Written by Larry S. Pierce: 8-89
Last Revised: 2-26-98
1. THE HAZARD OF ASBESTOS
The hazard that asbestos-containing materials (ACM) presents to
inhabitants of a building is primarily an airborne hazard. Asbestos fibers may be released
from the materials, become entrained in the air of the building, be inhaled by an
inhabitant, and lodge in the bronchia or lungs. Once there, the asbestos fibers do not
ever escape and it is thought that even small amounts can eventually produce lung cancer
or mesothelioma, a lung-lining cancer. ( Another asbestos disease, asbestosis, requires
much larger amounts of asbestos in the lungs than could be produced in a residence or a
workplace that is not involved in the asbestos business). Asbestos cancers have a long
latency period, 20-30 years, so that young people have a greater chance to be affected in
their lifetime than older people.
A number of asbestos or asbestos-like minerals are regulated. The most
common type of asbestos encountered is called "serpentine asbestos", which
consists of the mineral chrysotile. It is considered the least toxic of the asbestos
minerals. Less commonly encountered is a group of amphibole minerals, including
"amosite" (not a mineral but a mixture of the minerals grunerite and
cummingtonite), and the minerals crocidolite, anthophyllite, tremolite and actinolite. The
amphiboles occur in nature both as fibrous or asbestiform varieties and as non-fibrous
varieties. All the fibrous varieties of the above amphiboles are regulated by both the EPA
and OSHA. The non-fibrous varieties of the amphiboles are not regulated by the EPA or
OSHA. The fibrous amphiboles are considered to be more toxic than chrysotile, and are also
more likely to become airborne, due to their brittleness and shorter fiber length.
For regulatory purposes, the Environmental Protection Agency (EPA) and
OSHA have defined an asbestos-containing material as one which contains greater than 1%
asbestos. Materials having 1% or less asbestos are considered to be
non-asbestos-containing materials. The accepted method of determining whether a sample of
a material contains greater than 1% asbestos and the type of asbestos present utilizes a
polarizing light microscope. The sample is examined first at a magnification of about 10.
Then examples of each fiber type observed, and/or a representative portion of the sample
are mounted in oils of varying refractive index in order to document the optical
properties of the fibers. The optical properties are usually sufficient to distinguish the
asbestos types from interfering fibers, such as cellulose and fibrous glass. At
Fiberquant, fibers not definitively identified by polarized light are further analyzed
using scanning electron microscopy/energy dispersive spectrometry or by transmission
electron microscopy/energy dispersive spectrometry. Certain samples may also be quantified
using x-ray diffraction.
The presence of asbestos in a material does not always pose a
significant hazard. Some substances are easily crumbled or reduced to powder by hand
pressure, termed "friable", whereas others do not produce powder by hand
pressure, "non-friable". A friable material would be more likely to produce
airborne fibers than a non-friable material. Also, a damaged or broken material would be
more likely to produce airborne fibers than one in good condition. Even a normally
non-friable material can produce airborne fibers when highly damaged or abraded. These
factors are all to be considered before deciding what the hazard of a given material is,
or the course of action to use in dealing with that material.
Once asbestos is determined to be present in a material, several
options of dealing with the material are possible. The first option would be to leave the
material as is and untouched. This is often the option of choice for non-friable
materials, materials which are in non-public areas and therefore only affect a few workers
trained in asbestos hazards, and materials which are isolated from human contact. A second
option is encapsulation, which in its broadest definition means to enclose the material
without removing it. The enclosure can consist of a constructed barrier, for instance, of
finished drywall over a surface coating, or of painted canvas over pipe insulation.
Alternatively, the encapsulation can be a sprayed polymer of two types: penetrating
encapsulant, which soaks into the material it is sprayed on, and bridging encapsulant,
which only seals the surface, like paint. Even though the release of fiber is minimized or
eliminated with encapsulation, the asbestos is still present, and the potential for fiber
release always exists. In many cases, the asbestos will have to be removed anyway at a
later date as per NESHAP (see below). The third option is removal, in which the
asbestos-containing material is scraped off, chipped off or otherwise gotten rid and taken
out of the building. Preparation of the building so as to prevent contamination of the
premises is extensive and disposal of the material is expensive, so removal is the least
economical of the three options. It has the advantage that the asbestos is for the most
part gone (except those parts of the building that are inaccessible.
At present, there are no Federal or Arizona State laws requiring the
encapsulation or removal of asbestos-containing materials in order to occupy a building.
However, the Occupational Safety and Health Administration (OSHA) prohibits occupation of
a work area (without respiratory protection) if either 1) the eight hour average fiber
concentration exceeds 0.1 fibers/cc or 2) a 30-minute fiber concentration exceeds 1.0
fibers/cc. Neither of these levels is likely to be exceeded during normal building
occupation unless heavy damage is inflicted to a asbestos-containing material. The
National Emission Standards for Hazardous Air Pollutants (NESHAP), a Federal law,
prohibits the renovation or demolition of greater than either 160 square feet of
asbestos-containing surfacing material, or 260 linear feet of asbestos-containing pipe
insulation without adequate precautions against fiber release. For friable materials, this
means that renovation is done by an abatement contractor and demolition is only allowed
after the material has been removed. Therefore, removal of friable asbestos-containing
materials will be required during some point in a building's lifetime, if only at the end.
Non-friable materials can fall under NESHAP regulations if they can become friable during
the renovation or demolition. Naturally, becoming friable is highly dependent upon the
exact type and constitution of the material in question in addition to how it is handled.
Whether a non-friable material will be regulated must be decided on an individual basis.
2. THE HAZARD OF INDIVIDUAL TYPES OF ASBESTOS-CONTAINING MATERIALS
Many different types of building materials at one time contained
asbestos, such as beam spray, ceiling tile, floor tile, mastic and glue, etc. Each type
has distinct properties, hazards and possible courses of action. To be discussed here are:
a) beam spray, b) ceiling acoustical texture, c) joint compound and wall texture, d) floor
tile, e) mastics, f) hard glue, g) ceiling tiles, h), pipe or thermal system insulation,
and i) roofing.
A. BEAM SPRAY
Metal structural members in multi-story buildings are required to be
sprayed with an insulating layer that will provide several hours of evacuation time during
a fire before the members sag or collapse. During the years ~1935-1970, asbestos, usually
chrysotile asbestos, was commonly a component of beam sprays. The typical such spray has a
If enclosed or isolated in areas in which damage is unlikely, such a
spray would not represent a very high hazard. Unfortunately, the usual situations
encountered are: 1) beam spray exposed on vertical beams in storage areas, subjected to
scraping and bumping, 2) beam spray above dropped ceilings, where ducts, telephone wire,
etc. are installed and tended, causing damage, and 3) beam spray in or above plenum
airways, where air velocity and vibration may degrade the coating surface and produce
fibers. Often, one or a combination of these situations makes the presence of
asbestos-containing beam spray enough of a hazard to warrant removal. Beam sprays are
sometimes not able to support the additional weight of encapsulation.
B. CEILING ACOUSTICAL TEXTURE
Ceiling acoustical sprays consist of a bumpy material, such as mica or
plastic foam and a white mineral powder binder. Chrysotile asbestos was sometimes added to
the binder. These materials are used to cover up construction defects and irregularities
in ceilings (sometimes walls) and to soften the acoustical properties of an area. These
types of material could contain asbestos until 1973, when sprayed asbestos-containing
materials were banned in new construction.
Asbestos-containing acoustical sprayed-on ceiling material is currently
considered to present relatively little hazard when undamaged and in good condition. The
small percentage of asbestos fibers that are present are coated with and somewhat bound in
the matrix of the texture. Few fibers will escape from the binder under normal conditions.
Therefore, one of the options open to an owner of such a ceiling is to leave it in place.
However, the continued presence of such a ceiling does allow for fibers to be released in
several common ways: 1) whenever the ceiling is brushed, hit, bumped, or an attempt is
made to clean it, the matrix or binder will be disturbed and fibers will be released.
Large numbers of fibers can be released during installations in the ceiling, such as
hanging plants, ceiling fans, vents, etc. In families having small children, the ceiling
can be bumped on a regular basis by balls and other toys, exposing children, those most
vulnerable due to the long latency period of asbestos disease, to asbestos. 2) A roof leak
can water-soak the texture. If the soaking is extensive, the entire texture can delaminate
or separate from the substrate wallboard, causing slabs of asbestos-containing debris to
fall to the floor, with an associated massive release of fibers. 3) Finally, over time,
the binder of the texture will normally deteriorate slightly. Therefore, even in an
undamaged ceiling in good shape, the number of fibers being released will increase with
the age of the ceiling.
Acoustical ceilings are often amenable to encapsulation, a simple paint
layer being sufficient to prevent fibers from escaping. However, fiber release from
bumping or water damage is still possible even when encapsulated. Removal of ceiling
coatings involves sealing the area, wetting the material and scraping, and it an expensive
C. JOINT COMPOUND AND WALL TEXTURE
Joint compound or wall mud is a material consisting primarily of white
mineral powder. It is applied as a slurry to smooth joints between wallboard and to
eliminate irregularities and nail depressions in walls. Wall texture is a similar material
which is usually sprayed but can be trowelled onto walls to produce a pleasing,
defect-hiding texture. These types of materials commonly contained chrysotile asbestos
Since walls and ceilings patched and textured with these materials are
usually painted, the presence of asbestos-containing joint compound or wall texture
presents little, if any, hazard. Therefore, in the vast majority of cases, such materials
are left in place and as is. In fact, a poorly designed removal attempt is more likely to
create a hazard than remove one in this case. However, occupants or custodians of a
building containing these materials should be made aware of their presence and potential
health effects, since drilling a hole in a wall or any other disturbance of the wall
surface could result in a significant number of fibers becoming airborne. Especially
hazardous would be sanding a wall to smooth it.
Since there is rarely enough of a hazard due to joint compound or wall
texture to warrant removal during occupation of a building, most buildings will reach the
end of their lifetime with these materials present. NESHAP allows joint compound to be
analyzed with its associated wallboard, and only regulates such wall composites that
contain greater than 1% asbestos (and covering more than 160 square feet of area).
Flooring, including floor tile, sheet goods, resilient tile and
linoleum commonly contained asbestos from the 1920's until the 1980's. At present, it
still may be present in new tile, even though most large manufacturers have eliminated
asbestos from their formulations. Floor tile and linoleum usually contain asbestos
throughout, so as they wear or abrade, fibers can be released. Sheet goods and resilient
tile have a polymer-like top layer underlain by a spongy, friable fibrous layer. In
asbestos-containing sheet goods, this fibrous layer can contain up to 40% chrysotile
asbestos. Naturally, the underlayer is only exposed if the flooring is damaged.
Asbestos-containing floor tile and sheet flooring is considered to be
of minimal hazard when in good condition, since the fibers are held very tightly in the
vinyl or polymer matrix. Therefore, unless it is damaged, powdered, or deteriorated in
some way that allows fibers to escape, floor tiles can be left in place almost
indefinitely with little or no hazard to inhabitants. The only care needed is an
occasional inspection for damage and abrasion. Waxing would tend to seal the floor further
against fiber release.
Flooring will usually not fall under NESHAP, even if it covers more
than 160 square feet. It is NESHAP Non-friable Category I. That is, only if the tile or
flooring will become abraded or crushed during a renovation or demolition, will the
renovation or demolition be required to be an abatement. A dry removal using a
"chipper" might very well result in the release of fibers from a floor tile,
whereas removal of the same tile by lifting the entire tile with solvent would not release
Mastic is a sticky substance used for cementing purposes. Mastic is a
non-drying-type substance which is still tacky or flexible after setting up, while glue
(discussed below) drys to brittleness. Mastics have contained asbestos from the 1920's to
Older mastics are tar or asphalt-based and black in color. About half
we have tested contain chrysotile asbestos. Newer mastics are polymer or latex based and
may be yellow or white. These colors of mastics usually have not been found to contain
asbestos, except by contamination from some other material.
By definition, mastics remain tacky over time, as so would not be
expected to produce fibers even if exposed. They are NESHAP Category I Non-friable.
Therefore, unless exposed, weathered or worn, they do not represent a significant hazard
to occupation. They would not be expected to become friable except in the most destructive
demolition, and will therefore usually not be regulated under NESHAP. Even if their
removal is not regulated by NESHAP, they must be disposed of properly.
F. HARD GLUE
This category refers to those adhesives which dry or cure to become
brittle. They are usually encountered on baseboard vinyl moldings and on glued-on ceiling
tiles. They have been found to contain chrysotile asbestos as well as anthophyllite,
tremolite and actinolite. Asbestos can still be used in their formulation.
In place and undisturbed, these materials are non-friable (NESHAP
Category II) and usually not exposed to wear or air currents. Therefore, they pose no
threat of fiber release under normal conditions. They are brittle, however, and when
damaged or disturbed (molding ripped off the wall, for instance), they will become friable
and possibly release fibers. Whether they fall under NESHAPS is decided on a case by case
basis. Therefore, if glued-on ceiling or moldings are to be removed during a remodeling or
renovation, it depends on the material involved and the type of work to be done to
determnine whether the area should be sealed and the removal needs to be performed as an
abatement. If a building containing this type of glue is to be demolished, it is possible,
but not likely in the current thought, if more than a cubic meter of the glue is present,
that the glue would be regulated by NESHAP and therefore have to be abated before
demolition can proceed.
G. CEILING TILE
Ceiling tile occurs in two types of installation: dropped or suspended
and glued on. Dropped ceiling panels are usually 2'x4' or 2'x2' in size and held in place
by metal strips, which are, in turn, suspended from the roof by wires. Glued-on ceiling
tiles are usually 12"x12" and glued to drywall ceiling panels. In this section
of the country, ceiling tiles rarely contain asbestos, but are occasionally found to
contain about 5% amosite or chrysotile asbestos. In other parts of the country,
asbestos-containing ceiling tiles are much more prevalent, being used until the middle
1970's. Ceiling tiles are universally friable. Even if their faces are painted to
non-friability, their backs and sides are not painted and remain friable.
Glued-on asbestos-containing tiles may represent little hazard if in
good condition, well-adherred and painted. In such a permanent installation, few fibers,
if any will be released.
Dropped or suspended ceiling tiles, by the very nature of the
installation, are constantly being moved, disturbed and abraded, as they provide access to
piping and wires above them. In addition, the space above a suspended ceiling is often a
plenum, the return air system for the building, so that building air is constantly
circulating (sometimes at high velocities) over the back surface of the tile. For these
reasons, suspended asbestos-containing ceiling tiles are usually considered a significant
hazard to occupants regardless of their condition. Since they are easily pulled out,
removal is the treatment of choice, under controlled conditions, of course.
If a suspended ceiling occurs under an asbestos-containing beam spray,
enough beam spray could drop over the years to consider the tiles to be irreversibly
contaminated. Therefore, if a beam spray is being removed, new tiles are always placed
back, and the old discarded (since the old tiles are unlikely to have enough contamination
to exceed the 1% level, they usually do not have to be disposed of as asbestos waste).
H. PIPING OR THERMAL SYSTEM INSULATION
Asbestos-containing insulation was used on both hot piping systems and
cold piping systems from approximately the 1920's through 1975. Commonly found are
straight run lagging, elbow packing, and boiler lagging. The insulation materials in
themselves are friable and can contain large percentages of either serpentine or amphibole
asbestos. However, they are usually covered and held in place by wrapping. The wrapping is
customarily painted cotton canvas, which is considered to be a form of encapsulation.
Therefore, if the wrap is in good condition, the pipe insulation is considered to not be a
significant hazard to those workers even in daily contact with it. The workers must be
aware, though, of what lies behind the wrap and the possible health consequences of
breaching the wrap, or allowing the wrap to deteriorate. If the pipe insulation is high in
amphibole asbestos (more toxic than chrysotile asbestos), any damage to the wrap is
intolerable and cause for immediate repair. Extensive damage, such as deterioration of the
wrap or break-up of lagging would indicate removal as the treatment of choice.
Another asbestos-containing material related to piping systems is duct
wrap or tape. Used during the same period of time as asbestos pipe insulation, white,
chrysotile-containing duct tape was used to seal metal air ducts, seams in exhaust vents,
and components of furnaces and boilers. It is slightly friable when first installed and
becomes more friable with age. The fibers in it are usually long, so it does not tend to
powder and produce airborne dust and fibers readily. This, coupled with the small extent
of the typical usage make it a minor source of hazard in mechanical rooms and above
ceilings. Fiber release can readily be eliminated in most cases by covering the tape with
a thick layer of asphalt paint or tar. NESHAP would not require removal of duct tape
unless the amount in a building exceeded 160 square feet.
Asbestos-containing fabric was used as a vibration-damping material
between air-handling equipment and ducts. Even though the fibers used in fabric weaving
are necessarily long and therefore not prone to becoming airborne under normal conditions,
the conditions at vibration damping material are not normal. Vibration tends to fragment
fibers, and the air streaming by the material tends to pull fibers from their matrix.
Little data exists as to the number of fibers released from vibration damping material,
but the above considerations indicate that the material may represent a hazard to
occupants. Therefore, my recommendation for this type of material is to take the safest
action and remove it.
Asbestos, usually chrysotile in combination with bitumen (tar or
asphalt) and mineral fillers, has been used in roofing and tarpapers up to the present,
although most roofers no longer employ asbestos-containing materials.
Bitumen-based asbestos-containing roofing materials usually fall into
the non-friable category. Even if weathered to friability, such roofing generally presents
little or no hazard to building inhabitants, and its asbestos content is only a
consideration during removal or re-roofing. If roofing can become friable during the
removal or re-roofing, then NESHAP applies and the work must be done under controlled
conditions by qualified personnel.
3. A LIMITED SURVEY
AHERA legislation (1986) provided rules for asbestos surveys. The rules
yield a survey with a >95% chance of finding and documenting every source of asbestos
in a building. Such surveys will cost thousands even for relatively small buildings.
Therefore, surveys for lenders and homeowners are usually less thorough and are termed
"limited". A limited survey involves fewer samples (usually 1-3 per suspect
material, rather than 3-7) than AHERA), and no maps of asbestos occurrences.
Since various buildings (and even various parts of buildings) may have
been constructed at different times, some would have been built when asbestos was used
heavily in construction materials, and some of the newer ones would have been built when
many uses of asbestos in building materials had been banned. Therefore, the first step in
a survey is to document the year(s) of construction and remodeling for each structure to
be inspected. Once a year of construction can be definitely established, sampling of
certain materials may be eliminated.
For each building, a walk-through inspection is then performed, in
which representative portions if not all areas of construction are visited and observed.
Sometimes accessible areas may be assumed to be representative of inaccessible areas of
the same era construction. Hidden areas, such as attics, crawl spaces, under carpets and
behind tiles are checked when not too destructive.
Samples are taken of materials that could contain asbestos. The
sampling method employed is a modified grab sampling. In this method, samples are taken as
the material is observed, with multiple samples being taken of materials covering large
areas or of materials suspected of being inhomogeneous. The number of samples taken and
locations is left to the discretion, experience and judgement of the inspector. It is up
to the inspector to fully sample all possible phases of construction and suspect materials
within each phase. Unfortunately, this does not guarantee that all occurrences of asbestos
will be found. However, the alternative, random sampling, in which the location of samples
is determined by chance, does not guarantee finding everything, either, and would be much
The location and identity of each sample is documented, on a map or
plan of the building if one is available, by identity of a room or general locality if a
map was not available. The samples are then analyzed at Fiberquant using the EPA
"New" or "Improved" Method #600/R-93/116 (unless requested to use the
"Interim Method"), which includes polarized light microscopy with optical
dispersion staining. The detailed, written report for each sample is attached to each
building report. Summaries of the asbestos-containing occurrences are given in each
report. Recommendations for treatments of each occurrence are given in each report as
well. Where feasible, Asbestos Occurrence Maps, indicating the extent of each
asbestos-containing material throughout the building, are given in each report.