The Effects of Noise Pollution and Hearing of Metal Workers in Arak

Background: Noise exposure and subsequent hearing loss are important problems in metal
industry. The aim of this study was to determine the prevalence of noise induced hearing loss
(NIHL) and other risk factors associated with industrial noise exposure among metal workers in a
metal factory in Arak.
Materials and Methods: In this cross-sectional study, 743 metal workers who were exposed to
noise were involved. The environment noise was measured using both sound level meter according
to standards presented by national association of occupational health of Iran and ACGIH and
ANSI. Audiometry was used to assess the hearing loss in each worker according to ISO-85
standard.
Results: Of 1191 station points that sound pressure level was measured there, 224 points (18%)
were above the permissible level of 85 dB. In 967 points (82%), sound pressure level was in
precaution range (65<SPL<85). The sound pressure levels in all stations in compact-air units were
above the permissible level. The results of audiometry tests indicated that the greatest prevalence of
hearing loss was found in workers in sheeting, assembling and welding units (10%, 8.1%, and 7.3%
respectively). The greatest NIHL were found in workers between 41 to 50 years old and in workers
who had a history of 21-30 years working. The multivariate analysis showed that severity of noise,
age, history of working and days of working in the week were risk factors for NIHL (P<0.05).
Conclusion: Our findings indicated that the prevalence of noise induced hearing loss was high
among workers of a metal factory in Arak.