Choosing the Right Exposure Standard-January 2012

Monthly Round Up of Important Ideas and Standards in
Industrial Hygiene and Safety 

January 2012 

IN THIS ISSUE: Choosing the Right Exposure Standard

Choosing the right exposure standard can be confusing. When evaluating workplace exposure, industrial hygienists rely on various occupational exposure limits set by regulatory standards and reference guides. The purpose of these standards is to protect workers against the health effects of short-term and long-term exposure to hazardous materials.

Workplace Exposure Standards

  • Permissible Exposure Limits (PEL).  The Occupational Safety and Health Administration sets PELs. These standards are the most well known in the United States and are enforceable by law. Because PELs are a legal exposure limit, the rulemaking process involves the input of all affected parties. It is not based solely on current scientific data. In the 1990s, revision of PELs was overturned by the courts, leaving most unchanged since 1968. (Visit for more information on PELs.)
  • Threshold Limit Values (TLV). The American Conference of Governmental Industrial Hygienists (ACGIH) sets TLVs. According to the ACGIH, these benchmarks are based on science and are intended to “protect nearly all workers that may be repeatedly exposed, day after day, over a working lifetime, without adverse health effects.”  (Visit for more information on TLVs.)
  • Recommended Exposure Limits (REL). The National Institute of Occupational Safety and Health sets RELs. Like TLVs, RELs are not enforced by regulatory agencies and are based on current scientific evidence. Under the OSHA Act, the NIOSH is to “describe exposure levels that are safe for various periods of employment, including but not limited to the exposure levels at which no employee will suffer impaired health or functional capacities or diminished life expectancy as a result of his work experience.” (Visit for more information on RELs.)

Limitations of Exposure Standards

Every exposure standard has limitations. Industrial hygienists and other safety professionals do not rely solely on OSHA because the PEL may not be the safe limit which protects workers from harm. Results may vary due to employee differences, changes in operations, small sample population, error in collection, limitations on testing methods, etc. Accordingly, many industrial hygienists recommend protective measures and/or follow-up testing when results approach 50 percent of the limit. 

Exposure standards are an important tool in protecting the safety and health of your employees. For more information on this topic and to discuss your company’s safety and industrial hygiene needs, call OccuSafe at (214) 662-6005 or (303) 219-6973, or visit us at

OccuSafe Industrial Hygiene & Safety, Inc. provides skills and expertise to recognize, evaluate, and control hazards and injuries in the areas of industrial hygiene, occupational safety, and health. OccuSafe services companies of all sizes in a range of industries. 

This newsletter is published monthly by OccuSafe Industrial Hygiene & Safety, Inc. Feel free to forward it to friends and colleagues.



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