March 11, 2013

Mr. David Croft
United States Mint
U.S. Department of the Treasury
Denver, CO 80204

Dear Mr. Croft:

This letter is to follow up on the interim letter sent to you dated June 1, 2012, by the Occupational Safety and Health Administration (OSHA). We apologize for the delay. In your original June 28, 201l, letter you requested guidance on implementing your hearing conservation program (HCP) in compliance with the OSHA standard for occupational noise exposure, 29 CFR 1910.95. Your paraphrased scenario and questions are presented below, followed by our responses.

Background: The Denver Mint has over 300 employees who are currently enrolled in the HCP. In 2011, the Denver Mint began administering employee audiograms using a new audiometer equipped with insert earphones. Comparative audiograms for over 200 employees were not conducted using the supra-aural earphones which were used to measure these employees' baselines. Subsequently, it was brought to your attention that an OSHA letter of interpretation addressed to Dr. Fredrik Lindgren dated August 31, 1993, stated that at the time of conversion from supra-aural earphones to insert earphones, testing must be performed with both types of earphones. It is your belief that audiometric testing with insert earphones is more reliable, more hygienic, and more user-friendly. In addition, since 1993 when OSHA's interpretation was issued, the technology of insert earphones has surpassed that of previous testing methods.

Question 1: Will OSHA modify or rescind the Lindgren letter?

Response: Yes, the 1993 letter of interpretation to Dr. Fredrik Lindgren will be rescinded and archived. In consultation with the National Institute for Occupational Safety and Health (NIOSH), OSHA has been made aware of comparative studies that show the results of audiograms using both methods. Based on scientific developments and accepted practices in audiometric testing, NIOSH recommends that insert earphones may be used interchangeably with supra-aural earphones for obtaining audiograms. OSHA's original concern with audiometric testing using insert earphones was not whether they were reliable, hygienic or user-friendly. Rather, the concern was the ability to compare baseline audiograms conducted using supra-aural earphones with annual audiograms conducted using insert earphones.

Therefore, the Lindgren letter no longer reflects OSHA's current interpretation and enforcement policy on conversion from supra-aural earphones to insert earphones for audiometric testing in compliance with 29 CFR 1910.95.

Question 2: Does OSHA require retesting of all employees that have not received side-by-side testing, or can a percentage of these employees be tested if results are equivalent?

Response: Since OSHA is modifying its current policy, employees will NOT have to be retested with both types of earphones so that valid comparisons to their baseline audiograms may be made. The two original issues associated with insert earphones, according to NIOSH, were lack of well-established calibration procedures and correct identification of a standard threshold shift (STS) with the amount of ambient noise present in the test room. The first issue was addressed with the change to the American National Standards Institute (ANSI) consensus standards ANSI S3.6-1989 to ANSI S3.6-2010, which includes updated calibration procedures. With respect to the second issue, new data show that the threshold differences between supra-aural and insert earphones are unlikely to cause difficulty in correctly identifying an STS. Insert earphones may be used interchangeably with supra-aural earphones for obtaining audiograms. However, the employer should recognize the potential for discrepancies at the lower test frequencies (i.e., 500 and 1000 Hz). As a federal agency, if you believe the U.S. Mint is providing equivalent or more stringent protection to its employees than is required by the Occupational Noise Exposure standard, please refer to 29 CFR 1960.17, titled "Alternate Standards" for additional information.

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA's requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA's interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA's website at http://www.osha.gov. If you have further questions, please feel free to contact the Directorate of Enforcement Programs at (202) 693-2100.

Sincerely,

Thomas Galassi, Director
Director of Enforcement Programs

cc: Greg Baxter, Regional Administrator, Denver Regional Office