Potential Health Effects of Noise Among Plant Workers at Aluminum Industry in Dubai, UAE

Hussein H. Y.¹, Al Faisal W.¹, Al Marashdah A. M.², El Sawaf E. M.², Wasfy A. S.³

¹Health Affairs Department, Primary Health Care Services Sector, Dubai Health Authority, Dubai, UAE

²Health Centers Department, Primary Health Care Services Sector, Dubai Health Authority, Dubai, UAE

³Research and Statistics department, Ministry of Health, Dubai, UAE

Abstract

Background: It is estimated that about 600 million workers are exposed to workplace noise worldwide. The WHO estimates that approximately 15% of the workers in developed countries are exposed to noise levels which are harmful to hearing. Objectives: To study some of potential health hazards among plant workers at aluminum industry due to exposure to worksite noise. Methodology: A cross sectional study was conducted in Dubai Aluminum Company Limited (DUBAL). All workers in DUBAL were targeted in the study. The sample size was calculated by using computer program EPI-Info version "6.04". The sample size was 400 workers with 100% response rate. Stratified random sampling technique was used. Two groups were selected according to noise level exposure. An interview questionnaire was designed for collection of data. Results: Plant workers showed significantly higher blood pressure level than administration group whether systolic (127.37 + 12.01 mmHg and 123.85 + 15.13 mmHg respectively) or diastolic (81.92 + 8.85 mmHg and 79.66 + 9.75 mmHg respectively). The two groups also differ significantly in the mean total cholesterol level (203.62 + 38.52 mmHg and 189.08 +32.94 mmHg respectively) and LDL (134.2 + 36.71 and 122.58 + 35.67 respectively). There was significantly higher pulse rate among the high exposure group (77.37 + 15.02 beats/min) than among the moderately high exposure group (72.47 + 13.82 beats/min) and the low exposure group (70.21 + 11.96 beats/min). Conclusions: Headache and pulse rate were related to the level of noise exposure at work site. Blood pressure (systolic and diastolic), total cholesterol and low density lipoprotein were all related to the place of work. Injury at work site was higher among workers exposed to noise compared with the administration departments with an apparent higher frequency of injury among workers in areas with high level of noise exposure in contrast to the low noise exposure category. Recommendations: Technical control of the problem along with admistrative control and Awareness for the workers has to be developed in an integrated health prevention and control program.

Keywords

Noise, Plant Workers, Aluminum Industry, Dubai

Received:May 21, 2015
Accepted: May 28, 2015
Published online: July 8, 2015

@ 2015 The Authors. Published by American Institute of Science. This Open Access article is under the CC BY-NC license. http://creativecommons.org/licenses/by-nc/4.0/

1. Introduction

Noise is present in every human activity, and when assessing its impact on human well-being, it is usually classified either as occupational noise (i.e. noise in the workplace), or as environmental noise, which includes noise in all other settings, whether at the community, residential, or domestic level (e.g. traffic, playgrounds, sports, music).(1) Noise levels are measured in decibels (dB), approximately 60 dB is the level of normal talking. Exposure for more than six hours a day to sound in excess of 85 dB is potentially hazardous to health. Measurements in A-weighted dB (dB(A)) assess loudness and compensate for the human ear’s lower sensitivity to lower frequency and very high-frequency sounds. (2)

Noise is the most pervasive hazardous agent at workplaces (3-5) and it is still the most frequent occupational hazard in workplaces. It is estimated that about 600 million workers are exposed to workplace noise worldwide. (6) The WHO estimates that approximately 15% of the workers in developed countries are exposed to noise levels which are harmful to hearing. (5) Approximately 30 million American workers are exposed to hazardous noise on their jobs. (4) In most developing countries, industrial noise levels are higher than those in the developed countries. (3)

Noise has both auditory and non-auditory health effects. Although the direct physical consequence of loud noise, especially over a period of time, is hearing loss and tinnitus (auditory effect), noise at lower levels can have indirect impact on our physiological and psychological systems, that is, non-auditory effects. (2) Noise-induced hearing loss (NIHL) is one of the oldest occupational diseases (6) and is one of the most important occupational diseases arising from long-term exposure to unauthorized noise levels.(6-11) NIHL is characterized by a gradual reduction in hearing acuity because of continuous exposure to intense levels of sound pressure, causing damage to outer and inner hair cells of the Organ of Corti. (12) NIHL is measured by comparing the threshold of hearing at a specified frequency with a specified standard of normal hearing, and is reported in units of dB hearing loss. The first effects of exposure to excess noise are typically an increase in the threshold of hearing called temporary auditory threshold shift (TTS). This is defined as a change in hearing thresholds of an average 10 dB or more at 2000, 3000 and 4000 Hz in either ear. The hearing loss corresponds to a permanent increase in the threshold of hearing that may be accompanied by tinnitus. Because hearing impairment is usually gradual, the affected worker will not notice changes in hearing ability until a large threshold shift has occurred. Noise-induced hearing impairment occurs predominantly at higher frequencies (3000−6000 Hz), with the largest effect at 4000 Hz. It is irreversible and increases in primary aluminum production which is considered as one of the largest industries in the world today. According to the International Aluminum Institute, this industry directly employs over a million people worldwide and indirectly generates four times as many jobs in downstream and service industries. (13)

In all phases of aluminum production, workers are exposed to numerous chemical and physical hazards. Noise is a significant health risk in aluminum smelting and casting operations where it has been identified to exceed 90 dB(A). (3)

2. Objectives

To study some of potential health hazards among plant workers at aluminum industry due to exposure to worksite noise.

3. Methodology

A cross sectional study was conducted. The study was conducted in Dubai Aluminum Company Limited (DUBAL) which owns and operates one of the world's largest aluminum smelters. All workers in DUBAL were targeted in the study Exclusion criteria :History of ototoxic drug use, diabetes, severe or frequent ear infections, ear trauma, conductive or sensory hearing loss with a known etiology except for noise exposure. The sample size was calculated by using computer program EPI-Info version "6.04". the minimum expected sample size was 334. Our sample size was 400 workers with 100% response rate. Stratified random sampling technique was used. Two groups were selected according to noise level exposure: The first group (200 workers) in which the employees were classified according to the noise level exposure into three strata: Group 1: Low noise exposure : <85 dB(A), Group 2: Moderately high noise exposure: 85− <90 dB(A), and Group 3: High noise exposure: >90 dB(A). (14,15-19) An interview questionnaire was designed for collection of data. The questionnaire was reviewed by occupational and community medicine consultants to review the face and content validity.

Table (1). Noise related health problems among workers by place of work (DUBAL, 2010).

4. Results

Some of the noise related health problems are presented in relation to place of work in table (1). Problem which is significantly higher among plant workers than administration department workers include injury at work site (13.5% and 3.5% respectively). Stress at work was significantly lower among plant workers than administration workers (53.0% and 63.0% respectively) where other health problems do not differ significantly between the two groups.

Table (2). Potential health effects of noise among plant workers according to different levels of noise (DUBAL, 2010).

When plant workers are stratified by level of noise exposure (table 2), no significant difference was encountered except the significantly higher percentage of those complaining of headache due to noise at the high exposure level 23.9% than the moderately high (17.9%) and low (9.0%). Otherwise there is just an apparent higher frequency of injury at work site (17.9%) among the high exposure group in contrast to the low exposure category (16.7%).

Table (3) demonstrates the results of clinical examination of workers by place of work. Plant workers showed significantly higher blood pressure level than administration group whether systolic (127.37 + 12.01 mmHg and 123.85 + 15.13 mmHg respectively) or diastolic (81.92 + 8.85 mmHg and 79.66 + 9.75 mmHg respectively). The two groups also differ significantly in the mean total cholesterol level (203.62 + 38.52 mmHg and 189.08 + 32.94 mmHg respectively) and LDL (134.2 + 36.71 and 122.58 + 35.67 respectively). Other measurements did not differ significantly though they are apparently higher among the plant group than the administration group.

Table (3). Results of clinical examination and investigations of workers by place of work (DUBAL, 2010).

However when theses health effects were compared among plant workers with different levels of exposure (table 4), no significant difference between groups was encountered except the significantly higher pulse rate among the high exposure group (77.37 + 15.02 beats/min) than among the moderately high exposure group (72.47 + 13.82 beats/min) and the low exposure group (70.21 + 11.96 beats/min). Other measurements showed just apparent higher levels among the high noise exposure group than the other two groups as systolic, diastolic blood pressure, total cholesterol, LDL and triglycerides.

Table (4). Results of clinical examination and investigations of plant workers by noise exposure level (DUBAL, 2010).

5. Discussion

It was evinced that plant workers have significantly about 2.56 times the risk of developing hearing loss compared to administration workers with prevalence of 8.5% among plant workers and 3.5% among administration workers. In accordance with the definition of NIHL, (20,21,22,23) this finding can serve reliably the assumption that hearing loss among plant workers can be attributed to noise exposure at work site. Reputing the differences between this study compared to others regarding the criteria used for defining hearing impairment, yet, the prevalence rate of hearing impairment reported in the current study is comparable to those reported by other researchers who found prevalence rate ranging between 8.59 % and 59.7 %. (4, 22,24,25,26) In a study done by Chang et al., (2009) (24) that assessed the exposure levels of noise among male workers in a liquefied petroleum gas cylinder infusion factory, it was found that the hearing threshold for each frequency tested was significant between groups, especially for the frequencies at 4 k, 6 k, and 8 kHz. Seixas et al., Apart from noise induced hearing loss, many other health problems likely to be associated with exposure to noise at work site were studied as well. First of these health problems, was headache. When plant workers are stratified by level of noise exposure, a significant difference was encountered. Higher percentage of those complaining of headache due to noise was found at the high exposure level than at the moderately high and at low noise exposure level. Headache was proved to be a common non auditory deleterious health effect among workers exposed to noise at work site by many researchers. (27-29)

On the contrary, stress at work was significantly lower among plant workers than among administration workers. Wieclaw et al., (2006) (30) in their study found a consistent association between employment in human service occupations and the risk of affective and stress related disorders. On the contrary, Melchior et al., (2003) (31) found that, job stress is most prevalent among manual workers and office clerks and predicts the occurrence of sickness absence. Annoyance, speech interference and sleep disturbances displayed non-significant relations with the development of NIHL among workers exposed to noise. In a study about noise exposure in oil mills, Kumar, (2008) (32) concluded that as a subjective response, 63% of his study sample expressed that noise was interfering with their conversation during work and subsequently harmed their hearing. Jakovljevic et al., (2006) (33) in a study about sleep disturbance in relation to noise exposure detected that, noise annoyance, subjective noise sensitivity and neuroticism were significantly correlated with difficulties with falling asleep, time needed to fall asleep, poorer sleep quality, tiredness after sleep, and use of sleeping pills.

Some physical findings were also investigated in relation to noise level exposure as well as the development of NIHL. Pulse rate was significantly related to noise level exposure, where it was more rapid among the high noise exposure group than among the moderately high exposure group and the low exposure group. This finding revealed an agreement with the results of Salameh, (2005) (34) and Powazka et al., (2002) (35) who proved positive correlation between the noise level exposure and pulse rate among workers in their studies.

Regarding some other physical findings, it was concluded that plant workers had significantly higher blood pressure level (systolic and diastolic), higher mean total cholesterol level, higher LDL level and apparently higher triglycerides comparing with the workers in administration group. Based on noise level exposure, it was found that, all these parameters revealed just apparent higher levels among the high noise exposure group than among the other two groups. In their study, Zhao et al., (2009) (36) reported that noise exposure is a significant determinant of hypertension prevalence, but third in order of importance behind family history of hypertension and salt use.

Our results came in accordance with others who proved an association between noise exposure and hypertension. Salameh (2005) (34) concluded that high levels of noise pollution can affect adversely the blood pressure (systolic and diastolic). Raised blood pressure among workers exposed to noise at work was also reported by other researchers; Stanbury et al., (2008), Haralabidis et al., (2008) Lee et al., (2009) (37-39). However, Rizk and Sharaf, (2010) (40) in their study to assess the risk of hearing loss among a sample of fermentation plant workers in Egypt exposed to both noise and a mixture of organic solvents have reported no association between blood pressure and exposure to noise. Moreover, Janghorbani et al., (2009) (41) found that blood pressure had no significant independent association with noise-induced hearing.

Considering blood cholesterol, Standbury et al., (2008) (37) in their study that assessed the prevalence of self-reported hearing loss and work-related noise-induced hearing loss in Michigan found an association between noise exposure and elevated cholesterol. While Janghorbani et al., (2009)(41) reported no association between noise exposure and raised cholesterol and triglyceride. Also, work site injuries were marked with noise exposure. Where proved to be higher among plant workers exposed to noise compared to administration group, also an apparent higher frequency of work site injuries were reported among the high noise level exposure group in contrast to the low exposure category. A study was done to assess occupational noise as a risk factor for work-related injuries showed that, "work always exposed to high-level noise" and "work sometimes exposed to high-level noise" were associated with relative high risk for work-related injuries compared with "work with no noise". Based on these findings, the study concluded that, investing in hearing conservation programs, particularly those for controlling noise emission at its source, is justifiable aiming at both hearing health maintenance and reduction of work-related injuries.(42) Melamed et al., (2004) (43) in their study to explore the possibility that exposure to noise at work might interact with job complexity to affect the incidence of occupational injury among industrial employees, found that the joint exposure to noise and high job complexity is disruptive, resulting in higher distress and occupational injury risk, particularly among women.

Explicitly we can brief that exposure to high levels of noise can cause different types of health problems that might be auditory in the form of hearing loss or non-auditory effects. Using many sensible approaches, noise exposure at work site could be preventable and controllable hazard. As a sobering step, continuous monitoring of noise level as well as raising the alertness to detect signs of hearing loss or other manifestations are important measures. By virtue of these steps, our trials would give way to assuage the deleterious effects of noise exposure, these steps would serve reliably to keep workers healthy and certainly would be heralded with good productivity.

6. Conclusions

Headache and pulse rate were related to the level of noise exposure at work site. Blood pressure (systolic and diastolic), total cholesterol and low density lipoprotein were all related to the place of work. Injury at work site was higher among workers exposed to noise compared with the administration departments with an apparent higher frequency of injury among workers in areas with high level of noise exposure in contrast to the low noise exposure category.

Recommendations

Technical control of the problem along with admistrative control and Awareness for the workers has to be developed in an integrated health prevention and control program.

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