Noise-induced hearing loss (NIHL) is identified as one of ten leading work-related diseases and injuries by the National Institute of Occupational Safety and Health. It is the second most prevalent occupational health problem follows occupational lung disease in Korea. The occupational risk of NIHL in industries that expose workers to continuous high levels of noise is well established. There is a great individual variation in developing NIHL and several factors such as age, gender, ototoxic drug use, cigarette smoking, and prior ear disease have been considered to explain individual differences in NIHL. However, a limited literature describes a relationship between occupational noise exposure and personal risk variables and hearing loss in employees working at the airport.

The purpose of the study were to: (a) determine the prevalence and characteristics of hearing loss, (b) explore the relationship between hearing loss and occupational noise exposure, and (c) investigate the contribution of personal risk factors to hearing loss in employees working at the airport. The cross-sectional epidemiological study was conducted with 255 noise-exposed and 195 non-noise exposed full-time male workers at a large metropolitan airport in Korea. Four measures were used: (1) self-administered Occupational Hearing Questionnaire; (2) audiological assessment, otoscopic examination and pure-tone audiometry; (3) blood pressure measure; and (4) record review of baseline hearing and noise level of workplace where the employee currently works.

The results showed that the average airport workers exhibited a characteristic bilateral noise-induced permanent threshold shift with a dip at 6 kHz. The area of initial decline hearing sensitivity is seen at 3-6 kHz, the most sensitive frequencies to noise exposure. There was a significant difference in prevalence of hearing loss between the noise and the non-noise groups; 49.4% of noise-exposed workers had hearing loss in the higher frequencies and 14.5% had losses in the lower frequencies as compared to 6.7% and 0.5% of non-exposed workers, respectively.

Multiple regression model was applied to determine the dependence of the hearing loss on the occupational noise-related and personal risk factors. Occupational noise-related variables included noise exposure level and years of noise exposure. Personal risk factors included age, history of ear disease, non-occupational noise exposure, ototoxic drug use, cigarette smoking, hypertension, and the hearing protective devices (HPDs) use. The value $alpha$ = 0.05 was set for significance. An excessive occupational noise exposure stands out as the primary cause of the prevalence of hearing loss among the airport workers. The findings also revealed that several personal risk factors contributed significantly to worker's hearing, including age, non-occupational noise exposure, history of ear disease, ototoxic drug use, cigarette smoking, and the HPDs use. Recommendations for future research were discussed, as well as implications for effective hearing conservation programs.