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 http://www.osha.gov.

June 30, 1976

 
MEMORANDUM FOR: OSHA REGIONAL ADMINISTRATORS
 
FROM: MORTON CORN
Assistant Secretary of Labor
 
SUBJECT: Interpretation of Allowable Airborne Concentrations of Mercury
 

29 CFR 1910.1000, Table Z-2 contains the ceiling value for mercury. Historically the values in this table relate to the maximum allowable concentrations defined by ANSI as 8 hour time-weighted average.

Therefore, the allowable airborne concentration of mercury shall be interpreted as 0.1 mg/m(3) as determined on the basis of the full shift time-weighted average.