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Occupational Hearing Loss - Evaluating an Ounce of Prevention Where There Is No Cure

June 19, 2014 (8 min read)

First-in-its-kind study concludes better testing than that currently mandated could lead to earlier detection of affected workers

The old adage “what cannot be cured must be endured” most certainly applies to the permanency of hearing loss. Given the fact that there is no “walking-back” on hearing loss, is enough being done in the workplace to detect and prevent harmful exposure? Every day, millions of workers are exposed to potentially harmful noise levels or ototoxic chemicals. The federal government responded decades ago by regulating such matters as noise exposure and audiometric testing in certain industries. However, a recent study concludes that it may be time to update those regulations. Published in the April 2014 edition of the Journal of Occupational and Environmental Medicine, the study Prevalence of Workers with Shifts in Hearing by Industry, A Comparison of OSHA and NIOSH Hearing Shift Criteria, suggests that early indicia of hearing loss is being missed and that more could and should be done to protect aural health.

The research was undertaken by the National Institute for Occupational Safety and Health (NIOSH), the governmental body responsible for conducting research and making recommendations for the prevention of work-related injury and illnesses. It looked at shifts in hearing, i.e., documented changes in a worker’s hearing threshold, to detect or predict hearing loss. Obviously, the earlier hearing loss is detected, the sooner preventative measures can be implemented.


Risk Management Tip: According to Rebecca Shafer, JD, President of Amaxx Risk Solutions and author of Your Ultimate Guide to Mastering Workers’ Comp Costs, some of the largest occupational disease claims are hearing loss claims. “Pre-employment post offer medical testing should include hearing tests to establish a baseline if later on a hearing loss claim is made,” advises Shafer. “In many unionized shops, workers are employed by several different employers in a short period of time, so setting up baseline examinations makes it clear which employer is responsible for job-related injuries. Workers with a pre-existing condition such as hearing loss can be identified and evaluated. The employer can then require workers to wear sound protection and will only be responsible for any new or increased hearing impairments.” Shafer also advises that employers planning layoffs should require exit medical examinations especially if employees work in high decibel areas, or are exposed to chemical or other irritants that could cause hearing loss. “Technically every employer (not just those laying off) should have an exit examination process, but few do,” says Shafer. “Most only have a form or checklist requiring employees to state any known injuries, but hearing is one that is often unknown, undetected until later down the road.”


The various criteria used to measure occupational hearing loss is a veritable alphabet soup—namely NSTS, OSTS and OSTS-A. NSTS criteria were recommended by NIOSH in 1998 and require two consecutive audiometric tests showing a 15-dB or greater increase of threshold values at 500, 1000, 2000, 3000, 4000 or 6000 Hz frequencies in either ear. OSTS, OSHA’s current standard, is indicated when there is a 10-dB or greater increase in the average threshold at 2000, 3000 and 4000 Hz frequency in either ear. OSTS-A is derived from applying an optional age correction to a finding of OSTS.

Described by NIOSH as first-in-its-kind, the study examined the aural health of American workers by looking at (a) the prevalence of workers with NSTS and the risk of workers developing NSTS by industry; and (b) the prevalence of workers with NSTS, OSTS and OSTS-A across industries.

Study Methodology

The cross-sectional study analyzed the audiograms of workers aged 18-65, administered during the years 2001-2010, and previously submitted to NIOSH. The sample group was comprehensive. It comprised over a million and a half audiograms, from over half a million workers, at over seventeen thousand different companies. The largest age group was 46-55 year olds (29%), with 18-25 year olds making up the smallest category (6%). The region with the highest representation of workers was the Midwest (45%), followed by the South (20%), the Mid-Atlantic (16%) and the West (14%).


The data revealed that 20% of workers had an NSTS, 14% had an OSTS and 6% had an OSTS-A. For NSTS, most industries fell in the 17-23% prevalence range, with utilities, finance and insurance, and manufacturing slightly higher.

As for relative risks, men were at higher risk of developing NSTS than women (nearly 1.5 times greater); older workers (age 56 – 65) were nearly four times more likely to have NSTS than younger workers (18 – 25 year olds). The risk for NSTS was highest in the Midwest and lowest in the West when compared to the Southwest. The highest risk industries included utilities, finance and insurance, agriculture and professional services.

It is noteworthy that no matter which measuring stick was used, the same industries showed the highest levels of affected workers. Across the board, the greatest prevalence of hearing shifts (excluding the mining, construction and manufacturing industries) was indicated in utilities, followed by finance and insurance. What differed, and quite dramatically so, was the number of affected workers captured. For example, while NSTS showed a 27% prevalence of hearing shifts in utilities and a 25% prevalence in finance and insurance, OSTS captured only 19% and 16% respectively. OSTS-A captured less again at only 8% and 9% respectively.


Occupational Medicine Perspective: Leslie J. Hutchinson, MD, MPH, FACOEM, of HLM Consultants notes that in the U.S., job-related hearing loss is the most common work-related disease. “Millions of U.S. workers are exposed on the job to dangerous noise levels,” says Hutchinson. “Generally, if noise levels are high enough that they make the worker physically uncomfortable hearing them, they are high-risk levels.” Hutchinson further notes that many workers are also exposed to chemicals that are ototoxic or damaging to neurological mechanisms that mediate hearing. “Noise or chemical toxicant damage to hearing sensory cells in the ear is irreversible and permanent because the hearing sensory cells do not regenerate to replace damaged cells,” explains Hutchinson. Noise monitor evaluation of noise levels by area of the workplace can identify high-risk areas so that workers from those areas can undergo audiometric evaluation to determine who has suffered decrements in hearing. To prevent progression of hearing loss, Hutchinson recommends relocation of affected or at-risk workers to low-noise workplace areas, elimination or reduction of sound sources when possible, providing workers with hearing protection devices, and education about minimizing noise exposures. “Decades of experience with hearing conservation programs show that such measures look very good on cost-benefit analysis, saving hundreds of millions of dollars in medical evaluation and treatment and permanent disability costs,” says Hutchinson.


Pulling it all together

Overall, analysis of the data showed the prevalence of workers with OSTS was 32% lower, and the prevalence of workers with OSTS-A was 68% lower, than those with NSTS. When looked at by industry (including the mining, construction and manufacturing industries) the OSTS and OSTS-A criteria identified 28-36% and 66-74% fewer workers respectively. In other words, by not using the NSTS, employers are likely missing a significant number of affected workers who need intervention to prevent further hearing loss. The number of workers potentially falling through the cracks is troubling. Given the permanency of hearing loss, this study could be considered a clarion call to action.


So what type of action does the study suggest is needed? It concludes with three important points: (1) interventions should keep apace with our knowledge. NIOSH recommendations are over 15 years old and capture between a third and three quarters more affected workers than the systems currently in place; regulations should be updated accordingly; (2) ototoxic chemical exposure does not automatically trigger testing—this type of exposure should be “meaningfully addressed”; (3) industries which conventional wisdom tags as “low exposure” are not necessarily so—our notions of a “safe” workplace may therefore need to be readjusted.

This study will likely serve as an important reminder that hearing loss is permanent and that workplace interventions should occur as early as possible to detect hearing shifts and prevent further deterioration of aural health.


ADA & Employment Law Tip: How should employers accommodate workers with hearing loss? “A good website to check out is the Job Accommodation Network, which has a lot of useful information on ADA compliance for employees with hearing loss,” says Robin E. Kobayashi, JD, Workers’ Compensation Practice Lead Editor, LexisNexis Legal & Professional Operations. “Examples of accommodation include providing CART (communication access realtime translation) that can be transmitted live, whether in person or via Internet, making it easy to attend meetings, captioning any training videos, using assistive hearing devices, and providing captioned phones.” Employers need to know the benefits of hiring and retaining hearing impaired and deaf employees. “Did you know that hearing impaired and deaf employees are extremely dedicated, experts at problem solving, highly productive, and loyal to boot?” Kobayashi explains. “I urge all employers to take a second look at hearing impaired/deaf applicants and put them in the plus column when making hiring decisions. Don’t believe the hype that it will cost your company more to hire hearing impaired workers when there is so much assistive technology out there including free apps for speech to text to help these workers communicate with co-workers.”


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