Objective To understand the workers' noise exposure level and noise induced hearing loss (NIHL) in the middle-size auto parts manufacturing enterprises in a city.

Methods A total of 3 enterprises, 608 noise-exposed workers in a city located in Pearl River Delta were studied. The noise level at their workplaces were measured and NIHL was examined among these workers. Binary logistic regression was used to analyze the affecting factors of NIHL.

Results The noise level (L_{EX, W} value)at 39.6%(89/225)workplaces were higher than 85 dB(A)and totally there were 160 workers (26.3%)diagnosed as the cases with NIHL. The highest noise level at both the stamping and the drilling worksites were found and most were ranked as severe. The workers in these sites had higher morbidity of NIHL(P < 0.05). It was found that the equipment of protective facilities at worksites with higher noise level (ranked as moderate or severe) was better than that in other worksites(P < 0.01)and the proportion of wearing ear protectors among the workers at these sites was higher than workers at other sites with relatively lower noise level. The binary logistic regression analysis showed that the older age (over 40 vs. under 40 year old), longer exposure time(over 3 vs. less 3 years) and higher noise exposure level(the moderate and/or severe vs. the mild ranking) were risk factors(OR = 1.75, 2.03 and 1.99, respectively, P < 0.05), while effective equipment of protective facilities and wearing ear protector were protective factors(OR = 0.68 and 0.59, respectively, P < 0.05).

Conclusion The noise hazards in middle-size auto parts manufacturing enterprises in this city were severe and workers had a higher prevalence of NIHL. The improvement of technological process is the key to reduce noise level and the workers should be trained fully to understand the noise hazards and use ear protectors correctly. More attention should be given to older workers with longer exposure time.