Risk factors of hearing loss among thai naval officers on coastal patrol boats

Abstract

Naval officers are assigned at a variety of stations of a ship. Some of them are at risk of hearing loss while aboard the ship, because they are exposed to high levels nose at the assigned station or have chance to shoot guns. This study aimed to clarify the prevalence of hearing loss and its risk factors among Thai naval officers on coastal patrol boats. The subjects were 149 male naval officers, aged at 20 to 56 years, working on the coastal patrol boats. All subjects were asked to fill in a questionnaire on characteristics, personal histories and working conditions. Audiometrie threshold testing was performed at the audiometric frequencies of 0.5, 1, 2, 4 and 8 kHz in a sound proofroom. The noise levels and the organic solvent (toluene, xylene, ethyl acetate, butyl acetate, and cyclohexanone) concentrations in the working environment were measured on the common type of gun boats. The results are as follows. Ninety-eight percent of the subjects had the experience of gun shooting. Eighty-six percent of them, however, used no hearing protective equipment. Forty percent of them had hearing loss. The hearing losses were classified into 4 kHz-dip (22.8%), high frequency hearing loss (14.8%) and mixed hearing loss (2.0%). The equivalent A-weighted noise level (LAeq) was 100.6 dB in the engine room, but it was less than 85 dB at other stations. The organic solvent concentrations were less than the occupational exposure limit for organic solvents. Multiple logistic regression analysis showed that two factors were significantly associated with hearing loss. They were: age more than 35 years (OR=9.72; 95%CI: 3.53-26.75) and work experience more than 10 years (OR=3.04; 95%CI: 1.18-7.83). The high prevalence of hearing loss suggests that the Thai navy should develop hearing conservation program for naval officers on the coastal patrol boats.