The Scope for Early Diagnosis of Noise-Induced Hearing Loss Among Mine and Industrial Workers: A Brief Review

Abstract

Noise is a prevalent health hazard and is often regarded as a “necessary evil” of industrial operations. Persistent exposure to loud noise [>85 dB(A)] for a short duration may promote threshold shift which is usually temporary and recovers within a week. The longer exposure can cause a permanent threshold shift leading to permanent disability known as Noise-Induced Hearing Loss (NIHL). The NIHL is categorized under the major occupational diseases along with silicosis and coal worker pneumoconiosis; it is reported to be the most common sensory defect among the industrial workers by the International Labour Organization (ILO). Paradoxically, NIHL creates a much heavier burden in developing countries than in developed regions of the world. Noise exposure can typically damage the tympanic membrane, cochlear hair cells, Organ of Corti and tunnel of Corti and it accounts for the degeneration of proteins that eventually instigate irreversible damage to the ears. The problem is particularly severe in the mining sector. The studies have indicated that, by an age of 50 years, about 70–90% of miners might have developed NIHL, characterized by observing a notch at 4 or 6 kHz up on the audiometric assessment. The parameters such as intensity and frequency of noise, duration of exposure, and persons’ susceptibility are key players in the development of NIHL. Apart from these, genetic factors, diabetes, and ototoxic drugs are other parameters that may combine to worsen this condition. Among the various diagnostic techniques for the detection of NIHL, audiometry is considered as a gold standard method. However, these techniques can detect NIHL only after its inception. Early diagnosis of occupational diseases like NIHL is of paramount importance, and the study of biomarkers aided with proteomics and ELISA (Enzyme-Linked Immunosorbent Assay) techniques, holds the key to early diagnosis and remediation of the patients with NIHL. The first step is the detection of primary proteins and pathways perturbed within the micro-machinery of the ear. High throughput proteomic techniques such as MALDI-TOF–MS (Matrix-Assisted Laser Desorption/Ionization), LCMS (Liquid Chromatography coupled to Mass Spectrometry) etc. are being used for biomarker study and understanding the mechanism of disease progression apart from providing diagnostics and therapeutics applications. The identified new biomarker for NIHL can be compared with the available genetic database of hearing loss that would help to confirm its novelty and guide us for further research. The findings will also help to update information regarding cochlear proteins.