What is the difference between the NIOSH recommended noise exposure limit v. OSHA permissible noise exposure limit?
The US National Institute for Occupational Safety and Health (NIOSH) has a recommended standard for all industries (Centers for Disease Control and Prevention/NIOSH publication 98-126). This standard specifies an 85 dBA Recommended Exposure Limit (REL), and makes specific recommendations on the key elements of an effective hearing conservation program. The NIOSH standard is consistent with the exposure guidelines used by most scientific and regulatory bodies internationally, but NIOSH is not a regulatory agency and thus the standard is not mandated by law. It is designed to represent best scientific practice.
The US Occupational Safety and Health Administration (OSHA) exposure limit is regulatory - this is law and must be complied with. The NIOSH and OSHA limits are the two commonly used in the United States.
The graph below compares these two limits. As you can see, OSHA permits a worker to be exposed to 85 dBA for an allowable time of 16 hours per day. The NIOSH recommended allowable time for 85 dBA is 8 hrs per day. In addition to using a lower exposure limit than OSHA, the NIOSH standard uses a more protective 3 dB exchange rate that results in shorter allowable exposures at high noise levels than those of the OSHA regulation. For example, OSHA permits an exposure to 105 dBA for one hour per day, while NIOSH recommends that such an exposure last less than 5 minutes.
Hearing conservationists may be surprised to learn that neither the OSHA nor NIOSH limit is designed to protect every worker from suffering any NIHL. However, the NIOSH standard is the more health-protective limit of the two. For example, NIOSH estimates that approximately one in four workers exposed at the 90 dBA OSHA PEL eight hours per day over a 40 year working lifetime will suffer a compensable hearing loss from noise, compared to only about one in twelve workers exposed at the 85 dBA NIOSH REL.
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Rick Neitzel is a Research Scientist in the University of Washington (UW) Department of Environmental and Occupational Health Sciences and a Certified Industrial Hygienist. He is also a Candidate in the Environmental and Occupational Hygiene PhD program at UW. He is President-Elect of the National Hearing Conservation Association, having previously served as Director of Communications and Treasurer, and sits on the Noise Committee of the American Industrial Hygiene Association. His research interests include quantitative and subjective exposure assessment in industrial and non-occupational settings, as well as development and evaluation of effective occupational health interventions.
This Ask the Expert was created from information presented in the course, Construction Noise: How Bad Is It and What Can Be Done About It? by Rick Neitzel, published on 6/19/08. The recorded course can be viewed here: audiologyonline.com/ceus/recordedcoursedetails.asp?class_id=11395.