Objective To examine the relationship between cumulative noise exposure (CNELAeq.8h) based on individual noise level (8 h equivalent continuous sound level, LAeq.8h) and human hearing loss caused by non-stationary noise, and to explore the effectiveness of CNELAeq.8h to assess the non-stationary noise exposure levels.
Methods Workers (n=98) exposed to nonstationary noise from a steel mill and a steel structure factory were selected as the study subjects. Personal LAeq.8h was determined by a noise dosimeter. CNELAeq.8h was calculated from LAeq.8h and related working age. Meanwhile, questionnaires and hearing loss tests were performed for all subjects.
Results The results of stratified analysis for noise level and trend Chi-square test showed that the detection rate of high-frequency hearing loss increased with CNELAeq.8h levels (P<0.01). The results of logistic regression analysis showed that CNELAeq.8h was a risk factor for high-frequency and low-frequency hearing loss in selected workers, and the OR values were 1.261 and 1.109 respectively. There were significant correlations among CNELAeq.8h, LAeq.8h, working age, high-frequency hearing lo ss and low-frequency hearing loss. The results of linear regression analysis showed that CNELAeq.8h entered the regression model of high-frequency hearing loss (P<0.01).
Conclusion There is a good dose-effect relationship between CNELAeq.8h and highfrequency hearing loss. CNELAeq.8h may be used to assess the level of non-stationary noise exposure.
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