Mesothelioma & Asbestos

Mesothelioma is a form of cancer that is almost always caused by previous exposure to asbestos. In this disease, malignant cells develop in the mesothelium, a protective lining that covers most of the body's internal organs. Its most common site is the pleura (outer lining of the lungs and chest cavity), but it may also occur in the peritoneum (the lining of the abdominal cavity) or the pericardium (a sac that surrounds the heart).

Most people who develop mesothelioma have worked on jobs where they inhaled asbestos particles, or have been exposed to asbestos dust and fibre in other ways, such as by washing the clothes of a family member who worked with asbestos, or by home renovation using asbestos cement products.

Asbestos describes any of a group of minerals that can be fibrous, many of which are metamorphic and are hydrousmagnesiumsilicates. The name is derived for its historical use in lamp wicks; the resistance of asbestos to fire has long been exploited for a variety of purposes. Asbestos was used in fabrics such as Egyptian burial cloths and Charlemagne's tablecloth (which according to legend, he threw in a fire to clean). Asbestos occurs naturally in many forms; it is mined from metamorphic rocks.

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 some kinds of asbestos fibers, however, can cause a number of serious illnesses, including cancer. Many uses of asbestos are banned in many countries.

In 1989 the United States Environmental Protection Agency (EPA) passed 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 that legally contain asbestos, visit the EPA's clarification statement. Depending on the type of Asbestos, the cancer can be worse. It also depends on the amount inhaled. This is a welding occupational hazard.

Historic Usage of Asbestos

Items made of asbestos were held in so great an esteem as to be of equal value with gold; none but emperors and kings had napkins made of it. Supposedly, Charlemagne had a tablecloth made of asbestos. Cleaning an asbestos cloth was simple- it was simply thrown into a fire. Some antiquaries have believed that ancients made shrouds of asbestos, wherein they burnt 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 building funeral pyres.

Others assert that the ancients used asbestos to make perpetual wicks for sepulchral lamps. 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.

As early as 1898 the Chief Inspector of Factories of the United Kingdom reported to Parliament in his Annual Report about the "evil effects of asbestos dust". He reported the "sharp, glass like nature of the particles" when allowed to remain in the air in any quantity, "have been found to be injurious, as might have been expected" (Report of the Select Committee 1994). In 1906 a British Parliamentary Commission confirmed the first cases of asbestos deaths in factories in Britain and recommended better ventilation and other safety measures. In 1918 a US insurance company produced a study showing premature deaths in the asbestos industry in the United States. In 1926 the Massachusetts Industrial Accidents Board processed the first successful compensation claim by a sick asbestos worker. Many American injuries from asbestos exposure came from shipbuilders working during World War II.

Modern Usage

Asbestos linings were once used in automobile brake pads and shoes. Since the mid-1990s, a majority of brake linings, new or replacement, have been manufactured with 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.

Chrysotile is the form of asbestos that has been used commercially. In the United States, chrysotile has been the most commonly used type of asbestos. Chrysotile is often present in a wide variety of materials, including but not limited to:

• Sheetrock taping;
• Mud and texture coats;
• Vinyl floor tiles, sheeting, adhesives and ceiling tiles;
• Plasters and stuccos;
• Roofing tars, felts, siding, and shingles;
• "Transite" panels, siding, countertops, and pipes;
• Acoustical ceilings;
• Fireproofing;
• Putty;
• Caulk;
• Gaskets;
• Brakepads and shoes;
• Clutchplates;
• Stage curtains;
• Fire blankets;
• Interior fire doors; and
• Fireproof clothing for firefighters.

Amosite and crocidolite were used in many products until the early 1980s. The use of all types of asbestos in the amphibole group was banned in the mid-1980s. These products were mainly:

• Low density insulation board and ceiling tiles;
• Asbestos-cementsheets and pipes for construction, casing for water and electrical/telecommunication services; and
• Thermal and chemical insulation (i.e., fire rated doors, limpet spray, lagging and gaskets).

Asbestos-Related Diseases

Diseases caused by asbestos exposure include:

• Asbestosis - A lung disease first found in naval shipyard workers, asbestosis is a scarring of the lung tissue from an acid produced by the body's attempt to dissolve the fibers. The scarring may eventually become so severe that the lungs can no longer function. The latency period (the time it takes for the disease to develop) is often 10-40 years.
• Mesothelioma - A cancer of the mesothelial lining of the lungs and the chest cavity, the peritoneum (abdominal cavity) or the pericardium (a sac surrounding the heart). It is believed that mesothelioma is caused by generation of reactive oxygen species (ROS) by the asbestos fibers.  Asbestos exposure is linked to at least 50% of patients developing malignant mesothelioma. Malignant mesothelioma has a peak incidence 35-45 years after asbestos exposure. Median survival for patients with malignant mesothelioma is 11 months. Asbestos has a synergistic effect with tobacco smoking in the causation of pleural mesothelioma.
• Cancer - Lung Cancer has been linked to asbestos. Asbestos exposure alone can cause lung cancer, but asbestos exposure and tobacco smoking have a synergistic effect, greatly increasing the chances of contracting lung cancer. Cancer of the larynx has been linked to asbestos. Some studies suggest that asbestos exposure is linked to a slightly increased risk of stomach, pharyngeal, and colorectal cancer.

In the United States, an estimated 9000 people die each year of asbestos-related diseases, such as mesothelioma, asbestosis, lung cancer, and gastrointestinal cancer.

Other asbestos-related diseases :

• Pleural Plaques - discrete fibrous or partially calcified thickened area that 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.
• Pulmonary Fibrosis - many jobs - particularly those that involve mining or that expose workers to asbestos or metal dusts - can cause pulmonary fibrosis. Workers doing these kinds of jobs may inhale small particles (like asbestos fibers) that can damage the lungs, especially the small airways and air sacs, and cause scarring (fibrosis). 

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