A commercial term for a group of silicate minerals
that form thin, strong, heat resistant fibers. These minerals
include several varieties from the asbestos group, as well
as some varieties of amphibole. Asbestos was widely used as
a flame retardant in buildings through the middle 1970s, and
it is present in millions of buildings in the United States. It
was also used in vinyl flooring, ceiling tiles, and roofing
material. It is no longer used in construction since it was recognized
that asbestos might cause certain types of diseases,
including asbestosis (pneumoconiosis), a chronic lung disease.
Asbestos particles get lodged in the lungs, and the lung tissue
hardens around the particles, decreasing lung capacity. This
decreased lung capacity causes the heart to work harder, leading
to heart failure and death. Virtually all deaths from
asbestosis can be attributed to long-term exposure to asbestos
dust in the workplace before environmental regulations governing
asbestos were put in place. A less common disease
associated with asbestos is mesothelioma, a rare cancer of the
lung and stomach linings. Asbestos has become one of the
most devastating occupational hazards in U.S. history, costing
billions of dollars for cleaning up asbestos in schools,
offices, homes, and other buildings. Approximately $3 billion
a year are currently spent on asbestos removal in the United
Asbestos is actually a group of six related minerals, all
with similar physical and chemical properties. Asbestos
includes minerals from the amphibole and serpentine groups
that are long and needle-shaped, making it easy for them to
get lodged in people’s lungs. The Occupational Safety and
Health Administration (OSHA) defined asbestos as having
dimensions of greater than 5 micrometers (0.002 in.) long,
with a length to width ratio of at least 3:1. The minerals in
the amphibole group included in this definition are grunerite
(known also as amosite), reibeckite (crocidolite), anthophyllite,
tremolite, and actinolite, while the serpentine group mineral
that fits the definition is chrysotile. Almost all of the
asbestos used in the United States is chrysotile (known as
white asbestos), while about 5 percent of the asbestos used is
crocidolite (blue asbestos) and amosite (brown asbestos).
There is currently considerable debate among geologists, policy
makers, and medical officials on the relative threats from
different kinds of asbestos.
In 1972 OSHA and the U.S. government began regulating
the acceptable levels of asbestos fibers in the workplace.
The Environmental Protection Agency (EPA) agreed, and
declared asbestos a Class A carcinogen. The EPA composed
the Asbestos Hazard Emergency Response Act, which was
signed by President Reagan in 1986. OSHA gradually lowered
the acceptable limits from a pre-regulated estimate of
greater than 4,000 fibers per cubic inch (1,600 fibers per
cm3), to 4 fibers per cubic inch (1.6 particles per cm3) in
1992. Responding to public fears about asbestosis, Congress
passed a law requiring that any asbestos-bearing material
that appeared to be visibly deteriorating must be removed
and replaced by non-asbestos-bearing material. This remarkable
ruling has resulted in billions of dollars being spent on
asbestos removal, which in many cases may have been unnecessary.
The asbestos can only be harmful if it is an airborne
particle, and only long-term exposure to high concentrations
leads to disease. In some cases it is estimated that the processes
of removing the asbestos resulted in the inside air becoming
more hazardous than before removal, as the remediation
can cause many small particles to become airborne and fall as
dust throughout the building.
Asbestos fibers in the environment have led to some serious
environmental disasters, as the hazards were not appreciated
during early mining operations before the late 1960s. One
of the worst cases is the town of Wittenoom, Australia, where
crocidolite was mined for 23 years (between 1943 and 1966).
The mining was largely unregulated, and asbestos dust filled
the air of the mine and the town, where the 20,000 people
who lived in Wittenoom breathed the fibers in high concentrations
daily. More than 10 percent or 2,300 people who lived in
Wittenoom have since died of asbestosis, and the Australian
government has condemned the town and is in the process of
burying it in deep pits to rid the environment of the hazard.
In the United States, W. R. Grace and Co. in Libby,
Montana, afflicted hundreds of people with asbestos-related
diseases through mining operations. Vermiculite was mined
at Libby from 1963 to 1990 and shipped to Minneapolis to
make insulation products, but the vermiculite was mixed
with the tremolite (amphibole) variety of asbestos. In 1990
the EPA tested residents of Libby and found that 18 percent
of residents who had been there for at least six months had
various stages of asbestosis, and that 49 percent of the W. R.
Grace mine employees had asbestosis. The mine was closed
down, and Libby is now being considered a potential superfund
site by the EPA. The problem was not limited to Libby,
however, and 24 workers at the processing plant in Minneapolis
and one resident who lived near the factory have
since died from asbestosis. The EPA and Minnesota’s Department
of Health are currently assessing the level of exposure
of other nearby residents.
Further Reading
“Asbestos: Try Not to Panic.” Consumer Reports (July 1995):
Ross, M. “The Health Effects of Mineral Dusts.” In The Environmental
Geochemistry of Mineral Deposits; Part A: Processes,
Techniques, and Health Issues. Society of Economic Geologists
Reviews in Economic Geology 6A (1999): 339–356.
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