Safety and Health Requirements for Handling of Loads. The Key Item Method for the Risk Assessment

Transcription

1 Seite 1 von 13 Safety and Health Requirements for Handling of Loads The Key Item Method for the Risk Assessment Dr. Detlev Mohr Director of the Landesinstitut für Arbeitsschutz und Arbeitsmedizin Potsdam (presented on the international Conference Environmental, Occupational Health and Safety in Agriculture on the Boundary of Two Millenia" 7-11 September 1998 in Kiev) Manual handling of loads is a problem in every economic sector. In agriculture it is one of the main problems. At first let us have look on some results of an questioning. Nearly 20 percent of the enterprises of all economic sectors in the German Land Brandenburg answered in a voluntary questioning that they have workplaces which are determined by manual handling of loads. Manual handling of loads combined with long working times is a considerable risk for the lumbar spine.

2 Seite 2 von 13 Answers to questions about the combined stress by manual handling of loads and working times longer than 10 hours daily show that especially this is a risk factor in agriculture. Aim of the European Council Directive 90/269/EEC for the safety and health requirements for the handling of loads is to minimize the risk particularly of back injuries to workers while handling loads. It contains rights and obligations of the employers as well as of the workers. The employer shall take appropriate organizational measures, or shall use the appropriate means in order to avoid the need for manual handling of loads by workers. Where the need for the manual handling of loads by workers cannot be avoided, the employer shall take the appropriate organizational measures, use the appropriate means or provide workers with such means in order to reduce the risk involved in the manual handling of such loads. He has to arrange work and workstations in an ergonomic way, safe and healthy. He has to inform the workers or their representatives about all measures, all the risks and how to handle the loads correctly. Besides he has to train the workers. The workers have to

3 Seite 3 von 13 follow these instructions or have to inform the employer about new situations, risks or personal health problems. Certainly you are interested in the practical implementation of the provisions of this directive and the experience of the labour inspectors and occupational health administration with the enforcement of the transposed Council Directives into national law. Therefore I like to introduce to you our new German guideline for the assessment of working conditions during the manual handling of loads and the experiences by introducing and applying this method. The human organism requires an appropriate (adequate) body activity for the preservation and enforcement of important body functions, such as functions of the circulation and musculos-skeleton system. But misloads or overloads by heavy body work like handling of heavy loads in unfavourable postures can destroy or wear down biological material or cause health hazards. There is no sharp or over all exposure limit. In the Occupational Health Framework Directive of 1989 the fundamental obligations to encourage improvements in the safety and health of workers at work are determined. In the Council Directive 90/269/EEC the minimum health and safety requirements for the manual handling are specified.

4 Seite 4 von 13 The employers have the obligation to identify the risks at work and to eliminate these risks. If that is not possible, they have to assess the remaining risks and to minimize them. The risk assessment, the derivated ergonomic measures, the priorities, the deadlines and the responsibilities have to be recorded in a plan of measures. In Germany this fourth individual directive was transposed in Decembre of 1996 in national law by the so called Lastenhandhabungsverordnung", the decree on handling of loads. This decree is based on the Arbeitsschutzgesetz", the national law for occupational safety and health. Both laws are 1:1- transpositions of the Council Directives. If the minimum health and safety requirements shall be accomplished in practice, they have to be specified in national guidelines or in special guidelines for the economic sectors like accident prevention regulations.

5 Seite 5 von 13 Manual handling of loads is a problem in any economic sector. For that reason the chiefs of the labour departements of the German Länder decided to develop such an universal guideline for all employers and also for the labour inspectors to identify and to assess the risks of manual handling. The common principles of such guidelines defined by a group of German experts are published now. The screening methods for risk assessment should be rapid in use, sufficient in correctness, easy to use, logical in structure, universal in use, usable without special ergonomic knowledge, evident to the kind and amount of the risk and useful in the identification of ergonomic lacks. Risk assessment requires a practice in levels. In the first level practicians or employers of small enterprises themselves should apply such screening methods. If there is no evidence possible or the screening method isn t allowed to use, than quantitative methods of level two are to use by ergonomically skilled staff. In special cases like the derivation of individual stress-strain-relations only scientific investigations of the third level by scientists are required.

6 Seite 6 von 13 I like to introduce to you the so called KEY ITEM METHOD, a successful tested screening method for the risk assessment of manual handling of loads. With screening methods of level one the employers of all economic sectors are able to accomplish the obligations of the decree on handling of loads. These obligations are the assessment of hazardous activities, the minimizing of the not eliminated risks with the aim to prevent negative health effects and the documentation of the risk assessment. The labour inspectors should to be enabled to check and to verify the risk assessments documented by the enterprises. I don t want to annoy you with biomechanics of the spine or better of the lumbar spine. But from the biomechanics you can derivate the following principles to the behaviour in case of handling loads: For minimizing the axial pressure forces you have to minimize the loads to handle. For preserving the spring function of the spine and to improve the distribution of inner forces you have to lift the loads in an upright posture. For avoiding rotational and shearing forces in the spine you have to pick up and put down the loads close to the front of the body. For preserving the annulus fibrosus of the intervertebral disc you have to avoid picking up loads with a jerk. For maintaining the intervertebral disc supply of nutriments you have to minimize the distance and the duration of carrying. Now to the work sheet of the screening method. The key items are derived from the biomechanics of the spine or from the annex of the Council Directive. The four key items are the time or frequency of handling of loads, the loads themselves, the posture and the working conditions. 1st step: Estimation of time weight regular repetition of short longlasting holding and carrying time weight lifting or moving processes < 10 times per work shift total time< 30 min 1 10 to < 40 times per work shift total time 2

7 Seite 7 von min to < 1hour 40 to < 200 times per work shift total time 1 hour to < 3 hours 200 to < 500 times per work shift total time hours to < 5 hours 500 times per work shift total time 5 hours 8 The first step is the estimation of the time weight with the help of this table. The left column has to be applied in cases of repeated handlings, the right column in cases of long lasting carrying. 2nd step: Estimation of load weight load weight for men load weight for women load weight < 10 kg < 5 kg 1 10 to < 20 kg 5 to < 10 kg 2 20 to < 30 kg 10 to < 15 kg 4 30 to < 40 kg 15 to < 25 kg 7 40 kg 25 kg 10 The second step is the estimation of the load weight. It depends on the real weight and the gender of the worker. 3rd step: Estimation of posture weight posture, position of load - trunk is upright, not twisted posture weight 1 - load is close to the body - standing or walking a few steps - slight bending forward or twisting the trunk 2 - load is nearby the body - sitting, standing or walking for longer distances - deep bending from the waist or long leaning forward 4 - load away from the body or above shoulder height - sitting or standing - leaning far forward while twisting the trunk 8 - load away from the body - restricted stability of posture during standing, squatting or kneeling

8 Seite 8 von 13 The third step is the estimation of the posture weight according to the four figures and the related descriptions. 4th step: Estimation of the working weight execution conditions good ergonomic conditions, e. g. enough working space, even solid floor, adequate illumination, good gripping conditions - restricted work place (height too low, area < 1,5 m²) condition weight restricted postural stability (floor uneven, soft, slippery, sloping) The fourth step is the decision on the working conditions weight - Are they good or not good? The fifth step is the evaluation by calculating such a simple equation. The result of this calculation is the so called risk score. 6th step: Assessment risk risk score description zone 1 < 10 low load situation, health hazard due to the physical overstrain is unlikely to appear 2 10 < 25 increased load situation, an overload situation is possible for less resilient persons for this group 2) workplace redesign is helpfull 3 25 < 50 high increased load situation, physically overload is possible, even for "normal" persons, workplace redesign is recommended 3)

9 Seite 9 von high load situation, physically overload is likely to appear, workplace redesign is essential 3) In the final sixth step the risk score has to be compared with the values in the evaluation table. The result of the risk assessment is the ranking in one of the four risk zones and the risk score itself. According to the value of the risk score the employer is able to derive a plan of measures with priorities. At workplaces in risk zone 4 an ergonomic redesign is essential, in risk zone 3 recommended. But there is no sharp border between the risk zones! Which ergonomic redesign at the workplaces is required? The employer can see it from the weights of the key items in the risk score. So it is obvious where the reasons for the high risk are. Therefore this screening method is useful in the identification of ergonomic lacks, very easy to use and very helpful for the employers as well as for the labour inspectors. But you should know that the method is not suitable for the evaluation of individual stress in cases of occupational diseases or for the evaluation of activities like pushing or pulling. In cases of hazardous activities, indifferent evaluations or special questions more expensive methods of level 2 or 3 for the risk assessment are necessary. These have to be applied by ergonomically skilled and scientific or medical staff. This screening method was successfully tested at 400 workplaces. You are members of the occupational health administration. Therefore I am going to explain some experiences by introducing and employing this method in the labour inspectorates to you.

10 Seite 10 von 13 The test of the screening method by the labour inspectors of the Land Brandenburg took place in several economic sectors to check the universality of the application. The distribution of the 165 evaluated activities was randomly. At the same time the NIOSH-method, the same as in pren 1005, was tested, but the usage of this method was only allowed in 107 cases. Here are the results of both methods graded by the risk score. It is obvious that the results of the NIOSH-method are scattered.

11 Seite 11 von 13 After fitting with involution functions trends can be derived. Both methods behave similarly. Activities with higher risk scores are characterized by lower recommended loads. Both methods have evaluated the risks in a similar way. 42 evaluated activities are ranked into the risk zones 3 or 4. The reasons of the high risk score, derived from the weights of the key items are shown in the figure.

12 Seite 12 von 13 To the user of the NIOSH-method it is suggested that at first he has to reduce the real load weights to reduce the stress. He does not get any advice for other ergonomic design measures. Contrary to this lack of the NIOSH-method the key item method helps the user to identify the real reasons of the stress. In 86% of the evaluated activities the posture was the reason or one of the reasons for the health risk, but only in 30% of the cases the load weight was one of the reasons. In many cases the real load weights were already lower than the recommended loads. In these cases the user of the NIOSH-method gets a wrong piece of advice for the possibilities of design. So the key item method is suitable for use in labour inspections to check the enterprises' risk assessments and plans of measures.

13 Seite 13 von 13 The user comments of the 47 labour inspectors to the key item method were predominantly positive as well as the comments of 200 testers from enterprises. As the method is so simple and accepted by the test persons, the authors of the method have to warn of an application without any critizism. The risk scores are not absolutely correct, over- or underloads are possible, especially at the borders of the weighting zones. Interpolations can minimize these errors. The presented guideline on handling of loads is an excellent method for the labour inspectors to advice employers of small and medium sized enterprises or for the employers to inform themselves to inform about the risks of handling of loads and to fulfil the obligations of the decree on handling of loads. Dr. Detlev Mohr Landesinstitut für Arbeitsschutz und Arbeitsmedizin Postfach D Potsdam Germany