Standard Threshold Shift (STS)1
Required changes in the mining industry Part 1 (Introduction)
According to WHO-PDH NIHL is the most prevalent irreversible industrial disease and the biggest compensable occupational disease today. It is not surprising that NIHL is now regarded as a high profile problem in the South African mining industry. The response of the government has been a quick succession of legislative controls. Ever since the introduction of The Noise Regulations and Instruction 168 & 171, both the monitoring and control of noise in the workplace have been part of South African legislation. The recent changes in Milestone monitoring which introduces the STS for the mining industry will further assist mining companies to identify cases of NIHL earlier and thereby minimize noise induced hearing loss (NIHL), as well as reduce employee’s risk to other physiological and psychological effects associated with NIHL.
Let’s get back to the basics – What is hearing loss? Hearing loss is a decrease in the ability to perceive sounds. It can be partial or total, sudden or gradual, temporary or permanent. It can affect one ear or both. In general, the risk of hearing loss increases with age. So what is noise induced hearing loss? NIHL is a permanent hearing impairment resulting from prolonged exposure to high levels of noise. Excessive noise exposure is the most common cause of hearing loss. One important factor regarding this type of hearing loss is that it can be reduced or prevented altogether. Habitual exposure to noise above 85 dB will cause a gradual loss of hearing that usually develops over a period of several years. Since it is painless and gradual, the affected person might not notice it. They might, however, notice a ringing sound (tinnitus) or have trouble understanding speech especially in a noisy environment. The eventual loss can be debilitating for the person concerned, but this hearing loss will also cause unnecessary & preventable issues to the family of the person affected by the NIHL.
Ongoing hearing screening in the industrial sector e.g. mining has been performed for many years and there is substantial amounts of medical surveillance data that has been gathered over this time period. The question that arises is: What is being done with this data and is it being used as a tool to prevent losses (hearing & financial) or just for record keeping sake?
If audiometric tests are only performed for data capturing purposes and not for hearing conservation the purpose of legislation, namely to play an active role in the prevention of hearing loss in the workplace – is lost. The purpose of legislation is not to just monitor noise exposure levels and the effect thereof on employees. The purpose is to identify and monitor employees that are at risk of NIHL and put preventative processes in place. NIHL negatively impacts on the patient (worker), the company as well as the country since, NIHL is a preventable “disease” ???
The new STS calculation currently being introduced is a more sensitive way of identifying noise induced hearing loss as the values chosen are more specific for NIHL . STS requires that 2 baseline tests are performed. This is applicable to all employees, even if the person already has a baseline under Regulation 171. The implementation start date was July 2015 and baselining will be required to be in place by end December 2017. The Chamber of Mines(or MHSC) has allocated more than enough time to get these baselines tests performed, however the software currently being used do not perform these new STS calculations which will make reporting on the new NIHL milestones more difficult. With this in mind, mines will need to upgrade their audiometry software to enable the OH practitioners to test, track and report shifts in hearing function as per the Milestone reporting requirments.
The STS calculation is a formula adapted from the America OSHA STS requirement. The American STS formula uses age correction as part of the calculation. It should be noted that the modified South African standard does not use age correction. The formula is calculated by focusing on the 3 main frequencies normally impacted by noise i.e. 2000, 3000 & 4000Hz. The calculation incorporates these 3 frequencies for both ears individually. The results will be used to calculate possible losses over time by comparing future tests calculations to initial baseline calculations. With the introduction of the new STS (Standard Threshold Shift) requirements for audiometric testing, the mining industry and possibly at a later stage the general industry will need to review their current audiometric software and upgrade their software to include these STS calculations & reports.
PLEASE NOTE: The STS requirement currently does NOT replace the Instruction171 requirement and will be used in conjunction with Regulation 171 in the mining industry.