Rheumatism Foundry Workersoem.bmj.com/content/oemed/23/1/42.full.pdf · Rheumatism in Foundry Workers ... Foundry Expected Foundry Expected Foundry ... significantly less frequent

Brit. J. industr. Med., I966, 23, 42

Rheumatism in Foundry WorkersJ. S. LAWRENCE, M. K. MOLYNEUX, and IANTHE DINGWALL-FORDYCEFrom the Arthritis and Rheumatism Council Field Unit and the Nuffield Department of Occupational

Health, University of Manchester

In order to investigate loss of work from rheumatic diseases in the metal trades, employees in IOfoundries were questioned.Of 325 foundry workers aged 35 to 74 years, who had worked for at least IO years on the foundry floor,

299 were examined clinically and radiologically for evidence of rheumatic disease. Radiographs of thehands, knees, and dorsal and lumbar spine were taken as a routine, and the pelvis was included in thoseaged 45 and over. A comparison was made with a control series of radiographs, from men, matched forage, in a random population sample examined earlier in the town of Leigh.Rheumatic complaints in general were less frequent in the foundry workers than in the random sample,

and the foundry workers less often gave a history of prolonged incapacity (three months or more) due tothis cause.

Radiological evidence of disc degeneration in the lumbar spine, however, was more frequent in thefoundry workers than in the controls and was of greater severity. Further, the foundry workers morecommonly had symptoms and signs of lumbar disc prolapse. On the other hand, the controls had more

osteo-arthrosis of the hips and knees and lost more work from pain at these sites. This was associatedwith a difference of body habitus, obesity being less frequent in the foundry workers.Foundry workers directly exposed to hot conditions did not have less back or leg pain than those not

so exposed despite a greater prevalence of disc degeneration.Measurements of air temperature, humidity, and radiant heat were made in a foundry while pouring

was in progress. The air temperature rose from i80C. to 26°C. and the humidity ranged from 70% to54%. The mean intensity of radiation incident on the clothed surface of a foundry worker was012 watt/cm.2. This was compared with conditions during therapeutic exposure to radiant heat. Theradiant heat under conditions of 'heat therapy' varied between o i6 and 0o37 watt/cm.2. The possibleinfluence of radiant heat on the prevalence of rheumatic complaints is discussed.

Statistics produced by the Ministry of Pensionsand National Insurance in the United Kingdomindicate that, if unskilled workers are excluded, thegreatest number of claims for incapacity due toarthritis and rheumatism (excluding rheumaticfever) are made by persons engaged in metal,engineering, and allied trades. In June 1955, forexample, claims were received from 4,o80 workersin these trades compared with 5,760 unskilledworkers and 3,400 miners. The number of workersat risk is not accurately known but there can belittle doubt that this reflects in part the frequency ofsuch occupations in the community. In the absenceof reliable information on the size and age distribu-tion of this occupational group it was decided tocarry out a detailed survey. As foundry workersform a well defined sub-group and lose work more

frequently than any other metal workers, this surveywas limited to foundry workers. Statistics producedby the Amalgamated Union of Foundry Workersshow that rheumatism is an important cause ofincapacity in their members, coming second only torespiratory disease and influenza.

Little has appeared in the medical literature onthis subject but Vernon (I92I) found that puddlersof wrought iron lost an excessive amount of workfrom rheumatism and he attributed this to periodsof heavy work under high temperature conditionsfollowed by sitting about in draughts. Steel melters,who are also engaged in heavy intermittent work,lost more than the average amount of work fromrheumatism.

Method of Survey

Received for publication April IO, I965. Foundries, whether attached to large engineering42

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Rheumatism in Foundry Workers

shops or acting as independent units, are usuallysmall and employ on an average some 30 men. Itwas therefore felt that a survey of a single largefoundry would not give a representative sample. Itwas decided to include one foundry with more than2oo employees and to distribute the rest of thesurvey over a number of smaller foundries*employing 20 to I00 men.The survey was limited to men aged 35 and over,

who had worked for at least I0 years on the foundryfloor and were so working at the time of the surveyor were temporarily away from their work becauseof sickness or accident. No information was avail-able on foundry men who had left the industrybecause of illness but these were considered by themanagement to be few. Trades included weremoulders, coremakers, dressers and arc welders,pattern makers, and general labourers.

After a history had been taken of past illnesses andpresent symptoms, a clinical examination of themusculo-skeletal system was carried out on all menhaving the above qualifications. Radiographs weretaken of the hands, knees, and dorsal and lumbarspine as a routine and of the pelvis in those aged 45and over. Only a lateral view was taken of the spineand an anterior-posterior view of the other parts. Acomparison was made with a series of radiographsfrom the Leigh random population sample (Law-rence and Bennett, i96o) matched by age with thefoundry workers. As there were insufficient menaged 35 to 44 in the Leigh sample, 26 men in thisage group were obtained from an area sample inWensleydale (Bremnier, I96I) to complete the

*The following foundries took part in the survey:J. Needham & Sons, Stockport, Cheshire; J. R. Clayton,Stockport, Cheshire; Storey Foundry Co., Reddish, Cheshire;E. Pass & Co., Denton, Lancashire; R. Broadbent & Sons,Stalybridge, Cheshire; Ferranti Ltd., Hollinwood, Lanca-shire; J. Hodgkinson (Salford) Ltd., Salford, Lancashire;W. H. Bailey & Co., Patricroft, Lancashire; WarringtonLight Castings Co., Warrington, Lancashire; Wyman'sFoundry, Warrington, Lancashire.

Age Total

controls. The radiographs of the foundry workersand controls were mixed randomly and read 'blind'.The changes found were graded in accordance withthe Atlas of Standard Radiographs of Arthritis(I963).The sample of foundry workers totalled 325, of

whom 299 were examined, a completion rate of 92%%.The 8% who were not examined were mainly in the45-54 age group (Table I).

Age

35-4445-5455-6465+Not statedTotal

TABLE ICOMPLETENESS OF SURVEY

Total in Not Avail- Examined CompletionSample able or Rate (%)

RefusedExamination

I26 6 I20 95II9 I3 I06 8969 2 67 976 0 6 I005 5 -

325 26 299 92

Results

Rheumatic Symptoms Of the 299 foundryworkers who were examined, i88 (63%) gave ahistory of rheumatic complaints (Table II). Theexpected number, as determined by correction oftheLeigh random males to the age distribution of thefoundry workers, is 2I9 (X2 = 4.3, P < oo5). Ofthe i88 foundry workers with symptoms, I03 hadlost work from rheumatism and 26 had lost threemonths or more compared with expected rates ofI04 and 43. The difference between the number offoundry workers and controls who lost three monthsor more is significant (X2 = 6X3, P < 0.02). Thenumber of foundry workers with symptoms at thetime of the survey was 8o, and two were actually offwork from rheumatism, compared with an expectedI07 with complaints (X2 = 6-5, P < o oi) and fiveoff work. None had been off for three months or

Off Work

i Week -+ 3 Months +

Total withComplaints

Off Work

I Week + 3 Months +

35-44 I2045-54 I0655-64 6765+ 6Total 299Expected

*P < 0o05. tP < -01.

TABLE IIRHEUMATIC COMPLAINTS IN FOUNDRY WORKERS

Since Birth Now

Total withComplaints

746647I

I88*219

353829I

103104

10

97

26*43

303020

8ot107

I

2

3

43


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J. S. Lawrence, M. K. Molyneux, and Ianthe Dingwall-Fordyce

TABLE IIISITE OF PAIN IN FOUNDRY WORKERS AND CONTROLS

Total Off Work I Week + Off Work 3 Months +

Foundry Expected Foundry Expected Foundry Expected

SegmentalCI-4C5-D2

D3-IIDI2-L2

L3-4L5-S2

LocalFingersThumbs

WristsElbows

ShouldersHips

KneesAnkles

TarsiToes

Multiple Undefined*P < 0 05.tP < O-OI.tP < O-OOI.

more with rheumatic troubles at the time of thesurvey though this would be expected in three.Complaints were mainly of pain in the low back andgroins in the D12-L2 segmental distribution (TableIII). In no sites, apart from the wrists and elbowsand in the D3-II and L5-S2 distribution (sciatic),was pain more frequent in the foundry workers, andhere the differences were not significant. There was

significantly less pain at a number of sites in thefoundry workers, notably in the knees, ankles, andtarsi (P < o-ooi). Segmental pain in the legs andarms in the L3-4- and C5-D2 distribution was alsosignificantly less frequent in the foundry workers.Loss of work due to pain in the hips, knees, andtarsi and in the L3-4 segmental distribution was lessfrequent in the foundry workers.

Radiological Findings In the lumbar spinethe foundry workers had more disc degeneration ofgrades 2, 3, and 4 and less of grade o than the con-

trols (Table IV). Grade 3-4 disc degeneration was

encountered in i8% of the foundry workers and inII% of the controls and was more frequent at allages in the foundry workers (X2 = 4-5, p 0oO4).

The number of discs affected was similar in thefoundry workers and controls, 25% and 27%respectively having involvement of four or more

discs. The control group included 79 coal-miners

who are known to exhibit severe disc degeneration(Kellgren and Lawrence, 1952). When these were

removed the prevalence of grade 3-4 disc degenera-tion fell slightly, the mean equivalent rate, aftercorrection for age distribution, being io% com-

pared with I2% in the total control group and i8%in the foundry workers. The difference between thefoundry workers and non-miners, taking age intoaccount, is highly significant (P < o-ooi).Of the foundry workers, the moulders and general

labourers showed the greatest frequency of discdegeneration, 20% and 22% respectively havinggrade 3-4 disc degeneration. Grade 4 disc degenera-tion, however, was found only in moulders. Thehigh prevalence and severity of disc degeneration inmoulders cannot be explained by age distributionsince half of them were in the youngest age group,

but the labourers had less than a third in this age

group and would thus be expected to have a higherprevalence. There was no difference between those

44

1240t4690

12425

10

2*

i625

305*

31:

St

3:5

4*

I86o

4089

3422

I78

13I8

43I4

57I8

206

II

726

2959

7tI6

52

914

I9I*

I515

2*4

I327

2051

2314

106

IOI3

I88

35IO

85

8

34

6I5

ot5

20

34

20

4*3

I2

3.73.3

4-0I8.7

8-66.7

3.73-0

3.70ol0-II.4

I2-93-0

5.04.34.2


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TABLE IVLUMBAR Disc DEGENERATION

Total Grade of Lumbar Disc DegenerationX-rayed

Age

45

No. of Individuals withGrade I-4 Degeneration inFour or more Discs

0 I 2 3 4 2-4 3-4 Actual(%) (%)

Foundry Workers35-4445-5455-6465+Total

I17 27 17 62 9 2 62 9 10I02 7 II 63 I9 2 82 2I 3265 4 2 42 i6 I 89 26 276 0 0 3 3 0 IOO 50 3

290 38 30 170 47 5 76 i8 72

Mean equivalent rateControls35-4445-5455-6465+Total

I8%*

II4 48 I2 48 5 I 47 5 8103 12 12 66 13 77 13 4064 7 6 39 II I 80 I9 276 4 2 100 33 3

287 67 30 I57 3I 2 66 II 78

Mean equivalent rate I2%Controls without minersand heavy industry

35-44 i 75 34 8 31 I I 44 3 445-54 75 8 8 49 IO 0 79 13 2955-64 54 7 4 34 8 I 8o I7 2665+ 4 0 0 3 I 0 IOO 25 2Total 208 49 20 II7 20 2 67 II 6i

Mean equivalent rate IO%

93I4'5025

25

739425027

539484029

25

*P < O-OOI.

workers in the large foundry and those in the smaller had radiographs of this region (Table V). Controlfoundries as regards frequency and severity of radiographs of the dorsal spine were available inlumbar disc degeneration. only I I4, ofwhom 8I% had grade 2-4 disc degenera-

In the dorsal spine disc degeneration grade 2-4 tion. These were not selected in any way but repre-was found in 70% of the 289 foundry workers who sent the second half of the Leigh survey. After

TABLE VDORSAL Disc DEGENERATION

Total Grade of Dorsal Disc DegenerationX-rayed

Age No. of Individuals with Grade I-4Degeneration in Eight or more Discs

0 I 2 3 4 2-4 Actual(%)

Foundry Workers35-4445-5455-6465+Total

117 42101 2I

65 86 0

289 7I

3 66 6 0 6i 05 59 i6 0 74 2I 29 26 I 86 30 3 3 0 IOO I9 157 51 I 70 6

Equivalent average rateControls35-4445-5455-6465+Total

80%

44 II 3 25 5 0 68 I49 4 I 33 II 0 90 415 I I 9 4 0 87 I6 0 I 2 2 I 83 I

I14 i6 6 69 22 I 8I 7

Equivalent average rate 82%

02SI72

6

287'76

8


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J. S. Lawrence, M. K. Molyneux, and Ianthe Dingwall-FordyceTABLE VIA

RADIOLOGICAL OSTEO-ARTHROSIS OF THE HANDSFoundry Workers Controls

Total GradeX-rayed

0 I 2 3 4 2-4

TotalX-rayed

Grade

0 I 2 3 4 2-4

Distal Interphalangeal joints35-44 I20 I45-54 i0655-64 6765+ 6Total 299 2

Proximal Interphalangeal joints35-44 I20 145-54 I0655-64 6765+ 6Total 299 2

Metacarpophalangeal Joints

Io6 9 4 I76 8 I9 326 I7 I9 52 I 3 0I0 35 45 9

II6 0 4 0

94 5 7 0

50 5 II I4 I I 0

264 II 23 I

35-44 I20 II2 3 5 045-54 I06 83 I0 II 2

55-64 67 45 5 I3 465+ 6 3 I 0 2Total 299 243 19 29 8

Carpometacarpal and Intracarpal Joints35-44 I20 II3 6 I 045-54 I06 88 7 I0 I55-64 67 48 9 5 565+ 6 I 2 2 I

Total 299 250 24 i8 7*p < 0-05.

0 I19*0 io6O 67O 65+0 I8%* 298

00000

I19*io6676

8%* 298

0 119*0 io60 670 60 12% 298

0 II9*0 io60 670 60 8% 298

I05 6 7 I6i II 33 I27 II 24 50 I 3 2

I93 29 67 9

ii6 I 2 0

96 7 3 05I 7 8 I3 I 2 0

266 i6 I5 I

I05 9 5 072 i8 i6 040 9 i6 23 2 0 I

220 38 37 3

I06 I0 3 078 I3 I4 I43 II II I4 0 I I

23I 34 29 3

TABLE VIBRADIOLOGICAL OSTEO-ARTHROSIS OF THE SPnE ND LOWER LIMBS

Foundry Workers ControlsAge

Total GradeX-rayed

0 I 2 3 4 2-4

Total GradeX-rayed

0 I 2 3 4 2-4

II7 85 23 8 I102 64 25 II 265 39 I5 8 36 3 2 0 I

290 I9I 65 27 7

ioo 82 II 6 I64 43 I3 7 I6 4 0 2 0

170 I29 24 I5 2

98 93 3 2 0

64 52 8 4 06 4 I I 0

178 157 14 7 0

ii8 100 I2 6 0I03 73 I7 I2 I67 42 II II 36 2 I 3 0

294 217 41 32 4

0 II40 I030 640 60 12%* 287

0 7%* 280 I3%* 640 60 98

0 2% 280 6% 640 60 98

0 I140 IO10 670 5

0 I2%* 287

6I 33 I9 I50 36 I5 229 20 I2 32 I 3 0

I42 90 49 6

20 3 5 0

33 II I5 53 2 I 0

56 i6 21 5

26 I 0 I53 8 2 I5 I 0 0

84 10 2 2

95 IO 9 06o I9 I9 3I9 20 22 42 0 3 0

I76 49 53 7

46

Age

00000

00000

00000

00I0I

26%

5%

'3%

11%

Lunbar Spine35-4445-5455-6465+TotalHips45-5455-6465+TotalSacro-iliac Joint45-5455-6465+TotalKnees35-4445-5455-6465+Total

*P < o*oi.

00000 19%

O I8%0 31%00

0 4%0 5%00

00202 22%


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Age Total


TABLE VIIDisc PROLAPSE IN FOUNDRY WORKERS

Grade of Disc Prolapse

Cervical

Actual Expected

0 I 2 3 I-3 2-3

Lumbar

Actual Expected

0 I 2 3 I-3 2-3

I I 00

I 00

I 2 0 3-Il% I-41%

6 3 27 5 I3 5 2

0i6 13 5

correction for age distribution the proportions were8o% in the foundry workers and 82% in the con-trols. Changes were present in eight or more discs in6% of the foundry workers and 8% of the controlsafter age-correction. It may be concluded that thereis no increase of degenerative disc change in thedorsal spine in foundry workers.

Osteo-Arthrosis The foundry workers hadsignificantly less osteo-arthrosis than the controls inthe apophyseal joints of the lumbar spine and in thedistal interphalangeal joints of the fingers but par-ticularly in the knees and hips (P < o oi). In noneof the joints was there significantly more osteo-arthrosis in the foundry workers (Table VI). Thelowest prevalence of osteo-arthrosis of the hips wasfound in the miscellaneous group of foundryworkers, ofwhom only 3% had definite radiologicalchanges, and of osteo-arthrosis of the knees in thedressers, only 3% ofwhom were affected.

Rheumatoid Arthritis Only two foundryworkers were diagnosed as having rheumatoidarthritis on clinical examination, and in both casesit was of minimal severity. The expected number ina sample of this age distribution, as calculated fromthe random population samples in the North ofEngland, would be nine (Lawrence, I96I). Becauseof the small numbers there was no significantdifference between foundry workers and the generalpopulation. Radiological evidence of erosive arth-ritis was found in 26 (9%) of the foundry workersand in 2I (7%) of the controls. In all but one ineach group it was of minimal severity. Persons withsevere rheumatoid arthritis are unable to undertakeheavy manual work, which may well account for thelower prevalence of this disease in the foundryworkers.

Other Diseases A diagnosis of disc prolapsewas made in 36 of the foundry workers. Of those

with disc prolapse, 33 had lumbar prolapse alone,two cervical alone and one both. Of those withlumbar disc prolapse, i6 had it at grade i severity,and i8 at grade 2-3 (Table VII). The numbersexpected to have lumbar disc prolapse judged fromthe population sample in Leigh would be fivegrade i and five grade 2-3. There was thus more

than three times the expected amount of lumbardisc prolapse in the foundry workers, a very signi-ficant increase. The increased prevalence of lumbardisc prolapse was not limited to any one occupationin the foundry, those affected being evenly distri-buted among the occupational groups. Cervicaldisc prolapse was found to have approximately thesame prevalence as in the random sample.

Spondylitis was diagnosed on clinical examinationand confirmed by radiography in two foundryworkers. This prevalence of o-7% is not signi-ficantly greater than the prevalence of 0o4% notedin men from random population surveys in theNorth of England (Lawrence, I963). Radiologicalevidence of sacro-iliitis was noted in 4% of thefoundry workers and in 4% of the controls. Exceptin the two foundry workers with spondylitis, it wasof minimal severity. Other connective tissue dis-orders encountered were capsulitis or synovitis ineight foundry workers, Dupuytren's contracture intwo, bursitis in three, and gout in three.

Relationship of Symptoms and Loss ofWork to Radiological Changes

Comparison of Foundry Workers and Controls Arelationship between the radiological changes ofosteo-arthrosis in the hips, knees, and joints of thehands and pain in the region of these joints has beendemonstrated in random population samples (Bier,Bremner, and Lawrence, I965). Disc degenerationin the lumbar spine has similarly been shown to berelated to back-sciatic pain (Lawrence, de Graff, andLaine, I963). No relationship was found in those

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35-4445-5455-6465+Total

I20io6676

299

*P < 0*00I .

9.44%* 5-2I%*


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studies between dorsal disc degeneration and dorsalpain or between osteo-arthrosis of the dorsal orlumbar apophyseal joints and symptoms. In TableVIII the frequency of pain and incapacity at varioussites in the foundry workers is compared with the

Site of X-ray Changes

Disc degeneration lumbar grade 3-4 DI2-L2L3-4L5-S2

expected frequency determined from the Leighrandom sample after adjustment for age and fre-quency of radiological change. Despite a higherprevalence of lumbar disc degeneration in thefoundry workers there were fewer symptoms than

3 Months +

Expected

135.5 got 76 5 59 28.551.0 I2t 34-5 7t 13.533-0 25 210 i6 10-5

Observed

I50*5*

Osteo-arthrosis grade 2-4HipsKneesFirst carpometacarpal jointWristsDistal interphalangeal jointProximal interphalangeal jointMetacarpophalangeal joint

HipsKneesThumbsWristsFingersFingersFingers

7-0

5-8II-0OIIi-840-0I9-4

5 4-0

2 4-4i6 8-67 3-0iIt 8-oI0* 4.6

I 0-5 0'5 7-1 42 2-2 0

9 3-4 3I 2-0 II* 6-4 I2 3-7 I

Expected numbers are those which would have occurred had the ratio of radiological changes and symptoms been the sameamong the foundry workers as it was in the Leigh population sample.N.B.-This table is based on the total workers examined clinically. Of the foundry workers clinically examined, 97% had

a radiograph of the lumbar spine; of the Leigh controls, 96% were X-rayed.*P < 0-05 > O-OI.tp < O*00I.

TABLE IXSYMPTOMS AND ABSENCE DUE TO BACK AND LEG PAIN IN WORKERS EXPOSED TO

RADIANT HEAT IN THE FOUNDRYSegmental No. with Pain No. off Work

of Work Workers Distributionof Pain Expected Observed I Week +

Expected Observed

3 Months +

Expected Observed

DI2-L2 40 619-227.987-7

L3-4 '5.46.7

II-O33.I

41 22.5I5 IO-728 I5-884 490

7* I122 4-83* 7-2I2 22-2

29 io-68 4-9I4 7-55I 23-02* 5-I0 2-22 3-54 io-8

Heat 140 L5-S2 9-7 I3 6.4No heat 6i 4-3 4 2-8Mixed 89 7-6 7 4-7Total 290 2I-6 24 I3.9

Heat = moulders, furnace hands, and welders.No heat = core and pattern makers and dressers.Mixed = other.*Based on the total no. of workers who had radiographs of the lumbar spine.

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TABLE VIIISYMPTOMS AND INCAPACITY FROM PAIN AT CERTAIN SITES IN RELATION TO

AMOUNT OF Disc DEGENERATION OR OSTEO-ARTHROSISSite of Number with Pain Number off WorkSymptoms

Expected Observed I Week +

Expected Observed

Conditions No. of

HeatNo heatMixedTotal

HeatNo heatMixedTotal

I406Ii89

290

1406i89

290

9I2I2*

0*000

805

I3

3.5 4I.3 02-5 0

7-3 4


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expected and less incapacity from pain in the DI2-L2, L3-4, and L5-S2 segmental distribution. In thecase of the D12-L2, L3-4 pain this difference washighly significant (P < o ooi). Loss of work fromhip pain occurred in only one foundry worker. Inrelation to the amount of osteo-arthrosis, there wassignificantly less pain in the proximal inter-phalangeal (P < o-ooi) and metacarpophalangeal(P c oo5) joints in the foundry workers, and in thehips, first carpometacarpal, and distal inter-phalangeal joints it was also less, though not signi-ficantly so. Incapacity was less from pain at all sitesradiographed except the wrists but was significantlyless (P o o5) only in the proximal interphalangealjoints of the fingers. The miners did not have morethan the expected frequency ofsymptoms in relationto the degree of radiological change.

Comparison of Different Types of FoundryWorkers Since foundry workers are exposed toradiant heat more than other workers and since thepain threshold is known to be influenced by tissuetemperature, it is important to know whether a re-duction in symptoms is related to the degree ofexposure to radiation. The foundry workers havetherefore been divided into three groups (a) themoulders, furnace hands, and welders who are ex-posed to considerable radiation, (b) the core andpattern makers and dressers who work at somedistance from the furnace and the pouring ladles,and (c) a mixed group of general labourers whoseexposure varies.

In Table IX the prevalence of back and leg pain

TABLE XAGE DISTRIBUTION AND GRADEs OF Disc DEGENERATIONIN FOUNDRY WORKERS ExPosED AND NOT ExPOSED

TO HEATConditions of Work

Heat

Age of those .Y-rayed35-4445-5455-6465+Total

Grades of discdegeneration

Total0

2

342-4*P < O-OOI

No Heat

(%)67 4846 3326 I9I

I40

I4010 7.1I5 I10787 62- I23 I6-45 3-6

115 82

(%)28 46I5 26I8 29

6i

6iI5 24.6II i8-o30 49-25 8-20

35 57*

and resulting loss of work in those foundry workersexposed and not exposed to heat is shown and iscompared with the expected prevalence assessedfrom the population of Leigh. The relative amountsof lumbar disc degeneration are not taken intoaccount in this table. It will be observed that thoseworkers who were exposed to heat showed about thesame reduction in pain in the L3-4 distribution andin loss of work from this cause as those not exposedto heat, and the expected amount of pain in the othersites. The radiological changes of disc degenerationin the lumbar spine (Table X), however, were signi-ficantly greater at grades 2-4 in those working inheat (P < o ooi) despite the fact that these workerswere younger than those not so exposed and wouldbe expected to have less disc degeneration. Thus itwould be expected that the 'hot' workers wouldhave much more pain.

Discussion

One of the most striking features in this surveywas the low prevalence of rheumatic complaints inthe foundry workers, particularly those complaintsassociated with prolonged incapacity.

This contrasts with data from the Ministry ofPensions and National Insurance and with the find-ings of Vernon (I92I) already mentioned. The largenumber of claims on the Ministry of Pensions andNational Insurance may well reflect a very con-siderable number at risk in the population but itindicates the need for surveys of other groups ofmetal workers. Vernon's data were derived from acomparison between certain groups of workerswithin the foundries, and no comparison was madewith the general population.The low complaint rate which we have en-

countered in the foundry workers cannot beattributed to poor memory for past painful episodessince there were fewer complaints present at thetime of the survey. The deficit of prolonged in-capacity was related mainly to knee, thigh, andtarsal pain. The low frequency of thigh and kneepain may be explained in part by the diminishedfrequency of osteo-arthrosis in the hips and knees inthe foundry workers. It would, however, be ex-pected that some thigh pain would result from thelumbar disc degeneration, which was more severe inthe foundry workers. The third lumbar disc wasmore often affected than any other in the foundryworkers, and the fourth was also commonly in-volved. Pain referred from these segments of thespine is felt in front of the thighs (Kellgren, I940).Thus it would appear that some other factor isresponsible. A possible explanation is that the painthreshold is raised as a result of the warm dry

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PATTERN MAKERS

- 9

||4 |l 1 7 1

6 3

FIG. I. Thermal environment in the iron foundry. Location: (i) Ladle driver IO ft., 30';(2) mould making; (3) mould pouring (a) 20 ft., back pot, (b) Io ft., front pot, (c) io ft.,front pot; (4) full hot moulds; (5) tapping 20 ft., 600; (6) mould pouring front I5 ft.;(7) mould pouring front 20 ft., 300; (8) mould pouring side I5 ft., 5'; (9) mould pouringfront I2 ft.; (IO) mould pouring front 200, 300; (ii) after pouring; (I2) furnace.

atmosphere in the foundry, or from exposure toradiant heat from the molten metal. A relationshipbetween pain threshold and tissue temperature isknown to exist, and it has been found that thesymptoms of both disc degeneration and osteo-arthrosis are less frequent and disabling in minersworking in warm dry seams than in those in coldwet seams (Kellgren, McGowan, and Hughes, 1948;Lawrence, I955).

Because of a possible association between expo-sure to radiant heat and the low prevalence ofmusculo-skeletal pain in these foundry workers, itwas decided to study the conditions of work, par-ticularly with reference to air temperature, radiantheat, and humidity.Measurements were made in a typical small

foundry during the pouring of molten iron(I,5oo0C.). The intensity of radiation incident on

TABLE XITHERMAL ENVIRONMENT IN II POSITIONS

Position of Instruments inRelation to Hot Surface

Distance Angle(m.) (0)

Temperature

MeanRadiantTemp.

I RelativeHumidity

Dry Bulb Wet Bulb (%)

I Ladle driver

2 Mould making3 Mould pouring

4 Full hot mould

5 Tapping6 Mould pouring7 Mould pouring8 Mould pouring9 Mould pouringio Mould pouringii After pouring

(a) 3 30(b) 3 30

(a) 6 Back(b) 3 Front(c) 3 FrontCentre(I-5 m. above)

6 605 Front6 305 54 Front6 30

Centre(I-5 m. above)

OF. °C. OF. °C. OF. °C.(a) 0-05(b) 0-05

300 I49 65 i8 59 15 70 4 5345 174 73 23 64 I8 63 22-9 (a) 0-05

(b) 0o30(c) o-i6

379 I93 69 2I 6i i6 63 54.90-070l10

O-I4o-o6o-i8

0-15

330 I66 79 26 67 19 54 9-0Mean radiant heat energy O-I2

Technique of temperature and humidity measurements: (i) radiant heat, measured by radiation thermopile; (2) mean

radiant temperature of surroundings, measured by globe thermometer; (3) air temperature and relative humidity, measuredby dry and wet bulbs of whirling hygrometer.

5o

Location Vel.Air(m./min.)

Thermopile,RadiantHeat(watts/cm.')


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the workers was determined with a radiation thermo-pile. For comparative purposes, measurements ofthe intensity of radiation were made with the same

instrument during radiant heat treatment in a

physiotherapy department.Thermal measurements, made in i i places in the

foundry (Fig. i), indicate the variation of workingconditions (Table XI).The mean radiant temperature of the surround-

ings measured by the globe thermometer in loca-tions 2, 3, 4, and ii varied between 149gC. and193°C. These readings were taken during the shortperiod of intense radiant heat directed from thesurface of the molten metal. During these opera-

tions there was a relatively small increase in airtemperature and a reduction of humidity. The airmovement throughout the foundry was low, varyingbetween 4.5 and 54.9 metres/minute.

In the foundry, the radiant heat incident upon thebody of the lightly clothed workman varied betweeno o5 and o030 watt/cm.2, with a mean value ofO12 watt/cm.2, in eight locations. The exposure isintermittent and transitory, these conditions beingexperienced for approximately two hours on each oftwo days per week.The results obtained in the foundry using the

radiation thermopile have been compared with theradiant heat experienced during heat therapy(Table XII).

TABLE XIITHERAPEUTIC RADIANT HEAT

('Radiant' and Infrared)Method Power of Heat Distance

Source (W) (cm.)

Radiant heatRadiant heatInfraredInfraredInfrared

1000I0006006oo600

7658765858

Thermopile,Radiant Heat(watt/cm.2)

o-i60370-220.300-31

In comparison, a patient undergoing 'radiant heat'therapy can be exposed to between o-i6 ando037 watt/cm.2, whereas the exposure during 'infra-red' therapy is between o022 and 0-3I watt/cm.2. Innormal circumstances heat therapy would normallybe given for three periods of 30 minutes each weekfor two months. Relief of pain occurs in some 8o%ofrheumatic sufferers during such therapeutic expo-

sures and has a mean duration of I0 hours followingexposure to radiant heat (Lawrence and Sladden,I955). In some patients relief may last up to 48hours, and it seems reasonable to suppose that inthose with mild rheumatic disorders the complaintrate and capacity for work might be influenced by

the amount of radiation received in the foundry.The increased prevalence of disc degeneration in

the foundry workers is not unexpected. An associa-tion between heavy lifting and disc degeneration hasalready been demonstrated in other occupations(Lawrence, I955). Although mechanical lifting hasnow replaced much of the heavy manual workassociated with foundries, the earlier years mustinevitably have produced permanent changes in thediscs. The greater prevalence of disc degeneration inthose foundry workers directly exposed to hot con-ditions may be due to the heavier nature of theirwork, but a higher pain threshold might also play apart. The relatively high prevalence of symptomsdue to lumbar disc prolapse may be explained by thefact that pain in these cases is due to root pressurewhich may not be influenced by tissue temperatureto the same extent as referred pain. Moreover, theinitial symptoms of disc degeneration are more likelyto go unheeded by a worker in a warm environmentuntil rupture of the annulus ensues.The lower prevalence of osteo-arthrosis in the

weight-bearing joints, such as the hips, knees, andlumbar spine, suggests an influence of body habitus.Obesity has been shown to be associated with agreater prevalence of osteo-arthrosis in these jointsand was in fact less frequent in the foundry workers.Only I5% of the foundry workers were graded ashaving even minimal obesity compared with anexpected rate of 31% as judged from the Leighrandom sample in this age distribution. An unex-plained association between obesity and osteo-arthrosis of the distal interphalangeal joints wasnoted in the Leigh random sample and is reflectedin a low frequency of osteo-arthrosis in these jointsin foundry workers (Keligren and Lawrence, I958).The absence of obesity in foundry workers is pre-sumably associated with the strenuous nature of thework and the relatively warm working conditions.

We wish to express our thanks to members of theNorth Western Ironfounders Employers' Associationand the National Light Castings Ironfounders' Federa-tion, Glasgow and to officials and members of theAmalgamated Union of Foundry Workers and theTransport and General Workers Union for their willingco-operation in this survey.We are indebted to Professor R. E. Lane and Dr. W. R.

Lee for much advice, helpful comments, and criticism.

REFERENCES

Atlas of Standard Radiographs of Arthritis (I963). Blackwell,Oxford.

Bier, J., Bremner, J. M., and Lawrence, J. S. (I965). In press.Bremner, J. M. (I96I). Ann. rheum. Dis., 20, 149.Kellgren, J. H. (I940). Clin. Sci., 4, 303.

, McGowan, A. J., and Hughes, E. S. R. (1948). Ibid.,7, 13.

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52 J. S. Lawrence, M. K. Molyneux, and Ianthe Dingwall-Fordyce

Kellgren, J. H., and Lawrence, J. S. (I952). Brit. J. industr. - , de Graff, R., and Laine, V. A. I. (I963). In TheMed., 9, I'97. Epidemiology of Chronic Rheumatism. Ed. by M. R.

- and- (I958). Ann. rheum. Dis., 17, 388. Jeffrey and J. Ball under the direction of J. H. Kellgren,Lawrence, J. S. (I955). Brit. J. industr. Med., I2, 249. Vol. 2, p. 98. Blackwell, Oxford.- (I96I). Ann. rheum. Dis., 2o, ii. and Sladden, R. J. (i955). Ann. phys. Med., 2, 282.- (I963). Brit. J. clin. Pract., 17, 699. Vernon, H. M. (I921). J. industr. Hyg., 3, 93.- and Bennett, P. H. (I960). Ann. rheum. Dis., 19, 20.


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