Occupational and Environmental Medicine 1996;53:46-50

Lung function in Lancashire cotton and manmade fibre spinning mill operatives

David Fishwick, Angela M Fletcher, C Anthony C Pickering, Robert McL Niven,E Brian Faragher

AbstractObjectives-This survey was conducted toinvestigate current lung function levels inoperatives working with cotton and manmade fibres. Dust concentrations, smok-ing history, and occupational details wererecorded so that factors influencing lungfunction could be identified.Methods-A cross sectional study ofrespiratory symptoms and lung functionwas made in 1057 textile spinning opera-tives of white caucasian extraction. Thisrepresented 96-90/o of the total availableworking population to be studied. Most(713) worked currently with cotton. Theremainder worked with man made fibre.Lung function was assessed by measuringforced expiratory volume in one second(FEVI) and forced vital capacity (FVC).Exposure to cotton dust was measured inthe work area and personal breathingzones, and retrospective exposure to cot-ton dust over a working life was estimatedwith accurate work history and best avail-able hygiene data.Results-3-5% of all operatives had byssi-nosis, 55 (5.3%) chronic bronchitis, 36(3.5%) work related persistent cough, 55(5.3%) non-byssinotic work related chesttightness, and 56 (5.3%) work relatedwheeze. A total of 212 static work areadust samples (range 0-04-3-23 mg/M3n) and213 personal breathing zone samples(range 0-14-24*95 mglm3) were collected.Percentage of predicted FEV, wasreduced in current smokers (mean 89-5,95% confidence interval (95% CI) 88-91)in comparison with non-smokers (93.1,90.5-94.1) and FVC was reduced in opera-tives currently working with man madefibre (95.3, 93.8-96.9) in comparison withcotton (97.8, 96.6-99.0). Regression analy-sis identified smoking (P<0.01), increas-ing age (P<0.01), increasing time workedin the waste room (P<0.01), and male sex(P<0.05) as being associated with a lowerFEV, and FVC. Current and retrospectivecotton dust exposures did not appear aspredictor variables in the regressionanalysis although in a univariate analysis,FEV1 was reduced in those operativesexposed to high dust concentrationsassessed by personal and work area sam-pling.Discussion-This study has documentedloss of lung function in association withexposure to cotton dust. Those operativeswith work related symptoms had signifi-

cantly lower FEVy and FVC than asymp-tomatic workers. Although lung functionseemed to be affected by high dust expo-sures when operatives were stratified intohigh and low exposure groups, regressionanalysis did not identify current dust con-centrations as an independent factorinfluencing loss. Smoking habit was foundto explain most ofthe measured change inFEVy and FVC. It is likely that smokingand dust exposure interact to cause loss oflung function in cotton textile workers.

(Occup Environ Med 1996;53:46-50)

Keywords: byssinosis; lung function; cotton dust

Byssinosis is a respiratory disease primarilyassociated with workplace exposure to cottondust characterized by chest tightness that isworse on the first day of exposure to cottondust after a break from work. Despite early ref-erences to the disease known commonly todayas byssinosis,' 2 it was to be almost 100 yearsbefore serious epidemiological work wasundertaken both in the Lancashire cottonmills and in mills throughout the other cottonproducing countries of the world.34 The mostrecent study of this population has estimatedthe current prevalence of byssinosis to be3-6%.5 This seems to be falling in comparisonwith earlier papers.3

This cross sectional study was performed todocument the prevalences of work relatedrespiratory symptoms in current textile work-ers and to associate them with dust exposuresand measured lung function.

MethodsA cross sectional analysis of respiratorysymptoms and lung function was made at 11spinning mills in Lancashire. Two of theseprocessed man made fibre, one a mix of cottonand man made fibre and the remaining eightprocessed cotton alone. These comprised atotal consenting population of 360 man madefibre operatives and 730 cotton operatives. Ofthe possible population 97% took part fromvarying work areas in a standard spinning mill.Table 1 summarises the work areas. Table 2shows details of mean age, smoking habits,and sex distribution for each mill. The respira-tory questionnaire was modified from anMRC version designed to identify byssinosis,chronic bronchitis, work related wheeze, andcough.6 Non-byssinotic chest tightness is

Department ofThoracic andOccupationalMedicine,WythenshaweHospital, ManchesterD FishwickA M FletcherC A C PickeringR McL NivenDepartment ofMedical Statistics,University Hospital ofSouth Manchester,Withington Hospital,ManchesterE B FaragherCorrespondence to:Dr David Fishwick, c/oDr Pickering's Secretary,Chest Clinic, WythenshaweHospital, ManchesterM23 9LT.Accepted 17 August 1995

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Table 1 Occupational codings

1 Blow room, opening room operatives2 Card attendant3 Draw, speed frame tenters and combers4 Card room supervisors and instructors5 Other card room operatives6 Spinners7 Doffers8 Spinning supervisors and instructors9 Other spinning room operatives10 Winders11 Winding room supervisors and instructors12 Other winding room operatives13 Managerial staff14 Warehouse staff15 All areas16 Waste room operatives17 Open end mill main work area

shown as a separate category to byssinosis assome operatives complained of chest tightnessthat improved on rest days but did not con-

form to the classic definition of byssinosis-that is, worse on the first working day. "Workrelated" was defined as any symptom improv-ing on rest days or volunteered as being worse

at work.A full work history including current and

previous rooms of work, fibre type used, anduse of respiratory protection was recorded toplace operatives into occupational groups.

Operatives were defined by their current posi-tion and most tended to keep to a particularoccupation for many years.A full smoking history was also recorded.

For the purpose of analysis, operatives havebeen divided into current smokers and a com-bined category for ex and never smokers. Acumulative estimate of lifetime cigarette, cigar,and tobacco consumption has also been used(pack-years).

LUNG FUNCTION ASSESSMENTEach operative was asked to perform a repro-ducible forced expiratory volume in one sec-

ond (FEV1) and a forced vital capacity (FVG)(greatest value of three values within 5%). Asingle dry wedge spirometer (Vitalograph,Bucks, UK) was used for the entire study andmeasurements were made by one of two inves-tigators (DF and AMF). The FEV1 and FVCwere then converted to percentages of pre-dicted values for further analysis with predic-tion equations,7 based on a non-smoking

healthy European working population.Percentages of predicted values have beenused as these were thought to be the most eas-

ily manipulated, understood, and most clini-cally relevant to investigating textile workers.Only those operatives of white caucasianextraction have been used in subsequentanalysis.

Table 2 Personal characteristics and smoking habits by mill ofworkMill n Mean age (y) Men (%) Current smokers (%)

1 58 42 83 472 132 44 79 423 85 42 77 534 51 42 86 565 61 37 73 596 138 33 61 427* 151 37 62 588* 193 31 65 519 56 38 92 4910 32 39 92 4911** 86 37 61 51

*Man made fibre mill; **man made fibre and cotton blend mill.

COYllON DUST SAMPLINGThis was performed in the work area by staticL60 samplers (Rothero and Mitchell, NegrettiAutomation, Aylesbury, Bucks, UK) accord-ing to guidelines set down in the EH25 direc-tive from the United Kingdom Health andSafety Executive8 and as described in a previ-ous publication from this centre.5

Personal breathing zone cotton dust con-centrations were assessed in nine of the 11 cot-ton mills with the Institute of OccupationalMedicine dust sampling head alreadydescribed recently by our group.9

Operatives were each ascribed a static workarea dust concentration to serve as an estimateof their current cotton dust exposure and wereplaced into occupational sets to group opera-tives with similar occupations or cotton dustexposures. All man made fibre operatives weregiven a zero value. All values of current expo-sure were expressed in mg/mi of total dust lessfly.

Each operative was also assigned a personalcotton dust concentration in mg/M3 (exceptmill 2 as this closed before the dust samplingexercise).A measure was also made of cumulative life-

time exposure to cotton dust. The method,previously described,5 used current dust expo-sures in the work area, work history, andknown and estimated previous dust concentra-tions at each mill in the study. Cumulativeexposure of dust was calculated by addingtogether individual exposures in each positionat each mill while being blinded to the currentwork area and number of symptoms.

STATISTICAL METHODSLung function indices are presented as per-centage predicted value for each operative(percentage of predicted FEV, (PPFEV,), per-centage of predicted FVC (PPFVC)). Meansof these and the 95% confidence intervals(95% CIs) are used to compare lung functionbetween symptom and dust exposure groups.Statistical significance was set at the conven-tional 5% level.

REGRESSION ANALYSISForward stepwise analyses were performed toidentify those factors independently influenc-ing the level of current lung function and toestimate the relative magnitudes of theireffects. Percentages of predicted FEV1 andFVC were in turn tested against a variety ofpotential predictor variables including age,sex, current and previous workrooms, thethree variables of exposure to cotton dust (pre-sent and past exposure, and personal dust)and smoking data. For each lung functionvariable, the order in which significant factorsentered the equation is indicated along withthe corresponding P and cumulative R2 values.

ResultsTHE STUDY POPULATIONA total of 1057 operatives out of a possible1090 (97%) took part in the study. Those whorefused to take part in this study were of similar

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Table 3 Lung function results for operatives with and without byssinosis, across allfibretypes

PPFEV, PPFVCSymptoms Mean (SD) 95% CI Mean (SD) 95% CI

Byssinosis (n = 36) 76-0 (16 5) 70-0-81-5 85-2 (13 7) 80-1-89-7No byssinosis (n = 1008) 91-7 (17-0) 90-7-92-8 97-4 (15 8) 964-98-4Chronic bronchitis (n = 55) 82-7 (21-7) 770-88-4 90-8 (17-3) 85-5-96-2No bronchitis (n = 953) 92-3 (16-6) 91-2-93 3 97-8 (15-3) 96-8-98-4Non-byssinotic chet tightness (n = 55) 90 9 (19-4) 856-96-1 97 5 (19-3) 92-5-102-0No non-byssinotic chest tightness (n = 953) 91-8 (16-8) 90-7-92-9 97-4 (15 5) 966-98-4Work related wheeze (n = 56) 85-7 (16-7) 81 3-90 1 93 4 (15-2) 89-5-97-4No work related wheeze (n = 952) 92-1 (16-8) 91-1-93-2 97-6 (15-8) 966-98-6Work related cough (n = 36) 86-5 (19-7) 80-0-92-9 96-2 (16-0) 90 9-101 0No work related cough (n = 972) 91 9 (16-9) 90 9-93-0 97 5 (15-7) 96-5-98-4

Table 4 Lungfunction andfibre type.

PPFEV, PPFVCMean (95% CI) Mean (95% CI)

Cotton operatives 91 3 (90 2-92 8) 97-8 (966-99 0)Man made fibre 90-6 (88-8-92 3) 95-3 (93-8-96 9)

Table 5 Current static cotton dust concentration andcurrent personal dust exposure ranges (mglm3)

Current static cotton Current personal dustMill dust concentration range (n) exposure range (n)

1 0-15-3-23 (28) 0-25-16-71 (39)3 0-30-2-36 (26) 0 35-8 94 (25)4 0-12-0-71 (20) 0-17-8-32 (14)5 0-21-2-94 (26) 0-61-22-79 (22)6 023-1-89 (28) 0-48-6-03 (30)8 0-06-035 (19) 0-242-02 (20)

84 0.04-0 37 (6) 0-73-17-32 (7)9 0-34-180 (19) 056-24-95 (15)10 0 10-2-39 (20) 0-88-16-28 (10)11 0-040-28 (20) 0-14-223 (31)

age to those studied and from a range of workareas. Of all operatives 36 (3-5%) had symp-toms of byssinosis, 55 (5 3%) chronic bron-chitis, 36 (3-5%) work related persistentcough, 55 (5.3%) non-byssinotic chest tight-ness, and 56 (5-3%) work related wheeze.

LUNG FUNCTION ANALYSISReproducible lung function data were avail-able on 1043 (98-7%) of a total study popula-tion of 1057 operatives. There was no reasonto suspect that the operatives who refused tobe studied were significantly more impairedthan those who agreed. There were small butsignificant differences in measured lung func-tion between the sexes; mean (95% CI)PPFEVI in women 92-3 (90-5-94.1) and inmen 90-6 (89-3-91 9), and similarly forPPFVC in women 98-2 (96 5-99 9) and inmen 96-4 (95-2-97 5).The PPFEV1 was lower in current smokers

(mean 89-5, 95% CI 88-91) than in ex and

non-smokers (mean 93*1, 95% CI 90*5-94*1).The PPFVC did not differ between smokingcategories.

Table 3 contains lung function data aboutbyssinosis, chronic bronchitis, non-byssinoticchest tightness, work related wheeze, and per-sistent work related cough. Operatives withbyssinosis, chronic bronchitis, and workrelated wheeze had significant impairment oftheir lung function compared with operativeswithout these symptoms.Mean PPFEV, did not differ between opera-

tives currently working with either cotton orman made fibres and PPFVC was significantlyless in workers with man made fibres than incotton workers (table 4).

Table 5 shows the numbers of dust samplescollected and their range at each mill studiedand the differences between sampling tech-niques and between different mills.

Table 6 shows the univariate relationbetween current lung function in those opera-tives exposed to either low or high current dustconcentrations as assessed by current staticwork area and personal zone exposures. Ineach case the FEV, and FVC were lower in thehigh exposure group.

Regression analysis identified a measure ofsmoking, increasing age, increasing total time

worked in the waste room (a traditionallydusty area), and being male as being associ-ated with a lower PPFEV, and PPFVC.Tables 7 and 8 show the corresponding regres-sion results. Regression analysis did not iden-tify past exposure as an independent variableassociated with loss of lung function. Mean(95% CI) past exposure values (per yearworked with cotton) were 0 74 (0 70-0 77)mg/m3 in those with a PPFEV, of 90% or lessin comparison with 0-71 (0-68-0.74) for thosewith PPFEV, greater than 90%.

DiscussionBoth acute, shift related effects'0 and chronic,accelerated lung volume loss" associated withcotton dust exposure are described in the liter-ature. The design of this study did not enableus to measure across shift changes andmeasurements were made as near the begin-ning of each shift as possible to attempt toreduce any "acute" effect of cotton dust expo-sure. Lung function data were available inmost of the operatives in this study. Fourteenoperatives either refused to have the investiga-tion performed for varying reasons or wereunable to produce a satisfactory reproduciblespirometric curve.

In this study, female operatives were found

Table 6 Comparison ofPPFEV, in low and high exposure groups

Current static cotton dust Current personal dust

High exposure Low exposure High exposure Low exposure(> 0-5 mg/r3) (<05 mg/r3) (> 0 5 mg/r3) (<0 5 mg/m-)Mean (SD) 95% CI Mean (SD) 95% CI Mean (SD) 95% CI Mean (SD) 95% CI

n 432 611 263 497PPFEV, 90-1 (17-7) 88-5-91-7 92 0 (16-9) 906-93-3 90 4 (16-9) 88-3-92-4 92-8 (17-0) 91-2-94-2

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Table 7 Regression analysis results for PPFEVJ as the dependent variable

Predictorvariable Estimate SEM R2 value P value f

Smoking (pack-years) -0 0110 0-0021 6 34 <0 01 70-6Age -0-2399 0-04246 8-67 <0 01 26 5Duration in waste room (y) -1-012 0-3596 9 37 <0 01 8 1Cotton grade:

1 100-3 1-646 )3 108-2 2-282 I5 98-56 1-921 > 11-15 <001 5-26 102 4 1-837 I8 1027 2326 J

Sex 2-398 1 101 11-56 <005 4-75

Table 8 Regression analysis results for PPFVC as the dependent variable

Predictorvariable Estimate SEM R value P value f

Smoking (pack-years) -0-0048 0 0019 1-93 <0 01 20-5Age -0-1425 0-0396 5-37 <0 01 11-4Duration in waste room (y) -1-081 0-3354 6-36 <0 01 10 9Cotton grade:

1 100 4 1-535 )3 110 0 2 128 I5 101 1 1-792 4 33 <001 6-506 103-2 1-7148 1047 2 169

Sex 2-250 1-027 6-79 <0 05 4-80

to have significantly greater PPFEV, andPPFVC, both with univariate analysis andregression. Early epidemiological work tendednot to comment on differences between men

and women as most dusty occupations were

carried out by men. Subsequent studies have,however, identified some sex differences.'213Elwood et al'4 also documented less loss oflung function over time in women whosmoked than in men who smoked. This paperalso suggested other possible reasons for theobserved reduction in lung function of cottonworkers with particular reference to social cir-cumstances, nutrition, and their reducedheight. The differences in this study were

small and probably of no clinical significance.The effect of respiratory symptoms on lung

function, other than those of byssinosis, were

also considered in this study. Except for byssi-nosis, there is a paucity of epidemiologicalinformation in previous studies on symptomsand their associated physiological abnormali-ties.

Operatives without byssinosis who com-

plained of work related wheeze had a lowerPPFEVI and PPFVC than those without thissymptom. Some of these people volunteeredthe fact that they had asthma and that thework environment made the wheeze worse. Itis possible that a proportion of these peoplewere workers with pre-existing asthma thattended to be exacerbated at work. A propor-tion, however, had become wheezy as a conse-

quence of their work with cotton and thesignificance of this remains obscure as thesepeople seemed not to have had byssinoticsymptoms. A possibility is that some peoplebecome sensitised to a particular agent at workand have developed a form of occupationalasthma discrete from the condition byssinosis.

One of the long term purposes of this study isto consider this issue.

Operatives with non-byssinotic work relatedchest tightness and work related cough did notseem to have notably impaired lung functioncompared with operatives without this addi-tional symptom. This tends to imply that sig-nificant airflow obstruction was not the causeof these symptoms, although the lung functionassessment was made only on one occasionand consequently did not reflect physiologicalchanges when the symptom was being experi-enced nor did it enable conclusions to bedrawn about falls in FEVI in these people dur-ing a shift.

Chronic bronchitis was a commonlyreported symptom in those with byssinosis andalso an isolated symptom. As early as 1955,Schilling et al noted a smaller loss in lung vol-umes in cotton workers with chronic bronchitisthan in byssinotic workers. In this study, therewas a large overlap between byssinosis andchronic bronchitis, with 20% of all byssinoticworkers complaining of work related phlegmproduction on a regular basis compared with abackground rate in all other operatives ofabout 5%.15 This reaffirms the original con-cept suggested by Massoud et al of two distinctforms of byssinosis; pure byssinosis andbyssinotic symptoms with chronic bronchitis.'6

Schilling and Lond described early experi-ences in assessment of lung function inbyssinotic workers.'7 They documented dimin-ished maximum voluntary ventilation in gradeone and two byssinotic workers comparedwith control subjects from local Lancashireengineering firms. Belin et al comparedFEVO,75/body height ratio measurements from15 byssinotic workers with a non-byssinoticcontrol population of prisoners.'8 Thebyssinotic values were notably lower. Thesedata are difficult to interpret as smoking datawere not recorded. Beck et al and Zuskin et alsimilarly documented that byssinotic workershad lower mean FEV~s than non-byssinoticworkers.'3 19

The PPFEV, and PPFVC were lower insmokers compared with non-smokers acrossall fibre groups, and the regression analysisranked smoking pack-years as the strongestpredictor variable for both PPFEV, andPPFVC. The exact relation between smokingand lung function abnormalities in the pres-ence of exposure to cotton dust remains con-troversial. Early epidemiological studiestended not to include information on smokinghabit. Merchant et al documented decrementin lung function in smokers compared withnon-smokers, although men who smoked andhad occupations exposed lightly to dust hadsignificantly better lung function than those inheavily exposed occupations.'2 Their subse-quent work indicated that smoking and dustexposure may act independently to influenceloss in lung volume.20 Imbus concluded thatsmoking was far more important than dustexposure in causing loss of FEV,.2' When dustexposure was considered in this study, divisionof operatives into high and low exposuresseemed to suggest an effect of current expo-

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sure on measured lung function. The regres-sion analysis, however, did not identify arelation between current or past dust measure-ments and lung function. This is contrary tothe findings of Jones et al who studied lungfunction variables in cotton operatives andman made fibre control workers.22 Mill ofwork, current dust concentrations, and occu-pation had no bearing on impairment of FEV,and FVC although an association was foundbetween increased duration of exposure tocotton dust and impaired FVC.

Beck et al suggested that the effects of dustand cigarette smoke may both have an inde-pendent role in influencing loss of lung func-tion.23 They compared 477 cotton textileworkers with 932 non-exposed controls.Cotton workers were found to have signifi-cantly lower FEV, and FVC. The authors pos-tulated that smoking and dust may havedifferential discrete actions on the smaller andlarger airways, respectively; the combinationof which led to the clinical syndrome of byssi-nosis.The present study identified a function of

cotton grade and a measure of duration ofexposure to a known dirty environment as sig-nificant, although smoking pack-years was themost significant predictor of reduced lungfunction. Whether this finding indicates thatthere is a particular agent or quality of cottondust within the waste area that causes acceler-ated loss of lung function is unknown and thisstudy, due to its limitation as a cross sectionalanalysis, cannot add to this intriguing point.

In this study there did not seem to be anobvious effect of fibre type. In fact, meanPPFVC was significantly greater in cottonthan in man made fibre mills. This paradoxicaldecrement in workers of man made fibre haspreviously been documented.'2 The cause forthis finding is not fully understood, but mayrepresent the converse of the healthy workereffect in that operatives who cannot toleratethe cotton exposure, possibly with pre-existinglung disease, may move into a similarly skilledoccupation in a man made fibre process.

It was intriguing to find that the FEV, wassignificantly reduced from predicted values inasymptomatic operatives both in cotton andman made fibre mills. It is difficult to assumethat this was due to a subclinical effect of cot-ton dust on the airways as it occurred equally inoperatives exposed to man made fibre. It may,more likely, reflect the relatively high propor-tion of current smokers in both fibre groups.

In summary, this cross sectional study hasdocumented reduced lung function associatedwith workplace exposure to cotton dust.Operatives with byssinosis, chronic bronchitis,and work related wheeze had significantlyimpaired lung function compared with opera-tives without these symptoms. Women opera-tives and those working with man made fibresor blends seemed to have less impairment of

measured lung function. Regression analysisidentified smoking, however, as the most sig-nificant single determinant of a reduced FEV,and FVC although the duration of cottonexposure in the waste room did enter into theprediction for loss in FEV, and FVC. Thelikely situation is that smoking and dust expo-sure interact in a complicated manner to aug-ment the loss in lung volume.

This study was supported by grants from the Cotton IndustryWar Memorial Trust, the British Cotton Growers Association,Work Peoples Collection fund, Cotton Incorporated, and theCotton Foundation, USA.

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3 Cinkotai FF, Rigby A, Pickering CAC, Seaborn D,Faragher E. Recent trends in the prevalence of byssinoticsymptoms in the Lancashire textile industry. Br J IndMed 1988;45:782-9.

4 Lammers B, Schilling RSF, Walford J. A study of byssi-nosis, chronic respiratory symptoms, and ventilationcapacity in English and Dutch cotton workers with spe-cial reference to atmospheric pollution. Br Jf Ind Med1964;21: 124-34.

5 Fishwick D, Fletcher AM, Pickering CAC, Niven R McL,Faragher EB. Lung function, bronchial reactivity, atopicstatus and dust exposure in Lancashire cotton mill opera-tives. Am Rev Respir Dis 1992;145:1103-8.

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10 Jones RN, Butcher BT, Hammad YY, Diem JE,Glindmeyer HW, Lehrer SB, et al. Interaction of atopyand exposure to cotton dust in the bronchoconstrictorresponse. BrJ Ind Med 1980;37:141-6.

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12 Merchant JA, Kilburn KH, O'Fallon WM, Hamilton JD,Lumsden JC. Byssinosis and chronic bronchitis amongcotton textile workers. Ann Intern Med 1972;76:423-33.

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23 Beck GJ, Maunder LR, Schachter EN. Cotton dust andsmoking effects on lung function in cotton textile work-ers. Am3 Epidemiol 1984;119:33-43.

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