Noise induced hearing loss in a steel rolling mill company in Nairobi, Kenya
Abstract
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.
Publisher
University of Nairobi