Definition of Asbestos

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

States.

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.

See also MINERALOGY.

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