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INVESTIGA	TION OF INDOOR

Asbestos-Contaminated

Technical Review Workgroup Asbestos Committee
Office of Solid Waste and Emergency Response
U.S. Environmental Protection Agency
Washington, DC 20408

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1.0 PURPOSE AND SCOPE

The TRW Asbestos Committee developed this document to provide clarification to the
Framework for Investigating Asbestos-Contaminated Superfund Sites (U.S. EPA, 2008)
for indoor environments. This document provides recommended sampling methods and
strategies for evaluating the nature and extent of asbestos contamination in indoor
environments at Superfund sites. This document assumes that Steps 1-3 of the
Framework have been completed and further evaluation is required. The sampling
strategies and methods discussed are those currently employed by the Agency to estimate
exposures and the associated health risk in support of risk management decisions for
asbestos in indoor environments. This document is intended to provide supplemental
information at sites where indoor contamination by asbestos may be of concern.

The recommended sampling strategy to inform risk-based decisions in indoor
environments that may be contaminated with asbestos is to combine short-term activity-
based sampling (ABS) with long-term stationary sampling. The ABS should be designed
to evaluate short-term exposures associated with anticipated activities in the building.
Based on Agency experience, ABS with personal samplers (usually for time periods up to
a few hours) typically gives the most representative estimate of short-term, high-end
exposures that may occur during dust disturbance activities. Stationary samplers may be
used (usually for a time period of 8-24 hours) to characterize longer term exposure during
and after ABS sampling, as well as exposure during relatively quiescent activities
(e.g., watching television, sleeping). The combination of these sampling techniques
should provide useful information to support risk-based decisions within a building.

Applicability

This document is useful at sites where asbestos is tracked indoors or is transported
indoors via ambient air from outside sources to house dust or indoor air. Site
investigation under CERCLA routinely involves environmental sampling to determine
the nature and extent of contamination at a site, as well as to determine the concentration
of the contaminants in environmental media to assess risk associated with the site-related
contaminants. Where the contaminants have spread to indoor environments, the Agency
may evaluate the indoor environment to determine the extent of contamination and
characterize risk to inform site risk management decisions (U.S. EPA, 1993).

Indoor sampling for asbestos generally may be needed in homes or other buildings to
determine whether asbestos fibers have been transported from the outdoor environment to
indoor settings through a reasonably anticipated mechanism. If so, it should be
determined whether or not the asbestos in the indoor environment poses a health risk. The
decision of whether or not to sample indoors should be made on a site-specific basis.
Existing OSWER guidance on when indoor contamination can be addressed under
CERCLA may be found in the following memos: "Response Actions at Sites with
Contamination Inside Buildings" (U.S. EPA, 1993, 2009) and "Vermiculite Ore Asbestos
Sites: Evaluating Potential Indoor Residential Contamination" (U.S. EPA, 2006).

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2.0 COORDINATION WITH HEADQUARTERS

In general, CERCLA site investigations evaluating indoor environments to characterize
the nature and extent of contamination to support site risk assessment do not require
consultation with headquarters prior to or during the sampling events. Regions are,
however, strongly encouraged to consult with the TRW Asbestos Committee and OSRTI
when evaluating indoor asbestos exposures. For investigations under the removal
program, the Office of Emergency Management (OEM) has specifically requested that
Regions consult with Headquarters OEM prior to indoor residential site evaluations for
homes potentially impacted by asbestos (U.S. EPA, 2006, 2009).

3.0 CONDUCTING INDOOR SAMPLING

Considerations for Sampling

Multiple lines of evidence normally should be evaluated to determine if indoor air
sampling is necessary to ensure protectiveness of human health. When evaluating
whether indoor sampling is appropriate for a site, the project team (e.g., OSC/RPM, EPA
risk assessor, ATSDR) generally should consider a number of factors, including the
following:

mechanism(s) by which asbestos may have entered and been distributed in a
building,

time elapsed since the asbestos release,

severity of contamination found outside the building(s),

potential presence of other (non-site related) types of asbestos that may be

associated with building materials (e.g., flooring, insulation, or structural

materials), and

approaches to mitigate the possible disruption of the home occupants' daily
routines as a result of the sampling event(s).

The TRW Asbestos Committee can provide assistance in making a decision on whether
or not indoor sampling is warranted. The recommended decision framework for assessing
indoor environments is shown in Figure 1. This is based on the existing Asbestos
Framework (U.S. EPA, 2008), but has been tailored for indoor sampling as described
below.

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Asbestos Decision Framework for Indoor Environments

Step 1 - Review all available site information and data

•Does (did) the site use asbestos ormaterials contaminated with asbestos?

•Do site buildings contain asbestos-containing material (ACM) or asbestos?

•Is the site located within or near naturally-occurring asbestos (XOA) deposits?

	 y«

Step 2 - Has there been (or is there a threat of) a release?

•Airborne release of fibers or disposal of asbestos-containing solid wastes

•ACM-building debris remains on site

•Disturbance cfNOA by human construction of development

!Y«	

Step 3 - Are human exposure pathways currently present and complete?

Step 4 - Preliminary
Environmental Sampling

Conduct indoor air sampling using activity-
based sampling for a high-end activity or with
intensive dust disturbing methods in the indoor
environment. Collection of microvaccum dust

samples may be useful for determining
presence absence of asbestos orfor focusing
indoor air sampling locations.

Yes

and

Step 5 - More Detailed Environmental
Sampling

Following aQAPP, Conduct indoor air sampling
using activity-based sampling for a site-specific
activity in the indoor environment. Stationary air
samples could also be used to estimate long-term
exposure concentrations associated with quiescent
activities. Dust samples could be used to better
understand potential sources of contamination.
Determine air concentration to supportrisk basedsite
evaluation.

Step 6 - Implement response action or
institutional controls

*NFE = No Further Evaluation. Further
evaluation may be necessary if site conditions
change in the future.

Figure 1: Asbestos Decision Framework for Indoor Environments

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Sampling Objectives

Indoor sampling is similar to outdoor sampling described in Steps 4 and 5 of the Asbestos
Framework (U.S. EPA, 2008); the type and number of samples collected in the indoor
environment generally should be determined by the goals of the sampling event. For example,
when assessing asbestos contamination in an indoor environment, dust samples may help
determine if asbestos from a Superfund site is present in indoor environments, but they do not
provide sufficient information to determine the risk associated with exposure from asbestos
contamination. Because the primary route of exposure of concern for asbestos is inhalation, air
sampling is needed to support site-specific risk calculations. Thus, a combination of sampling
strategies is generally recommended to accurately characterize indoor environments for
determining whether action under CERCLA is warranted.

Interaction with Building Occupants

In the case of occupied buildings, advance discussions with the owner/resident are recommended
to explain the sampling process. Also, post-sampling communication is recommended to explain
the results. If the asbestos concentrations are found to be elevated, the actions that EPA intends
to take and/or that the owner/resident can take to reduce exposure to asbestos in dust should also
be communicated so that the owner/resident has a clear understanding of the implications of
sampling.

In most cases, it will not be necessary for the project team to consult with EPA's Human
Subjects Research Review Official (HSRRO) or Regional Equivalent prior to sampling inside
buildings that are occupied during sampling. This type of sampling does not constitute human
subjects research, but is usually being done for exposure assessment purposes1. However, should
the plan change to include information from or about human subjects - including conducting
surveys or interviews with residents - the plan must be submitted to the HSRRO for review and
approval, consistent with 40 CFR 26 and EPA Policy Order 1000.17 Change Al. The project
team should contact the HSRRO by phone or email if questions exist on whether or not aspects
of the ABS sampling project constitute human subjects research.

The determination of whether residents should be present during sampling will depend on the
type of sampling being conducted. If the sampling objective is to assess exposure conditions
using ABS to actively disperse asbestos fibers, then residents should not be present during the
sampling events to avoid the potential for exposures that would not otherwise occur but for the
sampling event. However, in cases where ABS methods can't be applied and the sampling
objective is to assess exposure levels under passive conditions, then it may be appropriate to
allow residents to remain during the sampling period. Regardless of the sampling methods,
owners/residents should not be asked to wear personal air samplers to assess indoor exposure.

1 Personal correspondence between Julie Wroble (Risk Assessor, U.S. EPA Region 10) and Toby Schonfeld (Human
Subjects Research Review Official, U.S. EPA Office of the Science Advisor), July 24, 2014.

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Quality Assurance Project Plan (QAPP) Development

QAPPs should be developed in accordance with existing Agency guidance (see
http://www.epa.gov/quality/qapps.html), including developing DQOs and having the QAPP
approved by a QA officer. QAPPs for evaluating indoor asbestos contamination typically should
specify a number of features, including: sampling objectives, the type of sampling (personal
samplers and/or stationary devices), number of sampling events, number and location of sample
points, sampling equipment, and sampling duration. Given the resources required and the likely
invasive nature of indoor air sampling investigations, sampling is often limited to one sampling
event and a few locations within a building. The QAPP should specify the analytical method,
pertinent quality assurance/control, and sensitivity that will be used to attain site-specific data
quality objectives. As part of the QAPP development, discussion among the project team to
select an analytical laboratory that can meet the required analytical sensitivity is recommended to
ensure that the sampling event will support site decisions. The project team should determine the
time frame needed for sampling results. In some cases, very fast turnaround times may be needed
if people are waiting for results to reoccupy spaces. Steps should be taken to ensure that the lab
can return sample results of determined detection limits within the timeframe needed to make
timely risk management decisions (see U.S. EPA, 2008).

Air Sampling

The goal of indoor air sampling is to determine an accurate estimate of the reasonable maximum
exposure (RME) concentration for building occupants2. The general recommendation for indoor
asbestos sampling to support risk-based decisions at buildings is to assess high-end, short-term
exposure associated with anticipated activities in the building in combination with long-term
sampling to assess ambient, long-term exposure.

For some indoor contaminants, collection of air samples with stationary monitors is adequate to
assess occupant exposures. However, asbestos fibers will settle out of the air into the surface dust
and greater exposures are anticipated when activities disturb this dust (suspending asbestos fibers
into the air). Thus, the air sampling strategy used for asbestos-contaminated indoor environments
should evaluate exposures during a range of activities to estimate relevant exposures.

The specifics of the sampling activity will be driven primarily by the needed analytical
sensitivity for a reasonable exposure. The pump flow rate and sampling time should be selected
to optimize the air volume collected to the analytical sensitivity needed. See ISO 10312, Table 1
(ISO, 1995) and www.epaosc.net (select Asbestos Data Management Support ERT web page).

2 In accordance with Risk Assessment Guidance for Superfund, Volume I (RAGS, Section 6.4.1, EPA, 1989), the
exposure frequency and duration assumptions made in developing TWFs should represent reasonable maximum
exposure (RME) scenarios.

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Activity-Based Air Sampling

Activity-based sampling (ABS) is the recommended practice for assessing short-term exposures
associated with site activities that disturb dust. Evaluating occupational exposures with
breathing-zone air samples for workers during their normal tasks is a well-established sampling
technique. Activity-based sampling (ABS) is an adaptation of this methodology to an
environment where the tasks are everyday activities (U.S. EPA, 2008).

Indoor ABS involves simply collecting air samples during an activity that is expected to suspend
asbestos fibers from indoor surface dust. Depending on how the ABS event is designed, the
information obtained from ABS may relate to screening using high-end dust disturbing activities
(Step 4 of the Asbestos Framework [U.S. EPA, 2008]) or site-specific exposure assessment
based on a combination of short-term ABS plus longer term quiescent or passive activities
(Step 5 of the Asbestos Framework [U.S. EPA, 2008]).

Figure 1 illustrates a similar approach to indoor sampling as was presented in the Asbestos
Framework, but aligns Steps 4 and 5 because it may be more difficult to repeat sampling events
indoors as compared with outdoors and because practically speaking, ABS is often done only
once at a given site. Since you may only get one chance to sample indoors, Step 5 would be
recommended in an attempt to get data for actual site-specific exposures. Data then would be
used to make risk-management decisions about the need for action, additional sampling, or no
further action.

Indoor ABS activities should be selected by the project team to characterize exposure from dust-
disturbing activities that would normally occur in the building (e.g., for residences this may
include sweeping, dusting, vacuuming). The Asbestos Framework (U.S. EPA, 2008)
recommends that preliminary screening (Step 4) be based on risk estimates from high-end
exposure scenarios. Indoor ABS for preliminary screening should include high-energy activities
anticipated to generate greater dust disturbance in an effort to create a high-end exposure
scenario.

Step 5 of the Asbestos Framework (U.S. EPA, 2008) recommends that ABS be conducted to
determine air concentrations to support site-specific exposure evaluation. Air sampling for Step 5
should represent exposures across a range of activities expected in the building, to include short-
term dust disturbing activities (e.g., for residences this may include sweeping, dusting,
vacuuming) as well as some longer-term quiescent or passive activities (such as watching TV,
sleeping, or cooking). In practice, exposures during several different types of activities would
likely result in different exposure levels. When considered together, these may provide a more
representative estimate of long-term exposure levels for residents. Given that indoor sampling at
someone's residence may result in an inconvenience to the property owner or occupants, it is
likely that there would be only one opportunity for sample collection. Further, if the goal is to
obtain information about likely exposures occurring at the site, then Step 5-type sampling may
be more appropriate than Step 4-type sampling (see Figure 1).

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Both the dust load and the asbestos content of the dust will contribute to the asbestos fibers
available for release during disturbance. Thus the most conservative ABS sample representing
the high-end of the exposure range would be a high energy activity, in an area with a high dust
load which contains asbestos. The location that is likely to have asbestos-contaminated dust at
the high end of the concentration range may be determined by site information (e.g., microvac
dust or wipe sampling) and/or professional judgment (e.g., high-traffic areas, dust collection
reservoirs, areas that are not regularly cleaned).

Indoor ABS is typically conducted by EPA or contractor personnel in protective gear using
personal samplers to characterize breathing zone exposure to asbestos fibers during a disturbance
activity (e.g., housecleaning). The goal is to determine a more representative estimate for an
exposure point concentration (EPC) (or a dust disturbance concentration differing from the
quiescent concentration) that could occur during an activity (or group of activities) in a building.
This exposure concentration can be compared to a risk-based level of concern (LOC, see Section
IV) or calculation of an excess lifetime cancer risk (ELCR) to inform a decision based on the
CERCLA risk range (see Section IV Example Calculations).

Stationary Sampling

Stationary air monitoring equipment has the capability to collect longer-duration samples
(approximately 8-24 hours), and samples with a higher volume than personal samplers to achieve
an improved analytical sensitivity. Thus, stationary samplers may be useful to help characterize
longer term exposure during and after ABS sampling or exposure during relatively quiescent
activities (e.g., watching television or sleeping) or to determine whether there is risk under
quiescent conditions (which may be useful for screening, since unacceptable airborne asbestos
levels during quiescent periods can be used to support risk management actions). Stationary air
sampling alone (i.e., without dust disturbance) limits the ability to quantitatively assess higher
exposures expected due to occupant activity in the building. Therefore, it is generally
recommended that ABS be used in addition to stationary sampling to inform risk-based site
decisions.

There may be instances where stationary air sampling with dust disturbance could be used as a
surrogate for ABS and the resulting data could be used to assess risk. For example, where it is
impractical to conduct ABS or where the building owner or occupants will not allow ABS, the
Agency has used other methods of dust disturbance with short and long term air sampling
(e.g., leaf blowers3, oscillating fans). Although these methods do provide some indication of the
releasability of fibers, airborne fiber levels measured after these surrogate dust disturbance
methods are not generally used to quantitatively inform risk estimates.

3 Leaf blowers are used for clearance sampling under AHERA (40 CFR Part 763, Subpart E—Asbestos-Containing
Materials in Schools).

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There may be instances where this is the only exposure information available to support site
decisions. In those instances, consideration should be given to the following: 1) exposures due to
actual human activity may be higher or lower than estimated by these surrogate methods, and 2)
air sampling with no dust disturbance may underestimate the potential indoor exposures. These
should be included as uncertainties in the risk assessment where appropriate.

Air Sampling Recommendations

The data obtained from stationary air sampling in an occupied building may not necessarily be
equivalent to ABS using breathing zone measurements of exposure. Therefore, the general
recommendation and preferred approach for indoor sampling to support decisions within
buildings is to use ABS with personal samplers to assess short-term exposure in
combination with long-term stationary sampling to assess quiescent, long-term exposure.

Dust Sampling

Dust samples may be collected on solid, nonporous surfaces to identify areas where asbestos is
present or absent. At this time, there is limited information available to correlate asbestos
content in dust with human exposure to support risk-based decisions at Superfund sites;
however, dust information may be used to support risk management decisions when
exterior high-level sources are present that result in high indoor dust levels (i.e., dust data
alone may trigger removal actions such as indoor cleaning in some instances). Dust samples
can be collected to provide a fiber loading per surface area in structures per square centimeter
(s/cm2). See Appendix C and ASTM D5755-09 and ASTM D6480-05 for descriptions of dust
sampling4 (Kominsky and Millette, 2010).

Where a limited number of dust samples are available, the user should exercise caution in
extrapolating those results to areas not sampled. Dust sample results can overestimate as well as
underestimate asbestos levels. The selection of sample locations is usually biased to suspected
higher level areas, so these results may not necessarily represent the indoor space as a whole, but
rather only represent the 100 square centimeters that was actually sampled. Additionally, the dust
analytical methods rely upon analyzing only a small portion of the sample. The results of this
analysis are then used to calculate the final result for the sample. Since asbestos is unlikely to be
distributed evenly across the sample, the final result being based on analysis of only a portion of
the sample is a source of substantial uncertainty.

Since the dust methods follow counting rules described in Asbestos Hazard Emergency
Response Act (AHERA) rules5, fibers that are too short to be included in the PCMe count of

4	The ASTM method provides AHERA counts unless otherwise specified. See Appendix C for more information.

5	See www.epa.gov/superfund/health/contaminants/asbestos/compendium/download/response_actions/table_4-
2_%20comparison_of_applicable_methods_for_measuring_asbestos_air.pdf

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corresponding air samples will be counted in the dust results. Correlation of dust and PCMe air
results will be particularly difficult for chrysotile, since chrysotile tends to have more short fibers
than amphiboles. The dust methods also involve indirect preparation of filters for analysis. For
chrysotile asbestos, indirect preparation often tends to substantially increase structure counts due
to dispersion of bundles and clusters (Hwang and Wang, 1983; HEI-AR, 1991; Breysse, 1991).
For amphibole asbestos, the effects of indirect preparation are generally much smaller (Bishop et
al., 1978; Sahle and Laszlo, 1996; Harris, 2009). For example, Libby-specific studies on the
effect of indirect preparation on reported Libby Amphibole (LA) air concentrations show that
indirect preparation usually increased reported PCME LA air concentrations, but these
concentrations were within a factor of about 2-4 compared to direct preparation LA (Berry et al.,
2014; Goldade and O'Brien, 2014).

Dust Sampling Considerations

As discussed in Section 8 of the Asbestos Framework (U.S. EPA, 2008), asbestos concentrations
in settled dust can be used for screening to inform risk management responses (such as early
removal actions like cleanup activities) when high-level sources are present. Analogous to a
situation where very high levels of asbestos are detected in residential soil and provide a basis for
a cleanup action, the project team may decide in the planning phase of the indoor assessment that
the presence of elevated concentrations of asbestos in indoor dust is sufficient for initiating a
cleanup action. For example, asbestos-contaminated indoor dust samples having greater than
10,000 structures/cm2 (total fibers) were identified as unacceptably elevated Millette and Hays
(1994)6. Lower screening numbers for dust have also been used as the basis for site-specific
cleanup: dust results greater than 5,000 structures/cm2 (total fibers) were considered sufficiently
high to warrant a response action at indoor environments impacted by the World Trade Center
collapse (U.S. EPA, 2003a, 2005) and Libby (U.S. EPA, 2003b).

Because of limitations in predicting the release of asbestos fibers from settled dust,
sampling of dust (such as microvac sampling) is not typically recommended as a stand-
alone means of assessing indoor exposures to asbestos. Also, asbestos-contaminated dust
concentrations less than the screening level generally require further evaluation (i.e., air
sampling) since there is insufficient information to conclude that levels below the screening level
would not present a health concern if the dust is disturbed by occupants during routine activities.
When conducting dust sampling, it is recommended that the project team establish a target
analytical detection limit for the samples and, if necessary, discuss this issue with the selected
laboratory.

4.0 EXAMPLE CALCULATIONS

Risk calculations can be used to estimate potential site risks or in the development of generic
screening levels and/or site-specific action levels. Generic screening levels and site-specific

6 This is also known as the Millette and Hays experience standard for asbestos in dust.

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action levels are used to determine the analytical sensitivity necessary to support decisions at the
site. Site-specific action levels and generic screening levels can be derived for ABS or stationary
air samples. In some cases, such as removal sites where decisions must be made quickly, risk
management decisions include comparing action levels to measured levels as described below.
Estimates of potential risks, as described in Section 5.5 of the Framework (U.S. EPA, 2008),
involves calculating excess lifetime cancer risks (ELCRs) for exposed individuals using data
obtained from ABS and stationary air samples and site-specific assumptions about exposure. An
example showing this type of calculation is presented below. The examples shown are for
residences; however, the concepts and considerations also can be applied to other buildings (e.g.,
commercial buildings) by modifying the exposure factors.

A risk-based level of concern (LOC) for asbestos in quiescent indoor air may be calculated by
rearranging the standard risk equation to compute the concentration of asbestos in air that
corresponds to a CERCLA specified risk level for an appropriate exposure scenario as follows:

Equation 1:

LOC for Asbestos in Air (f/cc) = Target Risk + [IURltl * TWF]

The standard Superfund residential exposure scenario (U.S. EPA, 1989) would apply to this
example. The LOC for asbestos7 in air was calculated using the time weighting factor for
Baseline Residential Exposures (TWF = 350/365 = 0.96, see Table 1 of the Framework [U.S.
EPA, 2008]), the 0-30 year age interval8 IURltl ([IURltl = 0.17 (f/cc)"1], see Table 2 of the
Framework [U.S. EPA, 2008]), along with the target risk levels of lxlO"4 and lxlO"6:

Equation 2:

LOC for Long-term Residential Asbestos Exposures for 1 in 10,000 risk (f/cc)

= lxl 0'4 : 10.17 Cf/ccy1 • 0.96]

= 0.0006f/cc

7	This example is for asbestos forms other than Libby Amphibole Asbestos. For sites where there is exposure to
Libby Amphibole Asbestos in the indoor environment, please contact the TRW Asbestos Committee.

8	In this example, it is assumed that this age group represents receptors who are first exposed to asbestos at the site at
birth and for a duration of 30 years. In the absence of a 26-year IUR (residential exposure in accordance with
Superfund assumption of 26 years of duration), the 30-year IUR 0.17 f/cc was used to err on the side of
conservatism.

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Equation 3:

LOC for Long-term Residential Asbestos Exposures for 1 in 1,000,000 risk (f/cc)

= lxl 0'6 : 10.17 Cf/ccy1 • 0.96]

= 0.000006f/cc

The inputs to the LOC calculation shown are generic screening values (though these may match
site-specific information in some cases). The LOC calculation can be made site-specific by
modifying the TWF and/or the age and duration associated with the IURltl- The sampling
results (airborne fiber concentrations in f/cc) from the stationary 24-hour (total) samples for each
decision unit could be compared to these risk-based LOC values for lxlO"4 and lxlO"6 risk levels
to inform site decisions and determine whether there is a basis for action under CERCLA. Note
that the LOC calculation from stationary air samples could trigger a response if the LOC is
exceeded.

Site screening: Step 4 to Risk Management Decision Point

After ensuring that the desired analytical sensitivity was achieved, the project team should
compare the air sampling results to the risk-based LOC based on the CERCLA risk range for
asbestos in air to help determine the appropriate next step, specifically whether action is
warranted under CERCLA (air concentrations above the LOC for a 10"4 risk level, no further
action (NFA) decision (air concentrations below the LOC for a 10"6 risk level), or additional
sampling is necessary to characterize risk (air concentrations within or close to the LOC for 10"4
to 10"6 risk range). While action is generally warranted when the carcinogenic risk level exceeds
a 10"4 excess lifetime cancer risk, action may also be warranted within the risk range based on
site-specific factors such as multiple contaminants, applicable or relevant and appropriate
requirements (ARARs), uncertainty, sensitive populations, etc. Specific considerations for
determining the potential for unacceptable risks from inhalation of asbestos fibers include
sampling and analytical constraints, the presence of multiple exposure scenarios (e.g., different
activities that may disturb dust), and scenarios characterized with ABS.

Preferred Indoor Sampling Approach Example: Simulating Residential Exposure using
Long-Term and Short-Term Sampling in an Unoccupied Residence

A single sampling event may be used to assess short- and long-term exposures that may occur in
the residence due to disturbance of settled dust. The short-term ABS event simulated
housecleaning by residents. Trained personnel9 conducted housecleaning activities (vacuuming,
dusting, and sweeping) for a total of 4 hours in areas with suspected asbestos contamination.

9 All persons with potential airborne exposure to asbestos should have appropriate training and use appropriate
personal protective equipment (PPE), consistent with a properly developed health and safety plan (HASP) that
follows EPA policies and Occupational Health and Safety Administration regulations.

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Personal samplers were placed on those conducting the ABS activities, and air samples were
collected during the event. Five stationary air samples were collected inside each residence
during the ABS event and for an additional 20 hours (for a total time was 24 hours.) This
approach only intrudes on a single day for the owners/occupants and should provide sufficient
information to support a decision for the building.

The short-term air samples may be used to evaluate whether risks are acceptable during the
disturbance activity through comparison to risk-based criteria for time-weighted exposure
scenarios. While these exposures are intermittent, there is the potential that cleaning activities
may result in a higher exposure level {i.e., greater chance for disturbing and inhaling fibers in
settled dust during cleaning). Assuming the 4-hour ABS represents weekly housecleaning, this is
a small fraction of the 168-hour week. Because of this, the ABS activity was supplemented with
long-term stationary sampling to assess exposure to ambient air in the building. The long-term
air samples may be used to evaluate whether risks are acceptable through comparison to risk-
based criteria for long-term exposure scenarios. In this example, risk-based LOCs are calculated
for both short-term, higher exposure {i.e., house cleaning) and longer term exposure when dust is
not being disturbed.

First Phase: Establishing Risk Based LOC for Comparison of Sampling Results

A risk-based LOC for asbestos in quiescent indoor air may be calculated as shown above with
site-specific substitutions. To determine a risk-based cleanup LOC for the house cleaning
scenario, exposures are assumed to be intermittent (4 hours per day once per week). As a result,
the LOC for asbestos in air was calculated using an assumed time weighting factor for cleaning
{TWF = 4/24 hours per day, 50/365 days per year = 0.023), the 20-50 year age interval10 IURltl
((0.075 (f/cc)"1), see Table 2 of Framework [U.S. EPA, 2008]), along with the target risk levels
of lxlO"4 and lxlO"6:

Equation 4:

LOC for Housecleaning Asbestos Exposures for 1 in 10,000 Risk (f/cc)

= lxl0'4 - [0.023 (f/ccy1 ' 0.075]

= 0.06 f/cc

10 In this example, it is assumed that this age group represents receptors who are first exposed to asbestos at the site
at the age of 20 and for a duration of 30 years until they are 50 years old. It is also assumed that a person would start
doing housecleaning at the age of 20 and not younger; hence, they would first be exposed to asbestos at the age of
20.

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Equation 5:

LOC for Housecleatting Asbestos Exposures for 1 in 1,000,000 Risk (f/cc)

= lxl0'6 - [0.023 (f/cc/1 • 0.075J
= 0.0006f/cc

The sampling results (airborne fiber concentrations in f/cc) from the 4 hour housecleaning
samples for each decision unit should be compared to these risk-based LOC values for lxlO"4
and lxlO"6 risk levels to inform site decisions and determine whether there is a basis for action
under CERCLA (see U.S. EPA, 2008 section 5.2). Caution may be needed for cases where
several activities that are near the LOC, but none exceed the LOC (e.g., multiple activities within
a home or exposure to asbestos indoors and outdoors).

The LOCs for long-term residential exposure as calculated above (see Equations 2 & 3) should
be used for assessing stationary air sample data.

Second Phase: Excess Lifetime Cancer Risk Calculation Using Sampling Results

Using the preferred approach, we assume data are available both for ABS and stationary
samples. Using assumed EPCs, we can calculate excess lifetime cancer risks by making
reasonable assumptions about exposure. If only stationary data are collected, then a comparison
to the long-term LOC as calculated above could be appropriate.

As noted in the general equation presented in Section 5.0 of the Framework (U.S. EPA, 2008),
the basic equation for estimating ELCR resulting from exposure to asbestos is:

Equation 6:

Risk (ELCR) = EPC • TWF • IUR

As noted above, when applying this equation to a less-than-lifetime exposure, TWFi and IURltu
values specific to the exposure scenario(s) must be used to calculate the appropriate ELCRi as
follows:

Equation 7:

ELCRi = EPCi • TWFi • IURltu

Where:

ELCRi = excess lifetime cancer risk for less-than-lifetime scenario i

EPCi = the scenario-specific exposure point concentration generated from activity-based
sampling

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TWFi = the scenario-specific time weighting factor

IURLTLi = the Inhalation Unit Risk corresponding to the age at first exposure and
exposure duration for the exposure scenario

Because CERCLA risk assessors may also need to characterize the cumulative risk to an
individual resulting from exposure to several environments (e.g., different operable units across a
site) or several scenarios (e.g., playing in the dirt, mowing the lawn, and indoor exposures), the
cumulative excess lifetime asbestos cancer risk can be summarized as follows:

Equation 8:

ELCRc = X EPCi* TWFi* IURLTLi"

Where:

ELCRc = the cumulative excess cancer risk attributed to exposure to multiple
environments or multiple scenarios over the course of the exposure duration of the
individual.

For the purposes of this example, we assume the EPC for housecleaning ABS is 0.03 f/cc. We
then calculate the ELCR calculation as follows:

Equation 9:

ELCRi = 0.03 f/cc * 0.023 * 0.075 (per f/cc) = 5.2E-05

The EPC for ambient air is assumed to be 0.0005 f/cc. The TWF should account for the fact that
some of the time in the residence is spent cleaning.

Where:

Adult scenario (ages 20-50)

TWF for cleaning is (4/24) * (50/365) = 0.023

Remainder of time at stationary: 24 hours/d - 4 hours/d (50/365) = 23.45 hours/day
Stationary TWF: 23.45/24 * 350/365 = 0.94

11 Note that in this context, "lifetime" refers to the risk of developing cancer sometime during one's lifetime from an
exposure of duration specific to the activity being assessed; it does not refer to risk from a lifetime of exposure.

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The ELCR for the remaining portion of the exposure is calculated as follows:

Equation 10:

ELCR2 = 0.0005 f/cc * 0.94 * 0.075 per f/cc = 3.5 E-05

The combined ELCRc is simply the sum of ELCRi and ELCR2 or 8.7E-05. At this risk level,
remedial managers may decide that action is not warranted as the calculated risk is less than the
level where action needs to be taken. However, in some instances or at some sites, action may be
determined to be necessary if this level of risk is considered to be unacceptable due to
uncertainty or applicable and relevant or appropriate requirements (ARARs). This decision is
usually made on a site-specific basis and involves risk managers and potentially regional
management.

For children who live at the residence, the stationary air data can be used to assess the risks to
children. The EPC for ambient air is assumed to be 0.0005 f/cc. In this example, we assume a
child lives in the house until age 20. The TWF would be the same as for the long-term residential
scenario (TWF = 350/365 = 0.96, see Table 1 of the Framework [U.S. EPA, 2008]), but the
toxicity value must reflect the 0-20 year age interval12 IURltl ([IURltl = 0.14 (f/cc)"1], see
Table 2 of the Framework [U.S. EPA, 2008])

Equation 11:

ELCR2 = 0.0005 f/cc * 0.96 * 0.14 per f/cc = 6.7 E-05

The child-specific ELCR should not be combined with the adult risk calculated above, but
should be presented separately.

References

International Organization for Standardization (ISO). 1995. ISO 10312:1995. Ambient air —
Determination of asbestos fibres — Direct transfer transmission electron microscopy method.
www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=18358

Kominsky JR and Millette JR. 2010. Evaluation of Asbestos in Dust on Surfaces by Micro-
Vacuum and Wipe Sampling. Journal of ASTM International: 8(5).

Millette JR and Hays SM. 1994. Chapter 8, Resuspension of Settled Dust. In: Settled Dust
Sampling and Analysis. Lewis Publishers.

12 In this example, it is assumed that this age group represents receptors who are first exposed to asbestos at the site
at birth and for a duration of 20 years. The 20-year IUR 0.14 f/cc was used for children.

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U.S. EPA. 1993. Memorandum: Response Actions at Sites with Contamination Inside Buildings.
Henry Longest, Director OERR. OSWER Directive 9360.3-12

http//www.epa.gov/superfund/resources/remedy/pdf/93-60312-s.pdf

U.S. EPA. 2002a. EPA/240/R-02/009 Guidance for Quality Assurance Project Plans
www.epa.gov/qualityl/qs-docs/g5-final.pdf.

U.S. EPA, 2003a. Interim Final WTC Residential Confirmation Cleaning Study

Volume 1. http://epa.gov/wtc/reports/confirmation_cleaning_study.pdffsee section 3.4]

U.S. EPA, 2003b. Libby Asbestos Site Residential/Commercial Cleanup Action Level and
Clearance Criteria Technical Memorandum. Draft Final. December 15, 2003

U.S. EPA. 2005. World Trade Center Residential Dust Cleanup Program. Final Report.
December 2005. http://epa.gov/wtc/reports/residential_dust_cleanup_final_report.pdf

U.S. EPA. 2006. Vermiculite Ore Asbestos Sites: Evaluating Potential Indoor Residential
Contamination.

http://www.epa.gov/superfund/health/contaminants/asbestos/compendium/download/site_cha
racterization/asbestos_indoor_oct_2006.pdf

U.S. EPA. 2008. Framework for Investigating Asbestos-Contaminated Superfund Sites (PDF)
(71 pp, 849K) OSWER Directive 9200.0-68, September 2008.
http://www.epa.gov/superfund/health/contaminants/asbestos/framework.htm

U.S. EPA. 2009. Superfund Removal Guidance for Preparing Action Memoranda

http://www2.epa.gov/emergency-response/superfund-removal-guidance-preparing-action-
memoranda

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