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OSHA requires a hearing loss be recorded on the OSHA 300 Log under three conditions:
- The presence of a Standard Threshold Shift (STS), defined as an average change of at least 10 dB at 2000, 3000 and 4000 Hz compared to the baseline audiogram. Aging correction factors are typically used unless prohibited by law
- The average hearing loss at 2000, 3000 and 4000 Hz exceeds 25 dB
- The change in hearing is determined to be at least partially work-related
Any software package can easily determine whether the first two conditions exist…it’s straightforward math. But the third condition involves a professional to exercise judgment.
While OSHA permits any “licensed healthcare professional” to exercise that judgment, it is most typically Audiologists and Physicians who are involved due to the scope of their licensure and their professional qualifications.
The following are factors typically considered when evaluating the work-relatedness of an STS for OSHA 300 Log recording purposes. These same factors are pertinent when evaluating a 25 dB Average Change for recording on the MSHA Form 7000-1 (see prior blog regarding the differences between the OSHA and MSHA noise standards). This list does not preclude additional information pertaining to a particular case. Rather, this is a non-medical explanation for the lay person, not for an Audiologist or Physician.
- Experience. Not all professionals are equal in this regard. Having the right academic training, professional degree, certifications and professional license are certainly important but the similarity between professionals often ends there. Simply put, there is no substitute for experience. A professional who has reviewed thousands of hearing tests, spent many hours in manufacturing facilities evaluating hearing conservation program effectiveness, and who has a wide breadth of knowledge concerning research findings pertaining to the field of hearing science is more likely to make a better decision than one who does not have this level of experience. It is imperative to know the qualifications of the reviewing professional.
- Workplace Noise Exposure Level. Generally speaking, the higher the noise level the greater the risk of long-term noise-induced hearing loss. Be aware that a noise exposure level less than 85 dBA TWA does not automatically mean that the STS is non-work related. It simply lowers the likelihood of it. There is risk of hearing loss with long-term exposure below 85 dBA TWA.
- Exposure Duration. The entire workplace noise exposure history should be considered, not just the current noise level. Generally speaking, the more years one is exposed, the higher the risk of long-term noise-induced hearing loss. In other words, the higher the employee’s workplace noise exposure (a function of both noise level and exposure duration), the more difficult it is to rule out workplace noise as a contributing factor.
- Configuration of the Hearing Loss. Noise-induced hearing loss tends to be high-frequency loss. Extensive low-frequency hearing loss tends to argue against workplace noise being a factor but does not rule it out. Configuration is important, but is only one factor.
- Noise Notch. The presence of a “notch” at 3000-6000 Hz tends to argue that there is a noise component to the hearing loss, though this notch could be caused by non-workplace noise. Importantly, the absence of a notch does not exclude workplace noise as a contributing factor. Not everybody who gets noise-induced hearing loss exhibits a noise notch. The presence or absence of a notch is only one factor.
- Progression of the Hearing Loss. Workplace noise tends to affect hearing during the first 10-15 years of exposure, so it is critical to examine the entire audiometric history.
- Bilateral Symmetry. Workplace noise tends to affect both ears more-or-less equally unless there is something specific about the job that would expose one ear unequally. It is important to note that asymmetry (one ear affected more than the other) can have a variety of causes (medical and gunfire, primarily) but asymmetry in and of itself does not exclude workplace noise as a consideration. It is simply one factor.
- Non-Workplace Noise Exposure must be considered, but it’s important to note that the presence of non-workplace noise does not automatically exclude workplace noise as a contributing factor.
- Medical Issues are considered, but the presence of medical factors does not automatically exclude workplace noise as a contributing factor.
- Hearing Protection. The use of hearing protection does not exclude workplace noise as a contributing factor. There is ample evidence in scientific literature indicating that the Noise Reduction Rating (NRR) of earplugs is in no way indicative of how much protection a person actually receives. Further, OSHA’s recommended 50% derating is completely unreliable. The amount of protection a person receives from his or her earplugs is completely unknown and cannot be determined with any degree of accuracy unless measured on the person under realistic conditions with specialized equipment. And even if this is done, that measurement says little about how consistently well the earplugs have been worn over the employee’s career. However, the professional’s thought process may change a bit if the employee has worn earmuffs long-term. Earmuffs reliably provide about 70% of the published NRR – there is much less variability in the protection offered by earmuffs compared to earplugs. If the employee has worn earmuffs long-term, this somewhat lessens the likelihood that the hearing loss is work related. Still, the use of hearing protection is just one factor.
- Pre-Existing Hearing Loss on the baseline audiogram is not generally taken into account since by definition an STS is determined by comparing the annual to the baseline audiogram. In other words, it is the amount of hearing change after the baseline audiogram that is relevant to the work-relatedness determination. It is recognized, however, that pre-existing hearing loss does tend to predispose one to lose hearing more quickly with continued noise exposure.
- Equipment Issues. The professional will likely assume that audiometric equipment used to perform hearing testing is properly calibrated and that the room in which testing is done at least meets OSHA background noise limits. Be aware that the professional is legally entitled to view these documents, if requested.
- Hearing Conservation Program Effectiveness. If the reviewing professional has a basis to believe that a company’s hearing conservation program (HCP) is highly effective at preventing workplace noise-induced hearing loss, that knowledge can be considered. Similarly, the professional can also take into consideration his knowledge of the HCP’s ineffectiveness. But regardless, it is the facts as they pertain to the individual that matter. A company can have a highly effective HCP that fails for a particular individual, and vice-versa.
What should be gleaned from the above is that the determination of work-relatedness is based on the careful weighing of multiple complex factors. The more experienced the professional, the better able is that professional to arrive at a sound judgement especially in the more complex cases.
It is also important to realize that to claim a hearing loss is Non-Work Related is to claim that workplace noise has contributed zero to the person’s hearing loss for the duration of his employment. If workplace noise cannot be ruled out as a contributing factor to any degree, then work relatedness cannot be ruled out as a contributing factor and the case should be recorded. This may seem an unrealistically high bar, but it actually isn’t. In fact, it is quite surprising how many cases turn out to be Non-Work Related.
Too, bear in mind that the reviewing professional must consider what can be legally and ethically defended to:
- An OSHA or MSHA Inspector
- That professional’s licensing board
- That professional’s certifying agencies
- A jury in a courtroom
If the professional does not believe that a decision of Non-Work Relatedness is likely to be successfully defended, then it is likely the professional will recommend the hearing loss be recorded on the OSHA 300 Log or MSHA Form 7000-1. While recording hearing loss is usually not what the employer would prefer, doing so when reasonable protects the employer, the employer’s nurse who has her own license to protect, those associated with the employer’s health & safety programs, as well as the reviewing professional.