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Resembling car and truck brakes, the linings of brake pads and brake shoes or discs on farm tractors wear out and require periodic replacement. Farm tractor brake components were often disassembled, cleaned out, reconditioned and recycled. From the early years of the 1900's through the 1990's, brake linings generally contained chrysotile asbestos, a carcinogenic fiber that if inhaled can lead years later to mesothelioma. The use of asbestos in brake linings was an industry standard. This was the case whether the tractor was manufactured by International Harvester, Ford, John Deere or any other manufacturer. The past presence of asbestos in brake lining materials placed mechanics and their assistants at a high risk of developing this deadly disease and other debilitating respiratory conditions.
Asbestos-containing brake shoes and discs have two primary components, the brake shoe or disc, a curved metal structure, and the brake lining, a pad of brown fuzzy material that is either bonded or riveted to the surface of the shoe or disc. Up until the 1990's, asbestos-containing tractor brake linings could be purchased at most any farm tractor store. Those who performed replacement brake work were likely exposed to airborne asbestos dust released into their garage or work area during the replacement process.
In order to replace a worn brake shoe or disc, a brake mechanic must remove both of the tractor's enormous tires and the brake drum that contains the brake shoe or disc in need of replacement. If the brake drum has rusted, its removal from a wheel shaft requires the use of tools, such as a hammer and a puller. After the brake drum has been successfully removed, a mechanic detaches the worn brake shoe or disc from within the drum and, subsequently, uses an air hose to remove dust and debris from the surfaces of these parts. When the mechanic uses a hammer and an air hose in the brake replacement process, he discharges loose asbestos dust into his breathing area and also into the breathing area of the other individuals within the vicinity of the mechanic's workspace.