Ergonomics

The guidelines

NIOSH

Reasons for development of NIOSH guidelines

Progress of the NIOSH guidelines

The parameters

Analysis for job on hand

When does the formula not apply?

Limitations of NIOSH Lifting Equation

At the outset it is important to know the efforts that are being made here. This is not an effort only to calculate the method of working that a person should follow in his working – there is also an attempt to review the methods of determining the limitations that should be placed. When the limitations are considered, there are different methods for deciding on the limitations, and talking more directly, there are three systems that are available. Only one of them is enforceable as a law, but that may not be what is best for the individual. One has to look at the welfare of the person who is doing the job and finding out a method through which both the worker and the employer may benefit. At the same time, this is not an act of mercy, but the decision has to be economical for the employer to continue his business. Otherwise both the employer and the employee will lose their economic viability. Thus a full discussion of the methods is required so that it is not felt that the decision taken is based on personal feelings and not on the correct position. At the same time, the decisions on these matters are still a little vague as there are a lot of concerned matters that should be studied so that one can come with a more definitive answer. Maybe what is required is a complete study of the problem at site and then a decision taken.

Introduction:

There is no doubt that it is important for individuals to work for their livelihood and the oldest form of work is physical work. This has been done from the beginning of time by man. As the most advanced country of the world, America has to ensure that justice is done to those who perform physical work for their livelihood. The methods will be discussed now.

Analysis

1. The problem:

The person whose case is going to be discussed works at a company which is involved in getting products from a major manufacturer and then sending it on to other organizations for sales. In short he works at a wholesaler of consumer goods. The job that he is directly involved in is getting the material when it arrives in trucks, storing them at the appropriate place in the store for the item, and then loading it on the truck for sending it to the receiver. The job is essential since the material that comes from the manufacturer is in lots of one item, while the supply that is made up of different items. In simpler terms his job is lifting and lowering material.

2. The Guidelines:

Regarding this type of jobs, there are three applicable guidelines. These three are – a) National Institute for Occupational Safety and Health or NIOSH Lifting Equation of the year 1991 b) Proposed American Conference of Governmental Industrial Hygienists or ACGIH Lifting Tables and c) Snook and Ciriello Psychophysical Tables as shown in Liberty Mutual Research, 1991. When these different guidelines are compared, there are more differences than similarities in them. The differences create a difficulty for the evaluation of these lifting and lowering activities, and thus the risks that are connected with the tasks are very difficult to determine. We shall study these in detail before deciding on our next step. (Faville; Shulenberger, 2004)

3. NIOSH:

For this type of an operation the applicable document is called the Applications Manual for the Revised NIOSH Lifting Equation by Waters TR, Putz Anderson V and Garg A of the National Institute for Occupational Safety and health. This document was published in January 1994. The copy can be obtained from U.S. Department of Commerce. According to them the difficulties with regard to job are due to repetitive elements, due to force and also because of awkward levels of postures. The maximum amount of danger is to the lower back. And the difficulties result because of sorting of packages and proper handling of the packages, delivery of beverages, manual efforts during the process of lifting weights which are more than that of 10 lbs, use of force as it is being a productive type of a job. The effects could occur to any part of the body. The problems result because of his lifting more than 75 pounds and also due to lifting more than 55 pounds for over 10 times in a single day, over an amount of 25 pounds below the part of the knees and over an amount of 25 times a day which is at arm’s length. He is also being involved in the process of push and pull with that of more than 20 pounds. This is considered as being equivalent as to push some 65 pounds weight box against a tiled floor, or trying to push a shopping cart which is being loaded with 200 pounds of weight. This job is being performed for over 2 hours in a single day. (Analysis Tools for Ergonomists)

What has to be noted here is that this model is based on biomechanical, physiological and epidemiological data. The entire analysis has some basic assumptions and these are that 1) Lifting and Lowering tasks have the same types risks for low back injuries as well and 2) The static friction between the worker and the floor surface is at least 0.4 or better coefficient of static friction due to the interaction of the shoe sole and the floor. It is clear that this does not take care of other factors that may arise from unpredictable conditions like very heavy loads, slipping or falling of the worker and also to consider other differences like lifting with only one hand, lifting while still being seated or kneeling, the entire exercise of lifting being carried out in a constrained or restricted work area, or lifting items which are wider than 30 inches. The other problem that has not been considered in these guidelines is of the sex of the worker. This means that the same weight limits are applicable for both male and female workers. (Faville; Shulenberger, 2004)

4. Reasons for development of NIOSH guidelines:

It had been recorded earlier that lower back pain and injuries were generally attributed to manual lifting activities. These are still the leading occupational health and safety issue facing preventive medicine. There have been many efforts to control this through different programs which had been directed at both workers and the job that they do, yet work related lower back injuries are still the cause for a large section of the suffering and loss to the country as a whole. The impact of this problem was summarized in a report in the Department of Labor, bureau of Labor Statistics in an article captioned “Back Injuries.” This was published in 1982. The findings of the Department of Labor was in line with the existing worker’s compensation data and that also states that “injuries to the back are one of the most common and most costly types of work-related injuries.” This was reported by the National Safety Council in 1990. (Applications Manual for the Revised NIOSH Lifting Equation)

According to the report made by DOL, back injuries are the reason for nearly 20% of all injuries that take place in the workplace, and result in nearly 25% of the annual workers compensation payments. This may be viewed as an old report, but a recent report, in 1990, by the National Safety Council noted that overexertion is the most significant reason for occupational injury, and accounts for 31% of all injuries. The back has been seen to be the body part most frequently injured and constituted as much as 22% of 1.7 million injuries that occur in a year. This leads to a situation where it is also the reason for the highest contributory factor for workers compensation systems. (Applications Manual for the Revised NIOSH Lifting Equation)

5. Progress of the NIOSH guidelines:

The problem was recognized by the National Institute for Occupational Safety and Health more than ten years ago. This was viewed as a growing problem and published the Work Practices Guide for Manual Lifting. This report published in 1981 contained a summary of the literature published before 1981 regarding back injuries. It also published the analytical procedures and a lifting equation for developing a recommended weight for two-handed, symmetrical lifting tasks. This was clearly an approach for minimizing the chances of low back injury from manual lifting. This analysis was tied up to the Action Limit. This is a term that denotes the recommended weight found out from the lifting equation. Further progress was made in 1985, and the National Institute for Occupational Safety and Health sought the opinion of others by convening an ad hoc committee of experts who reviewed the existing literature on lifting, including the NIOSH WPG. The literature review was finally released in a document called “Scientific Support Documentation for the Revised 1991 NIOSH Lifting Equation: Technical Contract Reports, May 8, 1991.” (Applications Manual for the Revised NIOSH Lifting Equation) This is an update and contains information on the physiological, biomechanical, psychophysical, and epidemiological aspects of manual lifting. This led to the recommendation by the ad hoc committee of the criteria for defining the lifting capacity of healthy workers. Since the basis of the previous calculation changed, the new criteria were used to formulate the revised lifting equation. (Applications Manual for the Revised NIOSH Lifting Equation)

At the same time, it should be clear that the NIOSH lifting equation is only one of the tools in the effort for prevention of work-related low back pain and related disability. It should also be realized that lifting is only one of the reasons for work-related low back pain and disability. Other reasons for back pain are “whole body vibration, static postures, prolonged sitting, and direct trauma to the back.” (Applications Manual for the Revised NIOSH Lifting Equation) Psychosocial factors, correct medical treatment, and job demands are also significant in the development of acute low back pain and may even lead to chronic disabling pain. (Applications Manual for the Revised NIOSH Lifting Equation)

6. The parameters:

The RWL is the new development in the NIOSH lifting equation. The RWL has been defined for a specific set of task conditions and that is the weight of the load that most healthy workers could perform over their duty hours, up to 8 hours and this should not increased chances of their developing lifting-related LBP or lower back pain. Here the workers should be free of adverse health conditions that would increase their risk of musculoskeletal injury. The estimate of the level of physical stress has been defined by the relationship of the weight of the load lifted and the recommended weight limit for the weight to be lifted. The lifting equation has been devised assessing the physical stress of two-handed manual lifting tasks. Thus, the application of the equation is limited to those conditions for which it was designed. In short, the lifting equation is meant to meet specific lifting-related criteria that cover all aspects of biomechanical, work physiology, and psychophysical assumptions and data. (Applications Manual for the Revised NIOSH Lifting Equation)

7. Other methods:

Another method is the ACGIH method and in general has the same assumptions as described for the NIOSH equation and adds some more. The specific definition given is that the method applies only to “two-handed, mono-lifting tasks within 30 degrees of the sagittal plane” (Faville; Shulenberger, 2004) What this means is that the body should not turn more than 30 degrees from the central plane. It also mentions that other factors based on judgment should be included when there is high frequency lifting or more than 360 lifts in an hour, enhanced periods of lifting that is more than 8 hours of lifting in a stretch, high twisting during the lifting exercise, lifting with one hand, lifting with the body in a seated or kneeling position, lifting in conditions of high heat and humidity, lifting items with shifting center of gravity like liquids, incorrect or unstable holding of the item or being in an unstable position with both feet not fully supported. (Faville; Shulenberger, 2004)

The third set of tables as designed by Snook and Ciriello take into account biomechanical and physiological stressors and based on the concept of a discreet population. The tables are designed to provide the maximum acceptable weight of lift, and the maximum possible frequency for lifting. This method accepts that there is no single maximum weight that is applicable for everybody as the capacity for lifting depends on the strength and endurance of the person concerned. Thus the best method for evaluating safe lifting or lowering is in terms of weights that most of the persons will be able to handle. The correct evaluation would be through determination of the percentage of population that would be able to handle the weight. The higher the percentage that would be able to handle the weight, the lower will be the risk. These tables apply to two handed symmetrical lifts and in situations where minimum force is required. At the same time, the limitations due to psychophysical responses and limitations due to coupling, floor coefficient, posture, etc. are also not considered. In terms of environment, the figures here have to be reduced by 20% when individuals have to work in hot areas. The greatest advantage of these tables is that they provide greater protection for females. (Faville; Shulenberger, 2004)

8. Analysis for job on hand:

Some methods were being used for the purpose of having to perform calculation of some factors for the person that we have been talking about. The first question points to the maximum amount of weight that the person should be able to handle. By analyzing and following the three methods, the maximum amount of weight which is being permitted was being given as 51 pounds by NIOSH whereas for the other methods, it was 70.5 pounds and 90 pounds. The recommendation was being chosen by keeping the issue of safety in focus, and thus it was being decided that the maximum amount of weight that any individual should be able to handle/manage was that of 51 pounds. Since it is considered difficult in order to judge the amount of weight of the individual parcels, the packages which are to be handled/managed were being defined in terms of the items that would come. The second question was in relation to taking the material from the truck, and for the purpose of protection, it was being made sure that the amount of height from which the material would be accrued or received is never considered to be higher or being greater than that of 70 inches, as that is being considered to be the amount of the safe height. (Comparison of Three Lifting Guidelines: Whom Do They Protect?)

For this purpose, one should ensure that suitable ramps had to be constructed. Another question is with regard to getting the material from the truck, and it was being decided that there workers would be available inside the truck in order to push the material towards the side parts of the truck. Hence it could be in a position to be safely collected from a maximum amount of a distance of 25 inches. The company which was sending the material was being asked to improve or better the quality of the grips and thereby mark the packages which were exceeding the quantity of 51 pounds shown in red, which would make the lift to become a combined total effort of the two lifters and not just of one single person. The area wherein the trucks which came for loading and unloading was being resurfaced by means of rough tiles; this was done so that adequate friction was to be developed in that particular area. These suggestions are being based on NIOSH and that is only considered as a recommendation and it cannot be legally enforced upon. (Comparison of Three Lifting Guidelines: Whom Do They Protect?)

9. Other tasks:

There are different sets of work conditions in which the application of the lifting equation could result in under or overestimation of the physical stress connected with a particular work-related activity. Some of the following task limitations noted now need of further research before it is possible to extend the application of the lifting equation. First, the revised NIOSH lifting equation is focused on the assumption that activities which involve manual handling are mainly for lifting and those activities do not require significant efforts as compared to repetitive lifting tasks. Examples of such tasks are inclusive of holding, pushing, pulling, carrying, walking, and climbing. When such non-lifting activities account for more than 10% of the activity of the worker, then measures of workers energy expenditures or heart rate might be needed to find out the demands of the other tasks. The existing revised lifting equation are not inclusive of risk factors that account for unforeseen conditions, like unexpectedly heavy loads, slips, or falls by the individual carrying the load, etc. Additional biomechanical analyses are probably needed to evaluate the physical stress that will be placed on joints from such from traumatic incidents. (Applications Manual for the Revised NIOSH Lifting Equation)

Again, if the environment is unfavorable, and what that means is if the temperature is outside the range of 19 degrees to 26 degrees Centigrade — 66 degrees to 79 degrees Fahrenheit or humidity not within 35% to 50% of relative humidity, then independent metabolic assessments would be made to judge the effects of these changes on heart rate and energy consumption. The other consideration is that revised lifting equation was not designed to evaluate tasks which involved one-handed lifting, lifting not in a standing position but while sitting or kneeling, or lifting while being within a constrained or restricted work space. Another question is of the equation not applying while lifting unstable loads. Here an unstable load would be defined as an item in which the location of the center of mass varies considerably during the lifting process, as would be happening in containers of liquid or incompletely filled bags, etc. Again, the equation does not apply when the task is of moving in wheelbarrows, shoveling, or high-speed lifting. When such task conditions arise, independent and task specific biomechanical, metabolic, and psychophysical assessments may be required. (Applications Manual for the Revised NIOSH Lifting Equation)

10. When does the formula not apply?

Revised NIOSH Lifting Equation does not apply if any of the following occur:

a) Lifting/lowering with one hand b) Lifting/lowering for over 8 hours c) Lifting/lowering while seated or kneeling d) Lifting/lowering in a restricted work space e) Lifting/lowering unstable objects f) Lifting/lowering while carrying, pushing or pulling g) Lifting/lowering with wheelbarrows or shovels h) Lifting/lowering with high speed motion (faster than about 30 inches/second) i) Lifting/lowering with unreasonable foot/floor coupling (< 0.4 coefficient of friction between the sole and the floor) j) Lifting/lowering in an unfavorable environment — i.e., temperature significantly outside 66-79 degrees F (19-26 degrees C) range; relative humidity outside 35-50% range” (Applications Manual for the Revised NIOSH Lifting Equation)

11. Limitations of NIOSH Lifting Equation

The different limitations of NIOSH Lifting Equation can now be summarized. One might say that in order for those lifting jobs wherein the application of the revised lifting equation will not be per say to the desires and wishes of the individuals who brought out with the formula. The correct method in order for finding and ensuring a more acceptable form of solution would be in order to attain a more conclusive ergonomic assessment. This is required as it might be required for the purpose of quantifying the level of extent of other physical stress factors that would have to be applicable almost at the same time. Some of the examples of such stresses are which are prolonged for a long time or frequent variations with regard to the positions which make the way for back postures which are non-neutral or which are seated postures. It could also be the process whereby it could be one of cyclic loading wherein there is the issue of vibration of the entire parts of the body or the effects of environmental issues which are not favorable for the human body with regard to elements like being posed to extreme levels of heat, or extreme levels of cold, high humidity, and so on. The results which would come out of these various events which are occurring would promote the prevalence of lower back pain among workers who are facing such severe conditions. Now at this stage, one might be compelled to inform that such evaluations are fine as far as theory is concerned, and would enable to help workers who are working on daily wages, but however it needs to be understood that in the country, today there are several people who are not working or do not jobs. These individuals are often being given jobs on purely temporary terms, and also they are also not being covered under the insurance schemes, so that when they be faced with aliments, they would have no where to turn for help. Is it not required that in such a situation that we make such methods compulsory.

Recommendations

One of major problems that exist now is that OSHA, which has the responsibility to define as to what constitutes a really “bona fide” ergonomic injury, has not been able to do so. All ergonomic injuries are defined in totality as “musculoskeletal disorders” or “MSD.” This is a scientific term that is being using for handling of responsibilities of business. The term refers to a group of injuries and even illnesses which have an impact on the musculoskeletal system. This does not refer to any single or specific disease. Thus it has become the responsibility for OSHA to develop specific guidance for specific industries. When this is done, OSHA may also develop the appropriate definitions and working norms that are to be followed. (Ergonomics: OSHA Drops the Other Shoe)

References

Analysis Tools for Ergonomists” Retrieved at http://hsc.usf.edu/~tbernard/ergotools/. Accessed 18 August, 2005

Applications Manual for the Revised NIOSH Lifting Equation” Retrieved at http://www.phppo.cdc.gov/cdcRecommends/showarticle.asp?a_artid=P0000427&TopNum=50&CallPg=AdvAccessed 18 August, 2005

Ergonomics: OSHA Drops the Other Shoe” (30 April, 2002) Retrieved at http://www.jacksonlewis.com/legalupdates/article.cfm?aid=82Accessed 20 August, 2005

Faville, Barb; Shulenberger, Chris. (16 November, 2004) “Applying Manual Material-

Handling Guidelines to Job Tasks” Retrieved at http://www.occupationalhazards.com/articles/12635Accessed 18 August, 2005

Shulenberger, Chris. C; Faville, Barbara A. “Comparison of Three Lifting Guidelines: Whom Do They Protect?” Retrieved at http://www.claytongrp.com/liftguide_art.html. Accessed 20 August, 2005

Ergonomics