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.

February 11, 1987

Mr. William B. Arnold
Brown and McDonnell
P.O. Box 1403
Biloxi, Mississippi 39533

Dear Mr. Arnold:

Please accept my apologies for the delay in responding to your letter of December 4, 1986, in which you requested information on Hydro Carbide Tungsten, otherwise known as cemented tungsten carbide with cobalt binder.

In your letter you specifically asked for "...all research material that went into the issuance of the warning that this product has the potential for causing transient or permanent respiratory diseases including occupational asthma and interstitial fibrosis." The Occupational Safety and Health Administration (OSHA) has not issued any such warning, and does not currently regulate tungsten carbide, per se. Cemented tungsten carbide, or "hard metal," is actually a mixture of tungsten carbide, cobalt, and sometimes other metals, such as titanium, or vanadium, and metal oxides or carbides. Hard metal generally consists of about 80 percent tungsten carbide, with the cobalt content ranging from 10 - 25 percent. When the cobalt content of hard metal is greater than two percent, the National Institute for Occupational Safety and Health (NIOSH) recommended that such mixtures be subject to the OSHA standard for occupational exposure to cobalt of 0.1 milligrams of cobalt (metal fume and dust) per cubic meter of air (0.1 mg/m3) as averaged over a workshift of up to 10 hours is a 40 hour work week. This NIOSH recommendation is based on their finding that for mixtures containing in excess of two percent cobalt, the contribution of the cobalt to the overall potential health hazard is greater than that of tungsten carbide and all other components.

Because I believe that the source of the "warning" to which you have referred may be the information provided under the heading "Health Hazard Data - Effects of Overexposure," as it appears on the Fansteel Company's Material Safety Data Sheet (MSDS) which you sent me, I suggest that you contact them with your request.

I have enclosed the following information on this substance which I think may be of use to you:

- An MSDS on Tungsten Carbide (cemented with cobalt binder) prepared by the Genius Publishing Corporation;

- A research paper (referenced is section 6 of the Genius Publishing Corporation MSDS) entitled "Case Reports: Cobalt Lung in Diamond Polishers" by N. Demedts, et al., published in the American Review of Respiratory Disease in 1984;

- A research paper entitled "Respiratory Disease in Tungsten Carbide Production Workers" by Dr. Nancy L. Springs, et al., published in CHEST in 1984; and

- A research paper entitled "Diffuse International Lung Disease in Tungsten Carbide Workers" by Drs. E. Osborne Coates, Jr. and John H. L. Watson, published in the Annals of Internal Medicine in 1971.

In addition, NIOSH published two documents of relevance to your request that may be helpful to you. They are the NIOSH "Criteria for a Recommended Standard for Occupational Exposure to Tungsten and Cemented Tungsten Carbide (NIOSH Publication No. 77-227) and their Occupational Hazard Assessment: Criteria for Controlling Occupational Exposure to Cobalt" (NIOSH Publication No. 82-107). Copies of these documents may be obtained by contacting NIOSH at the following address:

NIOSH Publications
4676 Columbia Parkway
Cincinnati, Ohio 45226

In your letter you also asked for any additional information we might have concerning the use of respiratory protective devices. I have enclosed a copy of the OSHA General Industry standard for respiratory protection, 29 CFR 1910.134, which delineates per requirements for the occupational use of respirators. I have also enclosed copies of two documents published by the American National Standards Institute (ANSI, a private group that published voluntary consensus standards which do not hold the force of law) that you may find useful. They are ANSI Standard Z88.2 -1980, "American National Standard Practices for Respiratory Protection," and ANSI Standard Z88.6 - 1984, "American National Standard Practices for Respiratory Protection." In addition, a good source for basic information on respiratory protective devices is the publication entitled "A Guide to Industrial Respiratory Protection" by John A. Pritchard, developed under contract at the Los Alamos Scientific Laboratory of the University of California. This document is available for a small fee from the National Technical Information Service (NTIS) and carries the document number U.S.G.P.O. 1977-777-018/32. The address for NTIS is:

National Technical Information Service
U.S. Department of Commerce
5285 Fort Royal Road
Springfield, Virginia 22161

I hope this reply will be of use to you. If we can be of any further assistance, please feel free to contact us again.


Richard D. Edsell
Office of Science and Technology Assessment