Practical tips to reduce hearing defects in mining industry

One of the highest prevalent chronic diseases in the mining industry, as per National Institute for Occupational Safety and Health (NIOSH), is Noise Induced Hearing Loss (NIHL). Some of the other industries where high risk of NIHL exists are wood product manufacturing, building construction, and real estate. It has been concluded after a lot of examination on the audiograms on workers that there is a need for better noise controls and hearing conservation strategies in mining, manufacturing and construction sectors.
 
One of the most common and preventable causes of NIHL is noise exposure. Though it is entirely preventable, but once acquired, it is totally irreversible. Pressure generated by high noise caused over 96% of workers’s compensation claims for hearing loss in the early 2000’s. Ageing, which is a non-work factor also causes hearing loss. But all man-made high noises act as additives to further increase the hearing loss of a worker at workplace. Audiometric results are the correct methodology to access the effects of NIHL vis-à-vis work related and non-work related hearing losses.
 
People working in mines (underground or open cast mines) have the highest incident of noise-induced hearing loss among all occupations. Nearly 80% of miners are exposed to noise levels that exceed 85 dBA. About 25% of these miners are exposed to noise levels higher than the 90 dBA Permissible Exposure Limit (PEL). Ninety per cent of all coal miners above the age of 50 have a hearing impairment. By the time coal miners retire, they are nearly guaranteed a moderate hearing loss.
 
The use of heavy equipment, the drilling of rock, and the confined work environment all contribute to high levels of noise exposure in mining. As a result, as many as 70% of all miners have NIHL significant enough to be considered a disability. In one study, it was found that almost half of the workforce of these miners never used hearing protectors. One NIOSH study found that by age 50, about 90% of coal miners and 49% of metal/nonmetal miners had a hearing impairment (as compared with 10% of the non-occupational noise-exposed population). Simply stated, most miners have a hearing loss by retirement.

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Many programs are underway to help reduce work-related noise induced hearing loss in the mining sector. Jurisdictions are undertaking or planning a significant amount of work in inspections and auditing, targeting highest risk sectors. Noise induced hearing loss is irreversible; therefore it is important to prevent exposure at the earliest possible opportunities. Many awareness programs have encouraged more companies to introduce a noise policy, and a noise control and hearing loss prevention program.
 
One of the major focus is to make the companies aware of the possibilities of using the higher levels (elimination, substitution and engineering control), and encouraging them to think about opportunities. 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.
 
As part of these awareness campaigns, opportunities lie in training in the use of hearing protectors (eg, how to fit properly), choosing appropriately and in customising the fitting (eg, by the use of custom-moulded devices). Education and training have a significant role to play in preventing work related hearing loss. With rate of hearing loss greatest in the first 10 years of exposure, it is important to prevent exposure at the earliest possible opportunities.
 
Noise exposure and noise-induced hearing loss are still prevalent in the mining industry. Most of the risk comes from the need to use heavy machinery underground, but careful design and new technology and materials can be used to minimise this. Some degree of residual hearing protection may well be required, but this should be part of a well-designed hearing protection programme.
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The author is the Lab Head at 3M’s R&D Centre in Gurgaon