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 13, 1998

Ms. Katerina Eftimoff
Porter, Wright, Morris & Arthur
41 South High Street
Columbus, Ohio 43215-6194

Dear Ms Eftimoff:

Thank you for your letter of May 1, to the Occupational Safety and Health Administration (OSHA) regarding the definition of a mixture under the Hazard Communication Standard (HCS), 29 CFR 1910.1200. You asked OSHA to make the determination of whether your client's product, Iroblast, is a "mixture" as defined by the standard. Please excuse this delay in our response.

OSHA does not make hazard determinations on a case-by-case basis, since it is the manufacturer who is most familiar with a product's composition, its intended uses, and the potential downstream exposures. We are not generally involved in the hazard determination process until it is brought to our attention that the manufacturer's MSDS may be incomplete or inadequate.

Regardless of the outcome of the manufacturer's determination of Iroblast as a "mixture" or a "single substance," all information listed under paragraphs [1910.1200(g)(2)(i) - 1910.1200(g)(2)(xii)] must be included on the MSDS. Since the use of Iroblast, as stated in your letter, presents hazardous exposures to employees during its intended use, these exposures, their health effects, and all other required information must be reported on the MSDS. We offer the following guidance for your client in making the determination of whether this product is a mixture or a chemical:

  1. A hazardous chemical is considered a mixture if the components retain their chemical identity after being combined. In this case, the components can be separated by mechanical means (evaporation, distillation, abrasion, etc.).
  2. A chemical reaction results in a change in the arrangement of atoms or molecules to yield substances of different composition and properties. When chemical reactions occur, the original components can not be separated by mechanical means.



We trust that this information is useful to you. Further questions can be directed to [the Office of Health Enforcement at (202) 693-1850].


Richard E. Fairfax
Acting Director
Directorate of Compliance Programs

[Corrected 10/20/06]