I O \ Naturally Occurring Asbestos:
\^IU*f Approaches for Reducing Exposure
Purpose and Intended Audience
This fact sheet provides an overview of approaches for reducing ex-
posures to naturally occurring asbestos (NOA). It is intended to make
general information about management options available to state and
local government officials, project managers, and environmental profes-
sionals. The information should serve as a starting point for identifying
current NOA management practices. In general, selecting an appropriate
approach to reduce NOA exposure should be determined on a location-
specific basis.
NOA management
approaches can reduce
but may not completely
eliminate potential
exposures to naturally
occurring asbestos.
Information contained in this fact sheet was obtained from the currently available literature, includ-
ing state and local government publications. To obtain more information on NOA management
approaches, including their performance and frequency of use, refer to the resources provided at the
end of this fact sheet.
Naturally Occurring Asbestos
NOA occurs in rocks and soil as a result of natural geological processes. Natural weathering or
human activities may disturb NOA-bearing rock or soil and release mineral fibers into the air, which
pose a greater potential for human exposure by inhalation.
The U.S. Geological Survey (USGS) has an ongoing project to map the locations of historical
asbestos mines, former asbestos exploration prospects, and natural asbestos occurrences. At least 35
states have reported NOA locations. To locate NOA areas in a specific part of the country, begin by
consulting the USGS reports (see below) and contact a state geologist.
U.S. Geological
Survey
California
Geological
Survey
Eastern United States http://pubs.usgs.gov/of/2005/1189/
Central United States http://pubs.usgs.gov/of/2006/1211/
Rocky Mountain States http://pubs.usgs.gov/of/2007/1182
Asbestos Reports, Maps and Guidelines for Geologic Investigations
http://www.conservation.ca.gov/cgs/minerals/hazardous_minerals/asbestos/
Pages/Index.aspx
This fact sheet is intended solely to provide general information on approaches that may be useful when addressing naturally occurring asbestos
(NOA). It is not intended, nor can it be relied upon, to create any rights enforceable by any party, including any party in litigation with the United States.
EPA considers NOA to be in an altered form if it has been disturbed by human activity; NOA is not considered to be altered if modified solely through
naturally occurring processes or phenomena, from a location were it is naturally found. This fact sheet may be revised periodically without public
notice. Use or mention of trade names does not constitute endorsement or recommendation for use.
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In this fact sheet, NOA does not refer to commercially processed, asbestos-containing material, such
as insulation and fire protection in buildings or automobile brake linings. Information about commer-
cial asbestos-containing products is available in other publications, including the resources mentioned
on EPA's asbestos Web page http://www.epa.gov/asbestos.
Approaches for Mitigating Exposures to NOA
The following general approaches to mitigate inhalation exposures to NOA are aimed at reducing
NOA releases from rock or soil into the air:
• Leave NOA material in place and undisturbed
• Cover or cap NOA material
• Limit dust generating activities
• Excavate and dispose of NOA material
Approaches for
reducing NOA exposure
are similar to practices
used for asbestos-
containing materials in
commercial applications.
Depending on the situation, a combination of engineering controls, work
practices, and institutional (administrative) controls may be needed to
implement an approach and reduce potential exposures to NOA. Selecting
an approach depends on factors including:
• Accessibility of NOA (ground surface vs. below ground surface)
• Types of activities that disturb NOA (construction project vs. gardening)
• Climate and weather conditions
• Current and future land uses
• Technical and administrative feasibility of the approach
Typical engineering controls involve the use of covers and caps, vegetation, fencing, landscaping, and
in some conditions, the application of water to suppress dust. Local factors, such as climate, influence
the extent to which these approaches are implemented. For example, areas with dry or windy condi-
tions may need more dust control than those with humid or less windy conditions.
Common work practices include limiting activities on NOA-containing areas, reducing driving speed
on unpaved roads that may contain NOA, and cleaning vehicles driven over NOA. For example,
during road construction or maintenance activities on unpaved areas where NOA is present, the As-
bestos Airborne Toxics Control Measure (ATCM) for Construction, Grading, Quarrying, and Surface
Mining Operations of the California Air Resources Board (ARB) requires that vehicle speeds not
exceed 15 miles per hour.1 Worker health and safety measures that include respiratory protection may
be warranted. For information, consult with Occupational Safety and Health Administration Asbestos
Standards for the General Industry and Asbestos Standards for the Construction Industry (http://www.
osha.gov/SLTC/asbestos/hazards.htmn.
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Examples of Engineering and Work Practices that Reduce Exposure to NO A
Excavation,
Grading, or
Utility Work at
Construction
Projects
Roads and
Parking Areas
(unpaved and
gravel roads)
Wet road surfaces with water using trucks, hoses, or sprinklers1
Wet piles of excavated material and cover them with tarps, plastic sheeting,
or other items1
Continuously mist the work area1
Install wind barriers around the work area1
Clean or decontaminate equipment and vehicles to ensure that no equipment
or workers track soil out of the work area (a gravel pad, tire shaker, or wheel
wash system may be used to clear soil from vehicles)1
Wet the work area using a spray system attached directly to rock cutting
or drilling equipment, such as a fine-mist sprayer or a variable-rate fogger
nozzle (similar to those used in fire fighting)2
Excavate utility trenches to an adequate depth and backfill them with clean
soil so that future repair work will not need excavation into potential NOA-
containing materials3
When transporting NOA-containing materials, avoid overloading trucks;
keep the material below the top of each truck compartment and cover
material with a tarp4
Limit personnel and vehicle access to the work area5
Identify NOA-containing areas with signs2
Reduce driving speed1
Reduce drilling or excavating speeds6
Excavate during periods of calm or low winds1
Cover roads with non-NOA-containing rock, chemical sealants or dust
suppressants, chip seals, limestone aggregate, petroleum sealants, or asphalt
cement paving1'7> 8
Wet road surfaces with water1
Install windbreaks or berms1
Reduce driving speed1
Avoid dusty areas, especially in windy conditions1
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Cover areas of rock and soil with clean soil, rock, vegetation, or other
material (see next section, General Considerations for Using Covers or
Caps)3-9
Pave over unpaved walkways, driveways, or roadways containing NOA1'10
Landscape areas with vegetation, such as NOA-tolerant plants, and add a
layer of organic mulch or NOA-free soil. Water plants often until they are
established to minimize erosion9
Water garden areas before digging9
Keep windows and doors closed on windy days and during periods when
nearby rock or soil may be disturbed, such as during construction9
Limit track-in by using entryway (door) mats, and wipe down pets before
they enter buildings to reduce the amount of soil tracked indoors4'9
Allow children to play in outdoor areas only if the area has a ground
covering, such as wood chips, mulch, sand, pea gravel, grass, asphalt,
shredded rubber, or rubber mats4
Relocate outdoor activities to areas that do not contain NOA (walk, run, hike,
and bike only on paved trails)4
Avoid dusty areas, especially in windy conditions"
General Considerations for Using Covers or Caps
One of the most common engineering controls is to place a cover system over the NOA. Cover materi-
als may include clean soil or rock, concrete, chemical sealants or dust suppressants, chip seals, limestone
aggregate, petroleum sealants, asphalt paving, geotextiles, wood chips, mulch, sand, pea gravel, shred-
ded rubber, rubber mats, and vegetation.
The complexity of cover systems can vary from simple (e.g., a single soil layer) to complex (e.g., mul-
tiple layers of varying materials). Several factors, including cover material properties and site character-
istics, affect the type of cover system appropriate for a particular area.
The availability of materials may influence the type of cover used. Materials that are readily available
and close to the NOA area may be more desirable and cost effective than materials found farther away.
For example, artificial turf and other imported materials may be more expensive than locally available
soils. The cover material will likely need to be assessed for NOA or other undesirable constituents.
Expected lifetime, maintenance, and monitoring requirements also affect the cost of covers.
The slope of the NOA area may influence the type and thickness of the cover material used. For
example, steep slopes may need vegetation or shotcrete (concrete or mortar sprayed onto a surface with
a pressurized hose) to promote slope stabilization. Steep slopes typically have a higher potential for
erosion and therefore may demand thicker cover material.
The thickness of the cover material should provide a safety factor sufficient to ensure that airborne
releases will not occur. Thicker covers may be needed in areas where there is a significant potential
for erosion. The surface of a cover should protect against erosion by wind and rain. Materials used for
erosion control typically include a layer of topsoil and vegetation. In areas where adequate vegetation is
not possible, gravel, admixtures, or riprap may be used for the surface layer. The thickness of the cover
may also depend on the presence of other cover components, such as irrigation lines.
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A geotextile, which is a geosynthetic material made of polymer fabric, may be placed below the cover
material to mark the presence of NO A and serve as an erosional indicator. Geotextiles also can provide
protection, reinforcement, drainage, and separation when applied to the soil surface or between layers
of materials. The California Department of Toxic Substances Control (DTSC) recommends that land-
scaped areas and play fields at schools include a geotextile marker covered by sufficient cover material
to provide an effective barrier to reduce NOA exposures.3 Placement of geotextile markers will demand
additional time and expertise.
Long-Term Management Approaches
For long-term management of areas with NOA, institutional controls (ICs) and a maintenance plan may
be desirable. In areas where NOA poses potential health concerns, local and state government officials
should consider providing educational material to supplement engineering approaches for reducing
exposures to NOA. The Agency for Toxic Substances and Disease Registry has developed a fact sheet
about asbestos and NOA for the general public entitled "Asbestos and Health: Frequently Asked Ques-
tions."4
Institutional Controls
For additional
information about ICs,
refer to the Land Use
Controls Web site at
htto://www.lucs.or<
Generally, ICs are administrative or legal mechanisms that are designed to
help minimize the potential for human exposure to contamination They also
protect the integrity of the engineering measures. ICs are generally divided
into four categories:
• Government controls include laws and permits (such as local zoning
laws and permits required for excavating or digging). Work that may
disturb NOA-containing soil may require government approval and may be subject to local or
state construction guidelines. In California, the ATCM of the California ARB requires owners and
operators to notify the local air quality management district within one business day of discovering
NOA, serpentine mineral, or ultramafic rock in an area to be disturbed by construction, grading,
quarrying, or surface mining operations.1 In Virginia, the Fairfax County Health Department requires
a compliance plan that includes air monitoring to ensure effective dust control during construction in
areas containing NOA.2
• Proprietary controls include property use restrictions based on private property laws, such as land use
easements or covenants.
• Enforcement tools include legally binding documents that require individuals or companies to conduct
or prohibit specific actions.
• Informational devices include deed notices, public advisories, and other measures (such as warning
signs and worker health and safety awareness training) that alert and educate people about an area.
Maintenance Plan
A maintenance plan can help ensure that engineering controls and work practices remain effective. In
California, for example, DTSC and school districts enter into an agreement to develop and implement
an approved long-term operation and maintenance plan under DTSC oversight. These plans generally
contain information about the following topics:3
• Building locations, utility line locations, and the thickness of cover material across the area
• Routine inspections
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Maintenance work, including erosion and storm water control
Procedures for repairing cover damage
Monitoring activities, such as perimeter or personal air monitoring
Reporting format and frequency
Restrictions on future activities that may expose NOA
Management of imported soil and future excavation or trenching activities
Additional
Information
Agency for Toxic Substances and Disease Registry - http://www.atsdr.cdc.gov/NOA
California Air Resources Board - http://www.arb.ca.gov/toxics/asbestos/asbestos.htm
• El Dorado County, California - http://www.co.el-dorado.ca.us/emd/apcd/asbestos.html
• Fairfax County, Virginia - http://www.fairfaxcounty.gov/hd/asb
• Sacramento County, California - http://www.airquality.org/compliance/
asbestosNaturallyOccurring. shtml
U.S. Environmental Protection Agency - http://www.epa.gov/asbestos/pubs/clean.html
References
1. California Environmental Protection Agency (Cal/EPA) Air Resources Board (ARB). 2002. Asbestos
Airborne Toxic Control Measure for Construction, Grading, Quarrying, and Surfacing Mining
Operations. Final Regulation Order. Section 93105. July 22. http://www.arb.ca.gov/toxics/atcm/
asb2atcm.htm
2. Fairfax County Health Department. Undated. "Control and Prevent!on of Asbestos Exposure from
Construction in Naturally Occurring Asbestos." http://www.fairfaxcounty.gov/hd/asb/pdf/tbrdpubfin.pdf
3. Cal/EPA Department of Toxic Substances Control (DTSC). 2004. Interim Guidance: Naturally
Occurring Asbestos (NOA) at School Sites. September 29.
http://www.dtsc.ca.gov/Schools/upload/SMBRP_POL_Guidance_Schools_NOA.pdf
4. Agency for Toxic Substances and Disease Registry. Undated. "Asbestos and Health: Frequently
Asked Questions." U.S. Department of Health and Human Services.
http://www.atsdr.cdc.gov/NOA/Asbestos-and%20Health.pdf
5. El Dorado County. 2003. Naturally Occurring Asbestos and Dust Protection. Ordinance. Chapter
8.44. June 12. http://www.co.el-dorado.ca.us/emd/apcd/PDF/Naturally_Occuring_Asbestos_June_
12.pdf
6. Fairfax County Health Department. Undated. "Basic Elements for a Naturally Occurring Asbestos
Compliance Plan." http://www.fairfaxcounty.gov/hd/asb/pdf/asb50.pdf
7. Cal/EPA ARB. 2002. "Fact Sheet #3: Ways to Control Naturally-Occurring Asbestos Dust." January.
http://www.arb.ca.gov/toxics/asbestos/3control.pdf
8. Cal/EPA DTSC. 2005. "DTSC Recommends Resurfacing of Serpentine Gravel Roads Based on
Garden Valley Study." April, http://www.dtsc.ca.gov/SiteCleanup/Projects/Garden_Valley.cfm
9. Cal/EPA ARB. 2002. "Asbestos-Containing Rock and Soil - What California Homeowners and
Renters Need to Know." Compliance Assistance Program. CAP 03-035. http://www.arb.ca.gov/cap/
pamphlets/asbestosbrochure.pdf
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10. Cal/EPADTSC. 2006. "Fact Sheet: Recommended Housekeeping Activities to Reduce Exposure
to Naturally-Occurring Asbestos in Schools." October, http://www.dtsc.ca.gov/Schools/upload/
Recommended_Housekeeping_for_NOA_102306.pdf
11. University of California Cooperative Extension. Undated. "Lake County Serpentine Landscape
Demonstration Garden." Asbestos Serpentine Soils Education Program, http://www.capcoa.org/noa/
%5B5%5D%20Lake%20Countv%20Serpentine%20Landscaping.pdf
List of Acronyms
ARB Air Resources Board
ATCM Airborne Toxic Control Measure
DTSC Department of Toxic Substance Control
ICs institutional controls
NOA naturally occurring asbestos
USGS U.S. Geological Survey
Office of Superfund Remediation EPA 542-F-08-001
and Technology Innovation March 2008
(5204P) www.epa.sov
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