Is My Air Safe? Understanding Occupational Exposure Levels

As a Certified Industrial Hygienist (CIH), I frequently interpret air sampling results for my clients.  I recently received a call from a conscientious safety manager who was struggling to interpret some results.  While many managers just want to verify they are compliant with OSHA regulations, this manager asked a different question – “Is my air safe?”  To answer that question, one needs to look a bit further than OSHA’s PELs.

Permissible Exposure Limits (PELs) are promulgated by OSHA and by state agencies (in state plan states).  The PELs are legally enforceable, but most have not changed since they were first promulgated in the 1970s.  The regulatory process has to address factors such as health effects, economic and technical issues, and ability to determine compliance.  As a result, the update process is slow and PELs in general have not kept up with the times.

Two organizations in the US provide occupational exposure level (OEL) recommendations that are not legally enforceable, but are based on updated scientific research and studies.  The National Institute of Occupational Safety & Health (NIOSH) (a department of the CDC) publishes Recommended Exposure Limits (RELs).  “NIOSH…REL[s] [are] based on risk evaluations using human or animal health effects data, and on an assessment of what levels can be feasibly achieved by engineering controls and measured by analytical techniques.”  NIOSH continually conducts research and updates RELs accordingly.

The American Conference of Governmental Industrial Hygienists, (ACGIH) publishes annual Threshold Limit Values (TLVs).  This member-based professional organization advances knowledge on occupational and environmental health.  TLVs are based on peer reviewed scientific literature and provide exposure levels at which no adverse health effect would be observed in a typical worker.  TLVs are health based and do not consider economics or technical feasibility.

After a little research and a bit of discussion with my client I was able to show him that his contaminant levels were below the PEL, REL, and TLV, and that even though there were traces present, they would not adversely affect his employees. 

 Eric Hartman, CIH, Operations Manager  – Seattle, WA

Tags: ACGIH, American Conference of Governmental Industrial Hygienists, IAQ, indoor air quality, NIOSH, Occupational Exposure Limits, OSHA, OSHA compliance, PELs, permissible exposure limits, Recommended Exposure Limits, RELs, Threshold Limit Values, TLVs