Noise Induced Hearing Loss among Industrial Workers in North India: A Tale of Various Influencing Factors.

To study the prevalence and determinants of Noise Induced Hearing Loss (NIHL) among industrial workers. To access the benefit of Distortion Product Oto Acoustic Emissions (DPOAEs) in its early detection as compared to Pure Tone Audiometry (PTA). Detailed in-person questionnaires were filled followed by general and otological examination viz. local and otoscopic examination. NIHL was assessed by tuning fork test, PTA and DPOAEs. 360 participants aged 20-55 years from 6 industries 4 at noise level of 81-90 dBA and 2 at 91-100 dBA. Prevalence of NIHL at 81-90 dBA and 91-100 dBA was 48% and 59% on PTA. Overall Prevalence from 81 to 100 dBA was 49.45% on PTA and 67% on DPOAEs. NIHL was more prevalent at higher noise level, age group higher than 40 years, duration of service greater than 16 years of exposure and continuous noise type. Noise Induced Permanent Threshold Shift (NIPTS) was found to gradually increase at higher noise level and with increase in duration of service. Noise exposure monitoring at work place, engineering controls to reduce noise levels, provision of hearing protection devices, periodic audiometric evaluation of employees and employee's education regarding NIHL are some of the significant aspects to be considered to prevent NIHL.