Observations of noise induced hearing loss in a heavy engineering industry in Kolkata

Noise is a major health threat in occupations where its level exceeds the permissible level (90dB). Most serious health effect is Noise Induced Hearing Loss (NIHL). Objective of the present study was to find out any relationship between occupational noise exposure and hearing impairment of the employees in a heavy engineering industry.

A cross-sectional study was conducted during May 2005 to April 2006 in a selected heavy engineering industry in Kolkata. All the employees working in the factory were included in the study. Data were collected through interview, physical examination, audiometry and environmental noise survey.

Among the total of 278 employees of this study, 235 employees were exposed above the permissible occupational noise level (90dB), out of whom 82 (34.90%) employees were deaf which was much more than the deafness among the nonexposed workers 3 (6.98%). Hearing impairment increased as exposure level increased and this was statistically significant (chi2 = 17.97, df = 2, p = 0.0001). Hearing impairment also increased with duration of exposure (chi2 = 7.12, df = 2, p = 0.0284).

Hearing impairment is associated with occupational noise exposure and thus pre-placement and periodical medical examination is of vital importance.