Center for Asbestos Safety in the Workplace

Occupational Lung Diseases

Occupational lung diseases are a major public health problem. They include:

• Silicosis - caused by exposure to silica. Often appears in workers near rock drilling, quarrying, and rock or mineral grinding.
• Pneumoconiosis - black lung disease - caused by exposure to coal dust
• Agricultural fibrosis - workers exposed to raw cotton dust and sugercane often develop respitory problems, sometimes referred to as "brown lung" disease.
• Asbestosis and Mesothelioma - caused by exposure to asbestos fibers.

Medical experts have shown that asbestos exposure causes serious illnesses, including:

• asbestosis - a chronic lung ailment
• lung cancer
• other random cancers such as cancer of the larynx
• mesothelioma

Millions of American workers were exposed to asbestos dust, including many of the more than 4 million workers in the shipyards in the peak years of World War II production.

While risk to workers increases with heavier and longer exposure to asbestos, it has been shown that even short periods of exposure can lead to mesothelioma.

The respitory effects of asbestos exposure are irreversible. It is not completely understood why asbestos produces such damaging effects, but it is clear that asbestos is a major health hazard, and its detrimental health effect have been known for years. Indeed, many researchers feel that almost all cases of mesothelioma are due to asbestos exposure. Cigarette cancer does not appear to contribute to this type of cancer.

Often a period of 20 years or more elapses between asbestos exposure and development of mesothelioma.

With today's workplace safety regulations, the risk of exposure is substantially less. However, mesothelioma and other asbestos diseases continue to crop up as a result of past exposure.

One of the very properties that made asbestos a prized building material - its durability - contributes to its detrimental health effects. Asbestos fibers are hardy and tend to stay in the body's tissues indefinitely.

If you or a loved one has been exposed to asbestos, click here.

Advice for doctors taking patients' occupational and environmental history.

ASBESTOS AND MINERAL FIBERS

Asbestos is a generic term for a number of hydrated silicates that, when crushed or processed, separate into flexible fibers made up of fibrils. The term asbestos, as used in 30 CFR 56/57.5001(b) refers to the following mineral fibers: chrysotile, amosite, crocidolite, anthophyllite asbestos, tremolite asbestos, and actinolite asbestos.

The term mineral fiber refers to particles greater than five µm in length which have a length at least three times greater than its width.

Fibrous talc is a magnesium silicate (Mg3Si4O10(OH)2) which is greater than five µm in length with a length three times greater than its width. Fibrous talc has the same fiber limit as asbestos. This is due to the similarity of the reaction in the lungs produced by fibrous talc and asbestos fibers.

Sources of Asbestos and Mineral Fibers:

In addition to asbestos mines, asbestos is found as a contaminant mineral in the host rock in non-asbestos mining operations. Asbestos or fibrous dust is created and released into the ambient air by the breaking, crushing, grinding, drilling, or general abrasive handling of a solid material having fibrous components. Chrysotile is the type of asbestos most commonly found in commercial products. Amosite and crocidolite are generally considered to be the most toxic.

Fibrous dust particles do not readily settle out of the air, but can remain suspended for long periods of time. As a result, accumulations of fibrous dust can continue to present an inhalation hazard when they are stirred up by vehicular traffic, by persons walking through them, or by the wind.

Asbestos exposure most often occurs from products brought on to the mine property, such as brake linings, asbestos welding blankets, and pipe insulation, or products that are used in building construction, such as transite panels. Replacement of these items with asbestos-free materials is encouraged, but should be done only by miners trained in asbestos removal and abatement methods.

Health Effects:
Asbestosis is a type of pneumoconiosis which results from the inhalation of asbestos fibers, and is also referred to as interstitial fibrosis. Fibers lodge in the lungs, causing a scar that may continue to grow even though there may be no further exposure to asbestos. Lung cancer is a simple term for carcinoma of the bronchus. Lung cancer is associated with all types of asbestos and is related to the degree of asbestosis present in the lungs and also to cigarette smoking, which greatly enhances the cancer-causing properties of asbestos. High rates of lung cancer have been observed in miners exposed directly and indirectly to asbestos dust.

Mesothelioma, another cancer associated with asbestos exposure, is a tumor made up of cells from the pleura (chest lining) or peritoneum (abdominal lining). Cancer of the gastrointestinal tract and of the larynx have also been associated with exposure to asbestos fibers.

Full-shift Limit: No miner shall be exposed to an 8-hour, time-weighted average airborne concentration of asbestos dust which exceeds 2 fibers, greater than 5 µm in length, per milliliter of air, as determined by the membrane filter method at 400-450 magnification, 4 millimeter objective, phase contrast illumination. More on exposure limit definitions.

Short-term Limit: No miner shall be exposed at any time to airborne concentrations of asbestos fibers in excess of 10 fibers, longer than 5 µm, per milliliter of air, as determined by the membrane filter method over a minimum sampling time of 15 minutes.