STATEMENT OF

#### **GREGORY P. MEEKER**

GEOLOGIST

U.S. GEOLOGICAL SURVEY

U.S. DEPARTMENT OF THE INTERIOR

BEFORE THE COMMITTEE ON ENERGY AND COMMERCE

SUBCOMMITTEE ON ENVIRONMENT AND HAZARDOUS MATERIALS

U.S. HOUSE OF REPRESENTATIVES

FEBRUARY 28, 2008

Mr. Chairman and Members of the Subcommittee, thank you for the
opportunity to present testimony on the mineralogy and geology of
asbestos. My name is Greg Meeker and I am a geologist at the U.S.
Geological Survey (USGS) in Denver, Colorado.

**Asbestos\
**Many minerals found in nature grow in a form referred to as
***fibrous***, that is, they possess physical properties similar to
organic fibers. ***Asbestos*** is a term applied to a special group of
fibrous silicate minerals that form as long, very thin fibers that
usually occur in bundles. When handled or crushed, the asbestos bundles
readily separate into individual mineral fibers. This type of mineral
growth form or "habit" is called ***asbestiform*** (National Research
Council, 1984; Skinner and others, 1988). The special properties of
commercial-grade asbestos---long, thin, durable mineral fibers and fiber
bundles with high tensile strength, flexibility, and resistance to heat,
chemicals, and electricity---make it well suited for a number of
commercial applications. This definition for asbestos is based on the
properties that make it valuable as a commodity. When asbestos
regulations were developed in the 1970's it was these commercial fibers
that were identified as most problematic from a health perspective
because they were the most common species encountered in mining,
processing, and manufacturing.

Although there are many asbestos minerals, some commercial and
regulatory definitions of asbestos focus on chrysotile, the asbestiform
member of the serpentine mineral group, and several members of the
amphibole mineral group, including the asbestiform varieties of (1)
riebeckite (commercially called crocidolite), (2)
cummingtonite-grunerite (commercially called amosite), (3) anthophyllite
(anthophyllite asbestos), (4) actinolite (actinolite asbestos), and (5)
tremolite (tremolite asbestos). Other environmental statutes address
asbestos more broadly, as other amphiboles are known to occur in the
fibrous and/or asbestiform habit (Skinner and others, 1988) but have not
been utilized commercially. These include, for example, winchite,
richterite (Wylie and Huggins, 1980; Meeker and others, 2003), and
fluoro-edenite (Gianfagna and Oberti, 2001; Gianfagna and others, 2003).

**Asbestos** **Mineral Nomenclature**

The academic mineralogy community has long classified minerals by name.
This mineral nomenclature has evolved dramatically over the years and
continues to evolve in response to advances in analytical technology and
many other factors. The current academic nomenclature system for
amphiboles is endorsed by the International Mineralogical Association
(IMA) and recognizes approximately 70 distinct amphibole minerals (Leake
and others, 1997). Under this world-recognized system, amphibole
minerals are named based on their chemical composition and the exact
chemical boundaries between different amphibole minerals are defined on
the basis of various mineralogical or other considerations. It should
also be noted that in most cases there is chemical gradation (called
***solid solution***) between the different amphibole minerals. That is,
there are rarely distinct natural chemical boundaries between the
amphibole minerals, only arbitrary boundaries defined by the IMA.

Prior to 1978, amphiboles were primarily identified by optical
properties using a transmitted light microscope. This optical
identification led to ambiguities and multiple names in the technical
literature for the same mineral. In 1978, the IMA's Committee on
Amphibole Nomenclature made the decision to redefine amphibole names on
the basis of chemical composition and published a classification system
that required the use of highly accurate chemical analyses (Leake and
others, 1978), with the intent to help reduce these ambiguities. The
current amphibole nomenclature established in 1997 is generally similar
to the 1978 nomenclature, with the exception that chemical boundaries
between several of the amphibole minerals were shifted. In addition to
the formal 1978 and 1997 changes in amphibole nomenclature, further
confusion results because common and commercial names for some
asbestiform amphiboles are still used in some geological or commercial
contexts; these include the names amosite, crocidolite, blue asbestos,
brown asbestos, and white asbestos.

The \"Libby, Montana amphibole\" provides an excellent example of the
difficulties that have arisen from the co-mingling of different
amphibole nomenclatures. During the years that the Libby mine was
active, geologists, miners, and regulators called the amphiboles
tremolite, soda tremolite, sodium-rich tremolite, and, in one case,
richterite. This terminology was used by the geologic and mineralogic
communities, as well as by the health, regulatory, and industrial
communities. The 1978 IMA change in nomenclature went largely unnoticed
or was simply ignored outside of the community of academic mineralogists
and geologists, and the Libby amphibole continued to be referred to as a
sodium-rich variety of tremolite. Beginning in 2000, mineralogists began
to reinvestigate the Libby amphibole and apply the current academic
nomenclature, first identifying it as winchite (Wylie and Verkouteren,
2000) and later as winchite, richterite, and tremolite (Meeker and
others, 2003). These findings have generated confusion in the asbestos
community regarding the identification and nomenclature of the Libby
amphibole and whether or not the material is regulated.

Some have taken the position that most of the Libby amphibole is
primarily winchite and richterite and therefore is not currently
regulated. However, if the nomenclature of Leake and others (1997) is
the regulatory touchstone, then the following must also be true. Prior
to 1978, all of the Libby asbestos (100 percent) would have been
considered to be a form of tremolite and regulated based on the existing
nomenclature at the time and the prescribed optical analysis methods for
asbestos promulgated under National Emission Standards for Hazardous Air
Pollutants (NESHAPs). Between 1978 and 1997 only 15 percent of the Libby
asbestos would have been identified as tremolite based on the 1978 IMA
system (Leake and others, 1978). Finally, after 1997, due to a
mineralogically defined change in the IMA chemical boundaries (Leake and
others, 1997), only 6 percent of the Libby asbestos would be classified
as tremolite. There is no indication that the regulators intended
different treatment for what remained the same underlying substance
during this time period. Nonetheless, the Libby amphibole has
historically been referred to as tremolite asbestos, and even today
could be considered to be a form of tremolite asbestos under the
guidelines established for standard Polarized Light Microscopy (PLM)
asbestos analysis.

The example above illustrates a subtle but critical point, the Libby
amphibole was not originally mistakenly identified as tremolite. The
Libby amphibole was correctly identified prior to 1978 as a sodium-rich
tremolite based on existing nomenclature and analytical methods. It was
also correctly identified as primarily winchite and richterite, after
application of the new academic nomenclature using more modern
analytical methods. In this example, the IMA inadvertently redefined a
regulated material for reasons totally unrelated to asbestos regulation.

Finally, it should be recognized that the nomenclature for amphiboles in
the academic community will likely change again in the future (Hawthorne
and Oberti, 2006) and new species of fibrous and asbestiform amphiboles
may be identified.

**Size and Shape of Asbestos Particles**

The size and shape of asbestos particles can vary substantially within a
single sample and from one sample to another, even if the mineral type
is the same. Historically, most commercial asbestos used in products has
been chrysotile (Virta and Mann, 1994). Chrysotile tends to have very
thin fibers that are often very long and flexible prior to processing.
Amphibole asbestos fibers, however, can display a large range of sizes
from very long and thin to thick, relatively short, and brittle. A
variety of sizes and shapes of amphibole asbestos fibers can occur
together and can be inter-grown at the microscopic scale. In addition to
the amphibole fibers that fit the commercial definition of asbestos,
other amphibole particle types can also occur, again intermixed at the
microscopic scale. These other particle types are often referred to by
mineralogists as fibrous (non-asbestiform), acicular (needle-like) and
prismatic (prism-like) (Meeker and others, 2006). Unfortunately, there
are no distinct boundaries between these particle types - they often
show a gradation from one to the next in the same sample or material.
Also, there is considerable disagreement in the asbestos community about
how to distinguish these particle types in a mixed sample and, more
importantly, how these different particle types relate to toxicity.
These issues were recently raised regarding naturally occurring asbestos
in the community of El Dorado Hills California (EPA, 2008; Meeker and
others, 2006).

***Respirable*** fibers are those fibers small enough to penetrate into
deep lung tissue. (Newman, 2001). Typically, not all fibers or asbestos
particles in a material are of respirable size. A soil or aggregate
sample containing 0.25 percent respirable amphibole fibers could contain
more than 25,000,000 fibers per cubic centimeter. However, larger fiber
bundles will continue to generate respirable fibers when disturbed. The
degree to which respirable fibers could be liberated into the air by
disturbance and become an inhalation hazard depends on many variables
including the type of fiber or asbestos, the type of soil or aggregate,
moisture content of the soil or aggregate, humidity of the air, and
other factors. Therefore, any reliable determination of actual risk by
direct measurement of the amount of fibers in the soil or aggregate
would be extremely difficult.

Most amphibole minerals encountered in the majority of rock and soil
types are not fibrous or asbestiform but occur as larger blocky or
massive crystals. When these larger amphibole crystals are crushed or
milled they break or \"cleave\" along specific directions that are
related to the crystal structure of the particles. These particles are
called ***cleavage fragments***. Cleavage fragment particles are
sometimes long and thin and are often difficult to distinguish from the
other particle types discussed above.

In addition to the amphibole and chrysotile particles discussed above,
other natural minerals exist that can occur as fibrous, or elongated,
particles of respirable size. These elongated non-asbestos particles can
be referred to as ***elongated mineral particles** **(EMP)***. One of
these minerals, fibrous erionite, has been associated with very high
rates of mesothelioma in Central Turkey (Baris, 1978). Fibrous erionite
occurrences have been described in some places in the United States
(Sheppard, 1996).

**Geology of Asbestos**

Geologists have documented that asbestos is formed only in specific and
predictable geologic settings (Van Gosen, 2007a). The rocks that host
asbestos minerals are consistently magnesium-rich (and often also
iron-rich) rock types that have been altered in form and composition by
metamorphic geologic processes; examples include altered ultramafic
rocks and metamorphosed dolomite-rich rocks. In general, asbestos
deposits are relatively rare and usually comprise a small volume of the
total host rock body. The areas in which asbestos has formed are limited
in extent in the United States. The USGS is conducting a study to map
the locations of known sites of natural occurrences of asbestos in the
United States (Van Gosen, 2005, 2006, 2007b). This work shows that
asbestos deposits of various sizes are known to occur in at least 35 of
the 50 States. The highest concentrations of asbestos deposits occur in:
the eastern States, in a belt stretching from east-central Alabama to
Vermont and Maine; the west-coast States of California, Oregon, and
Washington; the upper Midwest, in Minnesota and Michigan; and an area of
east-central Arizona. This work also shows that significant portions of
the United States are **not** geologically likely to have substantial
asbestos deposits.

In order to be of commercial value, asbestos must be in sufficient
quality and purity for the intended application, and must occur in
sufficient abundance to be mined at a profit. In nature, such
occurrences are very rare. Far more common is material that can be
present in small veins or pods and in quality that can grade from
asbestiform to fibrous to acicular to prismatic. The asbestiform
component of this material, when undisturbed by human activity, is often
called \"***naturally occurring asbestos***.\" As most commonly used,
naturally occurring asbestos (***NOA***) refers to asbestos that occurs
as a minor to major mineral component in some rocks, soils, sediments or
waters as a result of natural geological processes. The term NOA can
also apply to asbestos that has been transported by natural weathering
and erosion processes from its original geologic source rock into air,
soil, sediment or water. (Van Gosen, 2006). Not included in this
definition would be commercially processed asbestos-containing
materials, such as some insulation and fire protective materials in
buildings or some types of automobile brake pads, in addition to soils,
sediments, or waters contaminated by commercially-processed asbestos.

In addition, NOA **should** **not** include asbestos that occurs as
impurities in other processed industrial minerals. For example, some
products have been made using certain types of talc or vermiculite that
contain amphibole asbestos as a natural contaminant (Van Gosen and
others, 2004; EPA, 2008a).

Thank you for the opportunity to present this testimony. As a
non-regulatory natural science agency, the USGS works closely with other
Federal agencies and with non-Federal stakeholders to help answer many
important questions regarding the nature of asbestos-related minerals,
to develop new analytical methods and procedures for asbestos-related
materials, to develop asbestos-related standard reference materials, and
to provide important information about where asbestos-related minerals
occur in the United States.

 I am pleased to answer questions you might have.

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