What Is Asbestos?
The term asbestos is derived from a Greek word
A group of fibrous silicate minerals, the most common of which are:
Chrysotile, Crocidolite and Amosite.
Asbestos is non-flammable even at very high temperatures and is extremely
flexible and durable. Asbestos was described in a 1927 doctoral thesis
as follows: "The crude mineral is merely
a piece of rock or stone. It has truly been called a physical paradox being
both fibrous and crystalline, elastic and brittle, yet able to be carded
and so converted as to be spun and woven like wool, flax or silk. It would
appear to possess the characters of both vegetable and mineral while being
different from either; light and feathery as eiderdown, it is yet as dense
and heavy as the rock it resembles... The fiercest heat fails to consume it,
nor acids affect the strength of its fibres notwithstanding their delicacy;
a strand of it can be spun to weigh less than one ounce per hundred yards
length and fine cloth can be made from its fibres weighing only a few ounces
to the square yard. Its indestructible nature enables it to resist decay
under almost any conditions."
Types of Asbestos
Also known as white asbestos is a member of the Serpentine group,
so-named because the fibre is curly.
Chrysotile fibres are the most flexible of all asbestos fibres; they can
withstand the fiercest heat but are so soft and flexible that they can
be spun and woven as easily as cotton.
Resistance to alkaline attack makes chrysotile
a useful reinforcing material in asbestos-cement building products.
Traditionally it was the most widely used of all asbestos types, accounting
for approximately 95% of asbestos mined annually. Like the other forms of
asbestos, chrysotile can absorb organic materials such as resins and
polymers and can be used to strengthen particulates such as cement.
In 1994, 5,000 tonnes of chrysotile were imported into the UK; sales
of asbestos roofing slates rose by 25% in 1993.
Crocidolite is known colloquially as blue asbestos and is a member of the
Amphibole group. The needle-like fibres are the strongest of all asbestos
fibres and have a high resistance to acids. Crocidolite was used in yarn
and rope lagging from the 1880s until the mid 1960s and in preformed
thermal insulation from the mid 1920s until 1950.
The high bulk
volume of crocidolite makes it suitable for use in sprayed insulation; a
product which was first manufactured in this country in 1931 at the JWR
factory in Armley. Crocidolite is known to be the most lethal of all the
asbestos types. The import of crocidolite peaked in 1950, fell by 25% in
1960 and by 88% in 1970. The "import, supply and use of crude, fibre, flake,
powder or waste crocidolite or amosite" wasn't actually banned until the
Asbestos (Prohibitions) Regulations of 1985 came into force, although strict
guidelines had regulated its use since 1969.
Amosite is also known as brown asbestos and is, like crocidolite, a member
of the Amphibole group. Its harsh, spiky fibres have good tensile strength and resistance to heat.
In buildings, amosite was used for anti-condensation and acoustic purposes;
on structural steel it was used for fire protection.
Between the 1920s and the late 1960s amosite was used in preformed
thermal insulation, pipes, slabs and moulded pipe fitting covers. In the
UK amosite was also used widely in the manufacture of insulation boards.
The import of amosite was banned as of 1 January 1986 by The Asbestos
(Prohibitions) Regulations 1985.
Asbestos was nicknamed "the magic mineral" because its unique chemical
composition and physical properties made it suitable for use in thousands
of products from floor tiles to road signs, from sewage pipes to insulating
mattresses and making socks.
Historical records show that asbestos has been
used by man for over 4,000 years; in the 20th and 21st century it has been
used in over 3,000 products including cement building materials, pipework
lagging, insulating mattresses and rope, fire resistant insulation boards,
sprayed fire-proofing products, floor tiles and coverings, water and sewage
pipes, gas masks, friction materials for vehicle brakes and clutches, lifts
Boilers and pipework were lagged with asbestos products in hospitals, power
stations and throughout heavy industry.
Asbestos insulation products were popular in the shipbuilding and railway
industries and in the dockyards etc. The Royal Yacht Britannia, built in 1952,
was riddled with asbestos insulation which was stripped out upon discovery in 1980.
Sprayed asbestos insulation containing crocidolite was used in the roof space of
the House of Commons Chamber; linings of the ventilation ducts in the House of
Commons were insulated with chrysotile (white asbestos).
Asbestos in British buildings
There are no official statistics for the number of British buildings which
contain asbestos. The TUC believes that "asbestos is present in most schools and other public buildings erected since
the 1960s, especially in walls, ceiling and fire doors, lagging on hot pipes,
boilers and ovens and in wall cavities and lofts." According to
one industry expert all mature buildings in Britain, that is pre-1980, are
liable to contain this category 1 carcinogen. Alan Carneige, a risk manager
for insurance advisers Sedgwick UK Ltd., believes that "in any building more than fifteen years
old, and in some cases younger, there is likely to be asbestos."
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Asbestos products have been used on a large scale in British buildings for
fireproofing, acoustic and thermal insulation, condensation protection and
reinforcement in asbestos-cement products.
According to The Final Report of the Advisory Committee on Asbestos, the
use of chrysotile (white asbestos) was by far the most widespread in Britain.
Nearly 40% of the chrysotile imported into Britain in 1976 was incorporated
into asbestos cement building products, 22% was used in fillers and
reinforced cements and 12% went into floor tiles and flooring.
Other asbestos-containing materials used in
British buildings were: sprayed asbestos coatings, asbestos lagging,
insulation partition boards, ropes and yarns, cloth, millboard and paper,
asbestos cement sheets and partition boards, textured coating, mastics,
sealants, putties, adhesives, wall plugging compound, pipework and so on.