Assessment of Injury-Risks of Work-postures among Building Construction Workers in Anambra State

Assessment of Injury-Risks of Work-postures among Building Construction Workers in Anambra State

Godwin, Harold Chukwuemeka and Okere Chinedu, J. .

Department of Industrial/Production Engineering,Nnamdi Azikiwe University, Awka, Nigeria

Abstract

Work-Related Musculoskeletal (WMSDs) disorders have been traced to be common in building construction Industry. Studies have also been conducted to examine the general believe that Awkward Postures adopted by workers in various Work Fields can give rise to a wide range of Work-related Injuries. Besides, Risk impacts of manual handling of heavy loads like blocks, concrete mixture, and bags of cement, among others cannot be over-emphasized. This ergonomic study assessed the Injury-Risks in various Work Postures adopted by workers in building construction focusing on the bricklayers, the plasterers, the brick-makers, and their assistants. It covered sixteen building construction sites and fourteen brick-making factories in Anambra state, Nigeria. By observing the workers as they perform the tasks, the physical exposure to Risk was assessed using Ovako Working Postures Analyzing System (OWAS). Result of OWAS Assessment indicated Risk Index of 246.81 for Bricklayers, 281.37 for Plasterers, while Brick-makers and Assistants have Risk Index of

310.88 and 329.18 respectively. These high Risk Indexes obtained, revealed that a great number of the workers assume awkward postures, with Brick-makers and the Assistants being at higher level. OWAS recommended the need for corrective measures in improving working postures.

1. Introduction

   Work-related Musculoskeletal Disorders (WMSDs) covers a wide range of inflammatory and degenerative diseases, and disorders that result in pain and functional impairment (Kilbom et al., 1996) and may affect the bodys soft tissues, including damage to the tendon, tendon sheaths, muscles and nerves of the hands, wrists, elbows, shoulders, neck and back (Saldana, 1996). These disorders have caused a considerable human suffering and also economically very costly because of reduced working capacity and lessened production (Luopajarvi, 1990). Musculoskeletal Disorders (MSDs) accounts for over 50% of total work-related health problems experienced by workers across various work sectors (EUSOS 2002:108). These disorders have been found to be associated with numerous occupational risk factors, including physical work load factors such as force, postures, manual handling, repetitive work and vibration (Gerr et al., 1991); and individual factors. According to EASHW, 2004; Musculoskeletal disorders are particularly prevalent across a range of Construction industry trades with estimates suggesting that as many as 30% of the workforce may be affected. Annually, WMSDs accounts for over 50% of health-related problems among workers, leading to high medical cost and economic loss (EUSOS, 2002:108). Building construction processes encompasses various manual activities, which include the following: lifting/carrying of blocks, cement, concrete, sand etc. from one point (level) to another. During these operations, the workers adopt awkward postures which can cause work-related injuries. This study assesses the ergonomic risks associated with the various work postures/positions among workers in building construction.

2. Methodology

   Ovako Working postures Analyzing System (OWAS), was employed to assess the work-postures adopted by workers in the various Work Groups. The total of 211 work-positions/postures assumed by 80 workers as they perform their various tasks were assessed by OWAS, and based on the resulted Ovako codes obtained, the Risk Classes of the postures/positions were determined. OWAS classified work postures/positions into four ordinal scale action categories which are based on experts estimate of the health hazards of each work posture or posture combination (Mattila 993), as thus: Class 1: Natural position; Class 2: Positions which may be dangerous; Class 3: Dangerous position; Class 4: Very dangerous positions. Subsequently, the Injury-Risk Indexes associated with the work-postures for various work groups were evaluated. Index Risk (I) for each work group was calculated using I = [(a x 1) + (b x 2) + (c x 3) + (d x 4)] x 1; Where a, b, c, d are the frequencies of classes 1, 2, 3, 4 respectively. Based on OWAS, a posture with Index Risk (I) of 100 has minimum risk; whereas a posture with Index Risk that is more than 100 has higher risk, while Index Risk of 400 has maximum risk.

3. Results and Discussion

The results and demographics of the study are given below.

Assessment of Postures

The total of the 211 work-positions/postures assumed by 80 workers as they perform their various tasks were assessed using OWAS, and the resulted Ovako codes determined the risk classes of the posture/position. The posture risk indexes for various work groups are evaluated, as shown below.

Brick Layers

The postures adopted by 18 bricklayers as they perform the tasks, were assessed, and in 47 work positions, 13 different Ovako postures (codes) were obtained. These postures and their risk classes, as well as their associated frequencies are summarized below.

Frequency = Cn/N; where Cn = Number of occurrence for a given class;

N = sum of postures for all Risk Classes; N = 4 + 25 +10 + 8 = 47

Frequency Rate = Frequency x 100%

Table 1: Risk Classes and their frequency rates

The Index Risk (I) associated with these Risk Classes, among Bricklayers, is evaluated thus;

I = [(a x 1) + (b x 2) + (c x 3) + (d x 4)] x 1

Where a, b, c, d are the frequencies of classes 1, 2, 3, 4 respectively. a = 0.0851; b = 0.5319; c = 0.2128; d = 0.1702

I = 246.81

Plasterers

The postures adopted by 22 plasterers as they perform the tasks, were assessed, and 5 different Ovako postures were obtained in 56 work positions as shown below.

N = 2 + 0 + 39 + 15 = 56

Table 2: Risk Classes and their frequency rates

The Index Risk (I) associated with these Risk Classes, among plasterers, is evaluated thus;

I = [(a x 1) + (b x 2) + (c x 3) + (d x 4)] x 1 = 281.37

Brick-makers

For 18 brick-makers; 6 Ovako postures were obtained in 46 work positions. These postures and their risk classes are tabulated below.

N = 3 + 16 + 0 + 27 = 46

Table 3: Risk Clases and their frequency rates

The Index Risk (I) associated with these Risk Classes, among Brick- makers, is evaluated thus;

I = [(a x 1) + (b x 2) + (c x 3) + (d x 4)] x 1 = 310.88

Assistants

For 22 workers (assistants); 7 Ovako postures were obtained in 72 work positions. These postures and their risk classes are tabulated below.

N = 5 + 18 + 0 + 49 = 72

Table 4: Risk Classes and their frequency rates

The Index Risk (I) associated with these Risk Classes, among Assistants, is evaluated thus;

I = [(a x 1) + (b x 2) + (c x 3) + (d x 4)] x 1 = 329.18

Summary of the Frequency Rates for the Four Work Groups

Table 5 summarizes the frequency rates of all the work groups for each risk class, followed by the chart in figure 1 that clearly shows the result.

Table 5: Frequency rates for all the risk classes in all work sectors

Below is the Chart showing the frequency rates (%) of the various work groups

70.00%

60.00%

53.19%

61.90%

58.69%

68.06%

50.00%

40.00%

30.00%

20.00%

21.28%

17.02%

23.81%

34.78%

25.00%

class1 class2 class3 class4

10.00%

8.51%

3.17% 6.52% 6.94%

0.00%

Bricklayers Plasterers Brick-makers Assistants

Figure 1: the frequency rates of the four class risks for all the work groups

Overall Frequency Rates

The frequency rates for the four risk classes among all the workers are summarized in table 6, and subsequently followed by a graphical representation in figure 2.

Table 6: Overall frequency rates of each Risk class for all workers

50.00%

45.00%

40.00%

35.00%

30.00%

25.00%

20.00%

50.00%

45.00%

40.00%

35.00%

30.00%

25.00%

20.00%

23.22%

23.22%

23.22%

23.22%

For the 211 work-positions/postures assumed by 80 workers as assessed using OWAS; the result shows that 6.64% of the postures/positions adopted by the workers is injury-free (natural position), while 23.22% of the postures may be dangerous. Whereas 23.22% of the postures are dangerous, and up to 46.92% of these postures are very dangerous.

46.92%

46.92%

15.00%

10.00%

5.00%

0.00%

15.00%

10.00%

5.00%

0.00%

6.64%

6.64%

Class 1

Class 1

Class 2

Class 2

Class 3

Class 3

Class 4

Class 4

Figure 2: frequency rates for the four risk classes

Based on Ovako Risk Classes (already given), the result of the work postures/positions adopted by workers in Building Construction is summarized as shown in figure 3.

Postures

6.64%

Postures

6.64%

23.22%

23.22%

Good (6.64%)

Good (6.64%)

70.14%

Fair (23.22%)

70.14%

Fair (23.22%)

Dangerous (70.14%)

Dangerous (70.14%)

Figure 3: summary of the postures

Hence, only 6.64% of the positions are injury-free, while 23.22% assumed fair, whereas over 70% of the work postures/positions adopted by these workers are dangerous, and therefore can cause musculoskeletal disorders.

Risk Index

The Risk Indexes, calculated above, for the four Work Groups are summarized in table 7 with graphical representation in figure 4.

Table 7: Risk Index for the work groups

300

300

281.37

281.37

246.81

246.81

The Risk Index for each of the work groups is far beyond the minimum risk index (which is 100). This indicates that the postures/positions adopted by the workers are capable of causing work-related injury, and therefore need to be ergonomically re- designed.

350

310.88

329.18

350

310.88

329.18

250

200

Risk Index(I)

250

200

Risk Index(I)

150

100

50

0

150

100

50

0

Brick layers

Plasterers

Brick-makers

Assistants

Brick layers

Plasterers

Brick-makers

Assistants

Figure 4: Risk Index for various work groups in Building Construction

Conclusion

Based on the descriptive result of this study, it could be concluded that workers in building construction performs different activities in various awkward postures for a longer period of time and they suffer from discomfort and pain in different parts of the body, specifically in wrists, elbows, shoulders, neck and back regions. These awkward Postures could be accrued to poor work stations and improper work

methods. Hence, this study pointed out a number of ergonomic factors that needed to be addressed in order to ensure health, safety and reduced risks of developing Work-related Musculoskeletal Disorders among the workers.

References

European Agency for Safety and Health at Work (EASHW) 2004. Building in Safety Bilbao Declaration following the European Construction Safety Summit of 22 November. Bilbao, Spain.

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NIOSH. 1981. Work Practices Guide for Manual Lifting (WPG), NIOSH Technical Report. U.S. Department of Health and Human Services, National Institute for Occupation.81-122.

NIOSH. 1997. Musculoskeletal Disorders in the Workplace Occupational Health Report Publication No. 97-141. Dept. of Health and Human Services, Cincinnati.