Occupational noise exposure and hearing loss of workers in two plants in eastern Saudi Arabia

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Abstract

Objective: To determine the prevalence of hearing loss associated with occupational noise exposure and other risk factors.

Design: A cross-sectional study involving 269 exposed and 99 non-exposed subjects (non-industrial noise exposed subjects) randomly selected. Current noise exposure was estimated using both sound level meter and noise-dosimeter. Past noise exposure was estimated by interview questionnaire. Otoscopic examination and conventional frequency (0.25–8 kHz) audiometry were used to assess the hearing loss in each subject.

Results: 75% (202 subjects) from the exposed group were exposed to a daily Leq above the permissible level of 85 dB(A) and most (61%) of these did not and had never used any form of hearing protecion. Hearing loss was found to be bilateral and symmetrical in both groups. Bivariate analysis showed a significant hearing loss in the exposed vs non-exposed subjects with a characteristic dip at 4 kHz. Thirty eight percent of exposed subjects had hearing impairment, which was an 8-fold higher rate than that found for non-exposed subjects. Multivariate analysis indicated exposure to noise was the primary, and age the secondary predictor of hearing loss. Odds of hearing impairment were lower for a small sub-group of exposed workers using hearing protection (N=19) in which logistic regression analysis showed the probability of workers adopting hearing protective devices increased with noise exposure, education, and awareness of noise control. Hearing loss was also greater amongst those who used headphones to listen to recorded cassettes.

Conclusion: Gross occupational exposure to noise has been demonstrated to cause hearing loss and the authors believe that occupational hearing loss in Saudi Arabia is a widespread problem. Strategies of noise assessment and control are introduced which may help improve the work environment.

Introduction

Occupational exposure to excessive noise is commonly encountered in a great variety of industrial processes. The resulting injury of occupational hearing loss is a well-recognized and global problem, and affects many subjects both civilians and military (Fletcher and Chandler, 1983, Hessel and Sluis, 1987, Alleyne et al., 1989, Army Environmental Hygiene Agency, 1990). Occupational hearing loss continues to be among the 10 leading occupational diseases in both Canada (Alleyne et al., 1989) and the United States (Anon, 1986). In the US about 11 million workers are exposed to potentially hazardous noise levels in the work place (NIOSH, 1988). In Sweden, about 9% of the total work force are exposed continuously to a hazardous noise level (Ivarsson et al., 1992). Noise induced hearing loss (NIHL) is very costly. Approximately 100 million dollars are paid annually for compensation in Sweden (Ivarsson et al., 1992). The Canadian compensation board estimated the average cost per hearing loss claim to be C$14 000 (Alleyne et al., 1989). In the United States, compensation for hearing is estimated as US$200 million for the calendar year 1990 (Army Environmental Hygiene Agency, 1990).

Occupational hearing loss resulting from exposure to high noise level depends not only on exposure time but also on the frequency, intensity, and the type of noise (continuous or impact). During the last few decades, greater understanding of the effects of noise on hearing have led to minimum standards for noise exposure being adopted and legislation passed to limit noise exposure has been enacted in many countries. However, difficulties have arisen where there was no pre-employment audiometry and unknown previous occupational noise exposure as in developed countries.

In Saudi Arabia, many industries have been established since the 1970s. Many within the work force of these industries were and are exposed to occupational hazards and consequently are at high risk of work-related diseases. Though work-related diseases are amenable to prevention through the recognition, evaluation, and control of the hazards in an ideal world, effective practice of occupational health and hygiene has yet to be fully accepted and developed in Saudi Arabia as in the other developed countries. To date few studies have been conducted in Saudi Arabia to investigate the occupational hazards, such as noise, and its health effects on the working population. Against this background, the investigators designed and progressed an epidemiological study of noise exposure and hearing loss among workers in two plants in the Eastern Province of Saudi Arabia.

The specific objectives of the study were: to estimate levels of current and past occupational noise exposure, to determine the extent and pattern of hearing loss among the study population, to assess the risk factors that influence hearing loss at each of the conventional frequencies tested, and finally to evaluate the knowledge and practice of workers to noise hazards.

Section snippets

Subjects and methods

Workers from two factories in the Eastern Province of Saudi Arabia were selected for this cross-sectional study. One factory manufactured steel pipes and the other manufactured air conditioning units. The study was conducted between 1996 and 1999. 269 exposed subjects were randomly selected from a total workforce of 600 from the two factories. Similarly 99 non-exposed subjects (non-industrial noise exposed subjects) were randomly selected from the administrative staff of the two factories and

Statistical analysis

Data were analyzed using SPSS (version 6.0). Normality of the audiometric data was first tested by computing the skewness and kurtosis. Descriptive statistics, means, medians, standard deviations were calculated to describe central tendencies in each of the groups. T-test for independent samples, and median test were used to evaluate the differences between mean and median of the groups, and between right and left ears in each group respectively. Two-way analysis of variance was performed to

Demographic characteristics of the study population

The majority, 66% (244 subjects), of the study population were less than 35 yr of age. Of these, 170 (70%) were exposed. The mean of age of the total exposed subjects was 32.9 (SE=0.5) yr compared with 30.2 (SE=0.7) for the non-exposed subjects (P=0.003). Of the total exposed subjects, 182 (67.7%) had a current duration of exposure of less than 5 yr, with a mean of 4.5 (SE=0.3) yr for the total exposed subjects. However the majority of the exposed subjects (56.5%) worked for 5 yr or more before

Discussion

No significant difference was found between right and left ears of the exposed subjects after exclusion of those who reported firing guns. This finding indicates that the adverse noise effect is generally bilateral and symmetrical, as defined by Alberti (1988). The occurrence of hearing loss as a result of prolonged exposure to a noise level greater than 85 dB(A) without ear protection is well documented in the literature (Berger et al., 1978, Dobbie, 1985, WHO, 1986). The present study also

Conclusion

This study has clearly shown that the workforce within both factories included in this study are at high risk of developing noise induced hearing loss due to excessive occupational exposure to noise. Though legislation to control noise exposure exists in Saudi Arabia, poor compliance in relation to wearing and enforcement of wearing and/or attitude and education to hearing loss and noise exposure suggests legislation is poorly enforced. A well-defined, comprehensive, and enforcable noise

Acknowledgements

The authors are deeply indebted to the adminstration of the two factories that participated in this study, and particularly the participants for their co-operation.

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