Rafiee M, Zokaei M, Bayat Marzijarani M, Safarpour Khotbesara N. Risk of Manual Handling and Prevalence of Musculoskeletal Disorders among Rice Mill Workers in Northern Iran. AOH 2023; 7 (1) :1392-1400
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http://aoh.ssu.ac.ir/article-1-359-en.html
1- Master’s in Ergonomics, Ergonomics Department, the University of Rehabilitation and Social Health, Tehran, Iran. orcid: 0000-0001-8675-6279(Maryam.rafiee13688@gmail.com)
2- Social Determinatst of Health Research Center, Saveh University of Medical Sciences, Saveh, Iran
3- Student Research Committee, Saveh University of Medical Sciences, Saveh, Iran
4- Social Department of Health Research Center, Saveh University of Medical Sciences, Saveh, Iran , negar.sp513631@gmail.com
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Risk of Manual Handling and Prevalence of Musculoskeletal Disorders among Rice Mill Workers in Northern Iran
Maryam Rafiee 1, Mojtaba Zokaei 2, Mohaddese Bayat Marzijarani 3, Negar Safarpour Khotbesara 4*
1 Ergonomic Department, The university of Rehabilitation and Social Health, Tehran, Iran 2 Social Determinatst of Health Research Center, Saveh University of Medical Sciences, Saveh, Iran 3 Student Research Committee, Saveh University of Medical Sciences, Saveh, Iran 4 Social Department of Health Research Center, Saveh University of Medical Sciences, Saveh, Iran Corresponding authors: Negar Safarpour Khotbesara, Email: negar.sp513631@gmail.com
ABSTRACT
Background: Nowadays, a large proportion of work-related activities are performed manually, which has led to an increase in the prevalence of musculoskeletal disorders (MSDs). This study aims to assess the risk of manual material handling (MMH) and estimate the prevalence of MSDs among workers in rice mills in the northern part of the country. Methods: The study was conducted on 100 workers employed in 36 rice mills in Gilan Province using the census method. The Nordic questionnaire was used to determine the prevalence of musculoskeletal disorders, while the NIOSH equation, Snook table, KIM-LHC and MAC assessment methods were used to evaluate the risk of related activities. Data were then analysed using chi-squared test and Spss23 software. Results: The results of the KIM-LHC and MAC lifting methods showed a high prevalence of musculoskeletal disorders in the lower limb during lifting. Similarly, there was a statistically significant relationship (P=0.001 and P=0.002) between the Mac and Snook lifting methods. However, there was no significant relationship between the Niosh method and either the Kim-LHC or Mac-Lifting methods (P=0.10 and P=0.28). Conclusion: The results of the risk assessment using different methods showed a consistent and critical condition of the working environment in the rice mills studied. Therefore, it is imperative to take the necessary engineering and management control measures to improve the working conditions.
Keywords: Musculoskeletal disorders, Risk factors, Niosh, Work-related, Ergonomics.
Introduction
usculoskeletal disorders (MSDs) refer
to any type of pain, discomfort, or
disorder in muscles, tendons, ligaments, peripheral nerves, joints, bones, and blood vessels that arises due to repeated stress in a period of time.1, 2 MSDs account for 30% of total disability and 40%
of partial disability in the United States.3 Musculoskeletal disorders such as upper limb problems, neck, and back pain are the second most prevalent cause of sickness absence. According to statistics reported in the UK, a minimum of 28 million working days are lost annually, resulting in a cost of £7 billion per year.4 Despite advancements in mechanizing work processes, most work activities are still manual, which increases the prevalence of work-related musculoskeletal disorders.5, 6 One of these manual job activities is moving and carrying loads manually, which includes lifting, lowering, pulling, and pushing.7,8 These activities are classified dangerous based on factors like load characteristics, work environment, work station, and psychological factors, such as occupational stress.9-11 Manual transportation of goods can expose workers to unfavorable physical conditions such as forceful exertion, awkward posture, and repetitive movement leading to back pain, fractures, injuries, and waste of time and energy. Lifting heavy loads is the most important risk factor in the development of back pain.12,13 Manual material handling (MMH)has been identified by Health, Safety, and Environment (HSE) organization of England as one of the most important causes of occupational injuries and accidents.14,15 Ergonomic programs focus on preventing the MSD related to manual handling of loads and repetitive tasks by evaluating and checking MMH activities through methods such as Manual Handling Assessment Chart (Mac) method, NIOSH equation, the Snook tables, and the KIM_LHC method.16 In rice mills, manual handling of loads (70 kg rice bags) is often done manually, and improper physical posture is observed among workers, leading to a high prevalence of MSDs, especially in the waist area. Studies have been conducted to improve the working posture of workers with manual handling duties in rice threshing factories. By designing an appropriate tool, the risk level of the work situations can be determined and reduced. The risk factors related to MSD can be classified into two categories: sub-risk factors (age, work experience, duration of work, work load) and main-risk factors (posture, manual handling risks). In 2015, Etmadinezhad et al. conducted a study to evaluate ergonomic conditions of rice mill workers in Sari City.17 They investigated the working posture of rice threshing workers in Sari city using ovako working posture analyzing system (OWAS) evaluation method. The results showed that a significant portion of the workers' postures required corrective measures. The prevalence of MSD in rice mill workers is high, therefore, ergonomic intervention programs through engineering controls are recommended to control the ergonomic risk factors. Therefore, this study assesses risk assessment of MMH and the prevalence of MSD among rice mill workers in northern Iran. Furthermore, it highlights the need for ergonomic interventions to control ergonomic risk factors in the working environment of rice mills and prevent and control MSDs in workers. Moreover, the importance of evaluating permissible weight values for carrying loads was emphasized using valid evaluation methods.
Methods
This was a cross-sectional descriptive analytical study conducted in 2022 on 100 workers in 36 rice mills in Gilan province. The workers were included in the study through census and had no history of disorders affecting the musculoskeletal system, including non-occupational MSDs. The workers had a work experience of more than one year and were involved in MMH. A sample of images of MMH activities in the studied rice mill is presented in Figure1.
A written questionnaire was used to collect the data related to the desired variables. First, demographic characteristics such as gender, age, marital status, working hours, overtime, and sports activity were obtained through a demographic questionnaire. Second, the Nordic questionnaire was used to determine the prevalence of MSD among the participants. Full explanations were provided to ensure participants understood the questions. Finally, risk evaluations were carried out using the NIOSH equation, Snook tables, KIM-LHC and MAC methods for activities involving MMH, taking into account the cargo weight among other factors.
Figure1. Pictures of MMH activities in the studied rice mills
A: Nordic questionnaire
The Nordic questionnaire is a reliable measurement tool for evaluating MSD. It was first introduced in 1987 by Korina et al. and later translated, localized, and evaluated for validity and reproducibility by Mokhtarinia et al.18 The questionnaire evaluates the presence of burning, discomfort or numbness in different parts of body including neck, shoulders, upper back, elbows, waist, wrist, thighs, hips, knees and ankles over different time periods. This tool is used to assess MSD in a wide range of occupational groups. The questionnaire was completed through an interview with rice mills, and the disorders and discomforts of 9 parts of the body were investigated. This tool is often used in screening and epidemiological investigations of MSD.19
B: NIOSH equation
The Niosh equation, on the other hand, is used to calculate the recommended weight for load lifting which most healthy workers could do in one work shift without suffering back problems. This equation is the result of the relationship between the 7 coefficients mentioned in equation (1). To use the NIOSH method, first, the weight of rice bags (L), the horizontal distance between the hand (while holding the load) to the center of gravity of the body (HM), the distance from the ground to the height of the load placement (the height of the starting point of lifting the load) or (VM), the amount of moving the load (the distance between the original and the destination of the load) or (DM), the amount of rotation of the trunk from the sagittal level (AM), the number of repetition of lifting the load per minute (FM) and the conditions of hand grip with the load (pair) were measured (CM). The load was specified and the numerical values of each of the required variables were determined. Then, the necessary coefficients were extracted by calculating the amount of recommended weight load (RWL) using equation land, and calculating the lifting index (LI) according to equation (2), the permissibility/non-permissibility of the load carried by rice mills and the amount of physical stress applied to the body during lifting. The load was estimated and the necessity of implementing ergonomic interventions in the work environment was investigated. Thus, in activities where LI is equal to or smaller than one, the environment is ergonomic and the implementation of ergonomic interventions is not necessary.
In addition, when LI is determined between one and three, it is necessary to design and implement ergonomic interventions. If LI is more than 3, more basic changes such as automatic methods of carrying and lifting loads should be considered
in order to make the work environment
ergonomic.
RWL=LC×HM×VM×DM×AM×FM×CM (1)
LI= L(kg)RWL(kg)