(Author's Note: Read the text in italics if you wish to skim the article for significant differences or if later you wish to search for a particular item.)
The Mine Safety and Health Administration (MSHA) under the Federal Mine Safety and Health Act of 1977 has established a new Occupational Noise Exposure Standard published in the Federal Register, Vol. 64. No. 176, September 13, 1999. While this standard is similar to the Occupational Safety and Health Administration's (OSHA) Occupational Noise Exposure Standard (1971) and more recent amendment (1983) defining a hearing conservation program, there are significant differences. This outline, with comments, is an interpretation of the MSHA standard when comparing it to the more familiar OSHA standard. The complete standard may be found on the MSHA Web site.
PART 62: OCCUPATIONAL NOISE EXPOSURE
Purpose and scope; effective date
The purpose of this MSHA standard is to prevent occupational noise-induced hearing loss. It applies to surface and underground metal, nonmetal, and coal mines. The effective date is September 13, 2000.
Noise exposure assessment
The mine operator is responsible for establishing a system of monitoring to evaluate individual noise exposure. The evaluation must determine noise dosage. Dosage is expressed as a percent of allowable dosage. 100% dosage is equivalent to 90 dBA (decibels, A-scale) for 8 hours using a 5 dB step table, 100% is equivalent to higher levels for shorter periods (as 95 dBA for 4 hours, 100 dBA for 2 hours, etc). A miner's noise dose determination must reflect the full work shift
This requirement for monitoring requires the use of individual sampling equipment as noise dosimeter or the use of a sound level meter and the formula: D=100(C1/T1+C2/T2·.+Cn/Tn,). See 62.110 for details. In practice, it may be practical to use a dosimeter for the full shift. Area sound measurements could be supplemental but would not serve as a complete evaluation without use of the formula to calculate dosage as is sometimes done in OSHA sound surveys.
Miners and their representatives must have the opportunity to observe monitoring, and the mine operator must give prior notice of the date and time of intended monitoring.
In the OSHA standard, the employer does not have the obligation to give prior notice of the date and time of intended monitoring.
Mine operators must notify the miner of their exposure when the exposure exceeds the Action Level of 85 dBA TWA (time-weighted average), or 50% dosage Permissible Exposure Level of 90 dBA TWA or 100% dosage Dual Hearing Protection Level of 105 dBA TWA, or dosage of 800% This notification must be provided in writing within 15 days. The notification must provide the exposure determination and the corrective action being taken. A copy of the notification is to be kept for employment plus six months.
In the OSHA standard, the employee must be notified of the results of the sound survey but the method is not explicit. Many times the posting of an area sound survey will serve to inform employees of sound and exposure levels. Employees participating in dosimeter studies are often notified in writing. The MSHA requirement to notify, in writing, of exposure and corrective action within 15 days, unless previously notified within the last 12 months, is different from OSHA's. The 15 days would probably begin when the employer was informed of the results of the study. However, this timeframe is not clear in the Standard.
Miners with noise exposure equal to or exceeding the Action Level of 85 dBA TWA or 50% dosage are required to be enrolled in a hearing conservation program.
Permissible exposure level.
The mine operator must use all feasible administrative and engineering controls to reduce noise if the miner has noise exposure equal to or exceeding the Permissible Exposure Level of 90 dBA TWA, or 100% dosage. Miners with 100% dosage or greater must be enrolled in a hearing conservation program. When administrative controls are used the mine operator must post the procedures and provide a copy to the miner. No miner is to be exposed to sound levels exceeding 115 dBA as determined without adjustment for the use of any hearing protector.
MSHA is placing a strong emphasis on engineering controls. The requirement for engineering controls begins at 90 dBA TWA. The OSHA Standard requires the same thing, but the requirement for engineering controls is not enforced in federal programs until TWAs reach 100 dBA. Administrative controls are not usually successful, but should be considered. Note that no miner is to be exposed to levels exceeding 115 dBA, period.
Dual hearing protection level
If the exposure equals or exceeds 105 dBA TWA, or 800% dosage, in addition to enrollment into the hearing conservation program, the miner must use both earplugs and earmuffs.
The concept of a dual hearing protection level is specific to MSHA.
Hearing conservation program
The program includes monitoring, use of hearing protection, audiometric testing, training, and record keeping.
Hearing protection must be provided, with necessary replacements provided at no cost. Selection must be from at least two muff types and two plug types. The miner must be trained and fitted.
Hearing protection usage is to be enforced when miners exposures exceed the Permissible Exposure Level or are at or exceed a 100% dosage. Usage is also enforced when a miner with exposures between 85 dBA TWA and 90 dBA TWA (50% to 99% dosage) has incurred a standard threshold shift (STS) or when more than six months will pass before the miner can take a baseline audiogram.
The MSHA provision of two types of muffs and two types of plugs is specific to this standard. OSHA provides for a variety of hearing protection availability. Under OSHA enforcement practices, the employer may charge the employee for replacement hearing protection if the employee loses or mutilates existing protection. Of course, there would be no charge for disposable protectors. The requirement to use hearing protection if a baseline audiogram is not performed within six months is the same for both standards.
There is an emphasis on the mine operator's requirement to ensure that hearing protection is in good condition and is fitted.
The mine operator must provide audiometric tests and offer miners the opportunity for audiometric testing within six months of enrollment into the hearing conservation program or 12 months if a mobile van is used. The tests must be conducted by a physician, audiologist or qualified technician under the direction of a physician or audiologist.
Under MSHA, audiometric testing is not mandatory. The extension of grace period from 6 months to 12 months if a mobile van is used is common to both standards.
In the MSHA standard, a qualified technician is someone certified by CAOHC or another recognized organization offering equivalent certification. OSHA does not require certification, but does require demonstrated competency.
When securing a baseline test, the miner must be notified to avoid high noise levels the 14-hour period preceding the test and the mine operator must not expose the miner to high noise levels without hearing protection prior to the test. A new baseline may be established if the miner is away from the mine for more than six consecutive months.
Notification to avoid high non-occupational noise for 14 hours prior to securing a baseline is common to both standards. Both standards also consider the use of hearing protection an acceptable alternative to absence from noise. Allowing the establishment of a new baseline after six months is specific to MSHA. OSHA requires the use of any previous tests to manage the individualâs hearing if the tests are available. Annual hearing tests are to be offered at intervals not exceeding 12 months.
OSHA also requires tests be conducted annually.
Revision of the baseline audiogram is allowed when in the judgment of the professional reviewing the audiometric data, a Standard Threshold Shift is permanent or hearing has improved.
The conditions for revision of baseline audiograms are identical in both standards.
Audiometric test procedure.
Audiometric testing must be pure tone, air conduction testing for each ear using "scientifically validated" procedures. Test frequencies include 500, 1000, 2000, 3000, 4000, and 6000 Hz. An audiometric test record must include,
- Name and job classification
- A copy of all audiograms
- Evidence of correct procedure
- Any exposure determination
- Results of follow-up examinations.
The record must be kept for duration of employment plus six months.
The pure tone hearing testing requirements are the same for both standards. OSHA requires the audiometric record to include the following:
- Name and job classification
- Date of the audiogram
- The examiner's name
- Date of the last acoustic or exhaustive calibration of the audiometer
- Employee's most recent noise exposure assessment
- Background sound pressure levels in test room.
- OSHA requires that exposure assessments be kept for two years and audiometric test records kept for the duration of employment.
The MSHA requirement for "Evidence of correct procedure" is specific to this standard and needs clarification. It has been reported that they have left this open-ended to allow for technological advancements in instrumentation and that protocols should be established under the guidance of the professional supervisor
Evaluation of audiograms
Qualified persons who evaluate audiograms must be notified of the requirements of MSHA. The professional or qualified technicians under the direction of the professional, must determine if the audiogram is valid and if a Standard Threshold Shift or reportable hearing loss has occurred. The professional reviewer must be instructed not to reveal to the mine operator, without written consent of the miner, any specific findings or diagnoses related to the miner's hearing loss due to non-occupational causes.
The instruction to the professional, not to share or inform the mine operator of specific findings related to non-occupational hearing loss, is particular to MSHA.
A reportable hearing loss is defined as a 25 dB average change at 2000, 3000, and 4000 Hz when the annual test is compared to the baseline. Age adjustment is allowed.
The results of the hearing tests are to be provided to the mine operator within 30 calendar days of the test. One retest may be conducted within 30 calendar days of receiving the results in the event of a Standard Threshold Shift or reportable change. Age correction may be used in determining change in hearing, STS or reportable shift.
The requirement to obtain test results from a service provider within 30 calendar days of testing and allowing one retest is specific to MSHA. The MSHA condition that the retest period begins when the company receives the results is a clarification. Age correction for STSs is common to both standards as is allowing 30 calendar days to conduct a retest. Note that both standards allow a retest in the event of an STS.
MSHA requires a retest in the event an "invalid" test is secured. See the Comment in the following section (62.173).
Follow-up evaluation when an audiogram is invalid.
If an audiogram is considered invalid due to a medical condition that is occupationally related in any way, the miner is to be referred for further audiological or medical evaluation at no cost to the miner. If a valid audiogram cannot be obtained due to a non-occupational condition, the mine operator must inform the miner of the need for an otological examination. The professional examiner must be instructed not to reveal to the mine operator, without written consent of the miner, any specific findings or diagnoses related to the miner's hearing loss due to non-occupational causes.
It appears that a hearing test may be considered "invalid" if a medical condition (occupational or non-occupational) contributes to hearing change.
Therefore, if a miner received a hearing test and had a head cold that affected hearing, the hearing test would be considered "invalid." If possible, a "valid" test (retest) must be obtained within 30 calendar days of receiving the determination provided that the condition improves to the point that it does not affect hearing.
The payment of occupational audiological or medical referrals at the company's expense, and the requirement to notify the employee in the event that a non-occupational condition is identified, is common to both standards.
Follow-up corrective measures when a standard threshold shift is detected.
Within 30 calendar days of receiving confirmation of a Standard Threshold Shift (that has been determined by a physician or audiologist to be occupational) the mine operator must re-train the miner (See 62.180 Training), provide the opportunity to select a hearing protector and review engineering and administrative controls to identify and/or correct any deficiencies.
OSHA requires a written notification within 21 days of determination that an STS has occurred. MSHA allows 10 working days. The review of engineering and administrative controls to identify and/or correct any deficiencies is specific to MSHA.
Notification of results; reporting requirements
The results of the audiogram or follow-up evaluation must be reported to the miner within 10 working days of receipt. The notification must be in writing and must include the results and interpretation of the test and the occurrence of any STS or reportable shift. It must include the reasons for any further testing, if applicable. Reportable hearing loss must be reported to MSHA as noise-induced.
Again, a reportable hearing loss is defined as a 25 dB average change at 2000, 3000, and 4000 Hz when the annual test is compared to the baseline.
Within 30 days of enrollment into a hearing conservation program and every 12 months thereafter the miner must be given training. The training must include:
- The effects of noise on hearing,
- The purpose and value of wearing hearing protectors,
- The advantages and disadvantages of the hearing protectors to be offered,
- The various types of hearing protectors offered by the mine operator and the care, fitting, and use of each type,
- The general requirements of Part 62,
- The mine operator's and miner's respective tasks in maintaining mine noise controls, and
- The purpose and value of audiometric testing and a summary of the procedures.
- The operator must certify the day and type of training and records must be kept for duration of enrollment in the hearing conservation program plus six months.
There is no specific time allowed to initiate training in OSHA, and it is required annually. OSHA training must include:
- The effects of noise on hearing,
- The purpose of hearing protectors, the advantages, disadvantages, and attenuation of various types, and instructions on selection, fitting, use, and care, and
- The purpose of audiometric testing, and an explanation of the test procedures.
Training in MSHA is emphasized because audiometric testing and wearing of hearing protection at 85 dBA TWA is voluntary. The training in MSHA needs to convince the miner of the need to participate in the hearing protection and audiometric testing programs.
The Secretaries of Labor and Health and Human Services must have access to all records within 15 calendar days following a written request. Records include the miner's individual records under this Part, training certifications, and notices of exposure determinations. The first copy is to be provided at no cost and additional copies at reasonable cost. Records are to be transferred to a successor operator. The successor operator must use the baseline audiogram, or revised baseline, obtained by the original mine operator to determine the existence of a Standard Threshold Shift or a reportable hearing loss.