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

Asbestos Toxicity
What Are the U.S. Standards for Asbestos Levels?

Learning Objectives

Upon completion of this section, you should be able to

• explain the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for asbestos.
• explain the Environmental Protection Agency’s (EPA) maximum contaminant level (MCL) for asbestos in drinking water.

Introduction

The earliest evidence of asbestos-associated disease in workers was found in the 1930s by British studies (Lee and Selikoff, 1979). We now know that the toxic effects of asbestos depend on the nature and extent of exposure, particularly on the

• concentration of asbestos fibers involved in the exposure
• duration of exposure
• frequency of exposure
• type of asbestos fibers involved in the exposure
• dimensions and durability of the asbestos fibers

United States government agencies (OSHA and Centers for Disease Control’s center National Institute for Occupational Safety and Health (NIOSH)) began establishing standards for asbestos in the 1970s. US regulatory agencies such as EPA and OSHA recognize six asbestos minerals (chrysotile, actinolite, tremolite, anthophyllite, amosite, crocidolite) as legally regulated forms of asbestos out of the group of asbestiform minerals. Asbestiform minerals are defined as crystal aggregates displaying these characteristics groups of separable, long, thin, strong, and flexible fibers arranged in parallel or in matted masses. (ATSDR, 2001a) (ATSDR, 2001a).

Other regulations focus primarily on the concentration of asbestos fibers in air. Currently, we have

• a standard for asbestos in the workplace
• a standard for asbestos in drinking water
• regulatory requirements for school boards regarding asbestos in schools

Occupational Standards

In 1986, OSHA established the current permissible exposure limit (PEL) for asbestos in the workplace: 0.1 fibers/cc of air). PELs are an allowable exposure level in workplace air that are averaged over an 8-hour shift of a 40 hour workweek.

OSHA requires employers of all workers who are exposed to asbestos (regardless of exposure level) to

• provide training in the proper use of personal protective equipment (PPE)
• train workers in safety

In addition, OSHA requires workers who are exposed to asbestos above the PEL and who are employed in certain asbestos industries to

1. use PPE
2. to undergo medical surveillance in order to identify those with signs of asbestos-associated disease, remove them from further exposure, and
3. provide documentation for work-related injury claims.

Components of the required medical surveillance include

• a standard questionnaire
• a physical examination
• a spirometric test, and
• a chest X-ray.

For further information about OSHA requirements, you can visit

http://www.osha.gov/SLTC/asbestos/standards.html.

For further information about protection guidelines, contact NIOSH at 1-800-35-NIOSH or visit the website at

http://www.cdc.gov/niosh.

Environmental Standards

ATSDR does not consider the use of OSHA’s PEL for workplace exposures to be appropriate for environmentally exposed populations since residential and/or environmental exposures are 24 hours a day year round exposure rather than 8 hour day 40 hour week exposures. Children and the elderly are also not exposed in the workplace.

EPA has established a maximum contaminant level (MCL) for asbestos in drinking water: 7 MFL (million fibers per liter) in drinking water.

In addition, EPA has

• banned spraying of asbestos in building interiors (for fireproofing and ceilings)
• regulated uses of asbestos in industrial products and construction
• developed guidelines for proper treatment of in-place asbestos in old buildings
• recommended “no visible emissions” of asbestos

For more information on EPA rules and regulations regarding asbestos, visit the website at the following URL:

http://www.epa.gov/oppt/asbestos.

Schools

The Asbestos in Schools Identification and Notification Act of 1982 requires that local education agencies

• inspect schools for friable material.
• analyze these materials for asbestos content.
• post results and notify parents and employees if asbestos is found.
• maintain appropriate records.

EPA also warned school authorities that power buffing and power stripping of asbestos-tile floors in schools produces significant airborne asbestos levels. Floor maintenance must be performed by hand to prevent release of asbestos fibers.

Key Points

• OSHA’s PEL for asbestos in the workplace is 0.1 fibers/cc of air (8-hour TWA).
• OSHA requires asbestos workers in certain industries to be trained in PPE; they must undergo medical surveillance if exposed above the PEL.
• EPA’s MCL for asbestos in drinking water is 7 MFL (million fibers per liter) of drinking water.
• Local education agencies must inspect schools and analyze friable material for asbestos content, communicate results, and maintain records.

Progress Check