Agency for Toxic Substances and Disease Registry 
Case Studies in Environmental Medicine (CSEM) 

Asbestos Toxicity
How Are People Exposed to Asbestos?

Learning Objectives

Upon completion of this section, you should be able to

• identify the most important route of exposure to asbestos

Introduction

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

The primary route of asbestos entry into the body is inhalation of air or dust that contains asbestos fibers. Asbestos can also enter the body via ingestion. With dermal exposure, asbestos fibers may lodge in the skin.

Inhalation

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

• during work with asbestos
• during work in the same space as others working with asbestos
• on worker’s skin, hair, and clothing
• in areas surrounding a mining operation
• in areas of the world where construction or other human activity (such as gardening) results in disturbance of natural outcrops of asbestos-bearing rock
• in homes and buildings where renovations or demolitions disturb asbestos-containing building materials

The first four scenarios were common until the 1970s, when the 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).

Ingestion

Ingestion—a minor pathway of exposure—occurs through

• swallowing material removed from the lungs via tracheociliary clearance by a person who has inhaled asbestos fibers into the lungs
• 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 rain

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

Key Points

• The air pathway (inhalation of contaminated air or dust) is the most important route of exposure to asbestos, the route that most commonly leads to illness.
• Ingestion is a minor exposure pathway, but exposure can occur after swallowing of material cleared from the lungs.
• Heavy dermal contact is unusual, but it can lead to calluses or corns.

Progress Check