8-hour total weight average (TWA) permissible exposure limit (PEL).
OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.
October 6, 1995
Mr. Mark Nicas
University of California
Environmental Health Sciences
School of Public Health
140 Warren Hall
Berkeley, California 94720-7360
Dear Mr. Nicas:
This is in response to your letter of July 7, addressed to Mr. Joseph A. Dear, Assistant Secretary for the Occupational Safety and Health Administration (OSHA), requesting an interpretation on 8-hour total weight average (TWA) permissible exposure limit (PEL) as defined in 29 CFR 1910.1000 and in other substance-specific health standards.