Noise and Hearing Loss: An Occupational Concern and a Rising Chronic Condition

Introduction: Effects of noise at work

Work-related exposure to noise at levels hazardous to hearing and general health is a common occupational risk. About 22 million U.S. employees are currently exposed to hazardous occupational noise. Prevalence of exposure and preventable noise-induced hearing loss is highest in construction, manufacturing, and mining, but work-related noise is present in virtually every sector.¹ Overall, 12 percent of the workforce has difficulty hearing and, for 58 percent of them, these difficulties are attributable to noise exposures at work.²

Hearing loss has been linked to an increase in cardiovascular disease and stress, reductions in work performance, and higher accident and injury risk.^3,4,5,6

These consequences are alarming and so is this statement by the Centers for Disease Control and Prevention (CDC): Hearing loss is now the third most common chronic physical condition among all U.S. adults, after hypertension and arthritis.⁷

National surveillance program, a catalyst for action

About 15 years ago, the National Academy of Sciences identified a serious shortcoming in research efforts into occupational hearing loss prevention. The academy communicated the need for national surveillance to the National Institute for Occupational Safety and Health (NIOSH). The goal was to amass data that could provide insights into groups at high risk for occupational hearing loss and to spur more precise evaluation of which interventions were most effective. Subsequently, NIOSH has partnered with data collectors and private sector audiogram providers to substantially increase data and knowledge of work-related hearing loss. NIOSH has received numerous awards for its accomplishments.⁸

National surveillance and the Big Data it provides represent a major step forward. But effective workplace interventions against occupational hearing loss also require a strong ability to manage, analyze, and interpret data and to guide the response.⁹ Employers, as the “boots on the ground” in protecting employees from occupational noise-induced hearing loss, can look to occupational health providers, such as Concentra®, for help in this regard and also for assistance in understanding the compliance requirements of OSHA Standard 1910.95: Occupational noise exposure.

Understanding noise-exposure limits

When we examine the noise-exposure limits favored by the Occupational Health and Safety Administration (OSHA), the agency responsible for creating and enforcing workplace health and safety standards, and NIOSH, the research and educational institution that works to bring new scientific evidence forward into the occupational health and safety dialogue and eventually incorporate them into enforceable standards, we might conclude that noise regulations haven’t caught up with science.

OSHA has set a permissible exposure limit (PEL) of 90 decibels using the A-weighting frequency response (written as 90 dBA) over an eight-hour time-weighted average (TWA). If exposure time is cut in half to four hours, OSHA uses an “exchange rate” provided in the regulations to raise the exposure limit to 95 dBA, or by an increment of five. The principle behind the exchange rate is that a higher intensity of sound, measured in decibels, can be tolerated if the duration of exposure is less.

NIOSH, on the other hand, supports a recommended exposure limit (REL) of 85 dBA over an eight-hour TWA, a stricter limit than OSHA applies. NIOSH also has a more rigorous exchange rate. Instead of raising the exposure limit by an increment of five, as OSHA does, when exposure time is cut in half to four hours TWA, NIOSH raises the exposure limit by an increment of three.

The list below illustrates how the two agencies compare in the exposure time allowed (also called the “time to reach a 100 percent noise dose”) for each noise exposure level¹⁰:

Time to reach 100 percent noise dose: NIOSH REL vs. OSHA PEL

• 8 hours 
  NIOSH: 85 dBA
  OSHA: 90 dBA
• 4 hours
  NIOSH: 88 dBA
  OSHA: 95 dBA
• 2 hours 
  NIOSH: 91 dBA
  OSHA: 100 dBA
• 1 hour
  NIOSH: 94 dBA
  OSHA: 105 dBA
• 30 minutes
  NIOSH: 97 dBA 
  OSHA: 110 dBA
• 15 minutes
  NIOSH: 100 dBA
  OSHA: 115 dBA

So, what does it all mean? Here’s an example:

Assume an employee is exposed to noise registering 100 decibels, such as a power lawn mower, farm tractor, or garbage truck.¹¹ With such an exposure, OSHA, the enforcement agency, says the employee will reach the 100 percent noise dose in two hours while NIOSH, the research institute, says the employee would exceed the noise dose after a mere 15-minute exposure.

Employers may choose to exercise more vigilance in protecting employees from hazardous noise than OSHA requires – and they would be justified in doing so. Noise even lower than the OSHA threshold for hearing protection (90 dBA) is known to increase employee irritability and carelessness, interfere with communication and concentration, and decrease productivity.¹²

When a hearing conservation program is required

Under OSHA Standard 1910.95: Occupational noise exposure, OSHA requires employers to provide a Hearing Conservation Program for employees who are exposed to work-related noise equivalent to 85 dBA over an eight-hour TWA. At 90 dBA, OSHA mandates that employees be fitted and trained to wear hearing protection.

The OSHA standard proscribes the readings from an audiometric test and the amount of variation from the initial baseline test to a subsequent annual exam that signify when the employee has experienced a standard threshold shift, or a significant, permanent hearing loss. A standard threshold shift is a hearing loss of 10 dBA or greater in either ear as determined by the average of the readings at the frequencies 2000, 3000, and 4000 hertz (a measure of frequency or pitch). An occupational health provider is likely to also be concerned with a hearing loss below 10 dBA, which may indicate a temporary threshold shift, a temporary hearing loss that may become permanent without an intervention.

A hearing conservation program has three components:

• A baseline audiometric exam. OSHA requires that a baseline test be completed within six months of an employee’s first exposure to an eight-hour TWA at or above 85 dBA, but it can be delayed for up to one year when mobile test vans are utilized. To lessen the likelihood of measuring an employee with a temporary threshold shift, OSHA mandates that, prior to testing, the employee must not be exposed to any noise exceeding 80 dBA.
• An otoscopic exam, which can reveal any problems with ear structure – the external auditory canal, tympanic membrane, and middle ear – that could interfere with proper hearing.
• An annual audiometric exam, which is conducted toward the end of the shift and compared to the baseline exam.

The OSHA standard allows a re-test to be done the same day as the first test. If the second test confirms a standard threshold shift has occurred, the employer must:

• Notify the employee within 21 days of the test results indicating a standard threshold shift.
• Have a physician to determine causation – that is, whether work was responsible for the hearing loss.
• Initiate more aggressive hearing conservation measures for an employee with a persistent, work-caused standard threshold shift. The test result demonstrates that current hearing protection has not been sufficient to safeguard the employee’s hearing.
• Fit and train the employee in the use of more aggressive hearing protection.

If it is determined the hearing loss is not caused by work, the employee should be referred to the primary care physician for follow-up treatment.

Employers are required to provide audiometric testing at baseline and annual exams, hearing protection, and training at no cost to the employee. Hearing conservation programs are designed to prevent initial hearing loss, preserve and protect remaining hearing once any hearing loss occurs, and give employees the training they need to protect themselves.¹³

Hazardous noise mitigation options

The preeminent need to protect employees from hazardous occupational noise is well-served by audiometric and otoscopic examinations, but employers should not overlook important measures that can reduce risk, including:

• When feasible, eliminate any sources of hazardous noise exposure.
• Reduce the loudness and intensity of sound (measured in decibels) and its frequency or pitch (measured in hertz). However, don’t just lock onto one measurement; there is a need to take all physical properties of sound into consideration.
  
  Research into the community impact of noise from leaf blowers reveals that a growing number of people are becoming sensitive to low-frequency sounds. These sounds can cause serious health effects, such as vertigo, disturbed sleep, stress and agitation, hypertension, and disordered heart rhythms. Low-frequency noise like leaf blowers can travel over long distances and create heightened vulnerability – anyone in the vicinity can’t control the noise and can’t get away from it.^14,15  The autonomic nervous system interprets low frequency noise as sounds of a predator and a sign of danger. In response, it activates a “fight or flight” survival response.¹⁶

• Use engineering controls to modify or replace noisy equipment or to make changes in the transmission path of the noise.
• Implement administrative controls. An example would be to change an employee’s work schedule to avoid exposure to excessive noise.
• Provide and train employees in the use of personal protective equipment (PPE) to safeguard the ears.
• Provide education to help employees understand the need to protect themselves from damaging noise, both on and off the job.

Contact Concentra

Research shows that workplaces with appropriate and effective hearing conservation programs have higher levels of employee productivity and a lower incidence of absenteeism.¹⁷ Contact Concentra to learn more about audiometric testing and hearing conservation programs.

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NOTES

1. Themann CL, Masterson EA. Occupational noise exposure: A review of its effects, epidemiology, and impact with recommendations for reducing its burden. The Journal of the Acoustical Society of America. November 2019.
2. Kerns E, Masterson EA, Themann CL, Calvert GM. Cardiovascular conditions, hearing difficulty, and occupational noise exposure within US industries and occupations. March 2018.
3. Kerns E, Masterson EA, Themann CL, Calvert GM. Cardiovascular conditions, hearing difficulty, and occupational noise exposure within US industries and occupations - 2. March 2018.
4. Leather P, Beale D, Sullivan L. Noise, psychosocial stress and their interaction in the workplace. Journal of Environmental Psychology. June 2003.
5. Muzammil M, Khan AA, Hasan SN. Effect of noise on human performance under variable load in a die casting industry – a case study. January 2004.
6. Cantley LF, Galusha D, Cullen MR, Dixon-Ernst C, Rabinowitz PM, Neitzel RL. Association between ambient noise exposure, hearing acuity, and risk of acute occupational injury. Scandinavian Journal of Work Environmental Health. August 2014.
7. Occupational Hearing Loss (OHL) Surveillance – Facts and Definitions. Centers for Disease Control and Prevention.
8. Occupational Hearing Loss (OHL) Surveillance – Project Information. The National Institute for Occupational Safety and Health. Centers for Disease Control and Prevention. Last reviewed: May 18, 2021.
9. Dash S, Shakyawar SK, Sharma M, Kaushik S. Big data in healthcare: management, analysis and future prospects. SpringerOpen. June 2019.
10. Noise and Hearing Loss Prevention – Guidance and Regulations. The National Institute for Occupational Safety and Health. Centers for Disease Control and Prevention.
11. Noise Sources and their Effects. PPE Training. Purdue University.
12. Munzel T, Sorensen M, Schmidt F, Schmidt E, Steven S, Kroller-Schon, Daiber A. The Adverse Effects of Environmental Noise Exposure on Oxidative Stress and Cardiovascular Risk. Antioxidants and Redox Signaling. March 2018.
13. Occupational Noise Exposure. Occupational Safety and Health Administration. Department of Labor.
14. Walker E, Banks JL. Characteristics of Lawn and Garden Equipment Sound: A Community Pilot Study. Journal of Environmental and Toxicological Studies. SciForschen Open Hub for Scientific Research. November 2017.
15. “The reason why leaf blowers are singled out as the noisiest landscaping tool.” Total Landscape Care. December 14, 2017. Updated June 8, 2021.
16. The Polyvagal Theory in Therapy by Deb Dana. June 2018.
17. Occupational Noise Exposure. Occupational Safety and Health Administration. Department of Labor.