Sunday, May 3, 2015

OELs: The “HOT” Topic at this year’s AIhce in Salt Lake City

Those of you who read this blog regularly know that I am very interested in exposure limits, especially Occupational Exposure Limits (OELs).   They represent literally half of the risk assessment process done by most Industrial Hygienists when they compare the exposures they measure (EXP) to the OEL in the classic hazard index (HI) = EXP/OEL.     HI >1  L  HI < 1  J

As such, OELs are critical to the IH profession.
The histories of OELs as a whole is that they have almost invariably have come DOWN in value with time.  Indeed, I can only think of a single example where an OEL went UP.   That fact indicates to me that we have not done a particularly good job of understanding and explaining the uncertainty associated with our OELs.

Understanding the uncertainties associated with OELs and communicating the nature and size of the uncertainty as a part of the documentation has been a point I have been trying to make for some time.

In June I get to present some of these ideas again at the 2015 American Industrial Hygiene Conference & Exposition (AIHce) in Salt Lake City May 30 – June 4, 2015.

On Sunday, starting a 8am, I get to teach a Professional Development course with my friend and colleague Dr. Andy Maier (University of Cincinnati) and Dr. Dan Arieta (Chevron Phillips).   These folks are are a rare breed in the ranks of Industrial Hygiene;  namely, they are board certified toxicologists.  For my part,  I am less expert in the realm of toxicology by very enthusiastic about the subject as it relates to OELs.   The title of the PDC is:  The Hierarchy of Occupational Exposure Limits (OELs): A Suite of Tools for Assessing Worker Health Risk  (PDC402).    Some discussion topics with the presenters in this PDC are shown below:
Why the OEL Hierarchy Concept
Concepts of Toxicology for OEL users
The WEELs Keep Turning -  Setting Traditional OELs
To Be a Savvy OEL User – OEL Limitations
Activity - The Great OEL Debate
OEBs and other hazard-based techniques
Risk-Based OELs

On  Monday morning I get to talk about Risk Based OELs and the Risk@OEL during a Science Symposium Session entitled Occupational Exposure Banding (OEBs): The Solution for the Glacial Pace of OELs  from 10:30 am to 12:50 am.   The title of my talk will be:  Risk@OEL: An Approach to Conduct Tier 3 OEBs

My last presentation is Roundtable RT236 "Toxicological Challenges to the Derivation and Application of Occupational Exposure Limits (OELs)".   It will happen on Wednesday afternoon from 1 to 4:30pm.  I will be talking about  Aligning Occupational Exposure Limits (OELs) with Exposures, especially as they relate to bolus exposures.

I will write about the bullet points of these talks and offer the slides from them in future blogs.   In the meantime,  I am looking forward to meeting some of you at these events and hearing from you about what future topics you want to see in this blog and about what aspects of OELs are important to you.     


  1. I'm looking forward to your presentations, Mike! And I'm very happy that you agreed to participate in the toxicological challenges roundtable—your insight on the topic will be very useful.

    It is always great to see presentations around the derivation of OELs at AIHce, particularly as the science of dose–response assessment evolves. Greater opportunities provided to industrial hygienists to be able to understand the science behind OEL derivation are helpful, as it can improve the application of OELs by end-users. I'm also hopeful that a greater interest in the scientific basis of OELs might lead to continued increases in transparency in their derivation.

  2. Hi Mike, an old analysis by Roach and Rappaport (1990) ( suggests that OELs are often not based on science or risk but instead on achievability in the workplace. Not sure if that has changed much in the past 25 years.