A cross-sectional study of hearing thresholds among 4627 Norwegian train and track maintenance workers
Arve Lie1,2, Marit Skogstad1, Torstein Seip Johnsen2
1Department of Occupational Medicine and Epidemiology, National Institute of Occupational Health, Oslo, Norway.
Objective:
Railway workers performing maintenance work of trains and tracks could be at risk of developing noise-induced hearing loss, since they are exposed to noise levels of 75-90 dB(A) with peak exposures of 130-140 dB(C). The objective was to make a risk assessment by comparing the hearing thresholds among train and track maintenance workers with a reference group not exposed to noise and reference values from the ISO 1999.
Design:
Cross-sectional.
Setting:
A major Norwegian railway company.
Participants:
1897 and 2730 male train and track maintenance workers, respectively, all exposed to noise, and 2872 male railway traffic controllers and office workers not exposed to noise.
Outcome Measures:
The primary outcome was the hearing threshold (pure tone audiometry, frequencies from 0.5 to 8 kHz), and the secondary outcome was the prevalence of audiometric notches (Coles notch) of the most recent audiogram.
Results:
Train and track maintenance workers aged 45 years or older had a small mean hearing loss in the 3-6 kHz area of 3-5 dB. The hearing loss was less among workers younger than 45 years. Audiometric notches were slightly more prevalent among the noise exposed (59-64%) group compared with controls (49%) for all age groups. They may therefore be a sensitive measure in disclosing an early hearing loss at a group level.
Conclusions:
Train and track maintenance workers aged 45 years or older, on average, have a slightly greater hearing loss and more audiometric notches compared with reference groups not exposed to noise. Younger (<45 years) workers have hearing thresholds comparable to the controls.
