Auditory Effects due to Occupational Noise Exposure in Selected Industries in Jeddah, Saudi Arabia

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161

Ahmed S. Summan, Mohammad H. Goknil, and Magdy Y. Shamy Environmental Sciences Department, Faculty of Meteorology, Environment and Arid Land Agriculture King Abdulaziz University,

P.O. Box 80208, Jeddah 21589, Saudi Arabia

Abstract. Exposure to high levels of noise causes physiological and psychological effects such as hearing loss, fatigue and reduction in performance. This study was aimed to evaluate the auditory effects of exposure to different levels of occupational noise in some industries in Jeddah, Saudi Arabia. Results indicated that 97% of the 33 examined workers, representing three factories were exposed to high noise levels (L_eq), – greater than the recommended standard (85 dBA / 8hrs-day) in Saudi Arabia. Of those workers, 76% didn’t wear any hearing protectors. Hearing loss was developed mostly after the first ten years of employment in 20% of workers. Audiometric examinations of the studied workers showed that 6% had severe hearing loss at high frequencies of 4 kHz and 8 kHz. Moderately severe to mild hearing loss was observed both at high (4 kHz-8 kHz) and low (250 Hz-500 Hz) frequencies. There was a strong positive significant correlation between hearing loss and noise dose, age, and duration of exposure.

Keywords: Industrial Noise Exposure; Assessment of Noise Exposure; Auditory Effects

Introduction

Noise, which is essentially any unwanted or undesirable sound, is not a new hazard. Exposure to high levels of noise was reported to cause hearing impairment, interference with communication, physiological and psychological effects and changes in social behavior (Plog et al., 2002).

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Many industrial processes generate high levels of noise which was related to increased accidents and sick leaves (Melamed et al.,1992), decreased job satisfaction (Melamed et al.,2001), reduced performance (Muzammil et al., 2004), and job stress (Mursali et al.,2009).

Physiological effects of high levels of noise exposure such as changes in blood pressure (Melamed et al., 2001) and changes in nocturnal sleep architecture and heart rate (Gitanjali and Ananth, 2003) have also been reported.

Noise-induced hearing loss (NIHL) caused by occupational noise exposure is one of the important industrial health effects (Nelson et al., 2006 and Dobie, 2008). Occupational noise – induced hearing loss was reported as 2.9% - 79.8% among textile workers (Osibogun et al., 2000), 15.9% - 56.8% among metal workers (Guerra et al., 2005 and Ologe et al., 2006). Over 60% of operating engineers showed hearing loss in the noise-sensitive higher frequencies of 4 and 6 kHz in a study on workers in American construction industry. 38% reported ringing/ buzzing in the ear and 62% indicated having problems in understanding what people say in loud noise (Hong, 2005).

The present study was carried out aiming to evaluate the auditory effects of exposure to different levels of occupational noise in some industries in Jeddah, Saudi Arabia.

Materials and Methods

Investigated industries were selected after preliminary noise survey from major noisy industries in Jeddah; namely, steel factory, carpet factory, and water filter factory. Noisy locations in each factory were identified by visits and preliminary sound pressure level (SPL) measurements.

Assessment of Noise Exposure

Identified noisy locations in selected factories and number of workers in each location were as follows: Steel Factory; Slitting area (4 workers), tube forming area (4 workers), and tube collecting area (4 workers). Carpet Factory; Tufting area (6 workers), and printing area (5 workers). Water Filters Factory; Welding area (7 workers), and fabrication area (3 workers).

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The following measurements were carried out in each location during a three- months period: Sound Pressure Levels (SPL), Octave Band Analysis (1/1), Daily Noise Dose, and Audiometric Tests.

SPLs were measured during 8-hours period, once a week using Metrosonics db-301 Metrologger (auto recording sound level meter, range 60 – 123 dBA). Octave Band Analysis (1/1) was performed once a month using B & K 2215 octave band analyzer. Measurements were carried according to ISO 1999 standard. Metrologger and octave band analyzer were fixed safely at the locations of workers, 1 meter (maximum) away from machine, 1.25 meter above the floor and 2 meters away from walls during measurements.

Daily Noise Dose was measured during 8-hours period, once in fifteen days by using B & K 4431pocket dosimeter, fixed inside the pocket of the worker. Microphone was attached collar of the worker.

Measurements were carried according to ISO 9612 standard.

Audiometric tests were performed for all workers in each area, once during the period of investigation using Miaco manual audiometer type MA27 in the range of 250 – 8000 Hz. in a sound isolated room in each factory. Maximum permissible SPLs in the test room were meeting the requirements of ISO standard 8253.

The audiometric tests were applied for all workers once after shift.

The audiograms were compared to the following more commonly used classification system: 1) -10 dB to 25 dB = Normal hearing, 2) 26 dB to 40 dB = Mild hearing loss, 3) 41 dB to 55 dB = Moderate hearing loss, 4) 56 dB to 70 dB = Moderately severe hearing loss, 5) 71 dB to 90 dB = Severe hearing loss, and 6) Over 90 dB = Profound hearing loss (Clark, 1981).

Equipments were calibrated as described in their manual before each measurement.

Statistical Analysis

Grouping of workers was carried out as follows:

A) According to noise dose (based on preliminary survey data on SPLs); 3 groups of workers: Low exposure: 86-90 dB, Moderate exposure: 91-95 dB, and High exposure: 96-100 dB.

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B) According to hearing status; 5 groups of workers: 1) Normal hearing, 2) Mild hearing loss, 3) Moderate hearing loss, 4) Moderately severe hearing loss, and 5) Severe hearing loss (Clark, 1981). Statistical analyses were done using the analysis of variance, followed by the least significance difference test at 0.05 level of probability (Steel and Torrie, 2000).

Results and Discussion

Measured sound pressure levels for 8-hour work day period through the three-month survey at three factories are shown in Table 1.

Table 1. Noise Levels at Factories as L₁₀, L₅₀, L₉₀, and L_eq. Range of Noise Levels, dBA Factory Location

L₁₀ L₅₀ L₉₀ L_eq Slitting 94 - 121 77 - 87 65 - 74 87.1 - 101.5 Tube forming 97 - 121 89 - 95 76 - 85 93.0 - 99.5 Steel

Tube collecting 93 - 100 86 - 95 78 - 86 90.3 - 97.0 Tufting 85 - 90 76 - 88 61 - 80 83.2 – 97.5 Carpet

Printing 84 - 121 75 - 91 60 - 82 89.7 – 98.2 Welding 83 - 95 68 - 83 60 - 75 82.6 – 94.5 Water

Filters Filter Machine 87 - 97 78 - 91 60 - 79 85.9 – 93.8 L10: SPL exceeded 10% of the time, L50: SPL exceeded 50% of the time, L₉₀: SPL exceeded 90% of the time, L_eq: Energy equivalent SPL.

Table 1 shows that surveyed workers were exposed to high noise levels. Saudi Arabian Standards Organization (SASO) recommended an 8-hour noise exposure limit (L_eq) of 85 dBA with 5-dBA exchange rate (SASO, 2008). The equivalent noise levels (Leq) exceeded the SASO standard at all locations in each factory except one reading in tufting area of carpet factory and one reading in welding area of water filters factory.

Spectral analysis results of noise based on frequency 1/1 octave band showed that the noise levels in the steel factory were usually high at the high frequency (4-8 kHz) and ranged between 87 dBA and 98 dBA, while in the carpets and water filters factories the noise levels were usually high at the low frequency (63-500 Hz) and ranged between 86 dBA and 92 dBA.

Noise doses measured for workers who are actually exposed to noise during their day shift (8 hrs) in their job locations for steel, carpet, and water filters factories are shown in Tables 2, 3, and 4 respectively.

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Table 2. Noise Exposed Workers in the Steel Factory.

Noise No. Site Age

Current job years

Use of ear protectors

Exposure dB/8hrs-day

% of dose

1 Slitting 46 10 no 86 57

2 Slitting 36 10 no 95 200

3 Slitting 33 7.5 no 93 152

4 Slitting 38 6 no 95 200

5 Tube Forming 65 14 yes 96 230

6 Tube Forming 32 10 no 96 230

7 Tube Forming 30 4 no 91 115

8 Tube Forming 48 10 yes 93 152

9 Tube Collecting 48 11 no 88 76

10 Tube Collecting 28 3 no 91 115 11 Tube Collecting 36 11 no 92 132 12 Tube Collecting 45 14 yes 92 132

Table 3. Noise Exposed Workers in the Carpet Factory.

Noise No. Site Age Current

job years

Use of ear

protector Exposure

dB/8hrs-day % of dose

1 Tufting 50 9 no 92 132

2 Tufting 31 4 no 92 132

3 Tufting 43 11 no 91 115

4 Tufting 29 7 no 88 76

5 Tufting 32 7 no 90 100

6 Tufting 36 10 no 90 100

7 Printing 42 10 no 91 115

8 Printing 36 10 no 91 115

9 Printing 35 10 no 86 57

Table 4. Noise Exposed Workers in the Water Filters Factory.

Noise No. Site Age Current

job years

Use of ear

protectors Exposure dB/8hrs-day

% of dose

1 welding 45 10 yes 92 132

2 welding 47 9 no 95 200

3 welding 49 16 yes 97 264

4 welding 33 9 no 80 25

5 welding 37 9 no 98 303

6 welding 59 22 no 100 400

7 welding 55 9 no 93 152

8 filters machine 19 1 yes 86 57

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SASO permissible noise dose limit is 50% of dose. Presented noise doses are higher than the SASO limit for all workers in three factories, except one worker at the welding area of water filters factory. Present results also indicate that 97% of 33 workers from the three factories were exposed to high noise levels (Leq), which are greater than the recommended standard (85 dBA / 8hrs-day) in Saudi Arabia.

There were 30.3 % received a dose between 50 and 100 percent, 51.5% between 100 and 200 percent and 15.2 % above 200 percent among the group receiving a high dose. About 76% of the examined workers didn’t wear any hearing protectors. This finding is in agreement with Ahmed and his co-workers (Ahmed et al., 2001). They found that in steel and air conditioning factories in Dammam 75% of 269 workers were exposed to a daily Leq above the permissible level of 85 dBA and most (61%) of these didn’t or had never used any form of hearing protection.

The results of audiometric tests for all workers are shown (NIHL) in Table 5.

Table 5. Noise induced hearing loss detected in the worker population.

Frequency

250 Hz 500 Hz 4 kHz 8 kHz

Hearing loss status

% of group % of group % of group % of group

Severe - - 6 (both ears) 6 (both ears)

3 (right ear) Moderately

severe

6 (right ear) 6 (right ear) 15 (both ears) 3 (both ears) 3 (right ear) 6 (left ear) Moderate 27 (both ears)

12 (right ear) 9 (left ear)

27 (both ears) 3 (right ear) 6 (left ear)

Mild 12 (both ears)

27 (right ear) 18 (left ear)

21 (both ears) 15 (right ear) 6 (left ear) Normal

hearing

15 (both ears) 15 (left ear)

Table 5 shows that at 4 kHz frequency 6% of workers had a severe hearing loss for their both ears, 15% moderately severe and moderate hearing loss and 12% mild hearing loss. The presented results show that both hearing difficulty and hearing loss increase with noise doses more than 85 dBA, age, and period of exposure to noise at frequency 4 kHz.

This finding is in parallel with Neuberger and his co-workers (Neuberger

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et al., 1992); who reported that age and noise exposure level are the most important factors in predicting hearing loss at frequency 4 kHz.

In a study in Athens (Rachiotis et al., 2006) on electro production workers it was found that 44% of them had sensorineural hearing loss located mainly at 4 kHz. The sensorineural hearing loss which was detected in 71 workers among a group of 130 high level noise-exposed workers in a hydro-electric power plant were bilateral, symmetrical and affected mainly frequencies of 4-6 kHz (Celik et al., 1998).

Moreover, our results are in agreement with Ologe and his co- workers (Ologe et al., 2006), who found that the prevalence of hearing loss among their study population was high, and the average hearing threshold at 4 kHz significantly increased with an increasing noise exposure level. Bivariate analysis showed a significant hearing loss in the exposed vs. non-exposed subjects with a characteristic dip at 4 kHz.

Multivariate analysis indicated exposure to noise was the primary, and ages the secondary predictor of hearing loss (Ahmed et al., 2001).

The audiometric results of the present study clearly show that 39%

hearing loss (between severe and mild) at high frequency of 8 kHz for both ears. These results are in agreement with Ahmed and his co-workers (Ahmed et al., 2004), who found that 65.6% noise exposed workers have hearing loss at high frequency 8 kHz.

Table 5 also shows that 27% of the examined workers have a moderate hearing loss at 250 Hz and 500 Hz frequencies for their both ears. The percentage of workers having a mild hearing loss for both ears is 12% at 250 Hz and 24% at 500 Hz. This result is similar to the results of Ahmed and his co-workers (Ahmed et al., 2004) who indicated that the prevalence of audiometric hearing loss was 32.4% for the low frequency average (500 HZ, 1 and 2 kHz).

The present results indicate that hearing loss developed mostly after the first ten years of working and exposing to high levels of noise among 20% of the examined 33 workers from the three factories. This finding is in agreement with Celik and his co-workers in Turkey (Celik et al., 1998), who reported that hearing loss was developed within the first ten years of noise exposure of hydroelectric power plant workers.

Twenty four percent of the the examined 33 workers from the three factories who were used to wear hearing protectors also showed hearing

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loss problems. This might be attributed to the quality and inadequate use of hearing protectors.

Table 6 shows percentages of workers hearing status according to each noise dose group among workers involved in all tests of hearing assessment.

Table 6. Percentages of workers hearing status according to each noise dose group.

Hearing status Noise dose group N

1 2 3 4 5

Low (86 – 90 dB) 9 55.6% 33.3% 0 11.1% 0 Moderate (91 – 95 dB) 10 10% 20% 50% 20% 0 High (96 – 100 dB) 4 0 0 25% 25% 50%

1: Normal hearing, 2: Mild hearing loss, 3: Moderate hearing loss, 4: Moderately severe hearing loss, 5: Severe hearing loss.

N: Number of workers in each group.

These results indicate that severe hearing loss mostly appears among workers exposed to high levels of noise, moderate hearing loss mostly appears among the workers exposed to moderate levels of noise, and mild hearing loss and normal hearing appear mostly among the low noise levels exposed workers. These findings mean that there is a significant correlation between noise exposure level and hearing loss.

Table 7 shows the correlation coefficients results for the four traits.

Results reveal that the relationships are very significant and positive at (p

≤ 0.01) between age and hearing status, duration and hearing status, noise exposure (dBA), and hearing status.

Table 7. Correlation coefficients results for the four traits.

X1 X2 X3 X4

X1 1 0.60** 0.51* 0.63**

X2 - 1 0.57** 0.54**

X3 - - 1 0.66**

X4 - - - 1

X1: Age, X2: Duration, X3: Noise exposure dBA, X4: Hearing status.

*: Significant at 0.05,

**: Significant at 0.01 level of probability.

Conclusions

The present study shows that the levels of noise exposure in the three industries are usually higher than the standards adopted in Saudi Arabia (85 dBA / 8hrs-day). The major sources of the high levels of noise are machines and motors supplied in each industry and the type of

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processes. Ninety seven percent of the examined 33 workers were exposed to high noise dose exceeding the standard adopted in Saudi Arabia.

The results of the audiometric measurements showed that the workforce within the three industries included in this study are at risk of developing noise induced hearing loss ranged usually between moderate and severe hearing loss class. There is a very significant and positive correlation (p ≤ 0.01) between hearing loss and noise exposure, duration, and age.

The highest percentages of hearing loss among workers exposed to high noise levels above the permissible 85 dBA/8 hrs in each industry appeared at the high frequency of 4 kHz. This finding is in a general agreement with the previous studies. The hearing loss of 20% of the examined workers appears to develop mostly after the first ten years of noise exposure. The study shows that there is a need to apply hearing conservation program in each industry.

Acknowledgements

We would like to acknowledge with grateful thanks the general managers and production engineers in each industry for their cooperation and support.

Conflict of Interest

The authors declare no conflict of interest.

References

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