Asbestos

Asbestos, a mineral used as an insulator and fire retardant during much of the first half of the 20th century, is now a nearly ubiquitous environmental contaminant. Found frequently in buildings, asbestos may be present in a broad range of construction materials, from concrete blocks to flooring.

Asbestos is a human health threat because a single submicroscopic fibril, thousands of which make up a single asbestos fiber, can cause severe lung disease. Only when asbestos is pulverized are the dangerous fibrils released into a dust cloud, which may be inhaled or ingested. The safe removal of asbestos is therefore a delicate and time-intensive process and presents a high risk of exposure. Current practice is typically to leave asbestos undisturbed. It is estimated that billions of dollars would be required to eliminate asbestos from all affected buildings.

Asbestos exposure is most commonly associated with occupational exposure, though persons living in areas with naturally occurring asbestos or man-made mines may also be exposed. Historically, high-risk occupations have included mining, milling, working with insulation, shipbuilding/repairing, and working in the textile industry. Men are more commonly exposed to asbestos and, therefore, are more frequently affected by negative sequelae associated with exposure.

The most common diseases caused by asbestos exposure are mesothelioma, asbestosis, and lung cancer. If ingested, asbestos fibrils may also cause stomach cancer. Mesothelioma is a very rare form of cancer of the mesothelium, the membrane lining the various body cavities, which most commonly affects the mesothelium of the lungs or chest cavity, but may also affect the mesothelium of the abdomen or heart. Mesothelioma is nearly always associated with asbestos and is not related to smoking. Asbestosis occurs when asbestos fibrils irritate and scar lung tissue. This damage decreases the ability of the lungs to oxygenate blood, causing shortness of breath. There is no treatment for asbestosis, a progressive disease. The many diseases associated with asbestos exposure have a long latency period, typically many decades. Thus, studies assessing the risk of various health outcomes among asbestos-exposed persons require adequate follow-up time.

Asbestosis is a member of the group of diseases termed pneumoconioses. These diseases—coal workers’ pneumoconiosis (CWP), silicosis, asbestosis, mixed dust pneumoconiosis, graphitosis, and talcosis—all result from inhaling mineral particles, result in changes in lung tissue, and have no current treatment. From 1968 to 2000, deaths due to pneumoconioses decreased overall and for all specific subtypes except asbestosis. Rather, mortality due to asbestosis increased steadily from 77 to 1,493 during this period. The annual age-adjusted death rate for asbestosis increased from 0.54 per million population in 1968 to 6.88 per million population in 2000. Asbestosis increased throughout the United States during this time, though the coastal states saw the most marked rise, likely due to the shipbuilding industry. Since asbestosis mortality usually occurs 40 to 45 years after exposure, this upward trend in asbestosis mortality likely dates back to the post–World War II era. However, it is not expected that this trend will begin to reverse for at least several years, since asbestos use peaked in the United States in 1973. The peak in asbestosis deaths in the United States will likely be seen around 2013 to 2018.

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