Occupational Safety and Health Administration
Occupational Safety and Health Administration

The Permissible Exposure Limits (PELs) are limits for occupational exposure issued by the United States Occupational Safety and Health Administration (OSHA).

The PEL or OSHA PEL is a legal, regulatory limit on the quantity or concentration an employee can be exposed to, such as Respirable Crystalline Silica (RCS) in the air. The levels are usually based on an average weighted time (TWA) of eight hours, although some levels are based on short-term exposure limits (STEL). A STEL addresses the average exposure over a 15 to 30 minute period of maximum exposure during a single work shift.

Read related article here OSHA PUBLISHES SILICA FAQ

Chemicals are usually regulated in parts per million (ppm), or sometimes in milligrams per cubic meter (mg / m3). Measurement units for physical agents such as noise are agent-specific.

A Time-Weighted Average (TWA) is usually the average exposure to any hazardous gas at work based on an eight-hour workday or 40-hour work week. It is the maximum amount to which one can be exposed without significant adverse effects on health during that period. The worker may not re-enter the space for the remainder of the day once the TWA has been exceeded.

Although the STEL is a permissible average exposure over a short period, usually 15 minutes, and should not be exceeded more than four times a day if the weighted average time is not exceeded. If the predetermined limit is exceeded, the worker must remove himself for at least one hour from the hazard.

However, many OSHA ‘s PELs are outdated and inadequate to ensure the protection of workers ‘ health, since most OSHA ‘s PELs were issued shortly after the Occupational Safety and Health Act was adopted in 1970, and have not been updated since then.

Employers are to take into account the use of alternative occupational exposure limits as recommended by OSHA since the Agency considers that exposures above some of these alternative occupational exposure limits may be dangerous for workers, even if the exposure levels are by the relevant PELs.


What’s the alternative?

OSHA recognized that many of its PELs were outdated and inadequate for ensuring the protection of worker health. OSHA created new annotated tables, and are located at this weblink -> https://www.osha.gov/dsg/annotated-pels/

The following are examples of alternative approaches to chemical management:

  1. Informed substitution to safer chemicals and processes: Use the latest hazardous chemicals information to inform employers about safer substances and non-chemical alternatives.
  2. Hazard Communication and GHS S: Use the classification system HazCom 2012 as a tool for the classification and control of hazards.
  3. Health hazard banding: Organizes hazard groups or groups of chemicals with similar toxicities. Hazard banding in combination with worker exposure information can be a useful tool for assessing risks if toxicity data are not available.
  4. Occupational exposure banding: A method proposed by NIOSH for the evaluation of chemicals; the method classifies chemicals into five bands, each band representing a different level of hazard.
  5. Control Banding: Use label hazard statements and safety data sheets as guidelines for chemical controls.
  6. Task-based exposure assessment and control Categorizes work tasks in terms of exposure potential and implements controls to reduce exposure to safe levels.

This blog was written by Linda Rawson, who is the founder of DynaGrace Enterprises (dynagrace.com), an authorized distributor of the Nanozen DustCount 8899.  For further information, please connect with Linda on LinkedIn, or contact her at (800) 676-0058 ext 101.