[Effects on hearing due to the occupational noise exposure of marble industry workers in the Federal District, Brazil]

Abstract

Objective: To evaluate the prevalence of hearing loss, its degree and type, among workers in the marble industry in the Brazilian Federal District (FD).

Method: Workers from eight marble industries in the FD were evaluated by means of a cross sectional epidemiological study. An audiometry screening test (air conduction) was performed. Workers with hearing loss were submitted to liminal tonal audiometry air & bone conduction and speech audiometry tests using an audiometer AD-28 (Interacoustics). All subjects studied were submitted to a visual inspection of the external acoustic meatus.

Results: One hundred and fifty two workers were examined; mean age was 32 years (SD = 8.6); average occupational noise exposure was of 8.3 years (SD = 6.8). Audiometries demonstrated that 48.0% (n = 73) had some type of hearing loss. Among the workers with hearing loss, 50.0% had results compatible with noise-induced hearing loss (NIHL); 41.0% with incipient noise induced hearing loss, 5.0% with sensorineural hearing loss (all except NIHL) and 4.0% with conductive and mixed hearing losses. Among workers with NIHL, 57.1% had bilateral involvement, 17.1% in the right ear and 25.7% in the left ear. Among those with incipient NIHL, 13.9% were bilateral, 19.4% were only in the right ear and 66.7% were only in the left ear.

Conclusion: Abnormal audiograms were found in 48.0% of the sample. Among those with hearing loss, the predominant cause was NIHL, followed by those classified as having incipient noise induced hearing loss. Hearing loss usually started at 6 kHz, frequently in the left ear.