Occurrence of ocupational noise induced hearing loss among workers at Jomo Kenyatta International airport, Nairobi
Anino, Joshua Omondi
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Occupational noise induced hearing loss occurs among workers exposed to excessive amounts of noise for long durations. It is a common debilitating condition that is preventable. The average level of noise at Jomo Kenyatta International Airport is above the safe limit of 85dB. The objectives of the study were to determine the occurrence, socio demographic attributes, risk factors and prevention strategies for NIHL at JKIA. It was a cross sectional descriptive and analytical study. Stratified random sampling was used to recruit 249 workers of whom 162 were ground crew and 87 air crew. Data were collected using questionnaire interview, unobtrusive observations, clinical otoscopy and audiometric testing. Data was described by sample size, frequency, mean, median and standard deviation. Comparison of means was done using Nest. Chi square test and ANOVA was used to assess association of hearing level and various predictors. Pearson's correlation was used to assess variation of mean hearing threshold with age and exposure durations. Logistic regression was used to compare variables between those with and those without hearing loss. Prevalence of NIHL was 15.3%, with ground crew at 14.9% and air crew 16.1%. Male workers were affected more than female workers with a Male to female ratio of 4:3. 97% of those affected were non-managers, 3% managers. 68% resided in Embakasi Division close to the airport. Median duration of exposure to noise for the NIHL group was 8 years, range 1 to 27. Mean hearing threshold level (HTL) at 3, 4 and 6kHz for ground crew was poorer than air crew (p=0.015) and for unionized employees better than non-unionized (P=0.021). Mean HTL at 3, 4 and 6 kHz correlated positively with age of workers, duration of exposure and history of involvement in an accident at work. Those exposed for less than 10 years had significantly better mean HTL than those exposed for more than 10 years (P<0.01). Workers aged 50 years and above had a relative risk of NIHL of 13.2 (p=0.001) compared to 20 to 29 year age group. Male workers had poorer HTL at 4 kHz than their 'female colleagues (p=0.04). Fatigue at work correlated strongly to NIHL (p=0.028). 72% of workers utilized a noise safety program. Health education and use of personal hearing protection devices (HPDs) was the most common. Fifty nine percent of respondents were required by their company policy to wear HPDs. Fifty one percent considered noise safety a high priority. It was concluded that NIHL was prevalent at noise polluted areas in JKIA. Ground crew were more vulnerable than air crew. Older age and longer duration of exposure was associated with higher prevalence of NIHL. Frequencies that were involved in hearing loss were the ones sensitive to noise damage. Preventive strategies were present but only a small percentage of both normal and NIHL groups used them optimally. Periodic audiometric assessment is recommended targeting long serving and older workers, enforcement of HPD use through education and inbuilt administrative mechanisms, utilization of safety strategies like shift rotations, leave scheduling, sound proofing of rooms and use of quiet machinery. Access to safety information should be improved through posters, public announcement, training and seminars.