Glossary of Terms

• 1–percent threshold
• In general, EPA performed a cleanup, or removal action, of asbestos contamination if sampling results indicated that asbestos was present in amounts greater than 1 percent (based on the percentage of the area of a microscopic field) in soils or debris, or greater than 0.1 asbestos fibers per cubic centimeter of air. According to EPA, the “1- percent threshold” for asbestos in soils or debris is not a health-based standard, but is rather related to the limit of detection for the analytical methods available during the early years of EPA’s asbestos program (early 1970s), and to EPA’s desire to concentrate resources on materials containing higher percentages of asbestos. EPA has never determined that materials containing less than 1- percent asbestos are safe, and, indeed, scientists have not been able to determine a safe level for exposure to airborne asbestos.
• Asbestos
• Asbestos is a general name applied to a group of silicate minerals consisting of thin, separable fibers in a parallel arrangement. Asbestos minerals fall into two groups, serpentine and amphibole. Serpentine asbestos has relatively long and flexible crystalline fibers; this class includes chrysotile, the predominant type of asbestos used commercially. Amphibole asbestos minerals are brittle and have a rod- or needle-like shape. Amphibole minerals regulated as asbestos by the Occupational Safety and Health Administration (OSHA) include five asbestiform varieties: fibrous tremolite, actinolite, anthophyllite, crocidolite, and amosite. However, other amphibole minerals, such as winchite and richterite, can exhibit fibrous asbestiform properties. The vermiculite mined at Libby contained amphibole asbestos, with a characteristic composition that included tremolite, actinolite, richterite, and winchite. Unlike the OSHA regulations, CERCLA lists asbestos generally as a hazardous substance, and provides EPA authority to address all varieties of amphibole asbestos. The raw Libby ore was estimated to contain up to 26 percent asbestos as it was mined. The mined vermiculite ore was processed to remove unwanted materials and sorted into various grades or sizes. The ore shipped from the Libby mine to various sites across the United States to be further processed or used as a raw material in manufactured products contained 0.3- to 7-percent asbestos.
• CERCLA
• The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) [42 U.S.C. § 9601 et seq.], commonly known as Superfund, provides for the liability of persons responsible for releases of hazardous substances at contaminated sites and establishes a trust fund to provide for cleanup of these sites.
• Exfoliation
• This is a process in which vermiculite ore is heated in a furnace to approximately 2,000 degrees Fahrenheit until it expands, or pops. Facilities that exfoliated Libby ore were of particular concern to EPA because this processing method was likely to have released high concentrations of asbestos fibers and, thus, these facilities were more likely to have caused environmental contamination and exposure. According to the data that EPA collected, most (95 percent) of the vermiculite ore known to have been shipped from Libby between 1964 and 1990 went to facilities that exfoliated the ore.
• Mica
• Mica is a name given to a group of minerals that are similar in their physical properties and chemical compositions. They are all silicate minerals, that is, chemically they all contain silica. Mica resembles vermiculite in appearance. The principal use of ground mica is in gypsum wallboard joint compound, where it acts as a filler and extender, provides a smooth consistency, improves workability, and prevents cracking. Mica has been shown to cause pneumoconiosis—-a group of lung diseases caused by the inhalation of certain dusts and the lung tissues reaction to the dust--in workers exposed to high levels of mica dust during mining and processing operations.
• Perlite
• Perlite is a glassy volcanic rock with a pearl-like luster. It usually exhibits numerous concentric cracks that cause it to resemble an onion skin. Perlite is composed of silicon dioxide, alumina, potassium oxide, sodium oxide, calcium oxide, and trace amounts of metal oxides. Crude perlite ore is mined, crushed, dried in a rotary dryer, screened, and shipped to expansion plants. The major pollutant of concern emitted from perlite processing facilities is particulate matter—small solid and liquid particles suspended in the ambient air. Research studies have associated exposure to elevated levels of these particles in the air with damaging health effects.
• Phase I Environmental Site Assessment
• The purpose of a Phase I Environmental Site Assessment is generally to assess past and present land use practices and site operations and conditions, and to identify the potential presence of hazardous substances (including asbestos) and soil and/or groundwater contamination at a site. The Phase I assessment generally includes a (1) reconnaissance of the site and its vicinity, (2) historical review of use and improvements made to the property, (3) review of records of building, zoning, planning, sewer, water, environmental, and other government offices concerning the property and adjacent properties, (4) review of all state or federal environmental agency records and files affecting the property or adjacent parcels of land, (5) review of all reports filed under CERCLA and other statutes concerning environmental conditions and events, such as releases or threatened releases of hazardous substances on the property and adjacent properties, (6) inspection of the property and all improvements, (7) verification of whether present or past owners or tenants stored, created, or discharged hazardous materials or wastes, (8) interviews with neighbors to determine prior uses of property, and (9) review of building records and visual inspection of buildings to determine whether asbestos-containing materials are present. The Phase I assessment does not include sampling of soil or groundwater.
• Phase II Environmental Site Assessment
• The purpose of the Phase II Environmental Site Assessment is to determine whether identified historic on-site or off-site hazardous uses have damaged the soil and/or groundwater conditions beneath a property. These assessments generally include soil and air sampling, groundwater analysis, or other subsurface testing.
• Polarized contrast microscopy (PCM)
• This is the traditional method for measuring asbestos fibers in air and is the basis for many regulations (e.g., occupational exposure regulations). Results are often used to estimate health risk from asbestos in air. PCM has limited use because it cannot differentiate between asbestos and nonasbestos fibers. For this reason, it is sometimes used in combination with another method, such as Transmission Electron Microscopy (see below for definition of this analytical technique).
• Polarized light microscopy (PLM)
• This analytical method is used to visually estimate the percent of asbestos in bulk materials, such as soils and raw vermiculite ore. This type of analysis can distinguish between asbestos and nonasbestos fibers and different types of asbestos fibers but cannot reliably detect asbestos in low concentrations. Since EPA began its efforts to assess the sites potentially receiving ore from the Libby mine, it has worked with laboratories to refine the PLM analytical procedure to achieve detection levels of 0.2 percent.
• Potentially Responsible Party (PRP)
• CERCLA imposes strict liability on certain parties, such as property owners, for any contamination that may exist on a property. Such a party, called a “potentially responsible party” or PRP, may be held liable to clean up contamination caused by the release of hazardous substances.
• RCRA
• The Resource Conservation and Recovery Act (RCRA) gives the Environmental Protection Agency the authority to control hazardous waste from the “cradle-to-grave.” This definition includes generation, transportation, treatment, storage, and disposal of hazardous wastes.
• Stoner or Waste Rock
• Stoner rock, or waste rock, is generated when raw vermiculite ore fails to expand during the process of exfoliation. The stoner rock created when vermiculite ore from the Libby mine was exfoliated contained between 2- and 10-percent asbestos. At some of the exfoliation facilities, the stoner rock was disposed of in on-site landfills or placed in dumpsters for disposal in an off-site landfill. At some of the facilities, stoner rock was dumped outside of the plants and offered to the public. Some plant employees, children, and others could have been exposed to asbestos from handling or playing in the waste piles. Exposures would have occurred when children jumped or played in the waste piles, or when workers or area residents took the waste rock to their homes to use for gardening or landscaping.
• Transmission electron microscopy (TEM)
• This analytical method is more sensitive than PLM. TEM can distinguish between asbestos and nonasbestos fibers and types of asbestos fibers. It can be used at higher magnifications, enabling identification of smaller asbestos fibers than can be seen by other techniques. One disadvantage of this technique is that determining asbestos concentration in soil and other bulk material is difficult. Also, the TEM analytical procedure typically is more than 10 times costlier than PLM, which can be a limiting factor in its use.
• Vermiculite
• Vermiculite is a general term for a group of platy (layered) minerals that form from the weathering of micas by groundwater. Vermiculite undergoes a distinctive, prominent, accordion-like unfolding and expansion when heated to between 800 and 1,100 degrees Centigrade. After heat expansion, the vermiculite is very lightweight and possesses fire-and sound-insulating properties. Products that contain vermiculite include potting soil mixes, loose fill insulation, wallboard, and packing material. All vermiculite ores contain a range of other minerals that were formed along with the vermiculite. Vermiculite ores from some sources have been found to contain asbestos minerals, but asbestos is not intrinsic to vermiculite. The vermiculite ore that was mined in Libby, Montana, contained approximately 21- to 26-percent amphibole asbestos. When amphibole asbestos has been detected in vermiculite from mines other than Libby, the reported amounts have been much lower than those in the Libby ore. Samples of South African expanded and unexpanded ore that were analyzed showed amphibole asbestos levels of 0.4 percent and 0.0 percent. Vermiculite from mines in Enoree and Patterson, South Carolina were shown to contain less than 1-percent total asbestiform asbestos. Expanded and unexpanded ore from a mine in Virginia contained 1.3-percent amphibole asbestos; however, the asbestos fibers in the South African and Virginia samples were predominantly the nonasbestiform variety, while the asbestos in Libby ore is asbestiform.

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