Comparison of Noise-Induced Hearing Loss between Stone Processing Workers and Hotel Workers

Abstract

Stone processing industry is expanding due to economic expansion. It has a work process associated with noise exposure which could lead to hearing loss. Thus, there is a need to assess the impact of noise on the hearing of workers and to identify possible ocupational risk factors in order to manage the risk. The objectives of this study were to compare hearing capacity of stone processing workers with that of hotel workers, and to identify factors accelerating hearing loss. The samples were 56 workers in a stone processing factory and 39 workers in a hotel, both settings were in Chiang Rai province, Thailand. Noise intensity was measured by sound pressure level meter whereas hearing threshold was determined by audiometer. It was found that the noise level in the workplace of the stone processing group was higher than that of the hotel group (61.30-93.00 vs 50.00-73.70 dBA). The means of hearing threshold levels in stone processing workers at 500 and 1,000 Hz were significantly higher than those of hotel workers (at 500 Hz: left ear 28.39 vs 20.77, right ear 28.39 vs 21.41 dB; and at 1,000 Hz: left ear 22.59 vs 15.77, right ear 20.80 vs 15.90 dB, p<0.05). A significant difference of the mean hearing threshold levels between the 2 groups were not observed at 3,000-6,000 Hz, which was difference from the noiseinduced hearing loss pattern. A possible factor that explain hearing loss at low frequency was a coexposure of ototoxic agent which was generated from vehicle exhaust in the stone processing factory. The hearing loss at 500-2,000 Hz affects the workers’ daily life because this frequency is used for human communication, especially if this pathology becomes more severe. Therefore, the noise hearing conservation program should be implemented among stone processing workers, including noise exposure prevention and annually ear health checking to follow up noise-induced hearing loss.