Occupational hearing loss

Occupational hearing loss (OHL) is hearing loss that occurs as a result of occupational hazards. OHL, damage to one or both ears from exposures related to one's occupation, is a large but preventable problem. Organizations such as the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) work with employers and workers to reduce or eliminate completely hazards to hearing. Occupational hearing loss is one of the most common work-related illness in the United States.[1]

Hazards to the hearing of workers include industrial noise, and exposure to various ototoxic chemicals.[2] These exposures may also interact to cause more damage than either one would by itself. Many chemicals have not been tested for ototoxicity, so unknown threats may exist.

A 2016 study by NIOSH found that the mining sector had the highest prevalence of hearing impairment at 17%, followed by the construction sector (16%) and the manufacturing sector (14%). The public safety sector had the lowest rate of hearing impairment, at 7%.[1]

Personal protective equipment, administrative controls, and engineering controls can all work to reduce exposure to noise and chemicals, either by providing the worker with protection such as earplugs, or by reducing the noise at the source or limiting the time or level of exposure.

Background

Occupational hearing loss is defined as damage to either or both ears, at the inner ear or auditory nerve, that results from an exposure in a person's occupation.[3] Although high levels of noise are the main cause of occupational hearing loss there are also other factors in the work environment that can result in it. Chemicals, foreign bodies, vibration, barotrauma, along with other hazards can result in hearing loss. These losses that these workers obtain, affect many aspects of their life, mainly social interactions.[4]

Within the United States of America, approximately 10 million people have noise-related hearing loss. Over twice that number are occupationally exposed to dangerous noise levels. Hearing loss accounted for a sizable percentage of occupational illness in 2007, at 14% of cases.[5]

There are many organizations, including the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH) working to understand the causes of occupational hearing loss and how it can be prevented. They work to produce regulations and guidelines to help protect the hearing of workers in all occupations.[5]

Causes

Noise exposure

Exposure to noise can cause vibrations able to cause permanent damage to the ear. Both the volume of the noise and the duration of exposure can influence the likelihood of damage. Sound is measured in units called decibels, which is a logarithmic scale of sound levels that corresponds to the level of loudness that an individual's ear would perceive. Because it is a logarithmic scale, even small incremental increases in decibels correlate to large increases in loudness, and an increase in the risk of hearing loss.

Sounds above 80 dB have the potential to cause permanent hearing loss. The intensity of sound is considered too great and hazardous if someone must yell in order to be heard. Ringing in the ears upon leaving work is also indicative of noise that is at a dangerous level. Farming, machinery work, and construction are some of the many occupations that put workers at risk of hearing loss.

OSHA's current permissible exposure limit (PEL) for workers is an average of 90 dB over an 8-hour work day. They also use a 5 dB exchange rate, where an increase in 5 dB for a sound corresponds to the amount of time workers may be exposed to that particular source of sound being halved. For example, workers cannot be exposed to a sound level of 95 dB for more than 4 hours per day, or to sounds at 100 dB for more than 2 hours per day. Employers who expose workers to 85 dB or more for 8 hour shifts are required to provide hearing exams and protection, monitor noise levels, and provide training.

Sound level meters and dosimeters are two types of devices that are used to measure sound levels in the workplace. Dosimeters are typically worn by the employee to measure their own personal sound exposure. Other sound level meters can be used to double check dosimeter measurements, or used when dosimeters cannot be worn by the employees. They can also be used to evaluate engineering controls aimed at reducing noise levels.

Ototoxic chemical exposure

Chemically-induced hearing loss (CIHL) is a potential result of occupational exposures. Certain chemical compounds may have ototoxic effects. Exposure to organic solvents, heavy metals, and asphyxiants such as carbon monoxide can all cause hearing loss.[6][7] These chemicals can be inhaled, ingested, or absorbed through the skin. Damage can occur to either the inner ear or the auditory nerve.

Both noise and chemical exposures are common in many industries, and can both contribute to hearing loss simultaneously. Damage may be more likely or more severe if both are present. Industries in which combinations of exposures may exist include construction, fiberglass, metal manufacturing, and many more.[8]

Certain medications may also have the potential to cause hearing loss.[8]

It is estimated that over 22 million workers are exposed to dangerous noise levels, and 10 million are exposed to solvents that could potentially cause hearing loss every year, with an unknown number exposed to other ototoxic chemicals.[7]

Prevention

Engineering controls

Engineering control is the highest in the hierarchy of risk reduction methods when elimination of the hazard is not possible. These types of controls typically involve making changes in equipment or other changes to minimize the level of noise that reaches a worker's ear. They may also involve measures such as barriers between the worker and the source of the noise, mufflers, regular maintenance of the machinery, or substituting quieter equipment.[9][10] Examples of noise control strategies adopted in the workplace can be seen among the winners of the Safe-in-Sound Excellence in Hearing Loss Prevention Awards.

Administrative controls

Administrative control, behind engineering control, is the next best form of prevention of noise exposure.[9] They can either reduce the exposure to noise, or reduce the decibel level of the noise itself. Limiting the amount of time a worker is allowed to be around an unsafe level of noise exposure, and creating procedures for operation of equipment that could produce harmful levels of noise are both examples of administrative controls.[10]

Personal protection

Elimination or reduction of the source of noise or chemical exposure is ideal, but when that is not possible or adequate, wearing personal protective equipment (PPE) such as earplugs or earmuffs can help reduce the risk of hearing loss due to noise exposure. PPE should also not be used in substitution for engineering or administrative controls. It is important that workers are properly trained on the use of PPE to ensure proper protection.[10]

History

Occupational hearing loss is a very present industrial issue that has been noticed since the Industrial Revolution.[11] As industrial society continues to grow, this issue is becoming increasingly detrimental due to the exposure of chemicals and physical objects. Millions of employees have been affected by occupational hearing loss, especially in industry.[12] Industrialized countries see most of these damages as they result in both economic and living problems.

Within the United States of America alone, 10 of the 28 million people that have experienced hearing loss related to noise exposure. Rarely do workers express concerns or complaints regarding Occupational hearing loss. In order to gather relevant information, workers who have experienced loud work environments are questioned regarding their hearing abilities during everyday activities. When analyzing OHP, it is necessary to consider family history, hobbies, recreational activities, and how they could play a role in a person’s hearing loss. In order to test hearing loss, audiometers are used to and are adjusted to American National Standards Institute (ANSI) regulations. The Occupation and Safety Health Association (OSHA) of the United States of America requires a program that conserves hearing when noise levels are greater than 85 dB. This program includes: 1.”Monitoring to assess and record noise levels.” 2. “Periodic audiometry.” 3. “Noise Control” 4. “Education and record keeping.” Occupational hearing loss is very preventable.

References

  1. 1 2 "Hearing Impairment Among Noise-Exposed Workers — United States, 2003–2012 | MMWR". www.cdc.gov. Retrieved 2016-04-21.
  2. ↑ Johnson AC and Morata, TC (2010). "Occupational exposure to chemicals and hearing impairment. The Nordic Expert Group for Criteria Documentation of Health Risks from Chemicals." (PDF). Arbete och Hälsa 44(4): 177 pp.
  3. ↑ "Occupational hearing loss: MedlinePlus Medical Encyclopedia". www.nlm.nih.gov. Retrieved 2016-03-23.
  4. ↑ May, J. (n.d.). "Occupational hearing loss". American Journal of Industrial Medicine: 112–120.
  5. 1 2 "CDC - Facts and Statistics: Noise - NIOSH Workplace Safety & Health". www.cdc.gov. Retrieved 2016-03-30.
  6. ↑ EU-OSHA, European Agency for Safety and Health at Work (2009). "Combined exposure to noise and ototoxic substances". Combined exposure to noise and ototoxic substances. EU OSHA. Retrieved May 3, 2016.
  7. 1 2 "CDC - NIOSH Topic: Occupational Hearing Loss (OHL) Surveillance". www.cdc.gov. Retrieved 2016-03-28.
  8. 1 2 "Ototoxic chemicals - chemicals that result in hearing loss". Department of Commerce Western Australia. Retrieved 2016-03-28.
  9. 1 2 "NIOSH - Engineering Noise Control - Workplace Safety and Health Topic". www.cdc.gov. Retrieved 2016-03-30.
  10. 1 2 3 "Noise controls (Engineering, Administrative, PPE) | Mining Safety & Health Resource Center". miningsh.arizona.edu. Retrieved 2016-03-30.
  11. ↑ Sataloff, R & J (1987). "Occupational Hearing Loss". New York: Dekker.
  12. ↑ Al-Otaibi, S. (n.d.). "Occupational Hearing Loss". Saudi Medical Journal 21: 523–530.
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