Abstract:
Background Noise is the most common occupational hazard in the automobile manufacturing industry with the most workers exposed. Automobile manufacturing industry is a high-risk industry for noise-induced hearing loss.
Objective To understand the epidemiological characteristics of noise-induced hearing loss among workers in automobile manufacturing industry and explore related influencing factors.
Methods A questionnaire survey, individual noise recording, and pure tone audiometry were conducted among workers (n=656) exposed to noise from five automobile manufacturing enterprises. The data on age, sex, exposure duration, noise intensity, kurtosis, and hearing loss were obtained. The positive rates of high-frequency noise-induced hearing loss (HFNIHL) and speech-frequency noise-induced hearing loss (SFNIHL) were calculated, and each factor was compared between workers with and without HFNIHL. Chi-square test and analysis of trend were conducted among different groups of age, sex, exposure duration, A-weighted equivalent continuous sound pressure level normalized to a nominal 8-hour working day (LAeq,8h), and kurtosis. Logistic regression analysis was conducted to analyze the factors influencing the positive rates of HFNIHL and SFNIHL.
Results The exposure rates of non-Gaussian noise was 73.6%. The positive rates of HFNIHL and SFNIHL were 32.6% (214 workers) and 6.7% (44 workers), respectively. The HFNIHL workers showed older age, higher proportion of male, longer exposure duration, higher noise intensity (
LAeq,8 h), and increased kurtosis than those without HFNIHL (
P<0.05). The positive rates of HFNIHL increased with the increase of age, exposure duration,
LAeq,8 h, and kurtosis (
\chi ^2 
trend-age=49.25,
P<0.001;
\chi ^2 trend-duration=22.19,
P<0.001;
\chi ^2 trend-LAeq=6.91,
P=0.009;
\chi ^2 trend-kurtosis=8.56,
P=0.003). The results of logistic regression showed that age (
OR=2.13, 95%
CI: 1.67-2.71,
P<0.001), sex (
OR=2.29, 95%
CI: 1.44-3.62,
P<0.001), exposure duration (
OR=1.43, 95%
CI: 1.11-1.85,
P=0.006),
LAeq,8h (
OR=1.37, 95%
CI: 1.08~1.76,
P=0.011), and kurtosis (
OR=1.37, 95%
CI: 1.14-1.63,
P=0.001) were factors associated with the risk of HFNIHL, while only age was associated with the risk of SFNIHL (
OR=2.15, 95%
CI: 1.33-3.33,
P=0.001).
Conclusion Workers exposed to noise in automobile manufacturing industry are at a high risk of hearing loss. Age, sex, exposure duration, LAeq,8 h, and kurtosis are key influencing factors of hearing loss.
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