The names answer the question:  The Permissible Exposure Limit is the regulatory limit established by OSHA at 29 CFR 1910 Subpart Z.  All PELs are based on a time weighted average (TWA) for an 8-hour day and a 40-hour work week.  NIOSH publishes Recommended Exposure Levels based on a 10-hour work day and a 40-hour work week.

To step away from a work place for a minute, my daughter learned that driving on an icy bridge at the posted speed limit, skidding on the ice, smashing into the bridge, and tying up traffic for two hours still gets the driver a ticket for driving too fast for conditions.  It was recommended by the judge that she slow down under difficult or adverse conditions.

Given the adverse outcomes reasonably anticipated from exposure to benzene, I would recommend that work place exposure is kept below the posted limit.

The legal status of the exposed workers in one thing.  The moral status of the safety personnel who had a role in controlling exposures is another matter.  Put another way, what do you say to the survivors?  “We were fully in compliance with the regulatory PEL, sorry about the health condition of your father/mother/brother/sister?”

George Walton

Reactives Management Corporation

757-436-1033

From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**list.uvm.edu] On Behalf Of Jim Tung
Sent: Friday, December 03, 2010 4:23 PM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: [DCHAS-L] OHSA/NIOSH Permissible limits

Hello, all:

When the NIOSH pocket guide has different permissible limits (NIOSH versus OSHA), which is the better one to follow?

For example, benzene's limit for NIOSH is 0.1 ppm (10 hr workday), while OSHA's limit is 1 ppm (8 hour workday.)

Why the difference? From a legal perspective, which is a better choice?

Thanks in advance for any advice you might give; obviously, any advice people might give is non-binding, you're not responsible, legal mumbo-jumbo, blah, blah.

Cheers, Jim Tung

Lead Hazardous Waste Coordinator
Obiter Research LLC
Champaign, IL