Noise-induced hearing loss among textile workers in Lagos metropolis

A cross-sectional sample of 204 textile workers was selected randomly from all sections (including the non-production areas), and was initially screened to exclude subjects with pathological middle ear as well as those currently working in sections classified as non-noise but who had been exposed to excessive noise in the past. A total of 17 workers were thus excluded leaving 187 who were then assessed by means of air-conduction and bone-conduction audiograms obtained by the use of a manual (medicor-SA 3L), pure-tone audiometer. All audiometric tests were preceded by an otological examination to rule out the presence of any significant aural pathological conditions. The subjects were divided into 3 groups, based on the noise levels observed at their worksites using a Bruel and Kjaer type 2225 (integrating) sound level meter viz: the noise-exposed group (noise levels > 90 dBA); the less-noise-exposed group (noise levels 85-90 dBA); and the non-noise-exposed group (noise levels < 85 dBA). A comparative analysis of the data on hearing threshold levels of the 3 groups showed that the noise-exposed group had significantly (P < 0.05) elevated hearing threshold levels at all frequencies and in each age group, although the maximal threshold shifts were observed at the 4000 Hz frequency. Also, the hearing threshold levels for the noise-exposed group increased with the duration of noise exposure. The study clearly showed the deleterious effects of uncontrolled occupational noise exposure on unprotected workers. A very high prevalence rate of noise-induced hearing loss (79.8%) was recorded for the noise-exposed group. The less-noise-exposed group recorded a comparatively low figure of 11.3%. The weaving section alone recorded the highest prevalence rate of 84.5%, followed very closely by the spinning section with 71.0%. The lowest prevalence rate (2.9%) was recorded for the administrative staff.