The ASSOCIATION BETWEEN NOISE EXPOSURE

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Jul 17, 2014 - 8h),blood pressure (BP), Electrocardiograph of heart (ECG). ... research studies noise of four different occupational areas in electro-production.
The 21st International Congress on Sound and Vibration 13-17 July, 2014, Beijing/China

The ASSOCIATION BETWEEN NOISE EXPOSURE AND BLOOD PRESSURE AND ECG OF WORKERS IN EGYPTIAN FACTORIES Wanis Osiris G.. Biophysics Department, Cairo University, Giza, Egypt

Abd-Elfattah Mohamed A. and Shawky Hany A National Institute for Standards, Acoustic Department, Giza, Egypt. e-mail: [email protected] The present research studies noise of four different occupational areas in electro-production instruments factories participated in this cross-sectional study, where 102 workers were exposed to this noise. The study was divided into 4 parts with different factories and different activities as follows: 1- Factory No. 1 (Metal factory), 2- Factory No. 2 (Metal factory), 3Factory No. 3 (Enamel factory), and 4- Factory No. 4 (Cutting workshop). Measurements of major parameters were carried out in each factory, which included noise measurements such as: maximum and maximum peak sound pressure level (LAmax, LAPmax), minimum sound pressure levels (LAmin) and mean equivalent sound pressure levels for 8 h working day (LAeq, 8h),blood pressure (BP), Electrocardiograph of heart (ECG). On other hand, minor parameters of age, working years can be estimated. The following effects of the noise exposure levels were observed in the four different factories: The results of effect of noise on blood pressure and ECG of workers showed significant changes in systolic, diastolic blood pressure and heart rate at different age years and also at different working years in most of factories. So the results indicated that industrial noise could be possible contributing factor in the development of arterial hypertension and increasing of heart rate. Although the four parameters of ECG of workers P-wave, PR-interval, QRS interval and also QTc interval are normal at all factories. It may be concluded that noise pollution is emerging as an industrial problem. It is clear from the obtained results of the present investigation that the hazards of noise exposure in industries in many factories may cause increasing blood pressure, and heart rate.

1.

Introduction

1.1. Cardiovascular and physiological effects Hypertension or high blood pressure (BP) generally is defined as a systolic BP ≥ 140 mmHg and diastolic BP ≥ 90 mmHg. Complications of hypertension include damage to blood vessels in vital organs and thickening of the arterioles, which may result in myocardial infarctions, cerebrovascular accidents, peripheral vascular disease, or renal failure1. Hypertension affects an estimated 23% of the U.S. population age 20 to 74, and it is most prevalent among blacks. In 1999, there were 32 million medical office visits for hypertension evaluation2. Another study showed an increase in both diastolic and systolic BP associated with noise exposure3. Analysis showed confounding factors played an important role in the relationship between BP and noise. A more recent study conducted by Tomei4 found factory workers who were exposed to noise levels > 90 dB had higher average diastolic BP and a higher percentage of diastolic hypertension factory workers exposed to noise levels 200 mg/dl, body mass index >30). They also controlled for environmental factors by having the workers rest before their BP was measured and inICSV21, Beijing, China, 13-17 July 2014

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21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 structed the workers not to take any BP medication for 6 hours prior to evaluation. A positive relationship has been reported in several epidemiological studies between prolonged noise exposure and blood pressure levels5,6,7. However, due to methodological problems, the role of chronic exposure to noise as a risk factor for hypertension remains unclear. In several studies, major risk factors of hypertension such as overweight or alcohol consumption, were not controlled for and could thus account for the association observed. An effect of noise on blood pressure was demonstrated in human beings by experiments involving short periods of time only8,9. Studies suggest that noise-induced stress may increase the excretion of magnesium which may cause a magnesium imbalance, especially when dietary magnesium intake is marginal10. Serum magnesium deficiency, in turn, may produce progressive vasoconstriction, vasospasm and ischemia which, given time, may lead to hypertension and coronary heart disease of blood pressure has been shown to be negatively correlated to the concentration of intracellular magnesium levels may exacerbate the effects on the blood pressure of prolonged noise exposure11. The overall evidence for the effects of noise on cardiovascular functioning is suggestive of weak to moderate effects of community noise on blood pressure. Equivocal conclusions have been drawn from occupational studies of exposure to high levels of continuous noise as well as from research on community noise1,12,13. Increases in mean systolic and diastolic blood pressure of 3.9 and 1.6 mmHg, respectively, were given. However, since systolic and diastolic blood pressure is highly correlated, they appear to be of similar predictive value for the incidence of ichaemic heart disease14,15 In the elderly, systolic blood pressure seems to be a better predictor for cardiovascular mortality16. A study carried out in China offers strong evidence of an association between noise level and prevalence of hypertension.

2.

Material & method

2.1 Experimental setup and exposure facility The present research studies noise of four different occupational areas in electro-production instruments factories participated in this cross-sectional study, where 102 workers were exposed to this noise for 8 hours in 6 days every day at each factory. The study was divided into 4 parts with different factories and different activities as follows: Factory No. 1, No.2 (Metal factories), Factory No. 3 (Enamel factory) and Factory No. 4 (Cutting workshop), measurements of major parameters were carried out in each factory, which included noise measurements, blood pressure, ECG (electrocardiograph of heart). On other hands, minor parameters of age, working years can be estimated. 2.2 Description of factories In Factory No.1 includes 17 types of machines with different electric powers and forces, with 27 male workers exposed to noise level. But in Metal factory No.2 includes 8 types of machines with 25 male workers exposed to noise level, in Enamal factory No.3 includes 8 types of activities. Some workers in this factory exposed to chemical vapor and chemical powder, with 25 male workers exposed to noise level. And in factory No.4 (Cutting workshop) includes 6 types of machines as shown in Tables (1, 2, 3 &4). Noise emission from the machines, and total equivalent sound pressure levels in all factory were measured. All male workers exposed to noise level at that factory were randomly selected under environmental conditions. 2.3 Noise Measurement Workers are constantly exposed to variable amounts of noise from tools and activities of others working around them. Noise measurement was made using Type 1 Model 2260 Precision Integrating Sound Level Meter (Bruel and Kjaer, in Denmark), of accuracy 0.5 dB and resolution 0.1 dB to assess the noise level and frequency characteristic. The instrument was calibrated by using primary calibration system of Sound Level Meter type 9600. 2.4 Measurement procedure

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21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 The A-weighted sound pressure levels were measured for 8 h at an interval of 1 h per day (8 hours x 6 days). Furthermore, maximum and maximum peak and minimum of A-weighted sound pressure level (LAmax; LApmax; LAmin), and also mean equivalent sound pressure level (LAeq, 8h) at 8 h in 4 factories at each machine and positions with different activities were detected. Noise parameters were measured at each factory or at different positions according to ISO 9612, 200917. The mean equivalent sound pressure level (LAeq,8) for 8 h at each positions and machines for the 4 factories is calculated by using the following relation17  1  (1)   P (t ) dt  t2

L Aeq ,T

T  10 log    

2 A

t1

P02

  dB   

Where, P is A-weighted sound pressure, T (Total time of working) is equal to 8 hours; strating at t1 and ending to t2, equal to 1 h. T  (2) LEX ,8 h  L AeqTe  10 log  e  dB  T0  LAeqTe is the A-weighted equivalent continuous sound pressure level for Te, Te is the effective duration, in hours of the working day, T0 is the reference duration, T0 = 8 hours, The effective duration of the working day, Te is equal to 8 h, then LEX,8h equals LAeq,8h. The total equivalent sound pressure level or logarithmic mean LAeq,net8 at each factory from noise machines and different positions of activities can be calculated by 1 n L / 10  L Aeq ,net8  10 log   10 Aeq , 8  dB  m i 1 

(3)

Where m is the number of the independent machines or positions. 2.5 Study Population and Statically Evaluation Workers from 4 factories exposed to noise levels were randomly selected. The whole populations are divided into range of age and working years. Information collected from the questionnaire of workers included personal data; present and past occupation at any factory; present and past medical history of heart problems, blood pressure problems. All workers have any health problems were excluded from the study population. The final results are calculated from the average systolic and diastolic blood pressures, ECG of heart at each worker at 4 factories. they are statistically evaluated according to the software program of statistics version 618, according to t-test independent variables, and Standard deviation (SD) . 2.6 Blood pressure Blood pressure of workers was measured by using Automatic Wrist Blood Pressure Monitor Rossmax International, made in Germany, according to the standardized WHO method (World Health Organization)19. During blood pressure measurement the subjects were in the sitting position, after resting for at last 10 minutes. In each subject two measurements were made (Korotkoff phases I and V). To obtain correct reading when two readings of any worker differed by more than 4 mmHg in either systolic or diastolic pressure, measurements were repeated after further rest intervals until the difference met this criterion. 2.7 Electrocardiograph measurement Electrocardiograph (ECG) was measured for the selected workers from the 4 factories in chamber with relax table, by using NewTech Medical Limited Electrocardiograph (ECG), model ECG1501, made in USA. ECG machine connected to electrodes that attached to body surface of workers, which is applied with ECG cream. Before measurement, clean the stained electrodes with alcohol, ensure good contact between the worker body surface and the electrodes and keep the worker in relaxed without moving and talking; table for examination shall be comfortable. From the chart of ECG, five parameters can be calculated as follows: 1- P-wave interval, during normal atrial ICSV21,Beijing, China, 13-17 July 2014

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21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 depolarization, the main electrical vector is directed from the SA node towards the AV node, and spreads from the right atrium to the left atrium. This turns into the P- wave on the ECG. 2- PR interval: The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex. It is a simple calculation. 3- The QRS duration: The duration of the QRS complex is another useful (and simple) calculation. 4- The QTc interval: This segment tells the total duration of the ventricular event, from when the first cell depolarizes to the repolarization of the last cell (which should be the same cell). The QT interval is very dependent on the heart rate, so you will often see the designation "QTc", denoting that the printed interval has been corrected for the heart rate. 5Calculation of the heart rate: The R-R interval: The RR interval is the time between QRS complexes. The instantaneous heart rate can be calculated from the time between any two QRS complexes. The drawback of this method is that the calculated heart rate can be quite a bit different from the measured pulse even in a normal person due to variations in the heart rate associated with respiration (the sinus arrhythmia). The calculations of the pre-mentioned parameters of ECG is shown in Figure (1).

Fig. 1: Shows the P-wave, PR interval, width of QRS complex and QT interval

3 Results Results of the noise measurements of all factories are tabulated in Tables (1, 2, 3 and 4). The tables illustrate the values of the main parameters for 102 workers exposed to different types of machines with different operations in all factories. The overall noise level and exposure to noise in all factories were about 93.9, 90.4, 86.5 and 87.0 dBA respectively. 3.1 Distribution by age and working years The workers in all factories are divided into five or six categories according to their age and four or five categories according to their working years of workers to cover the range of age and working years. Table 1. illustrates the parameters of mean maximum (LAmax), and maximum peak (LApmax) and minimum (LAmin ) sound pressure levels and mean equivalent sound pressure level (LAeq,8h ) and arithmetic mean sound pressure level at 8 h at each positions infront of machines (n=8) [mean (SD)] for factory No.1. MACHINES M1 M2 M3 M4 M5 M6 M7 M8 M9 M10 M11 M12 M13 M14 M15 M16 M17

LAPMAX (DBA) 113.6 (4.36) 110.3 (5.11) 113.8 (6.94) 110.5 (8.43) 114.9 (3.77) 115.1 (8.54) 108.8 (3.79) 107.3 (3.85) 107.6 (3.56) 113.3 (3.58) 117.0 (2.84) 114.4 (3.50) 112.4 (5.36) 110.9 (5.80) 114.7 (3.73) 116.9 (1.79) 110.3 (6.20)

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LAMAX (DBA) 101.3 (2.78) 98.9 (1.57) 100.4 (3.71) 96.6 (7.51) 100.6 (1.22) 102.9 (3.89) 114.5 (3.84) 94.7 (6.50) 114.8 (1.78) 99.9 (1.57) 101.4 (3.23) 101.2 (1.02) 99.4 (1.96) 98.7 (2.16) 99.3 (1.90) 103.1 (1.26) 100.2 (3.69)

LAMIN (DBA) 86.88 (0.72) 87.80 (0.87) 87.85 (4.51) 86.9 (1.15) 85.2 (1.19) 83.7 (1.01) 81.7 (0.69) 84.2 (6.25) 84.3 (1.51) 87.6 (2.73) 86.8 (3.53) 84.9 (0.60) 86.7 (1.15) 86.8 (1.34) 86.9 (1.34) 86.1 (0.77) 85.5 (1.71)

LAEQ,8H (DBA) 92.33 (2.20) 92.46 (1.30) 92.79 (1.36) 91.4 (1.96) 91.6 (1.18) 91.7 (2.27) 98.1 (1.41) 87.7 (2.29) 98.6 (0.77) 93.0 (1.72) 94.7 (1.70) 91.4 (0.48) 92.9 (1.42) 92.0 (1.09) 92.9 (0.73) 93.4 (1.09) 92.5 (1.82)

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21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 Table (2): . illustrates the parameters of mean maximum (LAmax), and maximum peak (LApmax) and minimum (LAmin ) sound pressure levels and mean equivalent sound pressure level (LAeq,8h ) and arithmetic mean sound pressure level at 8 h at each positions infront of machines (n=8) [mean (SD)] for factory No.2. MACHINES

LAPMAX (DBA)

LAMAX (DBA)

LAMIN (DBA)

M1 M2 M3 M4 M5 M6 M7 M8

104.7 (3.54) 107.2 (3.54) 103.4 (4.63) 100.9 (5.35) 100.9 (5.35) 102.2 (5.18) 109.5 (5.01) 107.2 (3.54)

98.0 (2.86) 99.7 (5.39) 96.6 (4.37) 95.5 (5.00) 94.8 (3.70) 96.7 (3.76) 99.1 (1.21) 99.6 (5.78)

78.4 (1.40) 79.4 (0.46) 78.3 (0.60) 78.2 (0.71) 77.9 (0.50) 76.9 (1.46) 76.6 (0.81) 76.7 (1.31)

LAEQ,8H (DBA) 86.0 (1.67) 89.7 (3.62) 85.3 (1.11) 85.6 (1.88) 85.0 (1.06) 85.1 (0.76) 94.0 (2.03) 95.1 (2.21)

Table (3): . illustrates the parameters of mean maximum (LAmax), and maximum peak (LApmax) and minimum (LAmin ) sound pressure levels and mean equivalent sound pressure level (LAeq,8h ) and arithmetic mean sound pressure level at 8 h at each positions infront of machines (n=8) [mean (SD)] for factory No.3. ACTIVITIES 1- BOILER 2- PICKING STORE 3-CHEMICAL TREATMENT 4- CONTAINER STORAGE 5- MILLS 6- SPRAY 7- DRYER+ HANGING 8- FURNACE

LAPMAX (DBA) 102.6 (0.58) 102.7 (0.50) 103.0 (0.59) 87.2 (4.02) 101.7 (0.22) 102.1 (0.57) 102.5 (0.51) 102.3 (0.61)

LAFMAX (DBA) 89.1 (0.26) 89.3 (0.05) 89.3 (0.17) 70.1 (3.21) 88.5 (0.26) 88.8 (0.12) 89.0 (0.15) 89.1 (0.25)

LAFMIN (DBA) 87.8 (0.26) 88.1 (0.10) 88.1 (0.46) 89.5 (2.46) 87.2 (0.15) 87.6 (0.24) 87.8 (0.19) 87.9 (0.29)

LAEQ,8H (DBA) 88.4 (0.24) 88.7 (0.08) 88.6 (0.30) 70.3 (2.44) 87.8 (0.08) 88.2 (0.14) 88.4 (0.18) 88.5 (0.27)

Table (4): . illustrates the parameters of mean maximum (LAmax), and maximum peak (LApmax) and minimum (LAmin ) sound pressure levels and mean equivalent sound pressure level (LAeq,8h ) and arithmetic mean sound pressure level at 8 h at each positions infront of machines (n=8) [mean (SD)] for factory No.4. MACHINES 1- CUTTING MACHINE 2- FORGING MACHINE AGE 1 3- FORGING MACHINE AGE 2 4- LATHE MACHINE 5-MACHINE AND LIFTING WEIGHTS 6- MACHINE GELG

LAPMAX (DBA) 102.6 (0.29) 103.0 (0.24) 102.2 (0.24) 103.1 (1.04) 99.9 (2.40) 97.1 (0.58)

LAMAX (DBA) 89.2 (0.23) 89.3 (0.15) 89.1 (0.15) 89.1 (0.08) 85.8 (2.12) 84.0 (0.63)

LAMIN (DBA) 87.2 (0.30) 87.2 (0.15) 87.7 (0.15) 87.8 (0.13) 84.9 (2.0) 83.1 (0.8)

LAEQ,8H (DBA) 88.0 (0.24) 88.1 (0.15) 87.8 (0.15) 87.9 (0.14) 85.0 (1.97) 82.6 (0.43)

3.2 Blood pressure and heart measurements The following US classifications of blood pressure apply to adults aged (18 years old) and older. They are based on the average of seated BP readings that were properly measured during 2 or more office visits20,21. In the UK, patients’ readings are considered normal up to 140/90 mmHg22. Table (5): Classifications of blood pressure for adults according to (NHLBI)22. CATEGORY HYPOTENSION NORMAL PREHYPERTENSION STAGE 1 HYPERTENSION STAGE 2 HYPERTENSION

SYSTOLIC, MMHG 33-40 y group show non significant increase. Mean systolic blood pressure at >40-47 y group shows significant increase, while the ICSV21,Beijing, China, 13-17 July 2014

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21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 mean diastolic blood pressure shows non significant increase. for >47-54 y group, the mean systolic blood pressure shows high significant increase, while the mean diastolic blood pressure shows significant increase. According to reference of mean heart rate from normal The data in Figure (2) show that the lowest mean heart rate at 20-26 y group, the highest mean heart rate at 48-54 y group at different age years. From figure (6) at different working years groups show that most of the mean systolic blood pressure values increase with increasing the working years group. The mean systolic blood pressure value at >6-11y group shows the higher value than that of the values of all groups. The mean systolic blood pressure at 6-11y group shows significant increase and the mean diastolic blood pressure shows non significant increase. Both mean systolic and diastolic blood pressures at >11-16y group show non significant increase, respectively. Both mean systolic and diastolic blood pressures at >16-21y group show non significant increase, respectively. The data in Figure (2) show that the lowest mean heart rate at 20-26 y group, the highest mean heart rate at 48-54 y group at different age years. It is clear from the results from Figure (6) that the lowest mean heart rate at < 1y group, highest mean heart rate at > 11-16y group at different working years. It is clear from the results from Figure (6) that the lowest mean heart rate at < 1y group, highest mean heart rate at > 11-16y group at different working years. At factory No.2, the relationships between mean heart rate and mean blood pressure values of systolic and diastolic are given in Figure (3) at different age groups. It is clear that there are increase of mean systolic blood pressure and the mean diastolic blood pressure values for the oldest >47-54 y group show the highest value than those of the all other age groups. The lowest values of mean systolic and diastolic blood pressure at < 20y group are detected. Both mean systolic and diastolic blood pressure at different age group show significant increase or decrease than normal values as describe in factory No1., and it is shown in Figure (3). It is clear from Figure (3) that lowest mean heart rate at 1-6y group, highest mean heart rate at > 11-16 y group. From figure (7) at different working years groups are shown that most of the mean systolic blood pressure values increase with increasing the working years. The mean systolic and diastolic blood pressure values at >11-16y group shows the higher value than that of the values of all groups. According to NHLBI for the normal systolic and diastolic pressures, the mean systolic and diastolic blood pressure at different working years group show significant increase or decrease at each group as shown in Figure (7). At factory No.3, the relationships between mean heart rate and mean blood pressure values of systolic and diastolic are given in Figure (4), at different age groups. It is clear that there are increase of mean systolic blood pressure and the mean diastolic blood pressure values for the >47-54 y group shows the highest value than those of all other age groups. The lowest values of mean systolic blood pressure are 127.6 mmHg at >26-33y group, and also the lowest value of mean diastolic blood pressure are 79.9 mmHg at the same group than that of all other groups. Both mean systolic and diastolic blood pressure at different age group show significant increase or decrease than normal values as describe in factory No1., and it is shown in Figure (4). According to the reference of different parameters, the data show that the lowest mean heart rate at 47-54 y group. From Figure (8), at different working years groups are shown that the mean systolic blood pressure values at 33-40 y group shows the highest value than those of the all other age groups. The lowest value of mean systolic blood pressure and diastolic blood pressure are 120.75 mmHg and 75.5 mmHg at < 20y group. According to NHIBI for the normal systolic and diastolic pressures, both mean systolic and diastolic blood pressure at different age group show significant increase or decrease than normal values as describe in factory No1., and it is shown in Figure (5). The data show that the lowest value of mean heart rate at >40-47 y group is detected, the highest value of mean heart rate at >33-40 y group. The mean heart rate at different age groups shows significant increase and decrease at each group. It is clear from Figure (9) that lowest mean heart rate at 1-6y group, highest mean heart rate at > 11-16 y group. The mean systolic and diastolic blood pressure values at >11-16y group shows the higher value than that of the values of all groups. The lowest values of mean systolic and diastolic blood pressure are 124.5 mmHg and 77.0 mmHg at 26-33 >33-40 >40-47 Age distribution (years)

mean heart rate

60 40 20 0 47-54

1-6

>6-11

>11-16

>16-21

Working distribution (years)

Fig. (2): Mean blood pressure and heart rate of workers at different age years at factory No.1 .

Fig. (6): Mean blood pressure and heart rate of workers at different working years at factory No.1. 160

180 160 140 120 systolic

100 80

diastolic

60

mean heart rate

40 20 0

26-33

>33-40

>40-47

>47-54

Age distribution (years)

Fig. (3): Mean blood pressure and heart rate of workers at different age years at factory No.2.

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Mean blood pressure and heart rate (mmHg and min-1)

Mean blood pressure and heart rate (mmHg and min -1)

diastolic

80

0 ≤20-26

systolic

140 120

systolic

100

diastolic mean heart rate

80 60 40 20 0 6-11 Working distribution (years)

>11- 16

Fig. ( 7): Mean blood pressure and heart rate of Workers at different working years at factory No.2.

7

180 160

systolic

140

diastolic

120

mean heart rate

100 80 60 40 20 0 26-33

>33-40

Mean blood pressure and heart rate (mmHg and min -1)

Mean blood pressure and heart rate (mmHg and min -1)

21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 160 140 systolic

120 100

diastolic

80 mean heart rate

60 40 20 0

>40-47 >47-54

6-11

>11- 16

>16-21

Working distribution (years)

Age distribution (years)

Fig. (4): Mean blood pressure and heart rate Fig . (8): Mean blood pressure and heart rate at workers of workers at different age years at factory No.3 at different working years at factory No.3 . 180

140 120

systolic

100 diastolic

80

mean heart rate

60 40 20

Mean blood pressure and heart rate (mmHg and min -1)

Mean blood pressure and heart rate (mmHg and min -1)

160

160 140

systolic

120 100

diastolic

80

mean heart rate

60 40 20 0

0 26-33

>33-40

>40-47

>47-54

Age distribution (years)

6-11

>11- 16

>16-21

Working distribution (years)

Fig. (5): Mean blood pressure and heart of Fig. (9): Mean blood pressure and heart rate of workers at Workers at different age years at factory No.4. different working years at factory No.4.

4 Discussion and Conclusion 4.1 Noise levels Results of the noise measurement show that overall noise levels and exposure to noise in the four factories under study [Metal factories (No.1 and No.2), Enamel factory (No.3), and Cutting workshop (No.4)] are 93.9, 90.4, 86.5, and 87.0 dBA, respectively. The daily noise exposure of workers in factories exceeds the maximum exposure limit of 85 dBA, which are quite higher than limits used for assessment of noise for community response specified by DE and IS: 998924,25. In addition the noise levels and exposure to noise for factories No.1 and No.2 (metal factories) (93.9 and 90.4 dB, respectively), exceed the maximum exposure limit of 90 dB, specified by OSHA26. The direct applications of DE and OSHA regulations in the working places under study are not valid, as most of the factories operate 8 h/d and 6 d/wk, (i.e., 48 h/wk), which is 20% higher than the exposure time per week in USA or European countries27. The different parameters of Leq, Lmax, Lmin, and Lpmax are exposure-response analysis that produce different types of noise. The standard metric for monitoring noise is the Leq, a based on the equal energy hypothesis (EEH), which states that equal amounts of sound energy produce equal amounts of damage regardless of their distribution over time The EEH implies a 3 dB exchange rate28. While the Leq integrates short term high levels on an equal energy basis, animal studies have demonstrated that peak levels above a ‘critical level’ of about 120–135 dB29produce more damage than expected using the EEH. This critical level, which is not well established in humans, marks the transition from metabolic to direct mechanical ICSV21, Beijing, China, 13-17 July 2014

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21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 damage to the hearing mechanism30,31. Construction workers are regularly exposed to peak noise levels greater than 120 dB; and an average of 18 minutes per shift included peaks greater than 140 dB implies by Neitzel32, but in present data the workers exposed to different maximum peak noise levels through 8 h per day. Although peak exposures are common in some work settings, and exposure to impulse noise may be more damaging than longer exposure to lower level sounds of the same total energy. Noise peaks (Lpmax) are defined in terms of their amplitude, duration, rise time, number of impulses and repetition rate; each of which affects the risk of hearing damage33. In general, from the data of Tables (3) and (4), it can be stated that the sound environment which the electro-production workers are within is quite noisy and potentially harmful to health, since the lower limit of 86.5 dBA at factory No.3 (enamel factory) is exceeded in most of the cases, and even more, the percentage of cases that go beyond the top limit of 87 dBA at factory No.4 (cutting workshop factory) is quite high. The obtained results are similar to that have been obtained in studies carried out in Germany by the BIA–BG Institute for Occupational Safety and Health34, which validates the present study. 4.2 Blood pressure and heart rate Noise pollution is increasingly being recognized as physical factor in the environment that is injurious to many aspects of health. Some of the scientists observed a rise only in systolic blood pressure35,36while many others found a significant increase in both systolic and diastolic blood pressure in response to noise. Babisch37could not see any association of noise and blood pressure, whereas Elise and co-workers38observed insignificant increase in blood pressure. Our obtained results show significant increase in systolic blood pressure, diastolic blood pressure in most of different age groups Figures (2, 3, 4 and 5). Many research scientists in the world have observed a significant rise in blood pressure in response to noise39,40. The actual mechanism for increase in blood pressure is not yet completely understood but it may be due to the following mechanism41, the catecholamines released from adrenal medulla as a result of activation of adrenergic system, the effect of suprarenal glands steroids, angiotensin and also the direct effect of noise on arterial wall tension influences the blood pressure and heart rate. Stimulation by noise, through sympathetic nervous system, causes an elevation of blood pressure by an increase in total peripheral resistance and myocardial contractility13. The repeated stimulation with noise could then accelerate the development of structural vascular changes in the peripheral resistance vessels and by this mechanism create a permanent blood pressure elevation to hypertensive levels42. Manninen and Aro43reported that, noise exposure at different working years in a group of male and female workers in an engineering industry, showed prolonged exposure to industrial noise first elevates the systolic blood pressure. If the exposure continues, the systolic blood pressure tends to return to around normal, but the diastolic blood pressure either rises or falls. However, the present results for metal and cutting workshop factories (No.1 and No.4), indicates that at first < 1y working group, a decrease of systolic blood pressure after long exposure is the same as previous studied. At >11-16y and working >16-21y years groups, the results indicate that, both systolic and diastolic blood pressure are elevated due to chronically exposed to noise. From the obtained results, it appears that long-term exposure to a stressful stimulus (intense occupational noise in the present case) may have produced repeated rise in the blood pressure and a decrease in blood pressure of systolic and diastolic with increasing of working years. The present study is consistent with the results of other studies suggesting that systolic blood pressure is first to respond to noise and diastolic after longer exposure44,45,46. The subjective perception of noise is considered by some authors as the primary factor that induces a cardiovascular reaction47. It is interesting to explore further the roles of working years as a contributor to risk of hypertension as it seems reasonable to postulate that risk should be function of cumulative exposure to noise. Cumulative exposure is a function of the duration of exposure, the present results being highly correlated with years worked as in the research of Zhao. The resting heart rates of noise-exposed subjects at metal factory (No. 1) was significantly higher at >47-54 y age group in comparison with the other age groups. The findings of working years group shows that the higher heart rate at >11-16 y working group than that of the other groups. The resting heart rate of noiseICSV21,Beijing, China, 13-17 July 2014

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21st International Congress on Sound and Vibration (ICSV21), Beijing, China, 13-17 July 2014 exposed subjects in metal factory (No.2) indicate significantly higher at >47-54 y age group than that of other groups. Also, the results of working years group show that higher heart rate at 47-54 y age group than that of other groups, and the findings for working years group show that higher at >16-21y group than that of all other groups. The resting heart rates of noise-exposed subjects at cutting workshop factory (No.4) is significantly higher at >33-40 y age group than that of other groups. The results at working years group show that higher heart rate at > 11-16y group than that all other groups. All these findings may be due to a habituating effect of repeated stimuli of continuous noise of sufficient intensity, as previously reported by Harris48. The results of the present study reveal that long-term exposure to noise produces an increase in blood pressure and heart rate, appears to alter the elasticity of blood vessels, and modifies the automatic balance. Some studies are consistent with the hypothesis of an association between long-term noise exposure and risk of cardiovascular disease based on conceptual stress modeling49. However, the present ECG analysis of different ages and different working years groups are most normal P-wave, PR-interval, QRS interval and also QTc interval at all workers in the investigated factories. Exposure to high intensity of 88-107 dBA, 6-8 h/day for long duration (10-15 years) cause biochemical changes which make the workers prove to cardiovascular pathology50. 4.3 Conclusion The present investigation nearly, is the first consistent study of its kind made for detection of noise problems in Egyptian's industry. It is clear from the obtained results of the present investigation that the hazards of noise exposure in industries in many different factories may cause increase blood pressure, heart rate. For future work, more and repeated measurements should be made to reduce variability and to fully quantify the effect of noise problems in Egypt.

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