Hearing status among aircraft maintenance personnel in a Swedish Commercial Airline Company

The aim was to study hearing loss in a population of aircraft technicians and mechanics and indentify predictors. Equivalent noise levels during a working day were measured and were 70-91 dB (A). Maximal noise level was 119 dB(A). A total of 336 aircraft maintenance personnel answered a self-administered work environment questionnaire (response rate 76%) and underwent audiometric test. The mean values for the hearing test at 3, 4, 6 kHz for the ear with the most hearing loss were compared with a Swedish population data base of persons not occupationally exposed to noise. At younger ages (-40 y) aircraft technicians and mechanics had more hearing loss compared to the reference group. Through multiple logistic regression analyses associations were found between age and hearing loss, and between exposure to solvents and reported annoyance due to hearing loss. In conclusion, aircraft technicians and mechanics may be exposed to equivalent noise levels above the Swedish occupational standard and have a higher age matched hearing threshold level at younger age compared to a reference group. Introduction Hearing loss is a problem at leisure activities and in many workplaces. In airline companies, hearing loss may have implications for safety communication between aircraft technician and mechanics, and cockpit during taxiing on platform. In addition to aging, occupational noise, genetic heredity, head injury, infections, certain drugs, high blood pressure and tobacco smoking (Lusk, 1997; Correa Filho et al., 2002; Ferrite & Santana, 2005; Uchida et al., 2005) are risk factors for hearing loss. Moreover, shooting and other impulse noise during leisure activities may also cause hearing loss (Nondahl et al., 2000), as well as non-impulse recreational noise as very loud toys, discos and exposure to electronically amplified music (Maassen et al 2001). Hearing loss is well documented in many studies and there is an international, standardized database for hearing threshold levels as a function of age, ISO 7029 (International Organization for Standardization, 1984), describing hearing threshold levels for an otologically normal population. In ISO 1990 (International Organization for Standardization, 1990) populations in USA are described. In addition, there is a Swedish database with hearing threshold levels for a population without occupational noise exposure (Johansson & Arlinger, 2002). In the aviation industry high noise levels are prevalent and the hearing ability of airline employees are usually followed by repeated audiometric tests. We have previously published data on hearing status and noise exposure in pilots and cabin crew (Lindgren 2008, Lindgren 2009). For both groups we concluded that they were exposed to equivalent noise levels below the occupational standard of 85 dBA, and they had normal age-matched hearing threshold levels. Another noise exposed group is the aircraft maintenance workers. Noise exposure occurs during maintenance work in hangar and on the platform during take-off and landing. However, there are still only a few studies on noise and hearing loss in aircraft maintenance workers. A Chinese (Chen 1992) study investigated hearing loss in aircraft maintenance workers, airport firemen, airport policemen, airline ground staff, and airport civil servants. The prevalence of a high-frequency loss was 42%, with the highest prevalence in maintenance workers (65%) and firemen (55%). Hong (2001) identified risk factors as noise exposure level, years of noise exposure, nonoccupational noise exposure, history of ear disease, ototoxic drug use, cigarette smoking, hypertension, and use of hearing protective device. Aircraft maintenance personnel may also be exposed to jet fuels and solvents and occupational exposures to organic solvents may have detrimental effect on hearing (Sliwinska-Kowalska 2007).. The combination of noise exposure and exposure to solvents may increase the risk of hearing loss. Subjects with noise and jet fuel exposure had an increase in hearing loss, even at fuel exposure estimates well below the threshold limit values (Kaufman 2005), and the effect of jet fuel appeared to be stronger at shorter duration of exposure. Kim (2005) studied the effect of occupational exposure to noise and organic solvents on hearing loss in male aviation industry workers. Pure tone audiometry from the workers biannual medical surveillance was used to assess hearing loss. Controlling for age, and compared to the unexposed, the relative risk of hearing loss was 8.1 in the both noise and solvents group, 4.3 in the only noise group and 2.6 in the solvents only group. Prasher (2005) compared aircraft maintenance workers to workers exposed to noise alone, to solvents alone, and to nonexposed.. There was a significant effect on pure tone thresholds for both noise and solvents+noise groups but the mean acoustic reflex thresholds showed a pattern of differences which differentiate noise from solvent and noise groups. The aim of the study was to investigate hearing thresholds and determine hearing loss in aircraft technicians and mechanics at a Swedish Airline Company, using reference data from a Swedish population data base of persons not occupationally exposed to noise, and to identify work related risk factors for hearing loss exposure to noise, occupation, years of employment and exposure to solvents. Study population and Methods Study population The study population consisted of all technicians and mechanics (maintenance personnel) employed in a Swedish airline company who had undergone voluntary audiometric test at the occupational health service in the years 2008 -2009. They were 327 males and 9 females, with a range of age of 22 to 67 years old. In total, there was 440 technicians and mechanics employed during this time period (76% participation rate). Due to the small