Dr.Guangyan Li or to Professor Peter Buckle, regarding the use of the exposure tool and other relevant issues, so that these can be added to this discussion page.
Thank you.
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Question:
In the second question (B1-B3), what does manual material handling tasks refer to? Only lifting tasks or does it also include push/pulls? For example, would pushing a lift assist be considered a MMH task or an 'other task'? (Canada)
Reply:
The answer is 'yes', the tasks should also include push/pulls and load carrying, as well as manual lifting. If a task includes both lifting and pushing/pulling, I should either look at the whole job and assess the element which gives the highest load to the back; or divide the task into two parts (i.e., lifting and pushing) and assess them separately (both using B1-B3).
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Question:
What approach do you take if you have 'other tasks' and MMH in the same job? Do you fill out the B1-B3 section or the B4-B5 section or both? and if you fill out both, how do you use the score sheet? (Canada)
Reply:
In this case, I would view the job as two parts and assess the MMH and 'other tasks' separately (using two QEC forms, one to check only for B1-B3 and the other check only for B4-B5, but not check both sections at the same time). If it is too difficult to separate the job into sub-tasks, you may just need to catch the 'worst' event of that job when the back is most heavily loaded, eg., when bending down and picking up an heavy object.
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Question:
For back movements repetition, do you count all back movements that are not neutral (i.e., >20 degree deviation)? (Canada)
Reply:
Yes, the back movements are counted every time when it is loaded (along with those movements).
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Question:
How did you determine the scale and catergorization for back motion frequency exposure in manual handling tasks (i.e., <3, =8, or >=12 motions per minute)? (USA)
Reply:
For manual handling tasks or heavy physical work, the movement of the back is categorized into 3 exposure levels, i.e., 'Infrequently' (eg. around 3 times/min or less), 'Frequently' (eg. 8 times/min) and 'Very frequently' (eg.12 times/min or more). Original construction of this assessment item was partially based on OSHA Draft Standard (1995) in which the back movement was categorized as 1-5 times per minute and more than 5 times per minute. However, epidemiological literature shows no sufficient evidence as to the 'safe' level of the back movement when performing manual handling tasks. For the construction of an earlier version of the QEC, back movement was assessed at 3 levels with suggested frequency of 1-5, 6-10 and >10 times/min respectively. However further experimental studies (reported in Li and Buckle, 1999) showed that the observers experienced difficulties distinguishing between the levels 'infrequent' and 'frequent', or between 'frequent' and 'very frequent', when the actual back motion was close to the boundaries (i.e., close to 5 or 10 times/min). Therefore, it was decided that the median value should be used to represent the corresponding frequency level. More details can be found in the above report regarding the 'construction evidence' of the tool.
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Question:
We are thinking of using the tool at our workplace. There are, however, a few risk factors that we would like to add to the checklist such as 'Is there any contact stress?' or 'Are there any clearance/accessibility issues?' For each of these additional questions we could assign a score ranging from 2 (for no) - 6 (for a lot) similar to the rating that you've assigned for all a1s, b1s, A1s B1s, etc. Is the tool still reliable if we add additional information to it? (Canada, 2001)
Reply:
It is an open debate on what constitutes 'risk factors' for WMSDs in a particular body area, what should be assessed and how. If you have strong evidence showing that some other factors should be included in the assessment process, you should by all means do so. However, according to the current scientific literature, the factors you mentioned seem not to be 'at the same level' (eg. in terms of the 'strength of association' with the WMSD outcomes, see NIOSH 1997) as those given in the QEC system. Besides, if you try to cover 'all' those possible risk factors in the assessment, it may make the whole process very complicated. My suggestion is to assess the tasks using the original QEC tool, with those 'additional factors' being assessed as a reference for that particular task.
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Comment:
The QEC scoring programme was a very clear explanation and the example is just what the users need. (UK, 2001)
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Question:
...I am doing a doctorate program in manufacturing engineering in Brazil. I have been reading your article about the QEC system and have downloaded the user's guide etc. The question is that I don't know how to get the final score. You can get separate scores for the back, shoulder/arm, wrist/hand and neck. Do you add these scores at the end to get one final score? With this final score, do you have a categories system or something like that to compare to make a judgement of the analysis? (Brazil, 2001)
Reply:
A good question! With this system, you get separate scores for each body part, i.e., the exposure score for the back, shoulder/arm, wrist/hand and the neck. It is suggested that the exposure to these body regions be considered separately so that you can identify the problematic areas. You may, however, combine these individual scores into one overall exposure score for a particular task, but by doing this a particularly 'high' score in the back, for example, can be counterbalanced by a 'low' score in the neck, which may lead to a suggestion that the task is safe (although it may be potentially unsafe for the back).
As for the 'action' levels/categories for these scores (or a final overall score), there is currently no evidence which shows how high the score is too high and how low is low enough for an individual doing a particular task. Although, based on my personal experience with risk assessment in industry, the individual exposure scores to each body part should be reduced below 50-60% of the highest possible score for that body part (eg. the highest exposure score for the back is 56 for manual handling tasks). Some research is currently being carried out to determine those 'action categories (or red, yellow, green zones), and the results should be available soon. So, please revisit the QEC web page for infomratin update.
(News update: some preliminary 'Action levels' for the QEC have recently been suggested in Brown (2001). Click here to see the results).
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Comments:
"I work as an Occupational Health Nurse. One of my jobs is to do Ergonomics Assessment for Work-related Musculoskeletal Disorder. I do not have any Professional Ergonomics certification. However, I read up a lot of topics on Ergonomics. I am also searching for the right kind of Ergonomics tool that I should use. That is, the tool that provides reliability on the assessment and it is user friendly. This is important for me because I am not trained in this field and also the tools should be uer friendly for the ESH Committee members. I am so glad that finally I manage to learn about the QEC tools that your goodself and Professor Peter Buckle has researched on. I felt that this tool is user friendly." (IC, Singapore, 2001)
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Comment:
"I've received (downloaded) the QEC software which is fantastic." (JM, Spain, 2002)
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Comment:
"An extraordinary piece of research which will have a major impact in our assessment of risk in the work place. Well done. (ME, UK, 2002)
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Question:
I saw QEC web page. I think one of the advantages of QEC is that it can assess everal parts of the body separately, but I cannot find any action level for each (body) part that (is) assessed. For example, what is the action level for the back? (MM, 2003).
Reply:
It is true that the action levels (percentage total) as suggested in Brown's study are for the upper body as a whole (calculated using total exposure scores). However the nature of the design of the QEC system is to enable repid assessment of the exposure levels (and the expousre changes following an intervention) for various body parts. It is recommended that, when an overall percentage score is found to be greater than 40%, the user refers to the original QEC score table and checks the individual scores of each body part so as to identify where a particular high exposure lays. To this point, the overall action levels should only be regarded as a general reference which leads to further identification of particular body areas that may need ergonomic attention. Please also refer to a previous Question/Reply (2001) about this issue.
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Question/comments:
In using the QEC system, one question that has come up is the disparity in the total score between the neck and the other body regions. A maximum total of 18 for the neck as opposed to maximums of 46 or over for the other body regions. It has been suggested that this indicates that the neck is not as significant in terms of exposure compared to the other body regions, and that the scores should be presented, certainly to management, as percentages. Has this been raised before by practitioners? (GD, UK, 2003)
Reply:
This is a good question and so far not many users have reached this far to raise this question, and my view is in agreement with yours. Obviously, the neck is exposed to fewer risk factors (in most countries at least*) than that of other body regions which are considered in the QEC. Therefore, its maximum total exposure score is smaller. However, this is considered not to affect the assessment outcome, since in assessing or presenting the risks, a calculated percentage value should be able to balance this 'weighting difference'.
* However, in some countries, women are seen to carry heavy loads with their head. In this situation the current checklist may not be applicable.
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Comment:
I am from the shipping industry and we experience a large number of back injuries. Your work would be of great assistance. (BDS, South Africa, 2003)
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Comments/Question:
I am a PhD student studying industrial ergonomics at the University of Birmingham. I have used QEC in my research to measure the effects of ergonomic intervention in a car manufacturing plant. I found it very useful and sensitive to ergonomic intervention.
I have a question related to workers evaluation: why is it not included in the bottom (last line) of the exposure scores calculation table as the other scores (back, shoulder/arm, wrist/hand and neck)? (KAS, Saudi Arabia, 2003)
Reply:
Thank you for your comments and the questions placed on the QEC web site.
Worker evaluation with respect to the physical aspects of the task (i.e., from a1-a4 to e1-e2) has been included in the score table for the calculation of exposure levels to the back, shoulder/arm, wrist/hand and neck. However, the last two questions 'Do you have difficulty keeping up with this work?' and 'How stressful do you find this work?' intend to obtain worker feedback about some psychosocial stressors of the work. At this time, scientific evidence is still insufficient to demonstrate the roles of these psychosocial factors in the development of WMSDs and how they may interact with other workplace factors. Therefore, the answers to the last two questions may be used as a reference only without needing to calculate a relevant exposure score. Please refer to pages 22-23 of the HSE Report (No.251/1999) for further details on this topic.
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Comments:
'We are looking for a tool that would help CSST (the Quebec Province's worker compensation board) inspectors assess MSD risk level as a first step to an intervention aimed at reducing MSD risk. After reviewing a number of tools published in the literature, we are seriously considering the QEC. This tool appears to be the only one to have gone through an extensive validation process based on a scientific approach. It is simple and quick to use.' (DI, Canada, 2004)
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Question:
In the scoring sheet for the back and shoulder/arm regions, all two-way combinations of the posture, frequency, duration, and force risk factors are included with the exception of the posture x frequency combination. What is the rationale for not including this combination in the score computation? Isn't there a chance that the risk related to awkward postures be underestimated in the current scoring scheme? (DI, Canada, 2004)
Reply:
At the time of scoring sheet construction for the exposure to the back and shoulder, there appears to be some evidence to show that a combination of 'higher' posture, force and duration tends to have stronger effect on the musculoskeletal system (or with higher risks for WMSDs) than their combined effect at relatively lower exposure levels. However, evidence is insufficient to show that this is always the case for the combination of posture and frequency of movement. Whilst some studies indicate that frequent adaptation of an awkward posture has negative effect on human body, some researchers have suggested that frequent change in posture can be a good thing (shown in several publications by Prof. Corlett, for example, in 1981&1983). In addition, it is believed that the 'posture factor' has been well represented in the two-way score tables based on the current understanding of the issues concerned (eg., for the back with static tasks: posture is considered 3 times, duration: 3, force: 2; for the back with dynamic tasks: posture: 2, duration: 3, force: 3, frequency: 2. For shoulder/arm assessment, posture: 2 (represented by work height factor), duration: 3, force: 3, frequency: 2). Nevertheless, as far as the assessment of exposure change is concerned (i.e., before and after an ergonomic intervention), whether with or without one more pair of such a combination (for which the scientific basis is still somewhat uncertain) would not influence the outcome of the assessment result.
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Question:
A question about time spent on task - We are not sure if we have to calculate the time when the risk is present. For example, for an 8-hour MMH task, the risk could be present only 3 hours. (BD, Canada, 2004)
Reply:
Thank you for your message left on the QEC web site. By defining the task duration in the QEC system, it was meant to indicate the total amount of time that the operator is involved in performing the tasks. For those who perform the same type of tasks on daily basis without a job rotation in the same work shift, the shift duration can then be used as the total job duration. For example, if it is an 8-hour shift, the task duration should be regarded as more than 4 hours. However, if there are different types of tasks (other than MMH) that are carried out during the entire shift, the actual duration for performing a single MMH task can be shorter, eg. less than 4 hours. This issue is thus situation specific.
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Question:
I would like to know your advice if the risk evaluation validity of a body part is better (with the QEC) if we calculate only the time when the risk is present. For example, in a repetitive task, if the risk is present only 25% of the cycle time for an 8-hour shift, do we check "2 hours"? (BD, Canada, September 2004)
Reply:
I agree with you on the good point that the evaluation validity (or accuracy?) of each individual body part would be better if the task duration could be counted for the time during which the actual risk is present. This is often under the condition that the task is performed intermittently in a work shift and it is not too difficult to quantify the amount of time a relevant risk is present corresponding to a particular body region. The duration factor in the QEC is meant to be used for all body parts involved in the task performance and the danger of reducing the duration to a 'risk present' one is that sometimes a risk may not be present for a body part such as the back, but at the same time, it may be present for another body part such as hand/wrist or shoulder/arm. This would call for a set of different exposure durations to cover the whole body parts concerned, thus making the checklist and the assessment procedure rather complicated. This has been one of the main concerns among health and safety practitioners as they want the tool to be very simple, easy and quick to use. There is also a reliability problem if the tool and the assessment procedure are too complex.
One of the key functions of the QEC is to evaluate the change in exposure before and after an ergonomic intervention. On this basis, as long as the tool user applies the same principle in assessing these exposure levels such as task duration, it should not affect the overall results as they are relative comparisons. This is especially the case when some physical workplace interventions are implemented (such as the change in workplace layout, task height, weight, work rate and work postures). But care should be taken if you want to use more than one task durations for the assessment of different body parts and the intervention involves the change in job rotation within each work shift.
However, if the risk assessment only want to focus risks to a particular body part such as the back (which is often the case in MMH), you then have a reason just to consider the risk present times for this body part, and the resultant exposure levels for other body parts are recorded for reference purpose only.
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Comment:
Your explanations were really clear and I know better now how to use the QEC efficiently. Thank you. (BD, Canada, 2004)