ERG021 August 2000 Page 1

Musculoskeletal Injuries — Part 5Assessing Ergonomic Hazards

This is the fifth in a six-part series of Safety Bulletins dealing withmusculoskeletal injuries

Musculoskeletal injuries, or MSIs, arereferred to by a variety of differentnames. These include repetitive straininjuries (RSIs), repetitive motioninjuries, cumulative trauma disorders(CTDs), work-related upper limbdisorders (WRULDs), and others. Ineach case, the name is used to describeinjuries of the bones, joints, ligaments,tendons, muscles, and other soft tissues.

The purpose of performing a workplacehazard assessment is to identify specificworkplace hazards that can cause oraggravate work-related MSIs, and tothen reduce worker exposure. Manychecklists and assessment tools areavailable from a variety of sources.

The hazard assessment checklistrecommended for use by this SafetyBulletin was introduced in May, 2000 bythe State of Washington, Department of

Labor and Industries, as part of thatstate’s ergonomics legislation (WAC296-62-051, Ergonomics). It wasselected on the basis that(1) it addresses very specific risk

factors identified in the scientificliterature as being related toMSIs;

(2) it presents clear, specificexposure limits (time and angles)for worker exposure to thevarious risk factors, somethingthat few other assessmentchecklists provide;

(3) it is relatively simple tounderstand and can be applied byboth employers and workers; and

(4) it is based on a comprehensive,multi-year literature review andpublic consultation process thatinvolved industry, labour, and thepublic.

WorkplaceHealth & Safety Ergonomics

August 2000

ERG021 August 2000 Page 2

The approach recommended by thisSafety Bulletin does not, and cannot,eliminate all MSIs among affectedworkers. The approach will reduce theincidence and/or severity of MSIscaused in whole or in part by the riskfactors listed in the hazard assessment.Non-work exposures and risk factorsinherent to the individual worker are notaddressed.

Use of this hazard assessment checklist,as with any of the recommendations orrecommended practices contained in theSafety Bulletins prepared by AlbertaHuman Resources and Employment,Workplace Health and Safety, isvoluntary. The use of other similarhazard assessment checklists isacceptable.

Is this a “caution zone job”?

A “caution zone job” is a job where aworker’s typical work activities meetone or more of the physical risk factorsand levels listed in Table 1. Typicalwork activities are those that are aregular and forseeable part of the job andoccur on more than one day per week,and more frequently than one week peryear. Caution zone jobs all have asufficient degree of risk to require thatsome modest precautionary steps betaken — ergonomic awareness trainingand a hazard assessment — but they donot necessarily have risks great enoughto require corrective action. Cautionzone jobs may not be hazardous. Thedurations listed in Table 1 — two hoursfor example — refer to the total amountof time per day workers are exposed tothe risk factor, not how long they spendperforming the work activity thatincludes the risk factor.

Actions employers should take

If there are no physical risk factorsexceeding the levels listed in Table 1,then no actions are required.

If one or more physical risk factorsexceed the levels listed in Table 1, thenthe job is a caution zone job and theemployer should provide the workerwith ergonomics awareness training andperform a hazard assessment using thechecklist presented in Table 2. Theergonomics awareness training is toprovide workers with a basic level ofunderstanding and knowledge. Thetraining for workers should include(a) how to use their workstation,

including how to adjust itsequipment and furnishings;

(b) how to use or select tools appropriateto the work they are performing;

(c) the safe work practices they areexpected to follow; and

(d) information describing the signs,symptoms, and methods ofpreventing MSIs.

Every worker in a caution zone job, andthe supervisors of these workers, shouldreceive basic ergonomics awarenesstraining.

A hazard assessment should beperformed(a) when a work process or operation

changes;(b) when a new work process is

introduced; and(c) prior to the design and installation of

a new workstation.

Whenever possible, affected workersshould be involved in the hazardassessment.

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Table 1 Determining if a job is a caution zone job

Physical Risk Factor Duration

Awkward bodypositions

(1) Working with the hand(s) above the head, or the elbow(s)above the shoulder.

(2) Working with the neck or back bent more than 30 degrees(without support and without the ability to change posture).

(3) Squatting.(4) Kneeling.

(1) More than 2 hourstotal per day.

(2) More than 2 hourstotal per day.

(3) More than 2 hourstotal per day.

(4) More than 2 hourstotal per day.

High hand force (1) Pinching an unsupported object(s) weighing 900 grams ormore (2 lbs) per hand, or pinching with a force of 180Newtons or more (4 lbs) per hand (comparable to pinchinghalf a ream of paper).

(2) Gripping an unsupported object(s) weighing 4.5 kg ormore (10 lbs) per hand, or gripping with a force of 340Newtons or more (10 lbs) per hand (comparable toclamping light duty automotive jumper cables onto abattery).

(1) More than 2 hourstotal per day.

(2) More than 2 hourstotal per day.

Highly repetitivemotion

(1) Repeating the same motion with the neck, shoulders,elbows, wrists, or hands (excluding keying activities) withlittle or no variation every few seconds

(2) Performing intensive keying.

(1) More than 2 hourstotal per day.

(2) More than 4 hourstotal per day.

Repeated impact (1) Using the hand (heel or base of palm) or knee as ahammer more than 10 times per hour.

(1) More than 2 hourstotal per day.

Heavy, frequent,or awkward lifting

(1) Lifting objects weighing more thana) 34 kg (75 lbs) once per day; orb) 25 kg (55 lbs) more than 10 times per day.

(2) Lifting objects weighing more than 4.5 kg (10 lbs) if done

more than twice per minute. (3) Lifting objects weighing more than 11.4 kg (25 lbs) above

the shoulders, below the knees, or at arm’s length morethan 25 times per day.

(2) More than 2 hours

total per day.

Moderate to highhand-armvibration

(1) Using impact wrenches, carpet strippers, chain saws,percussive tools such as jackhammers, scalers, or rivetingor chipping hammers, or other hand tools that typicallyhave high vibration levels.

(2) Using grinders, sanders, jig saws, or other hand tools thattypically have moderate vibration levels.

(Employers may assume that hand tools vibrating less than 2.5 m/s2, eight-hour equivalent, are not covered.)

(1) More than 30minutes total perday.

(2) More than 2 hourstotal per day.

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When analyzing caution zone jobs usingthe checklist presented in Table 2,employers should do so in a thoroughand systematic manner. This meanspaying attention to the physical demandsof the job (such as body position, force,and repetition), the layout of the workarea (such as reaches and workingheights), and the load lifting andhandling requirements of the job (suchas object size and shape). Workersperforming the caution zone jobs shouldbe encouraged to participate in theperformance of the hazard assessmentand any initiatives undertaken to reducethose hazards.

If the hazard assessment determines thatthe physical risk factors exceed thelevels listed in Table 2, then a hazard ispresent and the employer needs to takeaction. Each identified hazard should bereduced below the levels stated or to thedegree technologically and economicallyfeasible. The methods used to reduce thehazard(s) should not rely primarily onchanges in worker behaviour. Examplesof suitable methods for reducing hazardsinclude:§ changes to workstations and tools;§ reducing the size and weights of

loads handled;§ process redesign to eliminate

unnecessary steps or introduce taskvariety; and

§ job rotation.

If an employer cannot reduce thehazard(s) below the hazard level usingthe controls described above, theemployer should supplement thosecontrols with interim measures thatprimarily rely on individual workpractices or personal protectiveequipment. Examples of such practicesinclude impact gloves, team lifting, and

training on work techniques. Since theseare interim measures, the employershould continue to look for alternativemeasures that will address the hazard ona permanent basis.

Heavy, frequent, or awkwardlifting

The assessment checklist for heavy,frequent, or awkward lifting prepared bythe State of Washington, Department ofLabor and Industries (L&I) and includedin this Safety Bulletin, is based on theRevised NIOSH Lifting Equation[NIOSH-National Institute forOccupational Safety and Health (U.S.)].The equation was designed to helpevaluate lifting tasks and reduce theincidence rate and severity of lower backinjuries to workers. Its aim is to protectthe industrial working population fromlower back pain.

To simplify use of the original equation,to provide employers with theopportunity to achieve practicalimplementation in the workplace, and toprovide workers with an adequate levelof safety, L&I made important changesto the original equation’s Lifting Index.Readers interested in more informationon this issue should refer to page 78 ofL&I’s Concise Explanatory Statement,listed in the references at the end of thisSafety Bulletin.

Using the hazard assessmentchecklist

In many workplaces, more than oneworker may do identical or essentiallythe same jobs. It is not expected thatemployers will do a separate hazardassessment for every worker on everyshift on every day. Representative

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sampling of very similar jobs may beused. For example, if thirty workers useidentical wire strippers for the samerepetitive task, the employer may assesshow several workers do the job ratherthan all thirty. While employers maychoose to use representative sampling,they should design the sampling strategycarefully and appropriately. Forexample, a different sampling methodmight be needed for risk factorsinfluenced by the size of individualworkers. A short worker on a particularjob may work with his or her handsabove the head, while a taller workermight not. Choosing several averagesize workers for representative samplingwould not be sufficient to identify thoseworkers in the caution zone. Analternate, more effective approach mightbe to evaluate the postures used by theworkers at the two extremes of size aswell as the average or midrange.

It is acceptable practice to observetypical periods of work and calculate orestimate what the full day exposurewould be as long as there is a reasonablebasis for believing that the period ofobservation is representative. Forexample, consider a job in which aworker performs the same five-minutesequence of work repetitively for sixhours every day and 2 minutes of eachfive-minute sequence (or 40%) is spentinspecting parts with the neck bent. Theemployer could observe several workcycles and then calculate that 40% of sixhours or 2.4 hours is spent with the neckbent.

It is also permissible to rely on previousknowledge, evidence established forother purposes (e.g. time motion studiesor job safety analysis), or jobdescriptions instead of direct job

observation as long as there is areasonable basis to believe that suchinformation or knowledge is accurate,representative, and sufficiently detailed.Production data could be used toestimate the number of lifts per day formaterials handling jobs. If the employerhas intimate knowledge of regular workactivities, duration of exposures may beestimated with or without directobservation of the work. Where regularwork activities are not well known to theemployer, worker interviews can be usedto identify typical work. The employercould then observe relatively shortsample periods of actual work to validatethe interview information.

In the case of jobs with intermittent,unpredictable, or highly variable tasks,the following steps should be followedwhen performing the assessment:

§ First, it is necessary to identify or listthe different “typical work activities”that are part of the various tasksperformed by the worker(s) doing agiven job. Where this is not wellknown to the employer initially, thiscan be accomplished by observingworker(s) performing the tasksand/or by asking worker(s) toidentify the different tasks theyperform. It is important in this firststep to determine all the major taskstypically performed by the worker(s)as a routine part of their overall jobover time, including tasks that varyfrom day-to-day.

In workplaces where severaldifferent workers perform essentiallythe same job, a separate hazardanalysis does not need to beperformed on all workers, on allwork shifts, on all days. A

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representative sample of workersperforming the same job should beobserved performing the tasks,including workers of different sizes(e.g. short, average, and tall heights)where such individual differencesmight affect the outcome of thehazard analysis. One or moreworkers can be interviewed to helpidentify the range of tasks theyperform and to help estimate theapproximate percentage of their timespent performing the various tasks(this can be per day, per week, perjob, or whatever measure isappropriate for this job).

§ Second, determine whether or not therisk factor limits are exceeded. Thetasks identified in step one (for thisjob) are analyzed to determinewhether they include one or more ofthe specific physical risk factorslisted in the risk factor table, andwhether the risk factor(s) for this jobexceeds the limits. Hazardcontribution times from the differenttasks are “added up” to make thisdetermination. Where thisinformation is not readily availableto the employer from past/present

knowledge (e.g. from existing jobdescriptions, time motion studies, jobsafety analyses, production data,etc.) it must be determined.

One way to determine the hazardcontribution from one of severaltasks would be to determine thepercentage of overall job time spentperforming this one task, and thendetermine the percentage of timeduring that task that the worker isexposed to the ergonomic risk factor.For example, a task done for fourhours that involves working with thehands above the head only ¼ of thetime results in an awkward bodyposition risk factor duration (for thatone task) of 1 hour per day. Similarcalculations are done for all the othertask components of the job, and foreach risk factor that is present. Thecalculation can be done for a day, aweek, the duration of the job, orwhatever interval is appropriate forthat particular job. For comparisonwith the limits specified in the table,the total risk factor exposurenumbers should be converted to adaily basis.

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Table 2 Hazard assessment checklist

Awkward Body Positions

Body Part Physical Risk Factor Duration Visual Aid

Working with the hand(s) above thehead or the elbow(s) above theshoulder(s)

More than 4 hourstotal per day

Check (3)here if thisis an MSIhazard

qShoulders

Repetitively raising the hand(s) abovethe head or the elbow(s) above theshoulder(s) more than once perminute

More than 4 hourstotal per day q

NeckWorking with the neckbent more than 45º(without support or theability to vary posture)

More than 4 hourstotal per day q

Working with the back bent forwardmore than 30º (without support or theability to vary posture)

More than 4 hourstotal per day q

Back

Working with the back bent forwardmore than 45º (without support or theability to vary posture)

More than 2 hourstotal per day q

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Table 2 Hazard assessment checklist (continued)

Awkward Body Positions (continued)

Body Part Physical Risk Factor Duration Visual Aid

Check (3)here if thisis an MSI

hazard

Squatting More than 4 hourstotal per day q

q

Knees

Kneeling More than 4 hourstotal per day q

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Table 2 Hazard assessment checklist (continued)

High Hand Force

Body Part Physical Risk Factor Combined with Duration Visual Aid

Highly repetitivemotion

More than 3hours total perday

Check (3)here if thisis an MSI

hazard

q

Wrists bent inflexion 30° ormore, or inextension 45° ormore, or in ulnardeviation 30° ormore

More than 3hours total perday

Ulnar deviation

q

Arms,wrists,hands

Pinching anunsupported object(s)weighing 900 grams ormore (2 lbs) per hand,or pinching with aforce of 180 Newtonsor more (4 lbs) perhand (comparable topinching half a ream ofpaper)

No other riskfactors

More than 4hours total perday

q

Highly repetitivemotion

More than 3hours total perday q

Wrists bent inflexion 30° ormore, or inextension 45° ormore, or in ulnardeviation 30° ormore

More than 3hours total perday q

Arms,wrists,hands

Gripping anunsupported object(s)weighing 4.5 kg ormore (10 lbs) perhand, or gripping witha force of 340Newtons or more (10lbs) per hand(comparable toclamping light dutyautomotive jumpercables onto a battery)

No other riskfactors

More than 4hours total perday

q

Extension

Flexion

Flexion

Extension

Ulnar deviation

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Table 2 Hazard assessment checklist (continued)

Highly Repetitive Motion

Body Part Physical Risk Factor Combined with Duration

Using the samemotion with little or novariation every fewseconds (excludingkeying activities)

No other risk factorsMore than 6 hours totalper day

Check (3)here if thisis an MSI

hazard

qUsing the samemotion with little or novariation every fewseconds (excludingkeying activities)

Wrists bent in flexion 30°or more, or in extension45° or more, or in ulnardeviation 30° or more

AND

High, forceful exertionswith the hand(s)

More than 2 hours totalper day q

Awkward posture,including wrists bent inflexion 30° or more, or inextension 45° or more, orin ulnar deviation 30° ormore

More than 4 hours totalper day q

Neck,shoulders,elbows,Wrists,hands

Intensive keying

No other risk factors More than 7 hours totalper day q

Repeated Impact

Body Part Physical Risk Factor Duration Visual Aid

HandsUsing the hand (heel/base of palm) asa hammer more than once per minute

More than 2 hourstotal per day

Check (3)here if thisis an MSI

hazard

q

KneesUsing the knee as ahammer more than onceper minute

More than 2 hourstotal per day q

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Table 2 Hazard assessment checklist (continued)

Heavy, Frequent or Awkward Lifting

Find the Limit Reduction Modifier. Find out how manytimes the worker lifts per minute and the total number ofhours per day spent lifting. Use this information to lookup the Limit Reduction Modifier in the table below.

For how many hours per day?How many liftsper minute?

1 hr or less 1 hr to 2 hrs 2 hrs or more

1 lift every 2-5 mins. 1.0 0.95 0.85

1 lift every min 0.95 0.9 0.75

2-3 lifts every min 0.9 0.85 0.65

4-5 lifts every min 0.85 0.7 0.45

6-7 lifts every min 0.75 0.5 0.25

8-9 lifts every min 0.6 0.35 0.15

10+ lifts every min 0.3 0.2 0.0

Note: For lifting done less than once every five minutes, use 1.0

Limit Reduction Modifier: ____.______

Find out the actual weight ofobjects that the worker lifts.

Actual Weight = ________ lbs.

Determine the UnadjustedWeight Limit. Where are theemployee's hands when they begin tolift or lower the object? Mark that spoton the diagram below. The number inthat box is the Unadjusted Weight Limitin pounds.

Unadjusted Weight Limit: _______ lbs.

Calculate the Weight Limit. Start by copying theUnadjusted Weight Limit from Step 2.

Unadjusted Weight Limit: = ______ lbs.

If the worker twists sideways more than 45degrees while lifting, reduce the UnadjustedWeight Limit by multiplying by 0.85. Otherwise,use the Unadjusted Weight Limit

Twisting Adjustment: = _____.____

Adjusted Weight Limit: = ______ lbs.

Multiply the Adjusted Weight Limit by the LimitReduction Modifier from Step 3 to get theWeight Limit. X

Limit Reduction Modifier: _____.___

Weight Limit: = _____ lbs.

Is this a hazard? Compare the Weight Limit calculated inStep 4 with the Actual Weight lifted from Step 1. If the ActualWeight lifted is greater than the Weight Limit calculated, thenthe lifting is an MSI hazard and should be reduced below thehazard level or to the degree technologically andeconomically feasible.

Step 1

Step 2

Step 3

Step 4

Step 5

Note: If the job involves lifts of objects with a number of different weights and/or from a number of different locations, use Steps 1 through 5 above to:1. Analyze the two worst case lifts -- the heaviest object lifted and the lift done in the most awkward posture.2. Analyze the most commonly performed lift. In Step 3, use the frequency and duration for all of the lifting done in a typical workday.

This analysis only applies to “caution zone jobs”where workers lift 4.5 kg or more (10 lbs), useboth hands, and are not seated or kneeling whilelifting. For lifting with one hand or while seated orkneeling, use the “High Hand Force” section of thischecklist.

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Table 2 Hazard assessment checklist (continued)

Hand-Arm Vibration

Use the instructions below to determine if a hand-arm vibration hazard exists.

Step 1. Find the vibration value for the tool. (Get it from the manufacturer, look it up at this web site:http://umetech.niwl.se/vibration/HAVHome.html, or you may measure the vibration yourself). Thevibration value will be in units of meters per second squared (m/s2). On the graph below find the point onthe left side that is equal to the vibration value.

Step 2. Find out how many total hours per day the employee is using the tool and find that point on thebottom of the graph.

Step 3. Trace a line in from each of these two points until they cross.

Step 4. If that point lies in the crosshatched "Hazard" area above the upper curve, then the vibration hazard must bereduced below the hazard level or to the degree technologically and economically feasible. If the point liesbetween the two curves in the "Caution" area, then the job remains a “caution zone job” workers should betrained to understand how to use their workstation (including how to adjust its equipment and furnishings),how to use or select tools appropriate to the work they are performing, the safe work practices that they areexpected to follow, and an understanding of the signs, symptoms, and methods of preventing MSIs. If itfalls in the "OK" area below the bottom curve, then no further steps are required.

0

10

20

30

40

50

0 1 2 3 4 5 6 7 8

Time (in hours)

Vib

rati

on

val

ue

(in

m/s

2 )

Caution

OK

Hazard

Note: The caution limit curve (bottom) is based on an 8-hour energy-equivalent frequency-weighted acceleration value of 2.5 m/s2. The hazard limit curve (top) is based on an 8-hourenergy-equivalent frequency-weighted acceleration value of 5 m/s2.

Example:An impact wrench with avibration value of 12 m/s2

is used for 2½ hours totalper day. The exposurelevel is in the Hazard area.The vibration must bereduced below the hazardlevel or to the degreetechnologically andeconomically feasible.

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Other Safety Bulletins in thisseries

This six-part series of Safety Bulletinsconsists of the following titles:

§ Part 1 — Alberta Injury Statisticsand Costs

§ Part 2 — Symptoms and Types ofInjuries

§ Part 3 — Biomechanical RiskFactors

§ Part 4 — Workplace Risk Factors§ Part 5 — Assessing Ergonomic

Hazards§ Part 6 — Reducing Ergonomic

Hazards

A companion series specific to the liftingand handling of loads is also available.It consists of the following titles:

Lifting and Handling Loads§ Part 1 — Reviewing the Issues§ Part 2 — Assessing Ergonomic

Hazards§ Part 3 — Reducing Ergonomic

Hazards

Each of these Bulletins is availablethrough Workplace Health and Safetyregional offices or the Department’sInternet web site. Refer to the final page

of this Safety Bulletin for specificdetails.

References

Note: Each of the Department of Laborand Industries references are available atthe following Internet web address:www.Ini.wa.gov/wisha/regs/ergo2000

Department of Labor and Industries,State of Washington. WAC 296-62-051,Ergonomics. May 5, 2000.

Department of Labor and Industries,State of Washington. ConciseExplanatory Statement (RCW34.05.325.6a) WAG 296-62-051,Ergonomics. May 5, 2000.

Department of Labor and Industries,State of Washington. WAC 296-62-05174, Appendix B: Criteria foranalyzing and reducing WMSD hazardsfor employers who choose the SpecificPerformance Approach. May 5, 2000.

Waters TR et al. Revised NIOSHequation for the design and evaluation ofmanual lifting tasks. Ergonomics 36(7):749-776; 1993.

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For more information about workplace safety or safe work practices, contact the AlbertaHuman Resources and Employment, Workplace Health and Safety Call Centre bydialling toll-free:

% 1-866-415-8690

Deaf or hearing impaired call:

ä Edmonton (780) 427-9999 Other locations 1-800-232-7215

For more publications, visit our web site at: www.whs.gov.ab.ca

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ä Edmonton……(780) 427-4952 Calgary………..…(403) 297-6251