Noise-Induced Hearing Loss in Mining: Biological Mechanisms and Emerging Pharmacological Otoprotection

Abstract

Noise-induced hearing loss (NIHL) is a major occupational health problem, especially within the mining industry, where workers are frequently exposed to hazardous levels of occupational noise from drilling, blasting, crushing, and heavy machinery. While engineering controls, hearing protection devices, and audiological surveillance are key preventive measures, they may not completely prevent cochlear injury. This review focuses on the epidemiology, biology, and novel pharmacological preventive and mitigating otoprotective strategies for mining-associated NIHL. Excessive noise exposure causes oxidative stress, mitochondrial dysfunction, inflammation, excitotoxicity, synaptic damage, and hair cell injury, thereby providing a biological rationale for studying otoprotective therapies. Experimental studies have demonstrated promising effects of antioxidants, including N-acetylcysteine, D-methionine, and ebselen, as well as anti-inflammatory, metabolic, and regenerative therapies, but human studies remain limited and inconclusive. Limitations in effective drug delivery to the cochlea, the long-term safety of repeated drug administration, the lack of validated biomarkers, and the absence or near absence of mining-specific pharmacological trials are significant barriers. Pharmacological intervention should thus be considered investigational, additional to, and not a substitute for comprehensive hearing-conservation programs. Future studies should prioritize longitudinal occupational research, biomarker-guided risk assessment, mining-specific clinical trials, and clinically meaningful hearing outcomes.