Economic wood processing employs the use of industrial machines for cutting, shaping, milling, and sawing timber, thereby leading to the generation of high levels of noise. Published data from empirical studies have categorized noise as an environmental hazard of global significance. Furthermore, noise exposure limits for different industries and all the industrial machines available has not been formally established as it presently exists in developed nations around the world. Therefore, this study assessed the daily exposure of sawmills workers to noise in Southwestern Nigeria. Reconnaissance surveys were first carried out in Osun, Oyo, Ondo, Ekiti, Lagos, and Ogun States to select sawmills that were fully operational and fit for the study. Two fully functional sawmills in two cities of each State were eventually selected for data collection, making a total of 24 sawmills, while the Circular Machines (CM), Planer Machines (PM), and Band-saw Machines (BM) were the machines in each sawmill considered. Two machines each of CM, PM, and BM were considered in each sawmill, making a total of forty-eight (48) machines each of CM, PM, and BM. Sound data were collected between 7 am and 7 pm each day for six days (between Monday and Saturday) using Extech 407732 sound level meter and all stabilized measurements were taken three times at different intervals. The data collected were in three different periods: Machine No-work Period (NPm), Machine Idle Period (IPm), and Machine Working Period (WPm). A two–way Analysis of Variance (ANOVA) was carried out at
Noise is generally defined as an undesirable or an unpleasant sound whose origin can be traced to the Latin word “nausea”, which means seasickness [
Consequently, economic wood processing is one of the results or off-springs of urbanization, because economic wood processing employs the use of industrial machines for cutting, shaping, milling and sawing timber everyday [
Furthermore, the industries that are mostly exposed to noise pollution are metal, timber, base metal, paper, construction and fiber industries [
Noise levels generated by sawmills in operation may vary from 80 dB to 120 dB and studies have shown that prolonged exposures to high levels of noise can result in some health and workplace challenges, such as acoustic trauma, tinnitus, temporary threshold shift, permanent threshold shift, interference with the communication between employees, mental stress, irritation, cardiac disorders, high blood pressure, ulcer, asthma, pregnancy disorders, learning disabilities in children, loss of efficiency and concentration, sleep disturbance, vertigo, speech problems and migraines [
Thus, this study will determine the daily personal noise exposure level of sawmill workers, noise pollution level of the machines, and daily dose.
This study was carried out in Osun, Oyo, Ondo, Ekiti, Lagos, and Ogun States of the Southwestern part of Nigeria where reconnaissance surveys were first carried out to select the sawmills that were used and to determine whether the sawmills were fully operational. Two fully functional sawmills in two cities of each State were eventually selected and visited for data collection, making a total of 24 sawmills visited. Circular Machines (CM), Planer Machines (PM), and Band-saw Machines (BM) which are the commonest types of machinery in the sawmilling industries were considered. Two machines each of CM, PM, and BM were considered in each of the sawmills visited, making a total of forty-eight (48) machines each of CM, PM, and BM. Sound data were collected using Extech 407732 sound level meter and all stabilized measurements were taken three times at different intervals. Data were also collected between 7 am and 7 pm each day for six days (between Monday and Saturday, as Sunday is always a work-free day). They got to work early enough to start work, depending on the availability of electricity supply and if electricity supply was unavailable, the workers usually spent their time cleaning, arranging, and preparing the logs or planks for work before putting on the generator, in order to save time. Furthermore, data were collected in three different periods: Machine No-work Period (NPm) i.e., the period in the sawmill when no machine is in operation; Machine Idle Period (IPm), i.e., machine operation period after the machine has been switched on but the wood has not been loaded onto the machine; and Machine Working Period (WPm) i.e., machine operation period when the wood is loaded for sawing.
In this research, the noise measurements were carried out using ‘A’ Weighting and slow response as recommended in the manual [
A two – way Analysis of Variance (ANOVA) was carried out at
Also, a two–way ANOVA was carried out at
Alternative
A two – way ANOVA was also carried out at
Alternative
A Post-hoc comparison using Tukey’s Criterion as shown in
where Tu is the Tukey criterion
c is the number of groups
n is the total sample size
MSE is the Mean square error (from ANOVA table)
ni is the no of observation in a group
For each machine, Minimum Sound Level (lmin), Maximum Sound Level (lmax), Average Sound Level (lave), and Standard Deviation (σ), were determined. Also the following parameters were determined: Noise pollution level (Lnp) The daily personal noise exposure level Daily noise dose (D)
Noise Pollution Level (Lnp) was however determined using the relationship according to ISO/R13 –1959 [
where σ is the standard deviation of the sound levels collected.
The daily personal noise exposure level
where
(
The daily dose also was calculated using
where: D is daily noise dose (must not exceed unity)
t is actual exposure time at a given sound level
n is the number of discrete periods of exposure above 90 dB (A)
T is permissible exposure time per day.
NOTE: Maximum Exposure corresponds to D is 1.0. Thus, the control required for D > 1.0
Thus, the exposure indicator in
Noise level dB(A) | Indicator |
---|---|
<85 | minimum noise exposure |
85−90 | moderately high noise exposure |
>90 | high noise exposure |
The summary of the minimum and maximum sound levels for the machines at different periods presented in
The machine no-work period noise levels ranged from 42.8 (EK1) to 88.1 dB (OS1).
State | M/C | IPm | WPm | NPm | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Minimum Leq(dB) with corresponding |
Maximum Leq (dB) with corresponding |
Minimum Leq(dB) with corresponding |
Maximum Leq(dB) with corresponding |
Minimum Leq(dB) with corresponding |
Maximum Leq(dB) with corresponding |
||||||||
OSUN | CM | 82.4 | OS12 | 96.8 | OS22 | 96.4 | OS22 | 105.4 | OS11 | 57.9 | OS4 | 88.1 | OS1 |
PM | 89.5 | OS42 | 102.0 | OS11 | 95.4 | OS42 | 104.0 | OS11 | |||||
BM | 82.4 | OS21 | 98.5 | OS41 | 91.6 | OS21 | 103.6 | OS31 | |||||
ONDO | CM | 87.1 | ON22 | 97.9 | ON31 | 86.0 | ON21 | 109.6 | ON42 | 45.3 | ON1 | 86.8 | ON4 |
PM | 80.7 | ON21 | 96.4 | ON41 | 88.6 | ON21 | 102.5 | ON32 | |||||
BM | 88.9 | ON12 | 102.4 | ON41 | 93.4 | ON12 | 106.5 | ON12 | |||||
EKITI | CM | 84.8 | EK42 | 97.8 | EK31 | 91.4 | EK21 | 106.8 | EK12 | 42.8 | EK1 | 73.8 | EK4 |
PM | 84.8 | EK12 | 99.8 | EK11 | 95.8 | EK32 | 107.8 | EK31 | |||||
BM | 81.9 | EK31 | 97.4 | EK41 | 95.6 | EK11 | 104.9 | EK31 | |||||
OYO | CM | 80.7 | OY42 | 96.4 | OY32 | 91.9 | OY12 | 102.8 | OY31 | 43.7 | OY2 | 78.4 | OY1 |
PM | 80.2 | OY31 | 98.8 | OY41 | 95.9 | OY21, |
103.8 | OY41 | |||||
BM | 84.3 | OY22 | 95.1 | OY32 | 95.2 | OY32 | 103.6 | OY41 | |||||
OGUN | CM | 82.4 | OG12, |
96.6 | OG21 | 89.9 | OG32 | 103.9 | OG21 | 52.6 | OG3 | 85.7 | OG1 |
PM | 80.7 | OG31 | 98.0 | OG11 | 88.6 | OG31 | 104.0 | OG11 | |||||
BM | 85.0 | OG21 | 99.8 | OG42 | 95.4 | OG12 | 102.4 | OG42 | |||||
LAGOS | CM | 91.9 | LA42 | 101.8 | LGA31 | 95.4 | LA22 | 106.0 | LA31 | 58.9 | LA1 | 86.2 | LA2 |
PM | 80.6 | LA21 |
102.2 | LA12 | 95.9 | LA12, |
109.6 | LA11 | |||||
BM | 87.9 | LA22 | 102.1 | LA11 | 89.7 | LA32 | 102.1 | LA22 |
At machine no-work period, most of the workers in the environment of the machines were exposed to the minimum and safe noise, since Leq values in sawmills before the start of activities in the sawmills were lesser than 85 dB, while 87.5% of the sawmills had Leq values that were higher than 85dB after the start of sawmilling activities. This was so because there were little or no activities very early in the morning, compared to the afternoon when the traffic was usually high, buying and selling were on while shouting and talking were also on in the vicinity of the sawmills. Furthermore, the ANOVA results in
Therefore, the null hypotheses are accepted for
Post-hoc results of the comparisons using Tukey’s HSD test, as presented in
Source of variation | ||||||
---|---|---|---|---|---|---|
Types of Machine | 29.32466 | 2 | 14.66233 | 0.619149 | 0.539133 | 3.027783 |
Before/after the break | 0.053901 | 1 | 0.053901 | 0.002276 | 0.961982 | 3.874645 |
Interaction | 14.83757 | 2 | 7.418786 | 0.313274 | 0.731303 | 3.027783 |
Within | 6678.165 | 282 | 23.68144 | |||
Total | 6722.381 | 287 |
Types of Machine | 113.7809709 | 2 | 56.89049 | 5.126248 | 0.006505 | 3.027783 |
Before/after the break | 22.33347222 | 1 | 22.33347 | 2.012409 | 0.157122 | 3.874645 |
Interaction | 2.626536343 | 2 | 1.313268 | 0.118335 | 0.888442 | 3.027783 |
Within | 3129.602217 | 282 | 11.09788 | |||
Total | 3268.343196 | 287 |
Source of variation | ||||||
---|---|---|---|---|---|---|
States | 1032.243 | 5 | 206.4486 | 7.237399 | 8.87E-05 | 2.477169 |
Before/after the break | 4670.223 | 1 | 4670.223 | 163.7224 | 5.85E-15 | 4.113165 |
Interaction | 94.11657 | 5 | 18.82331 | 0.659883 | 0.656079 | 2.477169 |
Within | 1026.909 | 36 | 28.52525 | |||
Total | 6823.491 | 47 |
Source of variation | ||||||
---|---|---|---|---|---|---|
Types of Machine | 17.99611 | 2 | 8.998053 | 0.391165 | 0.676513 | 3.017049 |
Periods | 75162.45 | 2 | 37581.23 | 1633.739 | 1.1E-199 | 3.017049 |
Interaction | 53.55671 | 4 | 13.38918 | 0.582057 | 0.675799 | 2.393029 |
Within | 9730.353 | 423 | 23.0032 | |||
Total | 84964.36 | 431 |
Comparisons | Absolute difference | Critical value (Tu) | Results |
---|---|---|---|
IPm to WPm | 7.58 | 1.32 | Means are Significantly different |
IPm to NPm | 23.41 | 1.32 | Means are Significantly different |
WPm to NPm | 30.99 | 1.32 | Means are Significantly different |
Sawmill | IPm Lnp (dB) | WPm Lnp (dB) | ||||
---|---|---|---|---|---|---|
CM | PM | BM | CM | PM | BM | |
OS11 | 92.20 | 102.86 | 98.13 | 106.71 | 104.35 | 96.64 |
OS12 | 100.58 | 102.94 | 97.81 | 105.85 | 104.20 | 103.58 |
OS21 | 92.87 | 93.97 | 93.13 | 101.92 | 104.78 | 94.64 |
OS22 | 100.34 | 97.12 | 93.09 | 106.81 | 104.79 | 106.27 |
OS31 | 94.50 | 101.34 | 88.46 | 105.04 | 106.24 | 104.90 |
OS32 | 98.13 | 102.28 | 99.35 | 103.48 | 104.72 | 104.63 |
OS41 | 97.06 | 96.40 | 99.18 | 103.28 | 101.50 | 99.78 |
OS42 | 95.20 | 102.36 | 99.77 | 102.77 | 99.09 | 98.89 |
ON11 | 93.70 | 96.74 | 97.51 | 93.42 | 103.09 | 101.31 |
ON12 | 97.99 | 97.79 | 98.14 | 99.05 | 99.05 | 116.00 |
ON21 | 92.95 | 83.69 | 99.39 | 104.35 | 93.49 | 100.13 |
ON22 | 94.07 | 95.55 | 94.50 | 103.83 | 102.62 | 104.03 |
ON31 | 99.10 | 88.21 | 100.79 | 101.95 | 104.06 | 100.57 |
ON32 | 96.15 | 95.01 | 94.22 | 102.76 | 103.75 | 104.18 |
ON41 | 91.33 | 97.35 | 107.65 | 107.61 | 102.65 | 102.47 |
ON42 | 93.96 | 97.65 | 94.80 | 110.70 | 102.53 | 104.89 |
EK11 | 94.93 | 102.41 | 98.26 | 96.37 | 107.54 | 100.10 |
EK12 | 97.30 | 88.01 | 96.92 | 109.05 | 104.19 | 105.88 |
EK21 | 98.31 | 98.22 | 88.48 | 95.96 | 107.71 | 104.82 |
EK22 | 97.92 | 96.32 | 87.99 | 108.17 | 103.38 | 103.25 |
EK31 | 99.33 | 98.52 | 90.84 | 97.10 | 110.43 | 106.47 |
EK32 | 98.36 | 99.78 | 97.84 | 104.66 | 105.79 | 102.53 |
EK41 | 97.75 | 96.57 | 99.81 | 101.47 | 106.79 | 100.40 |
EK42 | 101.58 | 96.70 | 94.22 | 102.92 | 104.66 | 103.97 |
OY11 | 93.55 | 88.50 | 92.90 | 102.54 | 104.88 | 99.93 |
OY12 | 88.09 | 86.31 | 89.27 | 102.83 | 103.90 | 102.33 |
OY21 | 94.20 | 86.17 | 92.39 | 103.04 | 105.73 | 99.19 |
OY22 | 87.57 | 99.43 | 89.94 | 101.32 | 99.85 | 102.58 |
OY31 | 93.42 | 83.20 | 93.29 | 104.71 | 100.37 | 98.93 |
OY32 | 98.50 | 93.89 | 98.81 | 107.09 | 102.58 | 100.56 |
OY41 | 87.83 | 100.11 | 90.44 | 103.29 | 106.90 | 105.27 |
OY42 | 103.85 | 104.32 | 93.77 | 102.69 | 102.62 | 99.49 |
OG11 | 87.72 | 98.79 | 100.85 | 103.97 | 106.12 | 98.33 |
OG12 | 93.00 | 98.24 | 93.15 | 105.95 | 101.58 | 99.05 |
OG21 | 99.44 | 95.22 | 93.24 | 104.33 | 103.68 | 98.77 |
OG22 | 93.03 | 88.48 | 99.31 | 103.87 | 105.24 | 100.05 |
OG31 | 95.13 | 83.63 | 97.81 | 103.33 | 93.58 | 100.79 |
OG32 | 89.96 | 95.00 | 99.13 | 93.48 | 104.01 | 102.97 |
OG41 | 97.14 | 84.48 | 97.75 | 101.49 | 93.42 | 100.73 |
OG42 | 90.51 | 96.38 | 101.38 | 98.87 | 100.39 | 105.98 |
LA11 | 97.86 | 103.57 | 105.70 | 103.81 | 110.66 | 101.19 |
LA12 | 105.54 | 103.16 | 93.11 | 103.94 | 102.69 | 104.39 |
LA21 | 94.59 | 85.96 | 101.88 | 102.54 | 103.24 | 99.96 |
LA22 | 94.03 | 100.92 | 94.02 | 98.89 | 105.98 | 103.06 |
LA31 | 102.23 | 100.28 | 96.90 | 106.41 | 107.40 | 100.27 |
LA32 | 97.65 | 99.09 | 96.51 | 106.05 | 105.49 | 105.38 |
LA41 | 94.59 | 85.96 | 101.88 | 102.54 | 103.24 | 99.96 |
LA42 | 94.13 | 96.94 | 94.52 | 100.39 | 107.56 | 100.35 |
S/N | Noise level dB (A) | Duration per day (Hour) | S/N | Noise level dB (A) | Duration per day (Hour) |
---|---|---|---|---|---|
1 | 83 | 21.1 | 14 | 96 | 3.5 |
2 | 84 | 18.4 | 15 | 97 | 3.0 |
3 | 85 | 16.0 | 16 | 98 | 2.6 |
4 | 86 | 13.9 | 17 | 99 | 2.3 |
5 | 87 | 12.1 | 18 | 100 | 2.0 |
6 | 88 | 10.6 | 19 | 101 | 1.7 |
7 | 89 | 9.2 | 20 | 102 | 1.5 |
8 | 90 | 8.0 | 21 | 103 | 1.3 |
9 | 91 | 7.0 | 22 | 104 | 1.1 |
10 | 92 | 6.1 | 23 | 105 | 1.0 |
11 | 93 | 5.3 | 24 | 106 | 0.9 |
12 | 94 | 4.6 | 25 | 107 | 0.8 |
13 | 95 | 4.0 | 26 | 108 | 0.7 |
The results for an average duration of exposure, daily personal noise level
The least
Sawmill | CMs | PMs | BMs | ||||||
---|---|---|---|---|---|---|---|---|---|
Average duration of exposure (hr) | Average daily personal LEP,d (dB) | Average total exposure point | Average duration of exposure (hr) | Average daily personal LEP,d (dB) | Average total exposure point | Average duration of exposure (hr) | Average daily personal LEP,d (dB) | Average total exposure point | |
EK11 | 4.93 | 90.34 | 343 | 6.78 | 103.01 | 6527 | 5.19 | 94.27 | 893.17 |
EK12 | 6.75 | 101.05 | 4066 | 7.05 | 99.80 | 3075 | 5.14 | 96.01 | 1274.33 |
EK21 | 6.19 | 93.74 | 752 | 5.37 | 100.01 | 3403 | 6.29 | 100.02 | 3243.67 |
EK22 | 5.49 | 99.34 | 2722 | 6.54 | 99.31 | 2725 | 5.37 | 97.42 | 1760.50 |
EK31 | 7.16 | 93.99 | 803 | 6.75 | 103.17 | 6733 | 6.59 | 101.10 | 4291.50 |
EK32 | 7.23 | 98.72 | 2375 | 5.59 | 96.36 | 1405 | 4.92 | 97.56 | 1820.33 |
EK41 | 5.28 | 95.44 | 1109 | 5.23 | 100.21 | 3615 | 5.58 | 95.30 | 1109.50 |
EK42 | 6.24 | 98.15 | 2073 | 8.07 | 98.82 | 2487 | 5.89 | 97.68 | 1864.00 |
LA11 | 6.49 | 99.97 | 3154 | 5.77 | 105.30 | 10899 | 5.11 | 96.91 | 1587.00 |
LA12 | 5.94 | 98.34 | 2175 | 6.49 | 98.61 | 2322 | 6.64 | 97.15 | 1708.50 |
LA21 | 6.13 | 97.88 | 1949 | 6.34 | 97.11 | 1659 | 5.21 | 95.59 | 1161.00 |
LA22 | 7.36 | 94.68 | 934 | 6.73 | 97.83 | 1997 | 7.02 | 98.82 | 2439.33 |
LA31 | 6.30 | 102.17 | 5234 | 7.24 | 103.87 | 7847 | 5.94 | 95.74 | 1215.17 |
LA32 | 8.26 | 97.41 | 1779 | 5.74 | 99.37 | 2856 | 5.16 | 91.75 | 491.00 |
LA41 | 6.53 | 98.20 | 2096 | 7.18 | 97.49 | 1813 | 6.13 | 96.29 | 1376.33 |
LA42 | 6.31 | 93.89 | 778 | 6.24 | 100.89 | 3941 | 7.63 | 95.46 | 1156.67 |
OG11 | 6.96 | 95.74 | 2266 | 6.67 | 100.69 | 3851 | 5.54 | 95.93 | 1244.33 |
OG12 | 6.30 | 92.75 | 970 | 5.73 | 96.38 | 1392 | 6.37 | 94.74 | 960.67 |
OG21 | 7.30 | 98.79 | 3715 | 6.19 | 100.87 | 3892 | 5.32 | 94.11 | 820.67 |
OG22 | 5.91 | 92.69 | 969 | 7.30 | 97.29 | 1709 | 6.20 | 96.57 | 1471.83 |
OG31 | 6.76 | 97.70 | 2659 | 6.68 | 88.73 | 248 | 6.27 | 96.90 | 1573.67 |
OG32 | 6.79 | 87.85 | 240 | 5.29 | 97.33 | 1828 | 5.10 | 96.79 | 1553.17 |
OG41 | 6.26 | 96.34 | 1674 | 7.16 | 88.13 | 219 | 5.93 | 96.19 | 1404.83 |
OG42 | 6.03 | 92.29 | 739 | 6.66 | 95.95 | 1249 | 6.98 | 98.18 | 2110.33 |
ON11 | 5.39 | 89.03 | 254 | 6.54 | 99.01 | 2530 | 6.31 | 95.36 | 1119.83 |
ON12 | 5.42 | 93.52 | 721 | 6.35 | 95.05 | 1016 | 6.90 | 101.17 | 4775.17 |
ON21 | 5.95 | 90.87 | 410 | 5.92 | 87.99 | 204 | 7.18 | 96.90 | 1558.50 |
ON22 | 7.27 | 100.69 | 3715 | 6.75 | 96.35 | 1391 | 5.25 | 97.98 | 2058.33 |
ON31 | 6.90 | 98.54 | 2272 | 6.71 | 96.82 | 1589 | 5.39 | 96.16 | 1321.17 |
ON32 | 6.30 | 99.03 | 2544 | 6.15 | 99.19 | 2651 | 4.50 | 97.28 | 1721.00 |
ON41 | 5.01 | 98.36 | 2191 | 6.14 | 98.40 | 2210 | 5.78 | 97.82 | 1940.00 |
ON42 | 5.04 | 103.35 | 6862 | 6.85 | 98.55 | 2285 | 7.78 | 97.91 | 2135.33 |
OS11 | 4.77 | 98.32 | 2159 | 5.84 | 101.54 | 4562 | 5.55 | 93.54 | 722.83 |
OS12 | 4.93 | 98.09 | 2083 | 6.96 | 98.97 | 2548 | 5.72 | 95.49 | 1170.50 |
OS21 | 4.65 | 97.29 | 1696 | 7.97 | 101.44 | 4436 | 5.19 | 89.40 | 278.50 |
OS22 | 5.94 | 97.21 | 1705 | 4.97 | 97.48 | 1841 | 5.01 | 95.55 | 1193.17 |
OS31 | 6.50 | 100.10 | 3251 | 7.18 | 100.46 | 3603 | 5.57 | 99.66 | 3000.67 |
OS32 | 5.92 | 98.06 | 2053 | 6.53 | 97.59 | 1855 | 4.87 | 95.52 | 1183.50 |
OS41 | 6.34 | 99.40 | 2767 | 6.02 | 98.08 | 2058 | 4.47 | 93.97 | 804.33 |
OS42 | 4.84 | 97.19 | 1667 | 5.72 | 94.67 | 945 | 5.04 | 94.25 | 856.50 |
OY11 | 7.28 | 99.08 | 2563 | 6.66 | 98.24 | 2186 | 6.62 | 94.89 | 985.50 |
OY12 | 6.76 | 92.70 | 594 | 5.35 | 100.35 | 3457 | 4.94 | 96.17 | 1361.00 |
OY21 | 6.46 | 97.74 | 1883 | 5.45 | 95.46 | 1170 | 5.12 | 93.16 | 668.00 |
OY22 | 5.93 | 94.35 | 874 | 6.42 | 97.10 | 1654 | 5.49 | 97.42 | 1858.00 |
OY31 | 5.87 | 97.67 | 1876 | 6.13 | 94.39 | 882 | 4.70 | 92.77 | 610.33 |
OY32 | 5.65 | 95.05 | 1038 | 5.95 | 97.15 | 1681 | 6.40 | 95.09 | 1034.83 |
OY41 | 5.93 | 97.38 | 1768 | 6.41 | 98.88 | 2502 | 6.42 | 99.64 | 2979.00 |
OY42 | 7.61 | 98.95 | 2500 | 6.20 | 96.40 | 1425 | 5.40 | 94.57 | 921.83 |
Machine | State | Average duration | State | Average | State | Average total |
---|---|---|---|---|---|---|
of exposure (hr) | LEP,d (dB) | exp. point | ||||
CM | OS | 5.49 | OG | 91.26 | OY | 1636.96 |
ON | 5.91 | EK | 94.18 | OG | 1653.77 | |
EK | 6.15 | OY | 94.29 | EK | 1780.15 | |
OY | 6.44 | ON | 94.61 | OS | 2172.42 | |
OG | 6.54 | LA | 95.48 | LA | 2262.33 | |
LA | 6.67 | OS | 95.84 | ON | 2371 | |
PM | OY | 6.07 | OG | 95.67 | ON | 1734.42 |
OS | 6.4 | ON | 96.42 | OG | 1798.56 | |
EK | 6.42 | OY | 97.25 | OY | 1869.5 | |
ON | 6.43 | OS | 98.78 | OS | 2730.77 | |
OG | 6.46 | LA | 100.06 | EK | 3746.27 | |
LA | 6.46 | EK | 100.09 | LA | 4166.54 | |
BM | OS | 5.18 | OS | 94.67 | OS | 1151.25 |
EK | 5.62 | OY | 95.46 | OY | 1302.31 | |
OY | 5.64 | LA | 95.96 | LA | 1391.88 | |
OG | 5.96 | OG | 96.18 | OG | 1392.44 | |
LA | 6.1 | EK | 97.42 | EK | 2032.13 | |
ON | 6.14 | ON | 97.57 | ON | 2078.67 |
The calculated actual noise daily dose levels for each machine considered are presented in
Period | CM noise dose | PM noise dose | BM noise dose | ||||||
---|---|---|---|---|---|---|---|---|---|
Min | Ave | Max | Min | Ave | Max | Min | Ave | Max | |
IPm | 0.12 | 0.48 | 2.37 | 1.21 | 1.67 | 2.06 | 0.09 | 0.32 | 0.92 |
WPm | 0.50 | 1.95 | 4.13 | 3.29 | 4.05 | 4.77 | 0.60 | 1.72 | 3.66 |
Total | 0.76 | 2.42 | 5.08 | 4.73 | 5.72 | 6.64 | 0.69 | 2.04 | 3.94 |
Sawmilling activities are obvious sources of noise and are activities that generally involve human actions in trying to make the environment a better place. However, these activities have long term adverse effects on sawmill workers. Therefore, this study concluded that the main fundamental contributing factors that influenced the high noise level and high noise exposure are grouped under three activities, these are the antediluvian machinery (which involves poor maintenance, use of old and obsolete machines.), Poor workshop layout (poor housekeeping strategy and limited space) and the human factor (this includes negligence, lack of Personal Protective Equipment (PPE), and lack of training on occupational safety and health challenges arising from sawmilling activities).
Furthermore, as clearly explained in this research work; not less than 90% and 75% of all the machines in the working and idle periods respectively, generated more than 90 dB acceptable noise level, which is a high level of noise pollution. Moreover, over 95.8% of all the machines exposed the workers to daily personal noise exposure levels above 90 dB and over 96.5% of the machines exposed the operators to noise dose levels more than the acceptable level. These showed that most of the machines produced unacceptable noise, thereby putting the sawmill workers at a significantly high risk of occupational health illnesses and injuries.
It is hereby recommended that proper workplace practices should be implemented, proper maintenance practices should be encouraged, use of PPE should be encouraged, new and modern machines should be procured, alternative electricity generating sets should be placed farther from the working environment, training and occupational safety programmes should be made compulsory for all the workers and all the sawmill workers should be encouraged to go for audiometry tests for early detection of any hearing disorder.