The word Asbestos is derived from a Greek adjective meaning inextinguishable.
It is distinguished from other minerals by the fact that its crystals form long, thin fibers. Deposits of asbestos are found
throughout the world. The primary sites of commercial production are: the Commonwealth of Independent States, Canada,
Brazil, Zimbabwe, Russia and
South Africa.
The Greeks termed asbestos the "miracle mineral" because of its soft and pliant
properties, as well as its ability to withstand heat. Asbestos was spun and woven into cloth in the same manner as cotton. It was
also utilized for wicks in sacred lamps. Romans likewise recognized the properties of asbestos and it is thought that they
cleaned asbestos tablecloths by throwing them into fire.[citation needed]
Asbestos became increasingly popular among manufacturers and builders in the late 19th century due to its resistance to heat,
electricity and chemical damage, sound absorption and tensile strength. When asbestos is used for its resistance to fire or heat,
the fibers are often mixed with cement or woven into fabric or mats. Asbestos is used in
brake shoes and gaskets for its heat resistance, and in the past
was used on electric oven and hotplate wiring for its electrical insulation at
elevated temperature, and in buildings for its flame-retardant and insulating
properties, tensile strength, flexibility, and resistance to chemicals.
The inhalation of asbestos fibers can cause
serious illnesses, including mesothelioma. Since the mid 1980s, many uses of asbestos are
banned in many countries.
Types of asbestos and associated fibres
Six minerals are defined as "asbestos" including: chrysotile, amosite, crocidolite, tremolite,
anthophyllite and actinolite.
White asbestos
Chrysotile, CAS No. 12001-29-5, is obtained
from serpentine rocks which is common throughout the world. The rocks are called
serpentine because their fibers curl; chrysotile fibers are curly as opposed to fibers from amosite, crocidolite, tremolite,
actinolite, and anthophyllite which are needlelike.[1]
Chrysotile, along with other types of asbestos, has been banned in dozens of countries and is only allowed in the
United States and Europe in very limited circumstances.
Chrysotile is used more than any other type and accounts for about 95% of the asbestos found in buildings in America.[2] Applications where chrysotile might be used include the
use of joint compound. It is more flexible than amphibole types of asbestos; it can be
spun and woven into fabric. Chrysotile, like all other forms of industrial asbestos, has
produced tumors in animals. Mesotheliomas have been observed in people who were
occupationally exposed to chrysotile, family members of the occupationally exposed, and residents who lived close to asbestos
factories and mines.[3]
Brown asbestos
Amosite, CAS No. 12172-73-5, is a trade name for the
amphiboles belonging to the Cummingtonite -
Grunerite solid solution series, commonly from Africa, named as an acronym from Asbestos Mines of South Africa.
One formula given for amosite is Fe7Si8O22(OH)2. It is found most frequently as a fire
retardant in thermal insulation products and ceiling tiles.[2] This type of asbestos, like all asbestos, is hazardous.
Blue asbestos
Crocidolite, CAS No. 12001-28-4 is an amphibole from Africa and Australia. It is the fibrous form of the amphibole riebeckite. Blue asbestos is commonly thought of as the
most dangerous type of asbestos (see above and below). One formula given for crocidolite is Na2Fe2+3Fe3+2Si8O22(OH)2.
This type of asbestos is hazardous.
Notes: chrysotile commonly occurs as soft friable fibers. Asbestiform amphibole may also occur
as soft friable fibers but some varieties such as amosite are commonly straighter. All forms of asbestos are fibrillar in that
they are composed of fibers with widths less than 1 micrometre that occur in bundles and have
very long lengths. Asbestos with particularly fine fibers is also referred to as "amianthus". Amphiboles such as tremolite have a
crystal structure containing strongly bonded ribbonlike
silicate anion polymers that extend the length of the crystal . Serpentine (chrysotile) has a sheetlike silicate anion which is
curved, and rolls up like a carpet to form the fiber.[4]
Tremolite often contaminates chrysotile asbestos, thus creating an additional hazard.
Other asbestos
Other regulated asbestos minerals, such as tremolite asbestos, CAS No. 77536-68-6, Ca2Mg5Si8O22(OH)2; actinolite asbestos (or
smaragdite), CAS No. 77536-66-4, Ca2(Mg, Fe)5(Si8O22)(OH)2; and
anthophyllite asbestos, CAS No. 77536-67-5, (Mg, Fe)7Si8O22(OH)2; are less commonly
used industrially but can still be found in a variety of construction materials and insulation materials and have been reported
in the past to occur in a few consumer products.
Other natural and not currently regulated asbestiform minerals, such as richterite,
Na(CaNa)(Mg,Fe++)5(Si8O22)(OH)2, and winchite,
(CaNa)Mg4(Al,Fe3+)(Si8O22)(OH)2, may be found as a contaminant in products
such as the vermiculite containing zonolite insulation
manufactured by W.R. Grace and Company. These minerals are thought to be no less
harmful than tremolite, amosite, or crocidolite, but since they are not regulated, they are referred to as "asbestiform" rather
than asbestos although may still be related to diseases and hazardous.
In 1989 the United States Environmental Protection
Agency (EPA) issued the Asbestos Ban and Phase Out Rule which was subsequently overturned in the case of Corrosion Proof
Fittings v. U.S. Environmental Protection Agency, 1991. This ruling leaves many consumer
products that can still legally contain trace amounts of asbestos. For a clarification of products which legally contain asbestos
read the EPA's clarification statement.[5]
Production trends
In 2005, the world mined 2,200,000 tons of asbestos, Russia was the largest producer with about 40% world share followed by
China and Kazakhstan, reports the British Geological Survey.[6]
Uses
Historic usage
Asbestos was named by the ancient Greeks who also recognized certain hazards of the material. The Greek geographer
Strabo and the Roman naturalist Pliny the Elder noted
that the material damaged lungs of slaves who wove it into cloth.[7][8] Charlemagne, the first Holy Roman Emperor, is said
to have had a tablecloth made of asbestos.[9][10][11]
Wealthy Persians, who bought asbestos imported over the Hindu Kush, amazed guests by cleaning the cloth in simply by exposing it to fire. According to
Biruni in his book of Gems, any cloths made of asbestos (Persian: آذرشست, āzarshast or Persian: آذرشب, āzarshab) were called (Persian: شستكه) shastakeh[12]. Some of the Persians believed the fiber was fur from an animal (named samandar,
Persian: سمندر) that lived in fire and died when exposed to
water.[13][14]
Some archeologists believe that ancients made shrouds of asbestos, wherein they burned the bodies of their kings, in order to
preserve only their ashes, and prevent their being mixed with those of wood or other combustible materials commonly used in
funeral pyres.[15] Others assert that the
ancients used asbestos to make perpetual wicks for sepulchral or other lamps.[11][13] In more recent centuries, asbestos was indeed used for this purpose. Although asbestos causes
skin to itch upon contact, ancient literature indicates that it was prescribed for
diseases of the skin, and particularly for the itch. It is possible that they used the term asbestos for alumen plumosum, because the two terms have often been confused throughout history.[15]
Asbestos became more widespread during the industrial revolution, in the 1860s it was used as insulation in the U.S. and
Canada. Development of the first commercial asbestos mine began in 1879 in the
Appalachian foothills of Quebec.[16] By the mid 20th century uses included
fire retardant coatings, concrete, bricks, pipes and fireplace cement, heat, fire, and acid resistant gaskets, pipe insulation,
ceiling insulation, fireproof drywall, flooring, roofing, lawn furniture, and drywall joint compound.[11]
Approximately 100,000 people have died, or will die, from asbestos exposure related to ship building. In the Hampton Roads area, a shipbuilding center, mesothelioma occurrence
is seven times the national rate.[17] Thousands of metric
tons of asbestos were used in World War II ships to wrap the pipes, line the boilers, and
cover engine and turbine parts. There were approximately 4.3 million shipyard workers during WWII, for every thousand workers
about 14 died of mesothelioma and an unknown number died from asbestosis.[16]
Asbestos fibers were once used in automobile brake pads and shoes. Since the mid-1990s, a
majority of brake pads, new or replacement, have been manufactured instead with Aramid fiber
(Twaron or Kevlar) linings (the same material used in
bulletproof vests).
Kent, the first filtered cigarette on the
market, used crocidolite asbestos in its "Micronite" filter from 1952 to 1956.[18]
The first documented death related to asbestos was in 1906.[10] In the early 1900s researchers began to notice a large number of early deaths and lung problems in
asbestos mining towns. The first diagnosis of asbestosis was made in England in 1924.[8] England protected asbestos
workers about ten years sooner than the U.S. By the 1930s, England regulated ventilation and made asbestos an excusable work
related disease.[8][19] The term Mesothelioma was not used in medical literature until 1931, and wasn't associated with asbestos until
sometime in the 1940s.[10]
The United States government and asbestos industry have been criticized for not acting quickly enough to inform the public of
dangers, and to reduce public exposure. In the late 1970s court documents proved that asbestos industry officials knew of
asbestos dangers and tried to conceal them.[16]
In Japan, particularly after World War II, asbestos was used in the manufacture of
ammonium sulfate for purposes of rice production, sprayed upon the ceilings, iron skeletons, and walls of railroad cars and
buildings (during the 1960s), and used for energy efficiency reasons as well. Production of asbestos in Japan peaked in 1974 and
went through ups and downs until about 1990, when production began to drop severely.[20]
Modern usage
Serpentine group
Serpentine minerals have a sheet or layered structure. Chrysolite is the only asbestos mineral in the serpetine group. In the
United States, chrysotile has been the most commonly used type of asbestos. According to
the U.S. EPA Asbestos Building Inspectors Manual, chrysotile accounts for approximately 95% of asbestos found in buildings in the
United States. Chrysotile is often present in a wide variety of materials, including :
- joint compound
- mud and texture coats
- vinyl floor tiles, sheeting, adhesives
- roofing tars, felts, siding, and shingles
- "transite" panels, siding, countertops, and pipes
- fireproofing
- caulk
- gaskets
- brake pads and shoes
- clutch plates
- stage curtains
- fire blankets
- interior fire doors
- fireproof clothing for firefighters
- thermal pipe insulation
In the European Union and Australia it has recently
been banned as a potential health hazard[21] and is not
used at all. Japan is moving in the same direction, but more slowly. Revelations that hundreds of
workers had died in Japan over the previous few decades from diseases related to asbestos sparked a scandal in mid-2005.[22] Tokyo had, in 1971, ordered companies handling
asbestos to install ventilators and check health on a regular basis; however, the Japanese government did not ban crocidolite and
amosite until 1995, and a full-fledged ban on asbestos was implemented in October 2004.[22]
Amphibole group
Five types of asbestos are found in the amphibole group: amosite, crocidolite, anthophyllite, tremolite, and actinolite.
Amosite, the second most likely type to be found in buildings, according to the U.S. EPA Asestos Building Inspectors Guide, is
the "brown" asbestos.
Amosite and crocidolite were formally used in many products until the early 1980s. The use of
all types of asbestos in the amphibole group was banned (in much of the Western world) by the mid-1980s, and by Japan in 1995.
These products were mainly:
- Low density insulation board and ceiling tiles
- Asbestos-cement sheets and pipes for construction, casing for water and
electrical/telecommunication services
- Thermal and chemical insulation (i.e., fire rated doors, limpet spray, lagging and gaskets)
Health Issues
By the first century, Greeks and Romans had already observed, at least in passing, that slaves involved in the weaving of
asbestos cloth were afflicted with a sickness of the lungs. [23].
Prior to 1900
Early concern about the health effects of asbestos exposure can be found in several sources. Among the earliest were reports
in Britain. The annual reports of the Chief Inspector of Factories reported as early as 1898 that asbestos had 'easily
demonstrated' health risks[24]
At about the same time, what was probably the first study of mortality among asbestos workers was reported in France [25]. While the study describes the cause of death as
chalicosis, a generalized pneumoconiosis, the
circumstances of the employment of the fifty workers whose death prompted the study suggest that the root cause was asbestos or
mixed asbestos-cotton dust exposure.
1900s - 1910s
Further awareness of asbestos-related diseases can be found in the early 1900s, when London doctor H. Montague Murray
conducted a post mortem exam on a young asbestos factory worker who died in 1899. Dr. Murray gave testimony on this death in
connection with an industrial disease compensation hearing. The post-mortem confirmed the presence of asbestos in the lung
tissue, prompting Dr. Murray to express as an expert opinion his belief that the inhalation of asbestos dust had at least
contributed to, if not actually caused, the death of the worker[26].
The record in the United States was similar. Early observations were largely anecdotal in nature and did not definitively link
the occupation with the disease, followed by more compelling and larger studies that strengthened the association. One such
study, published in 1918, noted:
- All of these processes unquestionably involve a considerable dust hazard, but the hygienic aspects of the industry have not
been reported upon. It may be said, in conclusion, that in the practice of American and Canadian life insurance companies
asbestos workers are generally declined on account of the assumed health-injurious conditions of the industry [27].
1920s and 1930s
Widespread recognition of the occupational risks of asbestos in Britain was reported in 1924 by a Dr. Cooke, a pathologist,
who introduced a case description of a 33-year old female asbestos worker with the following: 'Medical men in areas where
asbestos is manufactured have long suspected the dust to be the cause of chronic bronchitis and fibrosis...[28]." Dr. Cooke then went on to report on a case in 1927 involving a 33-year
old male worker who was the only survivor out of ten workers in an asbestos carding room. In the report he named the disease
"asbestosis[29]."
Dr. Cooke's second case report was followed, in the late 20's, by a large public health investigation (now known as the
Merewether report after one of its two authors) that examined some 360 asbestos-textile workers (reported to be about 15% of the
total comparable employment in Britain at the time) and found that about a quarter of them suffered from pulmonary fibrosis
[30]. This investigation resulted in improved regulation
of the manufacturing of asbestos-containing products in the early 1930s. Regulations included industrial hygiene standards,
medical examinations, and inclusion of the asbestos industry into the British Workers' Compensation Act [31].
The first known US workers' compensation claim for asbestos disease was in 1927[32]. In 1930, the first reported autopsy of an asbestosis sufferer was conducted in the United states
and later presented by a doctor at the Mayo Clinic, although in this case the exposure involved mining activities somewhere in
South America[33].
In 1930, the major asbestos company Johns-Manville produces a report, for internal company use only, about medical reports of
asbestos worker fatalities.[34] In 1932,
A letter from U.S. Bureau of Mines to asbestos manufacturer Eagle-Picher states, in relevant part, "It is now known that asbestos
dust is one of the most dangerous dusts to which man is exposed".[35] In 1933, Metropolitan Life Insurance Co. doctors find that 29 percent of workers in a
Johns-Manville plant have asbestosis.[34]
Likewise, in 1933, Johns-Manville officials settle lawsuits by 11 employees with asbestosis on the condition that the employees'
lawyer agree to never again "directly or indirectly participate in the bringing of new actions against the Corporation."[35] In 1934, officials of two large asbestos
companies, Johns-Manville and Raybestos-Manhattan, edit an article about the diseases of asbestos workers written by a
Metropolitan Life Insurance Company doctor. The changes minimize the danger of asbestos dust.[35] In 1935, officials of Johns-Manville and Raybestos-Manhattan instruct the
editor of Asbestos magazine to publish nothing about asbestosis.[35] In 1936, a group of asbestos companies agrees to sponsor research on
the health effects of asbestos dust, but require that the companies maintain complete control over the disclosure of the
results.[34]
1940s
In 1942, an internal Owens-Corning corporate memo refer to "medical literature on asbestosis . . . . scores of publications in
which the lung and skin hazards of asbestos are discussed."[36] Either in 1942 or 1943, the president of Johns-Manville, Lewis H.
Brown, says that the managers of another asbestos company were "a bunch of fools for notifying employees who had
asbestosis." When one of the managers asks, "do you mean to tell me you would let them work until they dropped dead?" The
response is reported to have been, "Yes. We save a lot of money that way."[37] In 1944, a Metropolitan Life Insurance Company report finds 42 cases of asbestosis among 195
asbestos miners.[38]
1950s
In 1951, asbestos companies removed all references to cancer before allowing publication of research they sponsor.[39]. In 1952, Dr. Kenneth Smith, Johns-Manville medical
director, recommends (unsuccessfully) that warning labels be attached to products containing asbestos. Later, Smith testifies:
"It was a business decision as far as I could understand . . . the corporation is in business to provide jobs for people and make
money for stockholders and they had to take into consideration the effects of everything they did and if the application of a
caution label identifying a product as hazardous would cut into sales, there would be serious financial implications."[40]. In 1953, National Gypsum's safety director writes to the
Indiana Division of Industrial Hygiene, recommending that acoustic plaster mixers wear respirators "because of the asbestos used
in the product." Another company official notes that the letter is "full of dynamite," urges that it be retrieved before reaching
its destination. A memo in the files notes that the company "succeeded in stopping" the letter, which "will be modified."[41].
Asbestos as a contaminant
Most respirable asbestos fibers are invisible to the unaided human eye because their size is
about 3.0-20.0 µm in length and can be as thin as 0.01 µm. Human
hair ranges in size from 17 to 181 µm in width.[42] Fibers ultimately form because when these minerals originally cooled and crystallized, they formed
by the polymeric molecules lining up parallel with each other and forming oriented
crystal lattices. These crystals thus have three cleavage planes, just as other minerals and gemstones have. But in their case, there are two cleavage
planes that are much weaker than the third direction. When sufficient force is applied, they tend to break along their weakest
directions, resulting in a linear fragmentation pattern and hence a fibrous form. This fracture process can keep occurring and
one larger asbestos fiber can ultimately become the source of hundreds of much thinner and smaller fibers.
As asbestos fibers get smaller and lighter, the more easily they become airborne and human respiratory exposures can result.
Fibers will eventually settle but may be re-suspended by air currents or other movement.
Friability of a product containing asbestos means that it is so soft and weak in structure that it can be broken with simple
finger crushing pressure. Friable materials are of the most initial concern due to their ease of damage. The forces or conditions
of usage that come into intimate contact with most non-friable materials containing asbestos are substantially higher than finger
pressure.
Naturally occurring asbestos
Asbestos from natural geologic deposits is known as "Naturally Occurring Asbestos" (NOA). Health risks associated with
exposure to NOA are not yet fully understood, and current US federal regulations do not address exposure from NOA. Many populated
areas are in proximity to shallow, natural deposits which occur in 50 of 58 California counties and in 19 other U.S. states. In
one study, data was collected from 3,000 mesothelioma patients in California and 890 men with prostate cancer, a
malignancy not known to be related to asbestos. The study found a correlation between the incidence of mesotheliomas and the
distance a patient lived from known deposits of rock likely to include asbestos, the correlation was not present when the
incidence of prostate cancer was compared with the same distances. According to the study, risk of mesothelioma declined by 6
percent for every 10 kilometers that an individual had lived from a likely asbestos source.[43]
Portions of El Dorado county are known to contain natural asbestos
formations near the surface.[44][43] The USGS studied amphiboles in rock and soil in the area
in response to an EPA sampling study and subsequent criticism of the EPA study. The study found that many amphibole particles in
the area meet the counting rule criteria used by the EPA for chemical and morphological limits, but do not meet morphological
requirements for commercial-grade-asbestos. The executive summary pointed out that even particles that do not meet requirements
for commercial-grade-asbestos may be a health threat and suggested a collaborative research effort to assess health risks
associated with "Naturally Occurring Asbestos".[45]
Large portions of Fairfax County, Virginia were also found to be underlain
with tremolite. The county monitored air quality at construction sites, controlled soil taken
from affected areas, and required freshly developed sites to lay 6 inches of clean, stable material over the ground.[43]
Asbestos in the environment
Asbestos is in the air we breathe and some of the water we drink, including water from natural sources.[46] Studies have shown that members of general (non-occupationally exposed)
population have tens of thousands to hundreds of thousands of asbestos fibers in each gram of dry lung tissue, which translates
into millions of fibers and tens of thousands of asbestos bodies in every person's lungs.[47]
The EPA has proposed a concentration limit of 7 million fibers per liter of drinking water for long fibers (lengths greater
than or equal to 5 µm). The OSHA, (Occupational Safety and Health
Administration) has set limits of 100,000 fibers with lengths greater than or equal to 5 µm per cubic meter of workplace
air for 8-hour shifts and 40-hour work weeks.[48]
Asbestos is not part of a ASTM E 1527-05 Phase I Environmental Site Assessment
(ESA). A Building Survey for Asbestos is considered an out-of-scope consideration under the industry standard ASTM 1527-05 Phase
I ESA (see ASTM E 1527-05). ASTM Standard E 2356-04 should be consulted by the owner or owners' agent to determine which type of
asbestos building survey is appropriate, typically either a baseline survey or a design survey of functional areas. Both types of
surveys are explained in detail under ASTM Standard E 2356-04. Typically, a baseline survey is performed by an EPA (or State)
licensed asbestos inspector. The baseline survey provides the buyer with sufficient information on presumed asbestos at the
facility, often which leads to reduction in the assessed value of the building (due primarily to forthcoming abatement costs).
Note: EPA NESHAP and OSHA Regulations must be
consulted in addition to ASTM Standard E 2356-04 to ensure all statutory requirments are satisfied, ex. notification requirements
for renovation/demolition. Asbestos is not a material covered under CERCLA's innocent
purchaser defense.
In some instances, the U.S. EPA includes asbestos contaminated facilities on the Superfund
National Priorities list (NPL). Buyers should be careful not to purchase facilities, even with a ASTM E 1527-05 Phase I
ESA completed, without a full understanding of all the hazards in a building or at a property, without evaluating non-scope ASTM
E 1527-05 materials, such as asbestos, lead, PCBs, mercury, radon, et al. A standard ASTM E 1527-05 does not include asbestos
surveys as standard practice.
Asbestos construction in developing countries
Countries like India and China have continued widespread use of asbestos. The most common is corrugated asbestos-cement Sheets
or A/C Sheets for roofing and for side walls. Millions of homes, factories, schools or sheds and shelters continue to use
asbestos. Eternit Everest, Hyderabad Industries and RamCo are some of the major asbestos products manufacturers in India.
Cutting these sheets to size and drilling holes to receive 'J' bolts to help secure the sheets to roof framing is done on
site. There has been no significant change in production and use of A/C Sheets in developing
countries following the widespread restrictions in developed nations.
Other asbestos-related diseases
- asbestos warts – caused when the sharp fibers lodge in the skin and are overgrown
causing benign callus-like growths.
- pleural plaques – discrete fibrous or partially calcified thickened area which can be seen on X-rays of individuals exposed to asbestos. They do not become malignant or cause other lung impairment.
- diffuse pleural thickening – similar to above and can sometimes be associated with asbestosis. Usually no symptoms
shown but if extensive can cause lung impairment.
Litigation
-
Asbestos litigation is the longest, most expensive mass tort in U.S. history, involving more than 8,400 defendants and 730,000 claimants as of
2002 according to the RAND Corporation[49], and at least one defendant reported claim counts in excess of 800,000 in
2006[50].
Current trends indicate that the worldwide rate at which people are diagnosed with the disease will likely increase through
the next decade[51]. Analysts have estimated that the
total costs of asbestos litigation in the USA alone is over $250 billion.[52]
Litigation exists outside the United States in England, Scotland, Ireland, the Netherlands, France, Australia, and Japan among
other nations. See the companion article for further information.
The volume of the asbestos liability has concerned manufacturers and insurers and
reinsuers[53]. The amounts and method of
allocating compensation have been the source of many court cases, and government attempts at resolution of existing and future
cases.
Critics of safety regulations
|
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The neutrality of this section is disputed.
Please see the discussion on the talk page. |
According to Natural Resources Canada, chrysotile asbestos is not as dangerous as once
thought. According to their fact sheet, "...current knowledge and modern technology can successfully control the potential for
health and environmental harm posed by chrysotile".[54]
In May of 1998, Canada requested consultations with the European Commission
concerning France's 1996 prohibition of the importation and sale of asbestos.[55]
Canada claimed that the French measures contravened provisions of the Agreements on Sanitary and Phytosanitary Measures and on
Technical Barriers to Trade, and the GATT 1994.[55]
The EC said that substitute materials had been developed in place of asbestos, which are safer to human health. It stressed
that the French measures were not discriminatory, and were fully justified for public health reasons. The EC said that in the
July consultations, it had tried to convince Canada that the measures were justified, and that just as Canada broke off
consultations, it was in the process of submitting substantial scientific data in favour of the asbestos ban.[55]
Critics of Canada's support of the use of chrysotile asbestos argue that Canada is ignoring the risks associated with the
material. The CFMEU pointed out that selling asbestos is
illegal in Canada, but it is exported and most exports go to developing countries. Canada has pressured countries, including
Chile, and the UN to avoid asbestos bans[56]
Asbestos regulation critics include the controversial Junkscience.com author and Fox
News columnist Steven Milloy and the asbestos industry.[57] Critics sometimes argue that increased regulation does more harm than good and
that replacements to asbestos are inferior. An example is the suggestion by Dixy Lee Ray
and others that the shuttle Challenger exploded because the maker of
O-ring putty was pressured by the EPA into ceasing production of asbestos-laden putty.[58][59] However, scientists point out that the putty used in Challenger's final flight did
contain asbestos, and failures in the putty were not responsible for the failure of the O-ring that led to loss of the
shuttle.[60][59]
Asbestos was used in the first 40 floors of the World Trade Towers and ended up contaminating the air around lower Manhattan
after the towers collapsed.[61] Steven Milloy suggests that the World Trade Center towers
could still be standing or at least would have stood longer had a 1971 ban not stopped the completion of the asbestos coating
above the 64th floor.[62] This was not mentioned in the
National Institute of Standards and Technology's report
on the towers' collapse. Insulation that replaced asbestos is believed to have equivalent fire resistance, and any sort of
sprayed-on insulation, including asbestos-based material, would have been removed in large areas by the impact of the planes and
subsequent explosion.[63][64][65]
Substitutes for asbestos in construction
Fiberglass insulat
