Robert S. Dietz,M.B.A., Lisa Marie Bizzarro,B.A., Gary M. Johnson II,B.A.
Elizabeth Faith Christian,B.A., Salisha Elder-Christensen,B.S., Allison Haigh,B.S.
Peter M. Scheifele, Ph.D., LCDR USN (Ret.)
& Jennifer Tufts, PhD. University of Connecticut
Every year approximately 30 million people in the United States are occupationally exposed to hazardous noise. Although noise induced hearing loss is one of the most common occupational illnesses, it is often ignored because there are no visible effects. However, there is a progressive loss of communication, socialization, and responsiveness to the environment. Once acquired, noise induced hearing loss is permanent and irreversible.
Fortunately, noise induced hearing loss is preventable. The incidence can be reduced or eliminated through the successful implementation of hearing conservation programs. The Occupational Safety and Health Administration (OSHA) mandates employers provide hearing conservation programs for their employees in workplaces where noise levels equal or exceed 85 dB(A) for an 8 hour time-weighted average (TWA). An occupational hearing conservation program includes engineering and administrative controls to reduce noise exposures. It also involves employee training in the use of hearing protection and annual audiometry for all workers who are exposed to noise.
In this particular investigation, the workplace environment at Mystic Aquarium was examined. The ability to maintain an appropriate life support environment for aquatic mammals and other wildlife requires elaborate water treatment and filtering systems. These pumping and filtration systems are capable of producing noise levels that may intermittently or continuously influence employee noise exposures.
PURPOSES OF INVESTIGATION
1) To determine if noise exposure levels at Mystic Aquarium in Mystic, CT, required implementation of a hearing conservation program as outlined in OSHA 1910.45 Occupational Noise Standard.
2) To determine if five selected employees at Mystic Aquarium had any hearing loss resulting from occupational noise exposure.
3) To determine if the bilateral hearing sensitivity of five employees was within acceptable hearing limits based upon a visual examination of the ear and audiometric pure tone threshold test results.
Noise level measurements were collected using Quest Technologies Q-100 Type 2 noise dosimeters worn by: 1) Animal trainer while performing daily job routine 2) UConn faculty member who accessed all high-noise level areas within the facility 3) UConn student in back-up area at 16 sampled locations for 5 minute intervals
1)Range 70-140dB, A-weighted, Slow
2)Criterion 90dB, Exchange Rate 5dB
3)Projected Period 8.00Hours
Audiometric Testing: 5 employees
2)Obtained case history
3)Performed pure tone air conduction threshold testing using Tremetrics RA500 audiometer
4) Environment levels below OSHA 1910.45 (g)7D
Results – Noise Dosimeter Measures
Figure 1. % daily dose of noise for TWA 8:00.
This graph depicts the projected percent of TWA noise exposure for an animal trainer, a UCONN investigator, and employees working exclusively within the life support environment. These TWA projections are significantly below OSHA 1910.45 Table G-16 levels suggesting voluntary participation in any occupational hearing conservation program.
Figure 2. 16 sampled locations in back-up area.
Results – Audiometry
Figure 3. Hearing thresholds of 5 selected employees
The TWA obtained in all three conditions are less than the 85 dB (TWA) exposure limits for OSHA 1910.45 regulations.
The audiometric data for four of the five employees suggests normal hearing sensitivity bilaterally. One employee had elevated hearing thresholds at 500 Hz bilaterally.
One employee had normal hearing within the speech range, but had a 25dB difference at 8000 Hz between the right and left ear threshold levels.
Three of the five employees had poorer thresholds for the left ear than the right ear at 4000 Hz. The unilateral pattern observed in these participants would suggest the possibility of asymmetrical noise exposures.
Periodic audiometric testing would identify future changes from these baseline levels of hearing.
Conclusions & Clinical Implications
Models predicting occupational hearing loss require accurate noise exposure data. Information regarding recreational and occupational noise exposure was provided to the employees at Mystic Aquarium. Educating employees about hazardous noise is crucial in preventing noise-induced hearing loss. Equally important is periodic audiometric assessment to identify both occupational and non-occupational hearing deficits.
Accurate audiometric testing can identify unusual patterns in audiometric thresholds. These patterns can be the result of occupational or non-occupational etiology.
Rabinowitz, P.M. (2000). Noise-Induced Hearing Loss. American Family Physician, 61(9), 2749-2760.
Occupational Safety and Health Administration (homepage on the Internet). Washington, D.C. (cited April 18, 2007). Available from www.osha.gov.
Department of Health and Human Services: Center for Disease Control and Prevention (homepage on the Internet). The National Institute for Occupational Safety and Health. Atlanta, G.A. (cited April 18, 2007). Available from www.cdc.gov/niosh.