Noise induced hearing loss in a steel rolling mill company in Nairobi, Kenya
Background: Occupational noise induced hearing loss (ONIHL) is a significant economic and health concern in the developing world but the prevalence among factory workers in Kenya is not well known. The iron and steel industry employees are exposed to excessive occupational noise as compared to other industries, hence vulnerable to permanent deafness. ONIHL is a preventable condition with effective occupational noise control strategies. Objective: To determine the prevalence and risk of developing ONIHL in a group of production versus administrative non- production workers in relation to intensity and duration of noise exposure. Study Site and Population: This study was conducted in a busy steel rolling mill based in the industrial area of Nairobi Kenya. 114 workers were randomly recruited and distributed equally between the two groups. All participants were male, 93.9% were below 50 years old, and 62.8% had at least secondary education. Study Design and Methodology: This was a cross-sectional comparative study. Each participant had a structured questionnaire followed by tuning fork tests and a baseline audiogram. Noise mapping was done at various units Data Analysis: Chi-squared tests for categorical variables and analysis of variance tests (ANOVA) for continuous variables were performed. Independent predictors of NIHL were determined using backward stepwise logistic regression. A p-value of less than 5% (p= <0.05) was considered statistically significant. Results: A total of 39(34.2%) workers were found to have NIHL. From these, 17(81.0%) worked in the mill machine, 11(45.8%) were from the furnace, 5(41.7%) operated in the workshop and 6(10.5%) worked in the non-production administration unit. The total duration of being employed as a factory worker was a statistically significant factor (p<0.0305) associated with NIHL. Factory workers who had served for 10-19 years were mainly from the administration group 19 (33.3%) as compared to 6(28.6%) in mill machine, 5(20.8%) in furnace, and 3(25.0%) in the workshop. Exposure to high noise intensity was a significant factor (p < 0.0001) associated with NIHL. Mill machine workers had the highest risk of developing NIHL due to operating in the highest noise levels of 98.0 dB(A). The relative risk of developing NIHL for production unit workers was 33.1(95% CI 7.7-141.63). In this study, using HPDs was not a significant factor (p = 0.088) in prevention of NIHL. Only 15(13.2%) workers had a pre-employment audiogram done in this factory With the multivariate analysis, the factors associated with NIHL were duration of employment (OR 3.8, 95% CI: 1.17, 12.53; p=0.001), working in the production unit (OR 33.10 95% CI: 7.74, 141.63; p<0.001) and age (OR 3.03, 95% CI: 1.48, 6.17; p=0.03). Conclusion: This study demonstrates that hearing loss is common among steel mill workers within this region. These findings qualify for implementation of an effective hearing conservation and rehabilitation policy that will protect and improve the quality of life of these mill workers.