Combined exposure to noise and vibration and its effects on worker's hearing

Abstract

Objective: To assess the exposure of bus drivers to noise and whole-body vibration (WBV) and to examine the possibility of an association between these risk factors for noise-induced hearing loss. Methods: A cross-sectional study was carried out among 141 bus drivers who underwent an audiometry test. This group was classified and internally stratified in subgroups of "exposed" and "controls" according to cumulative working time as bus drivers. Their exposure to noise and vibration was assessed. The association between noise-induced hearing loss (NIHL) and the set of explanatory variables was analyzed through logistic regression. Results: The average (±standard deviation) weekly noise exposure of front-engine bus drivers was 83.6±1.9 dB(A), while rear-engine bus drivers were exposed to 77.0±1.1 dB(A). The weighted average of vibration acceleration was 0.85/m2. In the best adjusted model, the multivariable analysis showed that age (≥44; OR=2.54; 95% CI=1.15-5.62), diabetes (OR=5.46; 95% CI=0.95-31.4), and the level of noise emission [≥86.8 dB(A); OR=2.76; 95% CI=1.24-6.15] were risk factors for NIHL. In another model studied, WBV exposure was significant in determining NIHL. Conclusions: Bus drivers were exposed to significant WBV levels. The noise exposure was more pronounced in front engine than in rear-engine vehicles. No association between WBV exposure and NIHL was observed and no interaction was found between WBV and noise exposure. Further studies are required as other model indicated an association between WBV and NIHL.