miércoles, 25 de marzo de 2015

CDC - NIOSH Science Blog – A Story of Impact….

CDC - NIOSH Science Blog – A Story of Impact….

A Story of Impact….

Categories: Hearing Loss

It starts with an agency wanting to better protect its workers from hearing loss. The National Institute of Standards and Technology (NIST) is a non-regulatory federal agency within the U.S. Department of Commerce that conducts measurement research, develops technological standards and performs other important functions. NIST was upgrading the hearing conservation program for its 138 noise-exposed workers and wanted its criteria to be based on science. Current Occupational Safety and Health Administration (OSHA) regulations were being followed, but the medical officer questioned whether more could be done to protect worker hearing and needed evidence to support changes. NIST contacted the National Institute for Occupational Safety and Health (NIOSH) via the Occupational Hearing Loss Surveillance Project. NIOSH provided NIST with information and links to documents such as the NIOSH Practical Guide for Preventing Occupational Hearing Loss.
The primary NIST question was how to best identify workers who are developing a hearing loss. Occupational hearing loss can occur from exposure to loud noise or ototoxic chemicals on the job. Workers developing a hearing loss are detected when they have lost a measurable amount of hearing called a shift in hearing. A shift in hearing is intended to be used as a preventative measure – to identify an at-risk worker soon enough to intervene before he or she loses a significant amount of hearing. This intervention could include actions such as refitting hearing protection and training to prevent further hearing loss.
The criteria used by OSHA for shifts in hearing are called “standard threshold shifts” and allow adjustments to be made for a worker’s age (age correction). The age correction values used by OSHA originated from NIOSH in the 1970s and were derived from 1968-1972 study data – the best available at the time. However, since 1998, NIOSH has recommended more protective criteria for shifts in hearing, including using an updated formula called a “significant threshold shift” which does not allow age correction. NIOSH recognized that age-related hearing loss develops differently for different people, and that correcting for age would overestimate the expected hearing loss caused by age for some workers, and underestimate it for others. Research has shown that using the standard threshold shift with age correction may miss 68% of workers with shifts in hearing who need intervention. When using it without age correction, the standard threshold shift may miss 32% of these workers.
Unfortunately, once workers have sustained a standard threshold shift, they have already lost a substantial amount of hearing. Using the NIOSH recommended significant threshold shift formula, which is based on more recent evidence, identifies workers early enough that interventions can successfully prevent more serious losses in hearing.
About a month after contacting NIOSH, NIST updated their hearing conservation program based in large part on NIOSH research and recommended criteria. In particular, NIST used the recently published article “Prevalence of Workers with Shifts in Hearing by Industry: A Comparison of OSHA and NIOSH Hearing Shift CriteriaExternal Web Site Icon.” This peer-reviewed article demonstrates that using age correction when assessing individual workers for hearing loss prevention identifies significantly fewer at-risk workers for critical interventions.
NIST did it. You too can impact your workplace! Check out our web site for more information on occupational hearing loss surveillance and links to resources to better protect your workers. With the right strategies and products, occupational hearing loss is entirely preventable.
Elizabeth Masterson, PhD, CPH, COHC
Dr. Masterson is an epidemiologist in the NIOSH Division of Surveillance, Hazard Evaluations and Field Studies

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