Archive Notice - OSHA Archive

NOTICE: This is an OSHA Archive Document, and may no longer represent OSHA Policy. It is presented here as historical content, for research and review purposes only.

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

August 30, 1982

Mr. Dennis Averill
Safety and Industrial Hygiene
Department American Cyanamid Company
Bloomingdale Plant
Havre de Grace, Maryland 21078

Dear Mr. Averill:

Thank you for your letter of July 30, 1982, in which you requested clarification and documentation of the Occupational Safety and Health Administration's (OSHA) Permissible Exposure Limit (PEL) for chromates.

The OSHA standard for chromic acid and chromates that is found in 29 CFR 1910.1000, Table Z-2, was adopted from the American National Standards Institute (ANSI) standard, Z-37.7 (1971). The ANSI standard limits the maximum allowable concentration of chromic acid mist and dust of chromates and dichromates of the alkaline earth metals to 1 milligram of chromic acid anhydride (Cr03) in 10 cubic meters of air (0.1 mg/m3 as Cr03) for exposures not exceeding a total of eight hours daily.

After recognizing the error of printing the PEL under the column for ceiling values rather than under the column for 8-hour time-weighted averages (TWA), OSHA issued an interpretation of Table Z-2 standards in the Industrial Hygiene Field Operations Manual. This interpretation states, "The last two entries in Table Z-2 'mercury' and 'chromic acid and chromates,' should be considered as 8-hour TWA standards and not ceiling standards."

Regarding the OSHA standard for strontium chromate, since strontium is an alkaline earth metal, the standard for chromic acid and chromates listed in 29 CFR 1910.1000, Table Z-2, is applicable to strontium chromate. As stated above, the standard for chromic acid and chromates is a TWA rather than a ceiling value.

Finally, regarding whether the standard is based on chromium measured as Cr or Cr03, the standard for chromic acid and chromates is based on chromium measured as Cr03 (chromic acid anhydride or chromium trioxide). It should be noted that in situations where the cation in a chromate compound has a lower PEL than the chromate radical, then the lower PEL would be the applicable limit (e.g., for lead chromate, one should use the PEL for Pb rather than Cr03).

Per your request, please find enclosed a copy of the ANSI Z-37.7 (1971) and page II- 5 of the OSHA Industrial Hygiene Field Operations Manual. We hope that the above information will be helpful to you.


R. Leonard Vance, Ph.D.
Directorv Health Standards Programs