The Permissible Exposure Limit and the Threshold Limit Value for Asbestos Exposure

The Permissible Exposure Limit and the Threshold Limit Value for Asbestos Exposure

The Occupational Safety and Health Administration (OSHA) has maintained that “there is no ‘safe’ level of asbestos exposure for any type of asbestos fiber,” but despite these warnings, asbestos is still legal and still used in the United States.  Different government agencies have their own rules and regulations for asbestos control to maintain exposure levels in the workplace and the environment.  Those who work directly with asbestos consistently have a higher chance of contracting an asbestos-related disease than those who do not.  Regulations and guidelines have been installed to keep the level of asbestos exposure at a minimum and are necessary among those who are in danger of being exposed in the work place.

Permissible Exposure Limit (PEL)
The PEL is determined by OSHA with the purpose to protect workers against chemical exposures and other harmful substances he or she may be exposed to while on the job. The limit refers to the maximum amount of exposure that is allowed for a given substance and is calculated based upon OSHA’s air contaminant standard and the standard eight-hour work shift. There are approximately 470 PELs for an estimated 300 chemical substances that are considered health hazards.


The PEL for asbestos exposure is 0.1 fibers per cubic centimeter of air over an eight-hour time period, or 1.0 asbestos fiber per cubic centimeter of over a 30-minute period. The infographic to the right shows a tiny white dot of asbestos that is nearly 5 million particles, which in a cubic foot, equals 176 fibers per cubic centimeter. That means the tiny amount of asbestos pictured is actually 1,760 times over the legal PEL. OSHA has reduced the permissible exposure limits four times since setting them in 1971; from 12 fibers per cubic centimeter to what it is today, 0.1.

For more information regarding OSHA regulations on asbestos, refer to the OSHA fact sheet.

Threshold Limit Value (TLV)
The TLV is a guideline set by the American Conference of Governmental Industrial Hygienists. It is meant to provide a limit as to how much a person can be exposed to a certain chemical daily, and not have any adverse health effects. A TLV is based upon the known toxicity of substance in a human or animal and determined by published scientific research and journals that typically focus on occupational medicine, industrial hygiene, and toxicology.  The TLV is not a legal limit, therefore not legally enforceable, but as for the case of asbestos exposure the TLV is the same as the PEL – 0.1 fibers per cubic centimeter.

Preventing Cancer
This month is National Cancer Prevention month, and to prevent cancers like lung cancer and mesothelioma, it is important to educate yourself with the facts regarding where and how you can be exposed to asbestos, and the limits in which you can legally be exposed to. As mentioned before, there is no safe level of asbestos exposure, but studies have shown the amount and frequency of asbestos exposure contributes to your overall cancer risk. Those exposed to higher amounts of asbestos over longer periods of time have a higher chance of developing an asbestos-caused disease.


Gregg Bako, “Exposure limits: PELs and TLVs,” Safety and Health (August 1, 2012). [Link]


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