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Hearing loss among cement factory workers in Northwest Nigeria

Background: Exposure to noise has been observed to have deleterious effect on the health status of individuals working within the noisy environment. Continuous exposure to high and unwarranted sound remains a major cause of hearing disorder all over the world. Occupational noise-induced hearing loss (NIHL) constitutes a worldwide problem in industries and contributes about 16% of hearing loss among adults globally. Aims and Objectives: The aim and objective was to evaluate the impact of occupational noise exposure on the auditory performance of workers at a cement company. Methods: This was a cross-sectional descriptive study of consenting workers at a cement company (public liability company). A total of 341 respondents were recruited for the study with equal number of controls matched for age and sex. Ear examination was done and based on the exclusion criteria, 23 participants with diseased ears were excluded. There hundred and eighteen participants (616 for both study group and control group) each had an interviewer–administered, semi-structured questionnaire and underwent diagnostic pure-tone audiometry. A digital sound level meter (Type 2 well-calibrated TOMTOP-Model Number H4320) with a range of 30–130 dB was used to map out the sound in the respective departments. Results: One hundred and one (31.8%) noise-exposed workers had mild (23.3%), moderate (7.2%), and severe (1.3%) hearing loss in their right ears as against the 21 (6.6%) in the controls. This was found to be statistically significant (P = 0.000). Seventy-seven (24.2%) noise-exposed workers also had mild (17.9%), moderate (6.0%), to severe (0.3%) sensorineural hearing loss in the left ear with the controls having 6.3%; this was also found to be statistically significant (P = 0.000). The presence of notch at 4 kHz audiometric configuration was 14.5% and 17% in better and worse ears, respectively. Three hundred (94.3%) workers in the noise exposed group worked for <8 h in a day (40 h/week) irrespective of the intensity of noise they were exposed to. Conclusion: This study has revealed a high prevalence of sensorineural hearing loss in the factory. This pattern of sensorineural hearing loss, coupled with the significant presence of 4 kHz audiometric notch among the noise-exposed workers (16.9%) in the worse ear when compared with the controls (3.1%) in the worse ear, strengthened the assertion that the hearing loss of the workers was likely attributable to occupational NIHL.