International Journal of Industrial Ergonomics 35 (2005) 197204

low-back symptoms lasting a week or longer were highest in the workers with the job title molders (29.9%), followed by

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www.elsevier.com/locate/ergon0169-8141/$ - see front matter r 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.ergon.2004.08.007

Corresponding author. Tel.: +1508 497 0225; fax: +1 508 435 0482.E-mail address: patrick.demspey@libertymutual.com (P.G. Dempsey).cleaners (26.2%).

r 2004 Elsevier B.V. All rights reserved.

Relevance to industry

This study provides information on the prevalence of musculoskeletal disorders in foundries, and the results suggest

interventions for low-back pain should be a key priority. The selection of tools to minimize exposure to vibration is also

warranted.

r 2004 Elsevier B.V. All rights reserved.

Keywords: Foundry; Musculoskeletal disorders; Ergonomic assessment; Nordic questionnaireamong chinese foundry workers

Ling Leia, Patrick G. Dempseya,, Jian-guo Xuc, Lin-na Gea, You-xin Lianga

aSchool of Public Health, Liberty Mutual SafeWork Center at Fudan University, Shanghai 200032, P.R. ChinabLiberty Mutual Research Institute for Safety and Health, 71 Frankland Road, Hopkinton, MA, 01748 USA

cCixi Municipal Center for Disease Control and Prevention, Cixi, P.R. China

Received 12 April 2004; received in revised form 16 August 2004; accepted 17 August 2004

Available online 13 October 2004

Abstract

The goal of the study was to investigate risk factors for the prevalence of musculoskeletal symptoms (ache, pain, or

discomfort) among foundry workers in China using the standardized Nordic questionnaire. In addition, questions

describing work history and ergonomic conditions at work were used in the investigation of 617 foundry workers. The

study population consisted of 80.0% males and 20% females with a mean age (SD) of 34.4 (9.5) years and a median

foundry work experience of 3 years (range of 130 years). Most subjects had an education of junior middle school with

a mean (SD) of 6.8 (2.7) years of education. Among musculoskeletal symptoms, the one-year prevalence of low-back

symptoms ranked rst regardless of job title (25.032.4%). Risk factors for low-back symptoms lasting a week or

more in the previous 12 months were found to be smoking, lifting and vibrating tool usage. The prevalence ofRisk factors for the prevalence of musculoskeletal disorders

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Indu1. Introduction

Musculoskeletal disorders (MSDs) attributed towork include a group of conditions that involvethe nerves, tendons, muscles, and supportingstructures of the body such as intervertebral discs.Often attributed to or exacerbated by the workenvironment, these disorders are also referred to aswork-related musculoskeletal disorders (WMSDs)which can cause symptoms such as pain, numb-ness, and tingling, as well as reduced workerproductivity, lost time from work, temporary orpermanent disability. These disorders lead tonancial losses associated with workers compen-sation insurance, or similar forms of social securityin place.Highly repetitive work, forceful exertions, lifting

and forceful movements, and whole-body vibra-tion are examples of risk factors that have beenassociated with increased reporting of WMSDs(Bernard, 1997). Poor working conditions in heavymanufacturing often expose workers to multiplerisk factors for musculoskeletal disorders. Thelevel of risk depends on the duration a worker isexposed to risk factors, the frequency at whichthey are exposed, and the magnitude of theexposure.The metal casting industry has long been

considered to be a hazardous industry character-ized by exposure to both chemical and physicalhazards, such as silica, heat, and high forcesrequired to handle and manipulate molds andcastings during various phases of the formingprocesses. Although many changes have occurredin foundry technology and materials, the basicprocesses and the associated hazards have re-mained much the same in many foundries. In fact,metal casting is still a labor-intensive and complexprocess requiring signicant amounts of repetitivemanipulation and stressful physical and posturalloads. The work environment poses work safetyhazards for musculoskeletal disorders and acuteinjuries due to falling or moving objects, liftingand carrying loads, etc. (NIOSH, 1985). However,in the past, much more effort by safety and healthpractitioners was focused on the adverse healtheffects resulting from exposure to chemical risk

L. Lei et al. / International Journal of198factors. As a result, fewer studies of ergonomicproblems associated with work processes in themetal casting industry have been published, and inparticular, studies conducted in China.One conceptual model of the etiology of

musculoskeletal disorders (MSDs) was presentedby the National Institute for Occupational Safetyand Health (NIOSH, 2001). The mechanical loadswere depicted as being determined by the arrange-ment of work procedures, temporal exposurepatterns, equipment and the environment. Thisload would then cause a tissue response, whichmay or may not lead to an undesirable outcomesuch as symptoms or impairment. Organizationalfactors, individual characteristics and social con-text were depicted as factors that would inuencehow the relationship between load and potentialoutcomes. The metal casting industry, which wasthe focus of this study, is a typical industry withcomplex work processes that generate most, if notall, the risk factors, particularly high physicalloads.A tool commonly used for investigating the

prevalence of MSD symptoms in occupationalsettings is the standardized Nordic questionnaire(Kourinka et al., 1987). The questionnaire can beself-administered or used in interviews, and is wellsuited for studying the history of musculoskeletalsymptoms and disability in occupational popula-tions. The questions concentrate on symptomsmost often encountered in an occupational setting,particularly those affecting the low-back, neck,and shoulders. The reliability of the questionnairewas found to be acceptable (Kourinka et al., 1987).The questionnaire is subject to recall bias, how-ever, particularly since some questions ask formusculoskeletal symptoms and problems experi-enced during the previous 12 months.Based on pain complaints, there is also a need to

do a physical examination to exclude the presenceof a serious underlying medical condition. In theabsence of red ags, other more specialized testsare not warranted during the acute phase. Physicalexamination guided by the medical history usuallyincludes general observation of stance and gait,regional examination and possibly neurologic orother specic screening. Observation is useful toguide the regional examination. The regional

strial Ergonomics 35 (2005) 197204examination is mainly vertebral point tenderness

to palpation, when associated with other signs orsymptoms, is suggestive but not specic for spinalfracture or infection. Neurologic screening focuseson a few tests that reveal evidence of nerve rootimpairment, peripheral neuropathy, or spinal corddysfunction. These items are testing for musclestrength, reexes, sensory and motor examinations(Harris, 1998).The goal of this study was to investigate the

prevalence of musculoskeletal disorders in foundryworkers. In order to explore the potential factorsrelated to the prevalence of reporting musculoske-letal symptoms such as discomfort and pain, four

participating was being absent or away from the

task were eligible to participate, since the Nordicquestionnaire includes up to a 12-month recallperiod. Following the interview, the enrolledsubjects were divided into four groups in accor-dance with their job titles, including turner(standing posture), cleaner (static bending pos-ture), molder (bending and twisting posture, andheavy physical load), and other (less physically-demanding occupations). The other categoryincluded primarily supervisors, technicians, and amiscellaneous group.

2.2. Methods

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Sen

1. In

2. In

3. In

L. Lei et al. / International Journal of Industrial Ergonomics 35 (2005) 197204 199factory during data collection). Workers with atleast 12 months experience in the current work

Table 1

Components of physical examination

Tenderness Reex

1. Neck tenderness 1. Straight leg raise tests

2. Back tenderness 2. Straight leg raise intensied tests

3. Ankles reex

4. Knees reex

5. Pathologic (pathogenic) reexdifferent job titles in the foundry industry wereincluded in the study.

2. Procedures

2.1. Subjects

The study population consisted of 772 foundryworkers from three similar foundry factories in acity in east China. Manual materials handling andheavy physical loads were the main task char-acteristics involved in several of the occupationsstudied.Of the 772 workers, 617 were enrolled to

participate in the questionnaire investigation, witha response rate of 80% (the main reason for notThe data collection was initiated by rst seekingconsent of the subjects to participate. Followingthe consent phase, the investigators took measure-ments of body weight and height for each subject.An orthopedist then performed a physical exam-ination for all workers. The items included in theexam were categorized as tenderness, reex,sensation and motor function (see Table 1).Finally, each subject was interviewed individu-

ally by an interviewer well-trained before thesurvey, and having experience administering theNordic questionnaire (Kourinka et al., 1987)during a pilot investigation. The informationcollected from the questionnaire investigationcovered the following four major parts:(1) Demographic characteristics and back-

ground information: job title, age, gender, educa-tion, marital status, income, cigarette smoking andalcoholic drinking.

sory Motor function

side and outside of crus 1. Hip joint exionextension

side and outside of instep 2. Bend down and stand up

side and outside of sole 3. Knee joint exionextension

4. Toe extension

5. Thumb extension

6. Toe exion

7. Thumb exion

8. Fibula length

9. Heeling

10. Tibialis anterior muscle

11. Toeing

(2) Physical workloads: the work tasks involvinglifting, pushing and pulling loads and vibratingtools usage were assessed by three questions:a) What loads do you lift at your work usually?

None;p10 kg; 11 20 kg; 21 50 kg;450 kgb) What loads do you push and pull at your

work usually?

None;p10 kg; 11 20 kg; 21 50 kg;450 kgc) How often do you usually use vibrating tools

at your work?

Never;Seldom;Half day;Whole day

(3) Work-related factors: work history, employ-ment duration, heavy work activities at leisure,exercise, psychological and social status.(4) MSD symptoms investigation: The ques-

tionnaire used was the Standardized Nordic Mus-culoskeletal Syndrome Analysis Questionnaire

attributed to current work and lasting for at leasta week with no history of injury to that bodyregion (Bernard et al., 1994; Lemasters et al., 1998)were referred to as musculoskeletal symptoms-week plus (MSS-WEEK+). Statistical analyses,including multiple logistic regression, were per-formed with SPSS for Windows (version 10.0).

3. Results

The basic demographic and background infor-mation is summarized in Table 2. Those in theOthers category were, on average, older andmore experienced than workers in the remainingthree job titles, suggesting the possibility of ahealthy worker effect. The self-reported informa-tion on materials handling tasks and non-workhabits is presented in Table 3.

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le

jects

eavy

o

es

L. Lei et al. / International Journal of Industrial Ergonomics 35 (2005) 197204200(Kourinka et al., 1987).There were two case denitions analyzed: The

term musculoskeletal symptom (MSS) was used inreference to reports of neck, shoulder, low back, aswell as elbow, hand, hip, knee, and/or multiplejoints trouble (ache, pain, or discomfort) in the 12months prior to being interviewed. Symptoms

Table 2

Anthropometric and background characteristics of subject samp

Job title Molders

Sample size 284

Gender (male:female) 7.4:1

Age (yr). 34.579.8Years of school 6.472.7Employment duration (yr) 3.0 (134)

Height (cm) 163.876.3Weight (kg) 56.776.3

Table 3

Self-reported occupational exposure and leisure activities of sub

Lifting (kg) Push & pull (kg) Vibrating tool usage H

None 31.3% None 37.1% None 71.2% N

p10 kg 12.2% p10 kg 1.6% Seldom 12.3% Y1120 kg 16.5% 1120 kg 3.4% Half day 6.8%2150 kg 26.7% 2150 kg 7.3% All day 9.7%450 kg 13.3% 450 kg 50.6%(%)

activities at leisure Exercise (times/month) Sleeping (h)

95.8% None 75.4% ~6 4.7%

4.2% ~1 6.5% ~8 49.3%~3 5.7% ~10 41.3%X4 12.4% X10 4.7%3.1. Prevalence of musculoskeletal symptoms

The highest prevalence of symptoms was foundin the body part of back followed by shoulders,but there was no siginicant difference among thefour groups. The prevalence of MSS in other sites

Turners Cleaners Others

130 84 119

7.1:1 20:1 2.1:1

31.178.9 32.875.7 38.579.97.572.5 6.671.7 7.373.22.0 (128) 2.0 (122) 6.0 (137)

164.376.6 162.975.9 163.577.354.677.5 57.876.2 59.978.8

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Straight leg raise test Straight leg raise (intensied) test

0.4 0.4

0.8 0.8

1.2 0.0

0.0 0.0

0.5 0.3

dy pa

rist

.8a

.2a

.2

.7

.5

Table 6

Prevalence of musculoskeletal symptoms lasting a week or

longer (MSS-WEEK+)

Induwas varied with different work titles. The pre-valence of MSS found in the wrists and hand, andknees and ankles in turners was signicantly

Table 5

Prevalence of positive signs found by physical examination (%)

Groups No. Neck tenderness Back tenderness

Molder 284 7.0 16.9a

Turner 130 4.6 4.6

Cleaner 84 1.2 9.5a

Others 119 9.2 1.7

Total 617 6.9 10.4

aIndicates signicant difference.

Table 4

One-year prevalence of musculoskeletal symptoms (MSS) by bo

No Neck(%) Shoulder(%) Elbow(%) W

Molders 284 5.3 8.8 1.4 8

Turners 130 10.0 13.1 3.8 9

Cleaners 84 2.4 6.0 0.0 1

Others 119 6.7 15.1 2.5 1

Total 617 6.2 10.5 1.9 6

aIndicates signicant difference.

L. Lei et al. / International Journal ofhigher than those in other job titles, the sametendency was observed at wrists and hands ofmolders (Table 4).Table 5 summarizes the positive signs found

during the physical examination. The positive rateof back tenderness (16.9%) in molders wassignicantly higher than others, followed bycleaners (9.5%). There was no difference in necktenderness or the straight leg raise tests by jobtitles.

3.2. Prevalence of and risk factors associated with

MSS-WEEK+

The prevalence of MSS-WEEK+ differed byjob titles. For turners, neck and shoulder pre-valence was found higher than the other special-ties; cleaners and molders, however, had asignicantly higher prevalence of back symptomslasting a week or more (Table 6).Multiple logistic regression analysis (backwards

wald) indicated that a number of risk factors weresignicantly associated with the occurrence ofrt (%)

& hand(%) Back(%) Hip(%) Knee(%) Ankle(%)

32.4 4.2 1.4 2.1

26.9 5.4 7.7a 8.5a

25.0 2.4 0.0 1.2

26.9 2.5 1.7 4.2

29.2 3.9 2.6 3.7

strial Ergonomics 35 (2005) 197204 201MSS-WEEK+ of the neck, shoulders, and low-back (Tables 79, respectively). Variables initiallyentered into model were job title, body mass index(BMI), gender, marital status, education, income,smoking, alcoholism, duration of employment,age, lifting, pushing and pulling, vibrating toolsuse, work intensity, heavy loads at leisure, sleepinghours, and exercise. Two risk factors associatedwith neck MSS-WEEK+ identied were job title(signicantly higher in turners compared toother) and gender (Table 7). For shoulder MSS-WEEK+, risk factors identied were job title(signicantly higher in turners compared to

Group n Neck Shoulder Back

Molder 284 5.3 4.6 29.9a

Turner 130 8.5a 11.5a 15.4

Cleaner 84 1.2 2.4 26.2a

Others 119 2.5 5.9 14.3

Total 617 4.9 6.0 23.3

p 0.05 0.018 0.007

aIndicates signicant difference.

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InduTable 7

Risk factors associated with neck MSS-WEEK+ (n=617)

L. Lei et al. / International Journal of202others) and gender (Table 8). For low-back MSS-WEEK+, smoking, lifting, and vibrating tools usewere found to be signicant risk factors (Table 9).

OR 90%CI p

Job titles 0.05

Others 1

Turner 4.78 1.5314.95 0.02

Cleaner 0.62 0.094.36 0.69

Molder 2.58 0.867.71 0.15

Gender Male 1

Female 2.41 1.145.08 0.05

Table 8

Risk factors associated with shoulder MSS-WEEK+ (n=617)

OR 90%CI p

Job titles 0.02

Other 1

Turner 2.83 1.256.44 0.04

Cleaner 0.59 0.152.33 0.53

Molder 1.03 0.452.34 0.96

Gender Male 1

Female 3.11 1.635.93 o 0.01

Table 9

Risk factors associated low-back MSS-WEEK+ (n=617)

OR 90%CI p

Smoking (cig/day) o 0.01~1 1.00

~10 0.66 0.411.07 0.16

~20 1.01 0.671.52 0.97

X20 2.93 1.635.27 o 0.01Lifting (kg) 0.02

None 1.00

~10 0.84 0.441.62 0.66

~20 2.03 1.223.39 0.02

~50 2.05 1.323.18 0.01

X50 1.38 0.802.39 0.33Vibrating tool use 0.01

None 1.00

Seldom 1.51 0.92-2.49 0.17

Half day 2.19 1.21-3.95 0.03

Whole day 2.28 1.37-3.80 0.014. Discussion

The positive signs noted most often during thephysical examinations were neck and back tender-ness. Only a few persons had positive signs duringthe straight leg raise tests. Other physical exam-ination items including reex, sensory and motorfunction did not show any abnormal ndings.These rates could be affected by the healthyworker effect, since workers with decreased func-tion would not be present in the workplace toparticipate in the study, or would have been moreprone to seek employment in jobs with lowerphysical demands. Thus, the rates of positivendings could be underestimates.The rates of positive ndings during the physical

exam are cross-sectional whereas the symptomdata are based on recall of symptoms occurring inthe previous 12 months. This is most evident whencomparing the results in Tables 4 and 5, as Table 4shows high rates of MSS of the low-back reportedby workers in all job titles. The rates of positivendings during the physical exam are not onlylower than the rates of MSS, but there is morevariation in physical exam ndings among jobtitles. The patterns of physical ndings duringexamination tend to more closely follow the MSS-WEEK+ ndings, but there is some discordance,for example in the neck region that may be due tosmall sample size within groups and other sourcesof variation.Among the four groups of job titles studied,

molders had the highest prevalence of backtenderness (16.9%), followed by the cleaners(9.5%). Molders and cleaners also had the highestrates of self-reported low-back MSS-WEEK+(29.9% and 26.2%, respectively). Although thecleaners tended to work often in static bendingpostures, molders were also in static bendingpostures, but also manipulated heavy loadsincluding lifting tasks. Turners tended to workstanding with neck bent, while others includingsupervisors, technicians and miscellaneous work-ers engaged in a lighter work with more variedpostures.The prevalence of low-back MSS was highest,

followed by shoulder, neck, and wrist and hand

strial Ergonomics 35 (2005) 197204pain, regardless of job title. This result suggests

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Induthat the predominant ergonomic problems in themetal casting industry are related to exposures thatstress the low-back and upper extremities. This isconsistent with the materials handling demandsand awkward postures observed.From the crude data in which case denition

was not limited (MSS), there was no difference inlow back pain prevalence among workers in thefour job titles. However, when the case denitionof musculoskeletal symptoms lasting longer than aweek was analyzed, the prevalence of low backpain among cleaners and molders was signicantlyhigher than others and turners, while that of neckand shoulder pain in turners was the highest. Thismay be due to these jobs either causing moreinjury to soft tissues that leads to specicsymptoms lasting longer, these jobs may inhibithealing, or these jobs may lead to more symptomexpression due to the physical demands. Differ-ences in rates are also likely affected by recall biassince both denitions involved symptom history inthe prior 12 months.There is literature that has quantied how

different case denitions lead to different resultsin the prevalence of musculoskeletal disorders(e.g., Ozguler et al., 2000). Some outcomes arespecic diagnoses (e.g., shoulder tendonitis, epi-condylitis, tension neck syndrome) and others arenonspecic musculoskeletal symptoms (e.g., pain,tenderness, tingling, and numbness) in a specicbody region or all areas combined. For the currentstudy, two outcome denitions were chosen toreect different symptom levels. Any pain ordiscomfort in the past 12 months lasting morethan one week represents a more severe outcome,and presumably even though self-reported, repre-sents a more severe musculoskeletal condition. Interms of prevention and ergonomic efforts, thesemore severe cases would suggest where interven-tions to reduce pain and discomfort during workshould be targeted.According to a multiple logistic regression

analysis, the risk factors associated with neckand shoulder MSS-WEEK+ were work title andgender. For both body areas, turners had sig-nicantly higher risk compared to those in theother category. This is consistent with the

L. Lei et al. / International Journal ofphysical demands associated with manipulatingheavy loads by the turners. The MSS resultsin Table 4 showed relatively high prevalence ofneck and shoulder symptoms among turners,although these rates were not signicantly higherthan the rates for other job titles. No signicantdifferences for neck tenderness among workers indifferent job titles were found for the physicalexam.Low-back MSS-WEEK+ was associated with

smoking, lifting, and vibration tool exposure. Theassociation between smoking and low-back pain isunclear in the literature, as there are numerousstudies reporting positive associations, while otherstudies report negative associations (Dempseyet al., 1997). It should be noted that an effectwas only noted for those reporting smoking 20 ormore cigarettes per day. Job title did not have asignicant difference, likely because lifting de-mands entered the model and these are likely themost important job demand among different jobsassociated with low-back complaints. Molders hadthe highest lifting demands, thus there wassome collinearity between job title and liftingdemands, thus it is reasonable that only onevariable would be in the nal model. Since thesurvey questions were more related to low-backstressors than shoulder and particularly neckstressors, this is likely the reason that none ofthese items were signicant for the neck andshoulder models, whereas job title was signicantin those models.The most important limitation of the study is

the cross-sectional design. The association betweenrisk factors and MSDs cannot be inferred torepresent a causal relationship. The potential forrecall bias exists as well. The prevalence oddsratios reported are not as desirable as incidenceodds ratios. The signicant risk factors reportedmay increase the risk (incidence) of musculoskele-tal disorders, or they may increase the duration ofthe disorders in the exposed population. Finally,workers with one year or more of experience wereincluded due to the recall period. Thus, the sampleis biased since the workers that choose to leavebefore one year, some possibly due to injury, werenot included. In spite of these limitations, thestudy does add knowledge about work-related

strial Ergonomics 35 (2005) 197204 203musculoskeletal disorders among foundry workers

in China. Signicant opportunities for ergonomicintervention exist, and the current study providesinformation for focusing the interventions for thedifferent jobs studied.

Acknowledgments

The authors would like to thank David Lom-bardi and Santosh Verma for their critical reviewsof an earlier draft.

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L. Lei et al. / International Journal of Industrial Ergonomics 35 (2005) 197204204

Risk factors for the prevalence of musculoskeletal disorders among chinese foundry workersIntroductionProceduresSubjectsMethods

ResultsPrevalence of musculoskeletal symptomsPrevalence of and risk factors associated with MSS-WEEK+

DiscussionAcknowledgmentsReferences