Risk of hearing loss in noise-exposed workers: a retrospective cohort study

Objective To investigate the effect of intensity and duration of occupational noise exposure on hearing loss among workers.Methods With the data on pure tone audiometry and environmental noise monitoring from 2012 through 2014, we did a retrospective cohort study among 1 411 noise-exposed workers from Zhongshan city of Guangdong province.Results The noise exposure showed significant intensity- and time-dependent effect on binaural high-frequency hearing threshold among the noise-exposed workers(P<0.05);the average binaural high-frequency hearing threshold for all the noise-exposed workers were 30.88±7.21, 30.57±6.91, and 30.37±7.21 decibel hearing level(dBHL) for the measurements in 2012, 2013, and 2014.Compared to the measurements in 2012, the average binaural high-frequency hearing threshold of the noise-exposed workers was elevated in 2013(P<0.05), but there was a difference in the threshold between the measurements in 2013 and 2014(P>0.05).The average binaural high-frequency hearing threshold differed significantly by the intensity of noise(P<0.05) and the workers exposed to the noise of ≥88 dB(A) had the highest binaural high-frequency hearing threshold(32.83±9.45, 32.20±9.11, and 32.22±9.52 dBHL for the measurements in 2012, 2013, and 2014).Conclusion Our findings suggest that there is a dose-response relationship between intensity and time of noise exposure and binaural high-frequency hearing threshold among occupationally exposed workers.