The term "machine operators" encompasses a broad category of jobs. Anyone who works with any kind of machinery would fall within this broad job description. Grinding machine operators use machines to grind down metal into the desired shape. Frequently, part of that is shaping metal that may have asbestos coatings. Grinding machine operators, like mechanics, also sometimes rework brakes and other mechanical parts that have asbestos pads or linings. Even if the asbestos pad is removed, a lot of asbestos dust remains, and grinding makes it even worse. In a 1986 report, the Environmental Protection Agency went so far as to say that regrinding an old brake block lining could release seven million asbestos fibers per cubic meter, and a light grinding of new linings could release almost five million asbestos fibers per cubic meter. Medical experts agree that people who work with friction products are at risk for developing asbestos-related diseases such as mesothelioma or asbestosis. Floor resurfacing and polishing machine operators also face potentially large amounts of asbestos when the flooring surface contains asbestos fibers as many of them did through the 1970s.
Asbestos is resistant to fire, chemically inert, and provides efficient insulation against electricity and heat. These properties have made it popular for centuries. Asbestos was used extensively by the ancient Greeks and Romans for clothing and for tablecloths that could be cleaned by throwing them in the fire. Asbestos linings were frequently put into suits of armor worn by knights during the Middle Ages. During its peak use in the United States, between World War II and the mid-1970s, asbestos was used in about 3000 different products.
Asbestos fibers separate easily, and when they are disturbed, they slough off tiny fibers of asbestos dust. This dust is too small to be seen without a microscope, but clumps together so at times people will see dust coming off an asbestos product. These clumps, which look like specks of dust, actually contain thousands of asbestos fibers. When the asbestos dust separates from the main fiber it easily floats on the air. Any person in the area can then unknowingly breathe in the dust. When asbestos enters the human body it gets imbedded in the lungs, or in the membrane that surrounds the lungs and lines the chest cavity.
Asbestos is also a carcinogen that causes the asbestos cancer known as mesothelioma, or a cancer of the membrane that surrounds the lungs in its most common form - pleural mesothelioma - or other organs in more rare forms. Mesothelioma, like other asbestos-related diseases, has a lengthy latency period. Signs of the disease usually don't show up for 15 or more years after the asbestos exposure. The first symptoms of mesothelioma are shortness of breath during exercise. This symptom is so nonspecific and mild that people rarely notice it at the onset. Over time the problem becomes worse until the mesothelioma sufferer can't get a full breath of air even at rest. They also usually experience severe chest pain.
If malignant mesothelioma is caught in its earliest stages, doctors can sometimes remove the tumor and the surrounding tissue before the cancer metastasizes. Unfortunately, most people do not catch the disease in this early stage. By the time most people realize they have a health problem and seek medical attention, the cancer has spread. At this point, doctors have the person undergo chemotherapy and radiation, sometimes along with surgery, to try to slow the growth of the cancer. There is no cure for mesothelioma, and although there are now drugs specifically designed to fight mesothelioma as opposed to general anti-cancer drugs, the mortality rate is still very high. Few people live more than two years after being diagnosed with mesothelioma.