Hearing conservation program

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Hearing conservation programs are design to prevent noise induced hearing loss. A written hearing conservation program is required by the Occupational Safety and Health Administration (OSHA) “whenever employee noise exposures equal or exceed an 8-hour time-weighted average sound level (TWA) of 85 decibels measured on the A scale (slow response) or, equivalently, a dose of fifty percent.” [1] This 8-hour time-weighted average is known as an exposure action value. While the Mine Safety and Health Administration (MSHA) also requires a hearing conservation program, MSHA does not require a written hearing conservation program. MSHA’s hearing conservation program requirement can be found in 30 CFR § 62.150, and requires has almost the same exact requirements as the OSHA hearing conservation program requirements. Therefore, only the OSHA standard 29 CFR 1910.95 will be discussed in detail.

Program requirements

The OSHA standard contains a series of program requirements.

  • Engineering Controls: 29 CFR 1910.95(b)(1) requires that “feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels…personal protective equipment shall be provided and used to reduce sound levels…”
  • Monitoring: 29 CFR 1910.95(d) requires that monitoring be conducted when “any employee’s exposure may equal or exceed an 8-hour time-weighted average of 85 decibels.
  • Testing: 29 CFR 1910.95(g) requires an “audiometric testing program” for “all employees whose exposures equal or exceed an 8-hour time-weighted average of 85 decibels”.
  • Hearing Protectors: 29 CFR 1910.95(i) states that “employers shall make hearing protectors available to all employees exposed to an 8-hour time-weighted average of 85 decibels or greater at no cost to the employees”
  • Training: 29 CFR 1910.95(k) mandates an annual “training program” for “all employees who are exposed to noise at or above an 8-hour time-weighted average of 85 decibels…” and mandates certain aspects of the training that must be included. This includes the effects of noise on hearing; purpose, advantages, disadvantages, and attenuation of different types of hearing protectors; purpose audiometric testing.
  • Record Keeping: 29 CFR 1910.95(m) states that employers “shall maintain an accurate record of all employee exposure measurements…”

Sound survey

A sound survey is often completed to determine areas of potential high noise exposure. This type of survey is normally completed using a sound level meter (SLM). There are three types of sound level meters. Type 0 is precision instrument normally used in laboratories. A type 1 is for precision measurements taken in the field. Type 2 sound level meters are less precise than type 1 and are often used to take all-purpose sound level measurements. Noise monitoring is generally completed using a noise dosimeter that integrates “all continuous, intermittent and impulsive sound levels”[2] to determine a person’s noise exposure level.

Surveys must be repeated when there are significant changes in machinery and/or processes that would affect the noise level.[3]

Administrative and engineering controls

Administrative and engineering controls are the preferred method to prevent noise exposure. Normally, administrative and engineering controls do not require personal protective equipment and therefore are normally more protective. However, it is not always feasible to use administrative and engineering controls as the only ways to prevent noise over-exposure. The key is to maintain an 8-hour time-weighted average of less than 85 dBA so that personal protective equipment is not required.

Hearing protection device

If engineering controls fail to maintain an 8-hour time-weighted average below 85 dBA, then a hearing protection device (hpd) is required. There are two general types of hpd’s: earplugs and ear muffs. Each one has its own benefits and drawbacks. The selection of the proper hpd to be worn is commonly done by an industrial hygienist so that the proper amount of noise protection is worn. OSHA requires that hpd be given free of charge.[4]

Earplugs

There are four general classes of earplugs. These include: premolded, formable, custom molded and semi-insert.

-Premolded earplugs do not require the plug to be formed before it is inserted into the ear. This prevents the plugs from becoming soiled before insertion.

-Formable earplugs are made of a variety of substances. However, all each substance shares the common feature of being able to be shaped by the user prior to insertion. One drawback of this is the obvious need for the user to have clean hands while shaping the earplug. They do have the advantage of forming to the users ear, while many premolded earplugs do not accomplish this very well.

-Custom molded ear plugs are unique for each person, since they are cast from each user’s own ear canals. Therefore, they provide a personalized fit for each individual.

-Semi-inserts are generally a soft earplug on the end of band. The band aides in maintaining the earplug in position. They are often useful since they can be quickly removed and inserted.

Earmuffs

Earmuffs are another type of hpd. The main difference between earmuffs and earplugs, is that earmuffs are not inserted inside the ear canal. Instead the muffs create a seal around the outside of the ear to prevent noise from reaching the inner ear. Earmuffs are easy to wear and often provide a more consistent fit than an earplug. There are earmuffs available that use the principle of active noise control to help reduce noise exposures. However, earmuffs are not commonly worn by people who have sideburns or glasses, who find earmuffs to be uncomfortable.[5]

Noise reduction ratings

The United States Environmental Protection Agency (EPA) requires that all hearing protection devices be labeled with their associated noise reduction rating (NRR).[6] The NRR provides the estimated attenuation of the hearing protection device. However, it has been found that the “labeled manufacturers' noise reduction ratings (NRRs) substantially overestimated the actual field attenuation performance.”[7][8] To determine the amount of noise reduction afforded by a hearing protection device, OSHA recommends that 7 db be subtracted from the NRR. The NRR is generally given in a C-weighted format, so to obtain the A-weighted reduction, one must subtract 7 db. OSHA also recommends a 50% safety factor, therefore the final OSHA recommended reduction would be (NRR-7)/2.[9]

Audiometric testing program

Audiometric testing is a very important part of a hearing conservation program. Audiometric testing allows for the identification of those that have lost significant hearing. Additionally, the testing allows for the identification of those who are in process of losing their hearing. Audiometric testing is most important in identifying those who have permanent hearing loss. This is called noise-induced permanent threshold shift (NIPTS) [10]

Employee training and education

Proper training and education of those exposed to noise is the key to preventing noise-induced hearing loss. If employees are properly trained on how to follow a hearing conservation program, then the risk of noise-induced hearing loss is reduced. OSHA requires said training to be completed on an annual basis. Proper training is imperative since “even with a very modest amount of instruction attenuation performance can be significantly improved.”[11][12]

Record keeping

OSHA requires that records of exposure measurements and audiometric tests be maintained. Records are also required to have the following:

  • name and job classification
  • date of the audiogram
  • examiner’s name
  • calibration date
  • employee’s most recent noise exposure assessment
  • background sound pressure levels in audiometric test booths.

Noise exposure measurement records must be maintained for at least 2 years. Audiometric test records must be retained for the duration of the affected employee’s employment. Additionally, employees, former employees, representatives designated by the individual employee and the Assistant Secretary all must have access to these records.[13]

Program evaluation

Proper program evaluation is important in maintaining the health of hearing conservation program. The National Institute for Occupational Safety and Health (NIOSH) has created a checklist to help evaluate the effectiveness of a hearing conservation program. It can be found on their website.[14] NIOSH recommends that fewer than 5% of exposed employees should have a 15 dB Significant Threshold Shift in the same ear and same frequency.

The National Institute for Occupational Safety and Health is pushing a higher emphasis on a hearing loss prevention program rather than a hearing conservation program. While this change may seem superfluous, it is important to note the advancement. Prevention implies a response by the workplace caused by initial signs of employee hearing loss rather than instilling a new set of policies (such as “buy quiet”) and thinking (such as hearing protection training and education) to decrease the possibility of occupational hearing loss from happening in the first place.

The Buy Quiet policy is an easy way to progress towards a safer work environment. Many traditionally noisy tools and machines are now being redesigned in order to manufacture quieter running equipment, so a “buy quiet” purchase policy should not require new engineering solutions in most cases [15]. As a part of the “buy quiet” campaign, the New York City Department of Environmental Protection released a products and vendor guidance sheet in order to assist contractors for achieving compliance with the New York City Noise Regulations.

In order to make these plans effective, employees and administration need to be educated in occupational noise-induced hearing loss prevention. It is also necessary to identify and examine sources of noise first before being able to control the damage it may cause to hearing. For example, the National Institute for Occupational Safety and Health has conducted a study and created a database on handheld power tools for the sound power levels they expose their operators to. This Power Tools Database allows contractors in a trade-skill profession to monitor their exposure limits and allow them preparation to prevent permanent hearing damage.

See also

References

  1. ↑ 29 CFR 1910.95(c)(1)
  2. ↑ 29 CFR 1910.95(d)(2)(i)
  3. ↑ OSHA 1910.95 appendix (G)
  4. ↑ 29 CFR 1910.95(i)(1)
  5. ↑ Stephenson, Carol Merry. "Choosing the Hearing Protection That's Right For You". Retrieved 2009-07-30. 
  6. ↑ 40 CFR code of Federal Regulations, Part 211, Product Noise Labeling, Subpart B - Hearing Protection Devises
  7. ↑ Park, MY; Casali, JG (December 1991)."A controlled investigation of in-field attenuation performance of selected insert, earmuff, and canal cap hearing protectors". Human Factors 33(6): 693-714
  8. ↑ Berger EH, Franks JR, Behar A, Casali JG, Dixon-Ernst C, Kieper RW, Merry CJ, Mozo BT, Nixon CW, Ohlin D, Royster JD, and Royster LH. (1998) Development of a new standard laboratory protocol for estimating the field attenuation of hearing protection devices. Part III. The validity of using subject-fit data. J. Acoust. Soc. Am., 102:665-672.
  9. ↑ CPL 02-02-035 - CPL 2-2.35A - 29 CFR 1910.95(b)(1), Guidelines for Noise Enforcement; Appendix A
  10. ↑ Noise and Hearing Conservation Technical Manual Chapter: Noise and Health Effects (App I:C)
  11. ↑ Williams, W. (2004). "Instruction and the improvement of Hearing Protector Performance" Noise and Health Oct-Dec;7(25):41-77 http://www.noiseandhealth.org/article.asp?issn=1463-1741;year=2004;volume=7;issue=25;spage=41;epage=47;aulast=Williams
  12. ↑ Joseph A, Punch J, Stephenson M, Wolfe E, Paneth N, Murphy W (2007). The Effects of Training Format on Earplug Performance. Int J Audiology 46:609-618
  13. ↑ 29 CFR 1910.95(m)
  14. ↑ Noise and Hearing Loss Prevention: Hearing Conservation Program Checklist National Institute for Occupational Safety and Health
  15. ↑ http://www.cdc.gov/niosh/docs/96-110/pdfs/96-110.pdf

External links

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