September 26, 2001

Mr. Russell Umbraco
CALICO Lab Manager
California Department of Industrial Relations
Division of Occupational Safety and Health
1555 Doolittle Drive, Suite 140
San Leandro, CA 94577

Dear Mr. Umbraco:

Thank you for the questions you posed in June via e-mail to Robert Williams, Director, Cincinnati Technical Center. Those questions were forwarded to us through our Directorate of Health Standards. This letter constitutes OSHA's interpretations only of the requirements discussed. Your specific questions regarding OSHA's Occupational Noise standard, 29 CFR 1910.95, are restated below along with our responses.

Question:  What criterion level should be used for hearing conservation amendment? Some people believe it should be 90 decibel (dBA) and others think it should be 80 dBA.

Reply:  OSHA uses a 90 dBA criterion level, hence the 8-hour time weighted average (TWA) of 85 dBA being equal to a 50% dose. The American National Standards Institute's (ANSI's) S12.19 (1996), "Measurement of Occupational Noise Exposure," defines the criterion sound level as, "[t]hat constant sound level in decibels (dBA), which, if it continues for the criterion duration, would provide 100% of an employee's allowable noise exposure."

Question:  California regulations set the dosimeter threshold level at 80 dBA for hearing conservation and 90 dBA for compliance. Does the same distinction apply under Federal OSHA, or is it only the 80 dBA threshold?

Reply:  Federal OSHA uses the 80 dBA threshold to determine compliance with the hearing conservation provisions, and the 90 dBA threshold to determine compliance with the permissible exposure level (PEL).

Question:  What were the reasons for choosing the 80 dBA and 90 dBA threshold levels?

Reply:  The lower 80 dBA threshold was chosen to facilitate the proper identification of employees who need to be included in the hearing conservation program. This limit is consistent with accepted measuring techniques for dosimeters. According to ANSI, the lower threshold of a dosimeter should be 5 dBA below the level for which the measurements are being taken. For hearing conservation, the level was set at 85 dBA, or the equivalent noise dose of 50%, because the evidence suggests that a large percentage of the population whose exposures exceed this level over a working lifetime will incur noise-induced hearing loss. This level is also consistent with other OSHA health standards in setting an action level at half the PEL.

Please be aware that during the revision period, the period during which OSHA conducted rulemaking to establish the new provisions of the Hearing Conservation Amendment, only that section, 1910.95(b)(3), was opened for revision. Therefore, because the 90 dBA threshold level was retained for all other provisions of the remaining standard, no exposure below 90dBA can be used for documentation of 1910.95(a) and (b)(1) violations.

Thank you for your interest in occupational safety and health. 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 Compliance Assistance at (202) 693-2190.

Sincerely,




Richard E. Fairfax, Director
Directorate of Compliance Programs

cc:
Steve Witt, DIT
Bob Williams, Director, Cincinnati Technical Center
Bill Perry, HSP
John Barry, Region I