May 8, 2003

Ms. Linda Ballas
Linda Ballas & Associates
4413 Copper Creek Lane
Toledo, OH 43615

Dear Ms. Ballas:

Thank you for your January 21 letter to the Occupational Safety and Health Administration (OSHA) regarding the Occupational Noise standard. In your letter, you requested a clarification about how baseline audiograms should be revised. You also pointed out that two of our letters of interpretation provide contradictory guidance and are causing confusion among hearing associates. A corrected response appears below.

The Occupational Noise Standard, 29 CFR 1910.95, requires employers to establish and maintain an audiometric testing program for all employees whose exposures equal or exceed an 8-hour time-weighted average (TWA) of 85 decibels on the "A" scale (dBA). Annual audiograms are compared to the baseline audiogram to determine if hearing loss is occurring.

If a standard threshold shift (STS), defined as an average of 10 dBA or more at 2000, 3000, and 4000 Hz, occurs in either ear, the employer must follow certain procedures outlined in the standard, including notifying the affected employee in writing. Hearing loss cases that meet specific criteria must be recorded on the OSHA 300 log according to the recordkeeping requirements of 1904.10.

With regard to your request for a clarification as to how to revise the baseline, OSHA allows employers to revise the baseline by substituting the annual audiogram for the baseline audiogram when the reviewing professional determines that an STS is persistent. Such a revision would serve to prevent the same STS from being identified repeatedly for an employee whose hearing has stabilized. As a corollary, an annual audiogram may be substituted for the baseline audiogram when thresholds have significantly improved.

When the professional evaluating the audiogram determines that a baseline revision is appropriate, whether due to a persistent STS or improved thresholds, the baseline must be revised for each ear separately. For example, although an employee's annual audiogram shows hearing thresholds deteriorating in both ears simultaneously, occasionally an audiogram will show that an employee is suffering an STS in only one ear. This can sometimes be attributed to working near a loud noise source that is close to the affected ear. If such a shift is shown to be persistent in the judgment of the professional evaluating the audiogram, then the baseline audiogram may be revised due to the persistent STS. A baseline audiogram that shows a persistent shift for only one ear may be revised for only that ear. The baseline may not be revised for the other unaffected ear. This procedure is required because it provides a clear indication of how each ear is affected by noise.

Thank you for your interest in occupational safety and health and bringing these letters to our attention. The erroneous 1996 letter to Mr. Dean Harris will be removed from our website shortly. We hope you find this information helpful. 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 http://www.osha.gov. If you have any further questions, please feel free to contact the Office of Health Enforcement at (202) 693-2190.

Sincerely,

Richard E. Fairfax, Director
Directorate of Enforcement Programs