Damage risk criteria for twenty-four hour noise exposures

Details

• Personal Author:
  Davis, Rickie R.
• Description:
  Why it is important? U.S. Occupational regulations limit the eight hour exposure of workers to noise to 90 dBA or less. The National Institute for Occupational Safety and Health (NIOSH) recommends that workers not be exposed to more than 85 dBA for more than 8 hours per day. The NIOSH Criteria Document (1998) in Table 1-1 lists a Permissible Exposure Level of 80 dBA for 25 hours 24 minutes. There are occupations and situations where workers may be in an environment in which exposures may last 24 hours or even longer. What is known? Long term noise exposure research was primarily conducted in the period from 1960-1980 to determine contributing factors to noise-induced permanent threshold shift (PTS). Since it is unethical to induce a PTS in a human all of this research was conducted by inducing a TTS of 30 dB or less. (Parallel animal PTS research was being conducted at this time.) The overarching assumption is that TTS measured at 2 minutes post-exposure is a predictor of noise-induced PTS. After 8-16 hours of continuous noise exposure temporary threshold measures asymptote producing an Asymptotic Threshold Shift (ATS). The assumption is that because the ear is reacting to acoustical energy the ultimate PTS will not exceed the ATS. It has been suggested that ATS predicts the level of PTS after 10-20 years of constant occupational noise exposure. For a comprehensive review of the logic associated with the ATS research Melnick (1991) is recommended. In the late 1970's the Air Force in conjunction with EPA and NASA did a series of controlled 24 and 48 hour noise exposures. Nixon et al. (1977) did long duration (24- and 48-hour) noise exposures of 85 dBA pink noise. They found that in both exposures, ATS occurred at 8-16 hours into the exposure but that recovery from ATS was prolonged in the 48 hour exposure. Based on their data the authors suggest that a noise exposed person should be given the same amount of time to recover in quiet as the time exposed. Based on their exposures they recommend that long-term exposures in excess of 90 dBA should be avoided. [Description provided by NIOSH]
• Subjects:
  Hearing Hearing Loss Hearing Loss, Noise-Induced Noise Noise, Occupational Occupational Health Risk Assessment Risk Factors Safety Workplace
• Keywords:
  Acoustics Exposure-levels Exposure-limits Hearing-impairment Hearing-level Hearing-loss Hearing-threshold Noise-exposure Noise-induced-hearing-loss Noise-sources Risk-factors Sound-attenuation Work-environment Workers

  More +
• Publisher:
  Department of Defense Hearing Center of Excellence
• Document Type:
  Text
• Genre:
  Newsletter
• Place as Subject:
  Ohio ; OSHA Region 5
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DART - Division of Applied Research and Technology
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  8-12
• Volume:
  4
• NIOSHTIC Number:
  nn:20046991
• Citation:
  Pharm Interv Hear Loss 2015 Sep; 4:8-12
• Federal Fiscal Year:
  2015
• NORA Priority Area:
  Construction ; Manufacturing
• Peer Reviewed:
  False
• Source Full Name:
  Pharmaceutical Interventions for Hearing Loss
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:285d20ef1fd2c12b564e4d5202073bb5fa0b0566772a0711bbbd972c12e48b813afe787c2d827a6a70d1243ee799f59d821bee62021896b65313ce49216bc74a
• Download URL:
  https://stacks.cdc.gov/view/cdc/202235/cdc_202235_DS1.pdf
• File Type:
  [PDF - 726.41 KB ]