Evaluating the Effectiveness of Earplugs in Preventing Noise-Induced Hearing Loss in an Auto Parts Factory in China

A survey was administered to 385 noise-exposed workers from an auto parts factory and 1268 non-noise-exposed health department employees in China. Individual 8 h A-weighted equivalent sound levels (L(Aeq,8h)), earplug personal attenuation ratings (PARs), and pure-tone audiometric tests were performed. The average L(Aeq,8h) of noise-exposed workers was 87 dB (A) with a mean PAR of 7 dB. The prevalence of high-frequency hearing loss was 65% for noise-exposed workers and 33% for the non-noise-exposed employees. The use of earplugs had no observable effect on the prevalence of high-frequency hearing loss of the study participants (OR 0.964, 95% CI 0.925–1.005, p = 0.085). No significant relationship between the effectiveness offered by earplug use and high-frequency hearing thresholds at 3, 4, and 6 kHz was found (t = −1.54, p = 0.125). The mandatory requirement of earplug use without individualized training on how to wear HPDs correctly had no detectable effect on the prevention of hearing loss at the auto parts factory. The hearing conservation program at the surveyed factory was not effective. Periodic hearing tests, earplug fit testing, expanding the offer of different types of hearing protection, and employee education about the importance of protecting their hearing were recommended to the occupational health and safety program.