Archive | March, 2009

History of Asbestos

Asbestos has been used for more than 2,000 years. It was named by the Ancient Greeks, its name meaning “inextinguishable”. The Greeks also noted its harmful biological effects. Even though the Greek geographer Strabo and the Roman naturalist Pliny the Elder both observed the “sickness of the lungs” in the slaves that wove asbestos into cloth, they were in such awe of asbestos’ seemingly magical properties that they ignored the symptoms.

The Greeks used asbestos for the wicks of the eternal flames of the vestal virgins, as the funeral dress for the cremation of kings, and as napkins. It is rumored that Romans would clean asbestos napkins by throwing them in the fire. The asbestos cloth would come out of the fire whiter than it went in, so the Romans named asbestos “amiantus“, meaning “unpolluted”.

Use of asbestos declined during the Middle Ages, yet some say that Charlemagne had asbestos tablecloths. Marco Polo was also shown items made from asbestos cloth on his travels.

Asbestos use was brought back in the 1700s, but did not become popular until the Industrial Revolution during the late 1800s. It then began to be used as insulation for steam pipes, turbines, boilers, kilns, ovens, and other high-temperature products. Ancient observations of the health risks of asbestos were either forgotten or ignored.

At the turn of the twentieth century, researchers began to notice a large number of deaths and lung problems in asbestos mining towns. In 1917 and 1918, it was observed by several studies in the United States that asbestos workers were dying unnaturally young.

The first diagnosis of asbestosis was made in 1924. A woman had been working with asbestos since she was thirteen. She died when she was thirty-three years old, and an English doctor determined that the cause of death was what he called “asbestosis”. Because of this, a study was done on asbestos workers in England. Twenty-five percent of them showed evidence of asbestos-related lung disease. Laws were passed in 1931 to increase ventilation and to make asbestosis an excusable work-related disease. It would take the United States ten more years to make these steps.

In the 1930s major medical journals began to publish articles that linked asbestos to cancer. The re-discovery of asbestos-related diseases were put on the back burner for several years due to the emergence of silicosis (a lung disease caused by silica dust inhalation). The affected workers brought $300 million in lawsuits against their employers. This served as a warning to the asbestos companies, and afterwards they tried to cover up the health effects of asbestos. Asbestos companies continued to use asbestos in manufacturing and construction. Despite that many materials, such as fiberglass insulation, were created to replace asbestos, companies that used asbestos ignored the safer alternatives. They ignored the danger for the sake of profits, much like the tobacco industry. The conduct of the asbestos companies is especially egregious, however, because the victims were largely exploited workers who were unaware of the serious health risks they were exposed to on a daily basis.

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Common asbestos Products

Three-fourths of the world’s supply of asbestos is mined in Quebec, Canada, and other large deposits are located in South Africa. Asbestos can be mined in various ways, but the most common method is open-pit mining. However, only 6 percent of the mined ore contains usable fibers. The fibers are split from the ore by crushing, air suction, and vibrating screens. During that process they are sorted into different lengths, or grades. The Quebec Standard Test Method is the most widely used method of grading. It divides the fibers into seven groups, the longest in Group One and the shortest, called milled asbestos, in Group Seven. The length of the fibers and its chemical composition determine the kind of product that can be made out of the asbestos. The longer fibers are used in fabric, usually with cotton or rayon, and the shorter ones for molded materials, such as pipes and gaskets.

Asbestos has been used in various products since the 1900s, but the peak usage years were between 1950 and 1975. It was considered an ideal material to use, since it resembles fibers such as cotton and wool in its pliability and softness, yet it is inflammable and acid resistant.

Because of its cloth-like qualities, it can be woven and spun into fireproof garments. It was once used to create fireproof protection for firefighters and other people who worked with high heat. Asbestos was also used in gas masks. It could be woven into sheets to act as insulation and thermal proofing for pipes, boilers, and electrical products.

It could be spray applied as fireproofing as well. It coated brake linings and clutch pads, and other friction materials (because friction causes heat).

It was used in an array of construction materials. Asbestos was included in cement pipes, packing, jointing, gaskets, floor and ceiling tiles, paneling, roofing shingles, asphalt coats and sealant, and acoustical and decorative applications.

Here is a list of common asbestos products:

  • Building exteriors
    • asbestos cement siding panels – flat, corrugated, shingles or accent panels
    • asbestos cement soffits – flat or perforated panels
    • asbestos cement roof panels – corrugated
    • roofing felts and mastics
    • building overhangs – thermal spray
    • stucco
    • brick and block mortar
    • loose fill insulation in exterior wall cavities (vermiculite)
  • Flooring
    • vinyl asbestos tile
    • sheet vinyl flooring (asbestos paper backing)
    • floor leveling compound
  • Ceilings
    • t-bar ceiling tile
    • asbestos cement ceiling tile
    • acoustic and stippled finishes
    • plaster or drywall jointing materials
  • Walls
    • plaster or drywall jointing materials
    • stippled finishes
    • thermal spray
    • asbestos cement panels
  • Service Areas
    • insulation in boiler rooms – boilers, vessels, pipes, ducts, incinerators, floors, ceilings, walls
    • fan rooms – insulation of pipes, ducts, chillers, floors, ceilings, walls
    • machine rooms – insulation on pipes, ducts, floors, ceilings, walls
    • crawl spaces – insulation on pipes, ducts
    • wall cavities, insulation above ceiling spaces – pipe and duct chases, pipes, ducts
  • Pipes (insulation on either exposed or concealed pipes)
    • steam and hot water heating supply and return lines
    • domestic water supply and drain lines
    • chilled water lines
    • rain water and sanitary lines – asbestos cement or bell and spigot cast iron, insulated or bare pipe
    • gaskets in flanged pipe joints
  • Structural
    • fireproofing spray on beams, decks, joints, columns and other structural members
  • Miscellaneous
    • incandescent light fixture backing
    • wire insulation
    • fume hoods – internal linings and exhaust ducts
    • lab counters
    • elevator brake shoes
    • heating cabinet panels (asbestos cement)
    • fire dampers and fire stop flaps
    • diffuser backplaster
    • emergency generators – thermal insulation and exhaust manifolds
    • firestopping
    • theater curtains
    • welding blankets and screens
    • incinerators – internal insulation
    • cooling towers – panels and fill
    • duct tape
    • duct expansion/vibration isolation joints
  • Building products containing asbestos in an unbound or loosely bound form:
    • insulating cements
    • sprayed insulation – fire resistant, acoustic, thermal, condensation control
    • insulation block – magnesia or calcium silicate
    • textiles – not saturated, for lagging, curtains or clothing

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