Risk of Musculoskeletal Disorders within the Portuguese Ceramic Industry

Paz Barroso, M.F.C.

Departamento de Produção e Sistemas/Escola de Engenharia/ Universidade do Minho/ Azurém, 4800-058 Guimarães, Portugal

351 253 510 353, mbarroso@dps.uminho.pt

Gomes da Costa, L.F.T.

Departamento de Produção e Sistemas/ Escola de Engenharia/ Universidade do Minho/ Azurém, 4800-058 Guimarães, Portugal l.gcosta@netcabo.pt

ABSTRACT

This paper presents the results from a detailed ergonomic analysis carried out in order to assess the risk of musculoskeletal disorders in the Portuguese Ceramic Industry. Ten companies were visited, comprising the analysis of 40 different workplaces.

Results suggest that there is a moderate to high risk of musculoskeletal disorders at the lower back for most of the production stages. Regarding the risk of musculoskeletal disorders of the upper limbs this was found to be considerable for a large number of activities across the different production stages and for both the sanitary ware and pottery production processes.

Keywords

Musculoskeletal disorders, ceramic industry, ergonomic analysis of workplaces

INTRODUCTION

Nature of the Problem Analysed

In general modern manufacturing industries present a reasonably high incidence of musculoskeletal disorders, which affect a significant proportion of the working population.

This issue is generally brought to light through the recording of complaints of pain or of incommodity which are incapacitating to different extents, but which seem to be associated with the performance of certain professional activities, although in some cases these complaints may be associated with some sports or recreation activities.

Among specialists in this domain it is common the view that this is not a problem particular to a specific industry type, rather that it emerges from a number of task characteristics which, in fact, may be found across a considerable number of activities and industries. Data collected from different research studies on this domain shows that the industry types affected are several but that the variety of disorders seems to be relatively small – indicating a prevalence of disorders of the lumbar and cervical regions and at the upper limbs level (hand, wrist, elbow and shoulder).

The absence of detailed statistical data regarding the incidence of musculoskeletal disorders (MSD) in Portugal prevents an accurate definition of the extent of the problem. Nonetheless, having in mind what is known for other European countries in which a better statistical data recording exists it may be acknowledged that MSD are the cause of the loss of a considerable number of working days and that

these contribute significantly for the absenteeism figures.

The above points substantiate the importance of the effect of MSD on productivity levels and on the associated socio-economic consequences. Considering the number of workplaces in labour-intensive industry across Portugal and the little regard most companies devote to the prevention of MSD, it is acceptable to suggest that the numbers regarding the prevalence of MSD in Portugal are higher that those found for other EU countries. At this respect, a recent survey carried out within the EU [1] suggests that circa 30% of workers complain of pains at the torso-lumbar region and that this figure is of approximately 17% for musculoskeletal complaints at the arms or legs. The figures for Portugal, according to the same report, are respectively of 39% and 31%.

Main Risk Factors

Results available from ergonomic analysis of the risk of MSD in occupational environments suggest that it is considerable the number of workplaces and activities for which there is risk of MSD. Notwithstanding the fact that most of the analysis of the risk of MSD in Portuguese companies has been focused on the automotive industry, it is the authors’ belief that a similar scenario is likely to be found on the ceramic industry. This belief arises from the fact that there are similarities between many activities and demands found in automotive and ceramic industries.

It is widely recognised that major causes of MSD at the lumbar region are associated with manual handling tasks, and to the need of adopting incorrect and awkward postures. These facts were found in all companies visited throughout this study.

On the other hand several of the workplaces and activities analysed may be characterised by the need of repetitive movements, often performed in incorrect postures and requiring intense muscular activity.

In addition to the above mentioned risk factors, it is important to emphasise that several of the workplaces analysed require high work paces and are carried out through long periods of time.

Last, but not the least, it is worth stressing that many of the movements performed by operators require the application of considerable strength and flexion, extension or rotation of the joints close to their amplitude limits. These circumstances constitute aggravators of already risky situations.

METHODOLOGY

A preliminary visit to the different companies involved was carried out in order to, not only identify a range of representative workplaces for a more detailed analysis, but also to determine which risk assessment techniques best suit the goals of this research.

Two major categories of risks have been identified for the range of workplaces analysed – those activities associated with manual handling of significantly heavy parts, and those associated with repetitive movements of the upper limbs. On this basis different methodologies have been selected and applied for risk assessment.

Methodology for Risk Assessment of Manual Handling Tasks

Two different methods were applied for this purpose. These were selected and subsequently applied considering the restrictions set and the performance conditions registered.

The equation developed at the United States National Institute of Occupational Safety and Health (NIOSH) was applied for risk assessment of those lifting activities

which do not require load transportation and which are performed at a fixed position involving essentially movements performed in the sagittal plane ([2]).

This is a widely applied method for this type of activities and involves the quantification of a series of workplace variables which are known to determine the associated risk of lumbar MSD. On the basis of the parameters quantified the method proceeds with the computation of the recommended weight limit for those conditions.

Risk analysis is carried out comparing the weight limit determined and the weight which is handled. The higher the Load Index (LI), defined as the ratio between the weight handled and the weight limited computed, the higher the risk and the higher the percentage of workers exposed. The determination of the LI, as an estimate of the physical strain imposed on operators, is particularly pertinent and useful for those situations for which the weight handled exceeds the weight limited prescribed and when the restrictions imposed prevent the implementation of workplace amendments or the use of mechanically assisted devices.

Other useful applications of the NIOSH equation [2] encompass the ergonomic design of workplaces, namely:

• The identification of the workplace variables which are more problematic as far as the risk is concerned, and the possibility of assessing the impact of alterations of these variables on the overall risk level,
• The establishment of priorities regarding intervention on those workplaces which are associated with risk – this priority definition is done on the basis of the LI value,
• Comparison between different design alternatives – selecting those with the lowest LI values. Given the number of restrictions set for what regards the practical application of the NIOSH equation [2], this may not be applied whenever there is the need for displacement of the operator – for example when there is the need of transporting, pulling or pushing loads. For these situations another risk assessment methods has been selected – the Mital, Nicholson and Ayoub method [3]. This may be applied for risk assessment of activities which require any, or combinations, of the following tasks:
• Raise, with two hands, with one hand and by two people,
• One and twohand pushing,
• One and twohand pulling,
• One and twohand carrying,
• Holding loads in different positions,
• Materials handling in unusual postures (raise, push and pull),
• High and very high frequency handling (lifting/lowering, and carrying).

The method is based on the premise that the operator’s capability for performing a manual handling task depends on his/her capability for the performance of the individual tasks comprised in his/her workplace.

The practical application of this method encompasses a series of steps, including the identification of the individual handling task types performed and data collection regarding the workplace (spatial layout, characteristics and dimensions of the objects handled, shift length, distances covered, and length and frequency of rest breaks). Once the activity is characterised and the relevant information is recorded it is necessary to identify and define the percentage of the population which is to be satisfied.

Risk assessment is done comparing, for each individual task element identified and analysed, the actual work pace (rhythm) with that recommended. The ratio between these two figures is named “potential risk” [3]. Whenever this ratio exceeds one, it is of prime importance that changes are implemented in order to lower the associated risk level.

Methodology for assessing the risk of musculoskeletal disorders at the upper limbs.

The Rapid Upper Limb Assessment (RULA) technique was selected for thispurpose [4]. This is based on the identification of the major factors which are known to contribute to the incidence of MSD at the upper limbs. Among the risk factors included are the number of movements performed, whether there is the need for static muscular work, the muscular force applied, the posture adopted, whether there is the need for accurate and rapid movements, the frequency and length of rest breaks, age and physical fitness of the operators, anthropometric dimensions as well as some environmental factors such as lighting, thermal environment, noise and vibrations.

RULA is applicable both to industry and tertiary sector workplaces – generally to all those situations for which the nature of the activities performed is associated with the risk of MSD at the upper limbs.

In order to assess the risk of complaints and of MSD the RULA starts with the identification and characterization of the different postures adopted while performing each task. In addition it is necessary to determine the force exerted applied (if applicable) and the frequency of movements. Computation of the overall RULA score is done considering the combined effect of the different risk factors defined, through input of the different partial scores on a worksheet. Partial scores are obtained for classification of Group A (upper limbs and wrist) and Group B (neck, trunk and legs). The higher the overall score obtained (on a scale varying from 1 to 7) the higher the risk level which may be assigned to the task or activity.

RESULTS OBTAINED

Results regarding the Risk Assessment of Manual Handling Tasks

Results obtained from the detailed analysis carried out to a representative sample of workplaces suggest that this category of risk is present across the different stages of the production process, both in what regards the production of sanitary ware and pottery.

Underlying the high risk levels encountered is, essentially, the significant weight of the objects handled and the postures adopted for materials handling.

The former issue – that of the weight of the objects handled – appears to be more relevant for the sanitary ware production process, primarily due to the dimensions of the objects, but is also pertinent for some workplaces of the utilitarian ceramic production process, namely for those workplaces where there is the need of handling heavy and bulky rolls of pasta and in the packing and expedition sections.

As previously mentioned, it is frequent the adoption of incorrect postures during performance of several tasks. More significant examples are those tasks which require loading and unloading of pallets, of presses and of the wagons used for ovens (see figure 1).

ORP2004 - 3rd International Conference on Occupational Risk Prevention

Results regarding the Risk Assessment of Musculoskeletal Disorders at the upper limbs.

Among the risk factors underlying the occurrence of MSD at the upper limbsthose associated with the handling of heavy parts, with the repetitiveness of movements and with the need for incorrect postures appear to be the most relevant.

This fact is corroborated by the results found from the risk assessment of several of the workplaces analysed. It is important to emphasise that it is frequent to find workplaces and activities in which the three risk factors mentioned earlier coexist, hence enhancing the probability of incidence of musculoskeletal disorders.

Figure 1 – Example of inadequate posture associated with the manual handling of excessive load.

As far as the adoption of inadequate postures is concerned this appears to be more pertinent for finishing activities (sponging and sanding – see figure 2A and 2B), both for the sanitary ware and pottery production processes.

Figure 2A - example of inadequate postures adopted during finishing operations for pottery production process.

Figure 2B - example of inadequate postures adopted during finishing operations for sanitaryware production process.

Repetitiveness of movements, namely that associated with the need of extreme postures of the wrist, also appears in several of the activities analysed. It is worth

stressing that extreme postures of the joints usually constitutes an additional risk factor. The need for force exertion while adopting incorrect postures is also relevant for the arm and upper arm levels. This situation, which is known to increase the risk of musculoskeletal disorders for the shoulder joint, is evident for various workplaces, both for the sanitary ware and pottery production processes.

SUMMARY OF THE MAIN RESULTS FOUND

Packing material

Pottery and sanitary ware processes

Push/Pull stock cars

Table 1 – summary of the main risk factors found at the different categories of workplaces analysed.

MAIN SUGGESTIONS AND RECOMMENDATIONS

Sanitary ware Production Process

As previously mentioned, the major contributor to the high risk levels found are associated with the need of moving and handling heavy parts. Accordingly, priority should be given to the elimination or reduction of the activities associated with this type of effort. Main avenues for risk reduction encompass implementation (individually or combined) of some the following possibilities: acquisition of mechanical or electrical devices which assist handling and moving of parts (for example pallet trucks), mechanical manipulators for fixed workplaces, and, whenever possible, installation of conveyors or hanging baskets which provide the means for transportation between different workplaces. The latter requires integration of the different workplaces within the production line and may also require redesign of some installations.

Lower priority is assigned, in this particular type of industry, to the implementation of changes aimed at reducing the risks of MSD at upper limbs. Notwithstanding, it is recommended that redesign of some workplaces is undertaken in order to reduce risk levels.

The following subsections present possible solutions to reduce risk levels, according to the associated expected cost. This systematization, the authors believe, enables a simplified definition of what solutions to implement – on a cost/benefit analysis basis.

Low cost solutions

• Training and education programs for operators focusing on understanding of the suitable postures for materials handling. This measure, in order to be effective, requires refreshing programs and also attention must be given in order to understand whether the results obtained are the expected ones.
• Suitable maintenance programs – these should also focus on maintenance of operability of trolleys or of other transport means used.
• Improve floor finishing in order to facilitate trolley movements – this is particularly important since  many transportations are  made  through pushing/pulling of trolleys.
• Implement rotation schemes for those workplaces with highly repetitive activities. Activities with different physical demands should be included on these schemes. Frequency of rotation varies according to the repetitiveness of the task.
• Consider the possibility of more often breaks for highly repetitive tasks. For example 5 minute break after every hour. These breaks may be used for performance of simple and non demanding tasks, such as register of information, quality control, etc.
• Provide tools with suitable handles – which enable the operator to hold the

tool on a comfortable and suitable position. This will eventually improve the postures at wrist level and, accordingly, reduce fatigue.

Moderate cost solutions

• Install and/or improve pneumatic systems to raise rotational  support  of parts on activities such as finishing, manual glazing, kiln load/unload, and

visual inspection and selection of parts. This will enable better postures of upper limbs and neck, hence reducing the potential effect of an important risk factor. It is recommended that the system to implement is easy to use for otherwise operators will not apply it. For example the use of a foot operated pedal might constitute a suitable alternative for the activating mechanism.

• Acquisition of electrical tractors to avoid the need for manual traction of the stock cars and trolleys.
• Install mechanical means to replace manual handling of heavy parts; this is particularly  pertinent  on  sanitary  ware  production  process.  Workplaces which may require this solution are those of manual glazing, plaster moulds manufacturing, kiln car load/unload, and selection and packing of parts. As previously mentioned these mechanisms should be placed on  the  areas where the materials are handled.
• Installation of pallets support pneumatic systems – these should be of adjustable height and placed near the load/unload areas.
• Reorganize workplaces in order to increase task variety, that is, provide Job enlargement. This could also decrease the negative effects of highly repetitive tasks at psychological and motivational levels.

High cost solutions

• The mechanical systems as well as the rotational supports of adjustable height referred before are particularly effective if they can be articulated with automatic transport systems such as hanging baskets or conveyors. These high cost solutions also have important implications on the overall layout of the production process, the latter contributing further to increase global implementation costs. Nonetheless it is important to refer that this type of integrated solution constitutes a valuable means to  effectively reduce risk of MSD across different workplaces and activities.

Utilitarian Ceramic Production Process

Low cost solutions

• Furniture: good quality chairs with adjustable seat and lumbar  support height. Also adjustable feet support height should be provided. Work height should be defined considering the nature and requirements of the tasks performed.
• Provide tools with suitable handles – which enable the operator to hold the tool on a comfortable and suitable position of the wrist/hand. This will eventually improve the postures of the wrist and, accordingly, reduce fatigue.
• Training and education programs for operators focusing on understanding of the suitable postures for materials handling. This measure, in order to be effective, requires refreshing programs and also attention must be given in order to understand whether the results obtained are the expected ones.
• Implement rotation schemes for those workplaces with highly repetitive activities. Activities with different physical demands should be included on these schemes. Frequency of rotation varies according to the repetitiveness of the task.
• Consider the possibility of more frequent breaks for highly repetitive tasks. For example 5 minute break after every hour. These breaks may be used for performance of simple and non demanding tasks, such as register of information, quality control, etc.
• Suitable maintenance programs – these should also focus on maintenance of operability of trolleys or of other transport means used.
• Improve floor finishing in order to facilitate trolley movements – this is particularly important since  many transportations are  made  through pushing/pulling of trolleys.

Moderate cost solutions

• Install rotational supports for pieces on those activities such as unfired finishing (rasping and sponging), decal (colour transfers) application, and hand painting. This will enable better postures of upper limbs and neck, hence reducing the potential effect of an important risk factor.
• Installation of pallets support pneumatic systems – these should be of adjustable height and placed near the load/unload areas. This is particularly critical for hydraulic presses, rollers, kiln load and unload, in general for all those activities which require handle parts or materials from/to pallets.

High cost solutions

• It is highly recommended the implementation of transport systems similar to hanging baskets. Although this solution has already been implemented in some of the companies visited it is notorious that the system if far from reaching all workplaces. These high cost solutions also have important implications on the overall layout of the production process, the latter contributing further to increase global implementation costs. Nonetheless it is important to refer that this type of integrated solution constitutes a valuable means to effectively reduce risk  of  MSD  across  different workplaces and activities.

CONCLUSIONS

Main conclusions of this research project indicate that it is significant the number and variety of activities for which is considerable the associated risk, both of musculoskeletal disorders at the lumbar region and at the upper limbs.

In general terms it may be said that the risk of musculoskeletal problems at the lumbar region appears more often and more pertinently within the production process of sanitary ware, and that this is essentially associate with the handling of excessive loads.

The risk of musculoskeletal disorders at the upper limbs, on the contrary, appears to be more critical for the activities performed at the pottery production process.

The detailed analysis carried out to the different workplaces analysed enabled the identification of the major risk factors and, subsequently, of the main preventive and corrective measures to apply in order to reduce risk levels. It became evident that there are situations for which risk reduction will require the implementation of simple and low cost solutions. A representative example concerns those situations for which alterations on the dimensions of the furniture used would contribute to reduce the need for adoption of incorrect work postures.

Other situations require the implementation of more complex and costly solutions, such as the redesign of several workplaces throughout the production process.

Finally, it is worth referring that the implementation of organisational measures, such as workers rotation in order to reduce individuals’ exposure to those more demanding tasks, is likely to constitute an important contribute to reduce risk levels in several of the situations analysed. These organisational measures should only be implemented once all possible ergonomic changes have been analysed and eventually put into practice.

ACKNOWLEDGMENTS

The authors would like to thank all the companies which have participated on this project and also to Eng.º Francisco Silva and colleagues from Centro Tecnológico da Cerâmica e do Vidro.

REFERENCES

• 1. TUTB, 1999 Special Report – Muskuloskeletal Disorders in Europe. Newsletter of the European Trade Union Technical Bureau for Health and Safety. No. 1112, June 1999.
• 2. Waters, T.R. e PutzAnderson, V., Revised NIOSH lifting equation. In: Occupational Ergonomics – Theory and Applications, Ed. A. Bhattacharya e J. D. McGlothlin, Marcel Dekker, Inc., New York, 1996.
• 3. Mital, A., Nicholson, A. S. e Ayoub, M. M., Manual materials handling, Taylor