YabaniAssessment of Noise Induced Hearing Impairment n a Cement Factory

Abstract

ABSTRACT OBJECTIVE: GENERAL:- To assess the prevalence of occupational cement factory. SPECIFIC: (1) To measure the noise levels at different sections in the factory (2) To compare the prevalence of hearing impairment among workers of different age-groups. (3) To compare the prevalence of hearing impairment among workers with different lengths of exposure. (4) To determine whether the speech frequency range of those workers with hearing impairment is affected. DESIGN: Cross sectional study SETTING: Cement factory with a captured population of 308 workers. PARTICIPANTS: One hundred workers were selected at random from three hundred and eight workers. The selected workers were interviewed to discover other risk factors contributing to hearing loss. A recent auroscopic examination report was examined to rule out any ongoing ear infection. The workers then underwent audiometric assessment with a wide range qualitone Model WRB 6097 Diagnostic Audiometer calibrated according to American National Standard Institute (ANSI) 1969 standard. MAIN OUTCOME MEASURES: Noise levels at different locations in the factory were measured and prevalence of Noise-induced hearing loss assessed. RESULTS: The worst areas of toxic noise was the production section where noise levels ranged between 80 dBA and 108 dBA(decibels -Aweighted). Even though noise levels in the engineering section was below the threshold limit value, most of the workers from this section carry out maintenance work for long hours in the production section. Forty-two (42%) out of the 100 workers selected showed definite noise-induced hearing impairment, whilst 15 (15%) workers were strongly suspected of having noise-induced hearing impairment, 38 workers (38%) had good hearing acuity whilst 5 (5%) had excellent hearing acuity. Out of 42 workers who were forty years of age and below, 10 workers (23.8%) showed noise-induced hearing impairment, whilst out of 58 workers who were above forty years of age, 32 workers (55.2%) showed hearing impairment. Hearing normally declines with age. The effect of aging and noise exposure are additive, consequently the prevalence of noise induced hearing loss increases with age. Eleven workers (35.5%) of the 31 workers who had had noise exposure for up to five years showed noise induced hearing impairment (NIHI), for exposure between 6 and 10 years, 3 workers (23%) of 13 workers showed NIHI, for the exposure period 11-15 years, 6 workers (28.6%) out of 21 workers exhibited NIHI, and for those with exposure period 16 years and above, 22 (62.9%) out of 35 workers exhibited N.I.H.I. For the first 10 years of exposure to noise, 14 workers (31.8%) out of 44 workers exhibited N.I.H.I, whilst 28 workers (50%) out of 56 workers who had more than 10 years exposure exhibited NIHI, therefore the prevalence of noise induced hearing impairment increases with increasing length of noise exposure. Out of the 42 workers who had noise-induced hearing impairment, 37 of them (88.1%) had no problem engaging in normal conversation. Only 5 of the workers (11.9%) showed signs of mild defect in the speech frequency range. LIMITATIONS: Unavailability of pre employment baseline audiometric data. RECOMMENDATIONS: To Government (1) Government should update existing legislations and provide statutory regulations and code of practices for control of noise in industries. (2) The Government agency in charge of he should establish an occupational health service which could be integrated into the primary health care delivery service. (3) The Workmen's Compensation Scheme operated by the Labour Department is unsatisfactory, it should be updated to cover all occupational diseases. To Management (1) A hearing conservation programme should be set up in the industry. (2) Management should make sure that pre-employment medical examination are conducted for their workers followed by routine periodic examinations. (3) Management should organise regular meetings to discuss occupational health and safety problems with trade unions and supervisors. (4) Management should team up with managements of other factories to set up a well equipped occupational health service which will cater for their occupational health needs with a full or part time industrial physician. To Trade Unions (1) They should hold regular educational seminars on occupational health and safety for workers. (2) Whilst they make sure that management provides the necessary protective equipment, they should monitor to ensure that protective devices are worn always by workers and also ensure that newly employed workers undergo preemployment audiometric assessment.