Introduction

Exposure to asbestos can occur when asbestos-containing material (man-made or natural) is disturbed releasing asbestos fibers into the air. Asbestos that is embedded or contained in undisturbed solid materials presents a negligible risk of exposure.

Inhalation

The air pathway is the most important route of exposure to asbestos. It is the route that most commonly leads to illness. Exposure scenarios include inhalation of air that is contaminated:

• During work with asbestos,
• During work in the same space as others working with asbestos,
• From a worker's skin, hair, and clothing,
• In areas surrounding a mining operation,
• In areas of the world where natural weathering, landscaping, construction, or other human activity (such as gardening and outdoor recreation) results in disturbance of asbestos-bearing rock, and
• In homes and buildings where renovations or demolitions disturb asbestos-containing building materials.

The first four scenarios above were common until the 1970s, when the U.S. Environmental Protection Agency (EPA) began to regulate the industrial uses of asbestos and the Occupational Safety Health Administration (OSHA) developed workplace exposure standards [Seidman and Selikoff 1990]. Today, the last two scenarios are the more common because of declining use of asbestos in developed countries [British Thoracic Society 2001; NIOSH 2011a].

Ingestion

Ingestion-a less important pathway of exposure-occurs through

• Swallowing material removed from the lungs via mucociliary clearance in persons who have inhaled asbestos fibers into the lungs [NIOSH 2011b].
• Drinking water contaminated with asbestos (for example, from erosion of natural land sources, discarded mine and mill tailings, asbestos cement pipe, or disintegration of other asbestos-containing materials transported by rainwater).
• Eating biota, such as clams, that are contaminated with asbestos [ATSDR 2013].
• Incidental ingestion during swimming in contaminated water [ATSDR 2009].

Asbestos levels in most water supplies are well below the EPA maximum contaminant level (MCL), so significant exposure by drinking water is uncommon.

Skin

Today, with the appropriate use of personal protective equipment by those working with asbestos, dermal contact is rarely a significant exposure pathway. In the past, handling asbestos could result in significant dermal contact and exposure. Asbestos fibers could become lodged in the skin, producing a callus or corn, but not more serious health effects.

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