100 structures
Maximum Number of Fields/Grid Openings Counted 100 Fibers Light loadingg Moderate loadingh Heavy loadingi Minimum of 100 fibrous structures or 10 grid openings, whichever is first Dependent on volume of air collected and effective filtration area Adjustable
Statistically Balanced Counting (Yes/No)j No No No No Yes
Counting Rules:          
Length (L) > 5 µm > 5 µm Not specified ≥ 5 µm > 5 µm
Width (W) n/a > 0.25 µm Not specified Not specified > 0.2 µm, but <0.3 µm for PCMe
Aspect Ratio (AR) ≥ 3:1 ≥ 3:1 ≥ 3:1 ≥ 5:1 ≥ 5:1 or ≥ 3:1 for PCMef
Bundles (B) Counted as one fiber unless individual fibers can be identified by observing both ends of a fiber. Counted as one fiber unless individual fibers can be identified by observing both ends of a fiber. A particulate composed of fibers in a parallel arrangement, with each fiber closer than the diameter of one fiber. A structure composed of three or more fibers in a parallel arrangement with each fiber closer than one fiber diameter. A grouping composed of apparently attached parallel fibers.
Clusters (Cl) Not discussed in method Not discussed in method A particulate with fibers in a random arrangement such that all fibers are intermixed and no single fiber is isolated from the group. A structure with fibers in a random arrangement such that all fibers are intermixed and no single fiber is isolated from the group. Groupings must have more than two intersections. An aggregate of two or more randomly oriented fibers, with or without bundles, which occur as two varieties, compact and disperse.
Not discussed in method Not discussed in method Fiber or fibers with one end free and the other embedded or hidden by particulate. Fiber or fibers with one end free and the other end embedded in or hidden by a particulate. One or more fibers, or fiber bundles, attached to or partially concealed by a single particle or group of overlapping, non-fibrous particles. Occurs in two varieties, compact and disperse.

a National Institute for Occupational Safety and Health (NIOSH) Method 7400 for the determination of “Asbestos and Other Fibers by Phase Contrast Microscopy (PCM)”, Issue 2 (15 August 1994).
b NIOSH Method 7402 for the Determination of “Asbestos by Transmission Electron Microscopy (TEM)”, Issue 2 (15 August 1994).
c Methodology for the Measurement of Airborne Asbestos by Electron Microscopy (“Yamate Method”) by George Yamate, Satish C. Agarwal, and Robert D. Gibbons (July 1984). Contract No. 68-023266.
d U.S. Environmental Protection Agency (1987). Asbestos Hazard Emergency Response Act: Asbestos-Containing Materials in Schools. Final Rule and Notice (Appendix A: AHERA Method). Federal Register, 40 CFR 763, Vol. 52, No. 2, pp. 41826-41903, October.
e International Standard ISO 10312, Ambient Air – Determination of Asbestos Fibres – Direct-transfer transmission electron microscopy method, First Edition 1995-05-01.
f PCME stands for phase contrast microscope equivalent and indicates the fraction of structures observed by transmission electron micrscopy that would also be visible by phase contrast microscopy.
g For light loading (< 5 fibers per grid opening) count a total of 40 grid openings.
h For moderate loading (5 – 25 fibers per grid opening) count minimum of 40 grid openings or 100 fibers.
i For heavy loading (> 25 fibers per grid opening) count a minimum of 100 fibers and at least 6 grid openings.
j Statistically balanced counting is a procedure incorporated into some asbestos in which long structures (typically longer than 5 µm) are counted separately during a lower magnification scan than used to count total structures. This procedure assures that the relatively rare longer structures are enumerated with comparable precision to that of the shorter structures.

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Sampling & Analytical Issues

  1. What is activity-based sampling (ABS)?
    An empirical approach in which airborne concentrations of asbestos are measured during an event where the source material (soil or dust) is disturbed rather than predicted or modeled from source material concentration.

  2. What are appropriate scenarios for activity-based sampling?
    Activity-based sampling scenarios should be consistent with actual or projected activities at your site. For future residential land use scenarios, a generic raking scenario may be used to generate a screening reasonable maximum exposure (RME) estimate. The standard operating procedure (SOP) is located at http://www.ert.org/products/2084.PDF (PDF) (29pp, 325KB). Exit disclaimer

  3. What analytical techniques does EPA recommend for use at Superfund sites?
    There are a wide variety of analytical methods for asbestos, each with some advantages and limitations. For air, the most common methods are PCM (phase contrast microscopy) and transmission electron microscopy (TEM). PCM cannot distinguish asbestos fibers from other fibers. TEM is slower and more costly, but can distinguish asbestos types and can see fibers too small to be seen by PCM. TEM is the method required by Asbestos Hazard Emergency Response Act (AHERA) and International Organization for Standardization (ISO) Method 10312. For soil, methods that can detect asbestos at levels in the range of 1% or less are limited. The most common method is polarized light microscopy (PLM), which can be used either quantitatively (point counting mode) or semi-quantitatively (visual area estimation mode). Other techniques such as scanning electron microscopy (SEM) can also be used, but standardized approaches for quantification of low levels of asbestos are not yet well established.

  4. Concerning ABS samples, when is it appropriate to use personal samples vs. perimeter samples (upwind or downwind)?
    Area samples can be targeted to be co-incident with particular human activities, including those occurring for the purpose of ABS. While personal monitors are the best estimate of exposure to individuals whose activities match those wearing the monitors, area samples may also provide information regarding the surrounding airborne concentration and potential personal exposure. Area samples are also useful in providing data for evaluating: exposure to bystanders, releasability of asbestos from substrates, effectiveness of engineering controls, and selection of personal protection equipment (PPE). In using area samples to judge effectiveness of engineering controls, the samplers are often placed at the perimeter of the ABS area (i.e., upwind and downwind).

  5. What is an appropriate detection limit for ABS samples?
    Detection limits for personal monitors are typically 0.003 fibers per cubic centimeter phase contrast microscopy equivalent (PCME) (for 2 hour sampling ABS scenarios). This level was chosen because the risk values associated with this ABS exposure is typically within EPA’s risk range of 1 x 10-4 to 1 x 10-6. Under ISO counting rules, this detection limit for personal monitors is equivalent to an analytical sensitivity of 0.001 PCME structures/cc.

  6. What are the counting rules and limitations for each of the analytical methods?
    Response table pending from the analytical subcommittee.

  7. For a site-specific ABS Activity, clearing brush with brush hog, what duration would be appropriate for a one-acre area to draw enough air to get a good sample on the cassette?
    You must balance sufficient loading and representativeness with overloading with dust. Brushhogging may be dusty, so you will likely have to watch for overloading. Typically, 2-3 hours may give you enough air to get the needed sensitivity (0.005 or 0.001 f/cc). Two pumps should be used, one high flow at 10 liters/min and one low flow at 4-5 liters/min.
    Another option would be to have onsite PCM analysis to evaluate whether filters are overloaded.

  8. How many perimeter air samplers do you recommend for ABS
    Number per activity event will depend on wind pattern. If constant one direction wind, two downwind and one upwind, if variable during day, three or four with a further away "upwind'. Generally, 4 perimeter air samples around the area are used. Also, suggest using a portable meteorology station in the area to produce a wind rose (to know which perimeter samples are upwind and downwind). Typically 6 or more hours of sample time are needed to achieve the commonly accepted ambient air detection value (0.005 f/cc.

  9. How many background samples are necessary for ABS activities?
    Background is project dependent (e.g., land use considerations). Appropriate background samples may be mean upwind or located distant to the site (0.5 mile or so away

  10. What soil sampling depths would be appropriate for PLM analysis?
    Use historical site information to inform desired sampling depth. Also, consider frost heave (may be important for ACM?). Soil sampling to try to find discrete pieces of ACM is a challenge.

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Risk Issues

  1. Is EPA's Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) threshold of 1 x 10-4 to 1 x 10-6 to be used for managing asbestos?
    Yes, the cancer risk levels are appropriate for asbestos risk assessment.  It is important to note that current analytical methods may not be able to identify asbestos in air at levels much below a 1 x 10-4 cancer risk for chronic scenarios.  In addition, non-cancer hazard to public health may be significant and should be addressed qualitatively in the risk assessment. 

  2. What consideration should be given to the evaluation of risk to infants and young children who may be exposed to asbestos fibers?
    Because asbestos disease is not seen until years after exposure occurs, risks from asbestos are higher for people who are exposed early in life compared to later in life.  Risks of developing mesothelioma (a cancer caused by asbestos exposure) increase exponentially as a function of the time of first exposure.  Current risk models for evaluating asbestos risks take the age at initial exposure into account.

  3. Can tree bark sampling be used to assess exposures to asbestos?
    Asbestos has been found in tree bark from areas that have had large amounts of asbestos contamination in the surrounding air. The research that has been conducted to date indicates that sampling tree bark for asbestos may be helpful in determining if asbestos had been released in the area in years past*. However, the results cannot be used to estimate the potential health effects that may occur from the presence of asbestos in the bark. Uncertainties include: asbestos source contributions in the tree bark, unknown "background" asbestos levels in tree bark, sampling techniques for different tree types based on growth characteristics, and the development of reproducible exposure scenarios using the tree bark results. Other methods, such as collecting air samples while disturbing soil or tree bark in areas where asbestos may have been deposited, often called activity-based sampling, are preferred to collect exposure data for use in human health risk assessments. The TRW Asbestos Committee will attempt to keep up to date on new research findings on this topic to determine if further guidance can be provided.
    • Hart et al. 2009. An Evaluation of Potential Occupational Exposure to Asbestiform Amphiboles near a Former Vermiculite Mine. J Environ Public Health: 2009: www.ncbi.nlm.nih.gov/pmc/articles/PMC2799270/ Exit disclaimer
    • Ward et al. 2006. Trees as reservoirs for amphibole fibers in Libby, Montana. Science of the Total Environment. 367:460-465.
    • Hart et al. 2007. Evaluation of asbestos exposures during firewood harvesting simulations in Libby, Montana. Annals of Occupational Hygiene. 51(8):1-7.

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Removal and Remedial Questions

  1. Where can I find regulations that contractors must follow when removing asbestos?
    The procedures for asbestos removal can be found in Occupational Safety and Health Administration (OSHA) Regulation 29CFR1926.1101.

  2. Is 1% asbestos in soil a level of concern?
    The level of asbestos in soil that is a level of concern depends on many factors, and a value of 1% is not likely to be protective in many cases - See Clarifying Cleanup Goals and Identification of New Assessment Tools for Evaluating Asbestos at Superfund Cleanups (Michael B. Cook – August 10, 2004) OSWER Directive 9345.4-05 (PDF) (4pp, 120 KB). Therefore, EPA recommends the development of risk-based, site-specific action levels to determine whether response actions for asbestos in soil should be undertaken - further information is in the Framework for Investigating Asbestos-Contaminated Superfund Sites (PDF) (71 pp, 849K) OSWER Directive 9200.0-68, September 2008.

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