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.

April 1, 1999

Mr. Melvin E. Cassady, CIH
Cassady Safety and Health Services, Inc.
355 Concord Circle
Southampton, PA 18966

Dear Mr. Cassady:

Thank you for your letter dated September 2, 1998, addressed to Charles Jeffress, Assistant Secretary for the Occupational Safety and Health Administration (OSHA) on behalf of the Brass Division of Olin Corporation, seeking an interpretation of OSHA's Permissible Exposure Limits (PELs) for copper and zinc fume and dust. We apologize for the delay in providing this response.

In your letter you stated that you are representing the Brass Division of the Olin Corporation and you believe it is appropriate to air sample for copper and zinc fume by using a 10mm nylon cyclone or other particle fractionation device and to sample for the dust by using a 37mm closed-faced MCEF. You further state that the health effect resulting from exposure to zinc and copper oxide fumes is metal fume fever and that there is only one case of metal fume fever documented in the literature for copper fume. You therefore are requesting OSHA to clarify its position on the appropriate air sampling method for determining compliance with the OSHA permissible exposure limits (PELs) for copper and zinc oxide fume and dust exposure.

With respect to copper fume, OSHA is not persuaded by your argument that samples of only respirable copper oxide particles should be collected when employee exposure to copper fume is evaluated because the principal health effect of the exposure is metal fume fever. The origin of the OSHA PEL for copper fume, as well as the OSHA PEL for copper dusts and mists and the OSHA PELs for zinc oxide fume and zinc oxide total dust, is the 1968 booklet of threshold limit values (TLVs) issued by the American Conference of Governmental Industrial Hygienists (ACGIH). The documentation for these OSHA PELs, except the OSHA PEL for zinc oxide total dust, is contained in the 1966 edition of Documentation of TLVs issued by ACGIH. The PEL for copper fume applies to all copper oxide particulate that originates as copper fume, as well as to copper fume itself. The documentation of the copper fume PEL lists several health effects including metal fume fever, irritation of the upper respiratory tract, nausea, and metallic or sweet taste. The TLV was set at 0.1 milligrams of copper per cubic meter of air because this level would be sufficiently low in most cases to reasonably prevent pulmonary irritation from the copper fume. Since copper fume poses a hazard when deposited anywhere in the respiratory tract, samples of total copper oxide particulate must be collected to determine employee exposure to copper fumes.

With respect to zinc oxide fume, OSHA concurs that the PEL was set to prevent metal fume fever. OSHA has concluded that employee zinc oxide fume exposure measurements must be based on a total particulate air sampling procedure. While the documentation for OSHA's zinc oxide fume PEL did not specify the type of sampling that was done for determining the correlation between zinc oxide fume exposure and the occurrence of metal fume fever, it can be normally assumed that total particulate sampling procedures were used. Thus, if total particulate sampling procedures were used for establishing the OSHA PEL for zinc oxide fume, then those same sampling procedures must be used for determining compliance with the PEL.

The PEL for zinc oxide fume covers all zinc oxide particulate matter that originates as zinc oxide fume and has not yet settled out of the air. All solid zinc oxide aerosols existing by other means are considered dust particles covered under the zinc oxide total dust PEL and the zinc oxide respirable dust PEL.

We appreciate the opportunity to clarify this matter for you. If you have further questions, you may contact Mr. Gail Brinkerhoff of OSHA's Office of Health Compliance Assistance at (202) 693-2190.


Richard E. Fairfax
Directorate of Compliance Programs