A Hearing Conservation Program for Coal Miners
The industry needs such a program because engineering and administrative noise controls aren't viable, and use of hearing protectors is fairly low.
- By Tom Frank, Ph.D., Christopher J. Bise, Ph.D., Kevin Michael, Ph.D.
- Jun 01, 2003
NOISE-induced hearing loss (NIHL) is a major occupational problem in the coal mining industry. In large part, even though noise control was specified in the 1969 Coal Mine Health and Safety Act, this has occurred because the coal mining industry and equipment manufacturers have not placed as much attention on this hazard as they have on dust or roof control. In addition, engineering and administrative controls of noise are difficult to implement in a cost-effective manner.
In an effort to prevent the occurrence and reduce the progression of NIHL, the Mine Safety and Health Administration implemented a new regulation (MSHA, 1999) that became effective Sept. 13, 2000. Under the new regulation, if a miner's full-shift time-weighted average (TWA) is more than 85 dBA, the action level (AL) is exceeded and the miner must be enrolled in a Hearing Conservation Program. If the full-shift TWA is more than 90 dBA, the permissible exposure level (PEL) is exceeded and all feasible engineering or administrative controls must be applied to reduce noise exposure levels (NELs) to the PEL.
The feasibility of engineering or administrative noise controls is related to total cost of application and overall effectiveness of the control in reducing noise. Retrofit engineering controls have been shown to be largely ineffective, and the development of quieter mining equipment has been slow. To date, these approaches have not led to an acceptable reduction of NELs.
Most mine operators also deem administrative controls as infeasible. In underground mining, for example, moving the workers out of the noise is virtually impossible because they may be working several miles underground. In both above-ground and underground mining, extended work shifts are required to facilitate cost-effective operation. Valid arguments can be made that engineering and administrative controls should be a top priority. However, like many other industries, the coal mining industry is heavily reliant on hearing protection devices (HPDs) to prevent and reduce the progression of NIHL. For HPDs to be effective in a coal mining HCP, there needs to be 100 percent compliance and the HPDs must be worn effectively to reduce NELs to an acceptable level.
The Pennsylvania State University (PSU) and the National Institute for Occupational Safety and Health have been conducting research for the past three years involving the development and implementation of an HCP at a cooperating coal mine. The PSU/NIOSH HCP utilizes some unique approaches and has eight components: 1) job and age demographics, 2) measurement of NELs, 3) engineering and administrative controls, 4) hearing testing, 5) HPDs, 6) education, 7) recordkeeping, and 8) program evaluation. The purpose of this article is to describe some of these components and some of our findings.
Job and Age Demographics: Each miner is categorizing by his primary job using MSHA job codes and his age. As a result, we know several things about the workforce. For example, for the 257 miners in our database (of whom 169 are still employed at the cooperating mine), we know they have 42 different MSHA job codes, 80 percent work underground and are younger than the 20 percent who work above-ground, and their age forms a bimodal distribution having a median age of 41 years old.
NELs: NELs are used to determine each miner's participation in the HCP; however, because of the number of miners we found it impossible to measure each miner's NEL. As such, we measure NELs for at least 50 percent of the miners having the same MSHA job code using Type-2 dosimeters. Our criteria are 2 dB more conservative than the MSHA regulation, and we conservatively use the highest full-shift TWA for each MSHA job code. Interestingly, we have found that NELs varied by up to 10 dB across miners within the same job code. Thus, according to our criteria, participation in the AL is >83 to <88 dBA, in the PEL is >88 to <103 dBA, and in the dual hearing protection level (DHPL) is >103 to <113 dBA. These more conservative criteria only changed HCP participation in three of the 42 job codes, compared with the MSHA AL and PEL criteria.
After determining 90 percent of the miners have NELs >83 dBA, we decided all miners would participate in the HCP. For our miners, 10 percent are below the AL, 32 percent are in the AL, and 58 percent are in the PEL.
HPDs: Despite our best efforts, only 42 percent of the AL and 69 percent of the PEL miners wear HPDs. Obviously, we are striving for 100 percent compliance for PEL miners. Many miners not wearing HPDs are concerned wearing HPDs will prohibit them from hearing life-threatening warnings, such as "roof talk noise" potentially signaling a cave in. We have tried to correct their misconceptions and help them adjust to wearing a HPD. However, unless the mine operator has a zero tolerance rule, some miners will never wear a HPD.
Recently, we have started a mentoring program where older miners have the responsibility for making sure that younger miners wear HPDs. We have also used a test called Fit-Check to determine HPD attenuation on the end user. Fit-Check generates a single number rating of HPD attenuation called a Personal Attenuation Rating (PAR). The mean PAR for 116 miners was 9-16 dB lower than the NRR, depending on the type of ear plug. More importantly, individual variations were so great that any prediction about derating the NRR to determine real-world attenuation per individual could not be made. Further, repeated testing (six months after the first test) on 50 miners indicated the PAR significantly varied from test to test.
Given the variability in our NELs and HPD attenuation and the 31 percent non-compliance rate (for our PEL miners), the common practice of subtracting a derated NRR from the NEL to determine whether a miner's NEL is within a safe limit is seriously flawed.
Hearing Tests: We conduct hearing tests every six months, and about 90 percent of the miners participate during each session. Our standard threshold shift (STS) rate is about 2.3 percent, and no miner has had an STS >25 dB. Some of our other findings are that our AL and PEL miners have about the same degree of hearing loss, even though the PEL miners have higher NELs.
Both groups have more left than right ear hearing loss (most miners stand to the right of loud machines, exposing their left more than their right ear). The progression of hearing loss at 4000 Hz is not linear. The biggest jump occurs between miners 20-39 years old compared with miners 39-69 years old. Also, if the better-ear hearing loss at 2000 Hz is >35 dB, miners report significantly more hearing handicap than if their hearing loss is <35 dB.
Educational: At one time, the educational component consisted of traditional lectures during annual refresher training sessions. However, following feedback from focus groups, we found that miners know they are at high risk for NIHL and should wear HPDs. It also was evident they are not influenced by traditional presentations of facts, figures, or MSHA regulations.
Consequently, we revised the educational focus to facilitate changes in behavior to improve quality of life. Further, we now present training year round using active learning techniques, competence-based instruction, and personalization by incorporating information obtained from several components of the HCP.
An example of active learning would be to present a short talk to about 20 miners after which each miner completes a "minute paper" where they write down one thing they did not understand. Then small groups headed by a facilitator are formed to clear up the misunderstandings. Another example would be to present a real life scenario to a small group that must report its problem-solving solution to the entire group. As a final example, samples of different HPDs, including those dispensed at the mine, could be given to miners. The goal is to get the miners actively involved in trying them on, facilitate a discussion about HPDs, and having the miners select the ones they would like to use.
We have also developed a CD and video that can be viewed at the mine or at home. The CD contains five short segments related to hearing conservation. The video is generic to coal mine hearing safety; however, we have personalized it by adding clips that include miners at the cooperating mine. Further, we have developed 12 fact sheets, each one devoted to a different topic related to hearing conservation. Every month, a different fact sheet is put in a miner's pay envelope; we hope the fact sheet will find its way home to educate the miner's family and provide motivation.
Finally, we have significantly increased the time we spend with each miner following his hearing test and by sitting with miners in their ready room. During these times we talk about hearing loss, on- and off-the-job noise exposure, quality of life changes that might occur if they have an NIHL, and the pros and cons of wearing hearing aids.
For the past three years, we have been trying to develop a model HCP for the coal mining industry. Have we succeeded? If we look at our STS rate, we are not doing a bad job. On the other hand, if we look at our HPD compliance rate for our PEL miners, we have a long way to go.
We have learned that each component of an HCP needs continual refinement based on experiences and its effectiveness.
Acknowledgement: This research was funded by a grant from the National Institute for Occupational Safety and Health and the Centers for Disease Control (NIOSH/HHS-CDC, U60/CCU315855).
Mine Safety and Health Administration (MSHA). Health standards for occupational noise exposure, final rule. 30 CFR (Parts 56, 57, 62, 70, 71). Vol. 64, No. 176. Fed Reg, 1999, p. 49547-49634.
This article originally appeared in the June 2003 issue of Occupational Health & Safety.