Agency for Toxic Substances and Disease Registry
Case Studies in Environmental Medicine (CSEM) 

Asbestos Toxicity
Where Is Asbestos Found?

Learning Objective

Upon completion of this section, you should be able to

• identify where asbestos still exists in the United States.
• describe how asbestos is released into the air.

Introduction

Asbestos was widely used commercially until the 1970s, when health concerns led to some uses being banned and some voluntary phase outs (Seidman and Selikoff, 1990). Mining and milling of the raw material and production of asbestos has declined since the early 1970s, but asbestos is still used in some construction materials. Some asbestos-containing products, such as amphibole-contaminated vermiculite insulation, remain in many homes in the United States. Asbestos fibers are released into the air and dust when asbestos-containing materials are loose, crumbling, or disturbed.

In addition to being at risk for exposure from the commercial uses of asbestos, people in some areas of the world are at risk because of geological deposits of asbestos near the surface which release asbestos if disturbed.

Current Commercial Uses

Today, most asbestos used in the United States is imported. Asbestos is still used in

• brake pads
• automobile clutches
• roofing materials
• vinyl tile
• and, imported cement pipe and corrugated sheeting (American Thoracic Society 2004).

Former Commercial Uses

Until the 1970s, asbestos was widely used in the construction, shipbuilding, and automotive industries, among others. For example, asbestos was formerly used in the following items

• boilers and heating vessels
• cement pipe
• clutch, brake, and transmission components
• conduits for electrical wire
• corrosive chemical containers
• electric motor components
• heat-protective pads
• laboratory furniture
• paper products
• pipe covering
• roofing products
• sealants and coatings
• insulation products,
• textiles (including curtains)

These materials remain in many buildings, ships, and automobiles built before 1975 (Seidman and Selikoff, 1990)

Contaminated Commercial Products

Asbestos has been a contaminant in other products such as

• vermiculite in potting soil
• vermiculite home insulation

Vermiculite contaminated with amphibole asbestos was produced as late as 1990 from a mine near Libby, Montana. The mined ore was processed at more than 200 sites around the country, and contaminated vermiculite products were distributed nationally (ATSDR 2001a). Although all the new vermiculite in potting soil is amphibole free, pre-1990 products from that source may contain amphiboles, and many homes may still have vermiculite insulation in their attics.

For more information on amphibole asbestos and vermiculite insulation, please refer to the ATSDR website on asbestos.

Homes and Buildings

Some home-attic insulating materials produced before 1975 contained asbestos. Of particular concern is vermiculite insulation contaminated with amphibole asbestos, because this is a loose material that can easily be disturbed, causing asbestos fibers to be released into the air. Asbestos in friable (easily pulverized or crumbled) material is also a concern. Asbestos embedded in solid materials (such as wallboards) is less easily disturbed and therefore less likely to be released into the air unless it is cut, drilled, or sanded.

Many other home and building materials produced before 1975 contained asbestos including the following

• duct and home insulation
• fire protection panels
• fireplace artificial logs or ashes
• fuse box liners
• gypsum wallboard
• hair dryers
• toasters
• heater register tape and insulation
• joint compounds
• patching and spackling compounds
• pipe or boiler insulation
• pot holders and ironing board pads
• sheet vinyl or floor tiles
• shingles
• textured acoustical ceiling
• textured paints
• underlayment for flooring and carpets

The Natural Environment

Because of widespread human use of asbestos, its fibers are found in many or most parts of the environment. These background levels are extremely low, about 0.0001 fibers/cc of air (Holland and Smith 2003).

Asbestos is also present in the environment naturally, primarily in underground rock. In most areas, the rock is too deep to be disturbed easily, so asbestos fibers are not released into the air. In some areas, such as parts of California, Virginia and New Jersey (and across the globe in Turkey and Corsica), asbestos-bearing rock is close enough to the surface that construction and other human activities can disturb it, leading to release of high concentrations of asbestos fibers into the air and dust (ATSDR 2001a; Hasanoglu et al. 2003; Luo et al. 2003). For a map of sites in the United States where naturally occurring asbestos outcroppings, please see:

http://www.atsdr.cdc.gov/asbestos/sites/national_map/

The table below shows examples of sources of asbestos in the environment.

Mining, milling, and weathering of asbestos-bearing rock

Outdoor air and dust

Release of fibers from disturbed building materials (e.g., vermiculite insulation)

Indoor air

Manufacture, wear, and disposal of asbestos-containing products

Outdoor and indoor air and dust

Release of fibers from brake linings or crushed asbestos-containing rock used in road construction

Street dust

Erosion of natural land sources, discarded mine and mill tailings, asbestos cement pipe, disintegration of other asbestos-containing materials transported by rain

Drinking water

Key Points

• Until the 1970s, asbestos was widely used in the construction, shipbuilding, and automotive industries.
• Asbestos-contaminated vermiculite materials were produced until 1990.
• Some home insulation and other building materials produced before 1975 contain asbestos.
• Asbestos fibers are mainly released into the air and dust when asbestos-containing materials are loose, crumbling, or disturbed.
• In a few areas, asbestos-bearing rock close to the earth’s surface can be disturbed and release high concentrations of asbestos fibers into the air and dust.

Progress Check