Document daZjKRN3MjEYQmayez0GQD4a9

rItnra v, I VS 3. 35, 644-652 Epidemiological study of respiratory disease in workers exposed to polyvinylchloride dust C A SOL'TAR, L H COPLAND. P E THORNLEY. J F HURLEY, J OTTERY. W G K ADAMS, AND B BENNETT from the Institute of Occupational Medicine. Edinburgh, and Imperial Chemical Industries Limited abstract The respiratory health of workers exposed to polyvinylchloride (PVC) dust has been investigated in 818 men sampled from the work force of a factory manufacturing PVC. In a crosssectional survey, the lung function and prevalences of respiratory symptoms and chest radiographic abnormalities were compared with estimates of individual PVC dust exposures based on detailed occupational histories and current measurements of respirable PVC dust. Complaints of slight exertional dyspnoea were associated with PVC dust exposure, though age and smoking effects were much stronger. Theiforced expired volume in one second (FEV,) and forced vital capacity VC) were inversely related to dust exposure after ace.-height, and smoxintreffects had been taken mtoaccoun t. This effect was seen principally in cigarette smokers, and there'was suggestive evioence That FVCdust exposure-aod-cigatetle smoking interacted in the reduction of FEV, and FVC. Gas transfer factor was not related to dust exposure, the chest radiographs were read according to the ILO U C classification by three experienced readers. One reader recorded a low prevalence of small rounded opacities, and these were not related to age or dust exposure. Another reader recorded a higher prevalence of small rounded opacities category 01 or more, and these were related to age but not to dust exposure. The third reader recorded the highest prevalence of small rounded opacities (though none greater than category 11), and these were independently :elated both to age and to PVC dust exposure, indicating an efTect_of PVC dust on the appearances of the chest radiograph. These appearances were so slight that only the higher sensitivity of this reader in the interpretation of profusion of small rounded opacities on the ILO U,C scale enabled detection of this effect of PVC dust. In conclusion, exposure to PVC dust is associated with some deterioration of lung function, slight abnormalities of the chest radiograph, and complaints of slight dyspnoea. The mean decline in l-EV, associated with the average dust exposure experienced in the study was small, though some of the men with higher dust exposures may have suffered clinically important lass of lung function as a result of their occupation. The dust proJuced during the the manufacture of polyvinylchloride (PVC) includes a large pro portion by number of small particles of respirable size.'2 Administration of PVC dust to animals has been reported to cause inflammatory changes of the bronchioles and alveoli, including a proli feration of histiocytes and granulomatous lesions, ' and PVC formulations have been found to have cytotoxic eflects in vitro.8'1 These effects were caused in part by the plasticisers, stabilisers, and other additives in the PVC. and there is some evidence that the in vitro toxicity of PVC 4, JJrcss Cor rcpr.nt rc.| ,icms l)r C' A Soutur, Institute of (>c > .r'alioniil Mc<`i,,rne. Roshwr^n I sfitthuryh I.HR VSL dust is related to the presence of surfactant in the formulation.81' Case reports10 " have described pathological changes in the lungs of workers exposed to PVC dust. In several surveys of PVC workers increase of respiratory symptoms, abnormalities of lung function and of the chest radiograph have been described, although these findings have been dif ficult to evaluate, principally because of lack of satisfactory control groups, failure to take ade quate account of the c-flects of age. cigarette smoking, or general atmospheric pollution, and lack of clarity in descriptions of radiographic readings - Epidemiological stu Methods STUDY POPVLATIOThe sampft'Tr^e 1979 from lr'dt pensioners (men s manufacturer, m of age) who had 468 men leaving \ Men were selccategories of cui from factory re^ of dustiness base, measurements o dusts. The sam; ail men with he proportions of t! hundred and fifi dust exposures were replaced h' exposed groups Finally 8I n. currently emph men who had Is ment (`leavers' carbon monoxi sampled proper exposure categ> ENVIRONMEM si Current person dust were meain which PVt Preliminary est subjective obse on panicle size sion and emu sampling effort ently more d packing, and i One hundr. samples of rc from men in -l periods on Sfilters (type 1 . 80 <-m, msecyclone.'0 I h fraction of air Johannesburg all particles meter of I v'~. t greater thar i medical m h' A fu 1 occur Medical Res piratory S'I T Epidcmiolofti.al stodv of respiratory disease in workers exposed to polyvinylchloride dost 645 | Methods trained clerk. f Forced expiratory volume in one second (STUDY POPULATION (FEV,) and forced vital capacity (FVC) were The sample to he studied was selected in January measured using a modified Gaensler spirometer.1* 1979 from 15dl currently employed men, 339 The best of three measurements was used for pensioners (men who received a pension from the the analysis. manufacturer, most of whom were over 60 years Single breath transfer factor for carbon mon of age) who had retired since I January 1967, and oxide (Tlco) was measured by the breathhold 468 men leaving for other reasons since that date. ing method'" based on the modified Krogh (Men were selected for study according to broad technique (Transfer lest B. PK Morgan Ltd., categories of cumulative dust exposure derived Chatham. Kent). Effective alveolar volume (Va) from factory records and preliminary estimates was measured by helium dilution in the same of dustiness based on inspection of the plant and single breath, and used in the calculation of measurements of size ranges of typical PVC Tlco and Kco. The means of two observations dusts. The sampling scheme aimed to include were used in the analysis of these measurements. all men with heavier dust exposures, and lesser A full-size postero-anterior chest radiograph was I proportions of those with lighter exposures. One taken by a standard technique (95--120 kV). hundred and fifty-six men with high or moderate The chest radiographs were read independently dust exposures did not attend for survey, and using the ILO U/C International Classification were replaced by reserves drawn from moderately of Radiographs of Pneumoconioses" by three | exposed groups. readers highly experienced in this work. The * Finally 818 men were studied, comprising 663 readers had all been shown previously to pro | currently employed men, 98 pensioners, and 57 duce readings that correlated with measurements f men who had left for reasons other than retire of dust exposure in coalminers and to be highly ment ("leavers"). Single breath gas transfer for consistent in their readings when presented with carbon monoxide was measured in 332 men the same films on separate occasions. They did, sampled proportionally but randomly from each however, represent a range of interpretation of exposure category. profusion of small opacities recorded using the ENVIRONMENTAL SURVEY Current personal exposures to respirable PVC dust were measured by occupation in each plant ILO U/C scale, and were known to differ con sistently from each other in the prevalences of small rounded opacities they recorded. in which PVC was manufactured or processed. Preliminary estimates of dustiness were based onsubjective observation by the sampling team anif on particle size measurements of typical suspen sion and emulsion PNC dusts, and the major sampling effort was directed towards the appar ently more dusty occupations in the drying, packing, and mixing areas. One hundred and thirty reliable personal samples of respirable PVC dust were obtained from men in 44 different occupations for full shift periods on Sartorius cellulose ester membrane filters (type 11301). diameter 37 mm, pore size 80 Mm, inserted into a Casella Simpeds 70 cyclone."' This device samples a "respirable" PVC OUST INDEX Every occupation within the population under study was allotted a PVC dust concentration on the basis of the measured current dust levels. Sixty-six such job/dust categories were derived from the measurements made and from knowl edge of the factory conditions. A "dust index" was derived from the current dust measurements and the occupational history such that the current dust levels in each of a man's occupations in the plastics factory was multiplied by the years he had spent in that occupation, and this figure added to the figures derived from his other occupations in the factory. fraction of airborne dust in accordance with the Johannesburg Convention." including lOO^ of all particles with an equivalent aerodynamic dia meter of 1 Mm. 50".. of those of 5 Mm. and none greater than 7 Mm. STATISTICAL METHODS The data were studied initially by cross-tabula tions, graphical methods, and summary descrip tive statistics. Multiple linear regression analyses of the lung function results were carried out. MEDICAL SURVEY with subsequent examination of residuals. The A full occupational history was recorded, and the radiographic and respiratory symptoms results Medical Research Council Questionnaire of Res were studied b\ maximum likelihood logistic piratory Symptoms'* was administered h> a analysis " * c. l * 1 f . * l> ` ,i . it! ; !>f ::i ! ii* i A \ j (I 11 11 V' : M *I ! ! n IIS! i I Si?: j!li 1!)? ills !;ii iH: :< *;j! i:|i r'. :lf 646 Results ENVIRONMENTAL SURVEY Respirable dust levels were highest in the older plants and those making polymer by the emulsion method. The highest mean average respirable dust exposure for any occupation over a shift was 2 8S mg/m3 (SDl-84). The distribution of calculated dust indices (years X mg/m1) for the 818 men studied in the medical survey is shown in fig 1. MEDICAL SURVEY Features of the population of 818 men are set out in tables 1 and 2. It was noted in preliminary analysis that the number of years worked at the PVC works or work in an outside industry in which noxious materials were used were of trivial importance in explaining the prevalence of symptoms, lung function and radiographic abnormality, after index of dust exposure, age. and smoking habit had been taken into account. Respiratory symptoms Analysis of respiratory symptoms was based cn the answers to the questionnaire. Two hundred and fifteen men (26%) admitted to dyspnoea on exertion grade. 1 ("shortness of breath when hurrying on level ground or walking up a slight hill"). Prevalence was approximately three times higher in the smoking groups (32% in cigarette smokers) than in the non-smokers C A Soutar ltd 1 Ep&miotogu Table 1 Features of SI8 men studied, according to a t urrenlly employed, pensioner, or other leaver stetWL . Dust index is expressed in years x mg/m', but dots not represent actual dust exposure, since only currr*.\ dust levels are known Table 2 Nu< Current morkers Pensioners Number 663 Mean age Cyrs) 44 2 ISO) no > Mean height (cm) 173 0 (SO) (6 5) Mean weight (Kg) 77 7 (SD) (10 5 Mean dust indea 13 39 (SO) (12 84) Years at the plane 14 34 (SD) (8 48) Mean FEV| (1) 3 54 (SD) <0 S3) Mean FVC (1) 4.62 (SD) (Oil) Mean FEV|/FVC 0 76 ISDI 40 OS) 9S 63 4 (7 1) 170 2 (5 4) 75 6 (10 8) 14 23 <11 86) 16 63 (8 06) 2 43 (0 73) 3 41 (0 78) 0 70 (0 11) Leavers 57 43 2 (10 2) 171 2 (6 2) 77 4 <13 5) 4 16 (6 6) 5 46 (3 48) 3 S3 (0 72) 4 34 (0 80) 0 78 (0 06) X-- wwokfn > If ftlOkf > vnokcn Ea makm ' , No relaf dot index ^utum, a>t &. 1 Forced esr Preliminar> loss of FF\ categories, according t ' Bent statu (10%). A strong age effect was also apparent, prevalence approximately doubling for every 13 . account in account of years of age in this population. A dust efTect wit eonsumpti> indicated (p=0054) after adjustment for age >|r Within i and smoking, and-this effect was clear in current1. h 'as signt' cigarette smokers (p<002, 10 dust index units fp<0-0251 increased the estimated prevalence by a factor nor The si of about 20 0) after allowing for age and life index wa time cigarette consumption. The dust efTect was models of not demonstrated in the other smoking cate-, . More d gories. though these differences between smoking j effect of s' categories could have arisen by chance (p<0-5).` | category > pensioner- jf ferences ' have aris- men in s> pattern t>i an inter cmploym ,ng (tahU in currer After Fig 1 Frequency of dust indices. = number of men with dust exposure =fl. Table 3 lor emphnot shots Variable Height u*" Weight (U Age t>n I ^ Liletiff* <1000 pw.> Pull indu- DTH 000043424 t at Epdemialogical study of respiratory disease in workers exposed to polyvinylchloride dust Ilo TiMe 2 Numbers of men and Imean dusl indices) of 818 men grouped by age and smoking category tus. S ent .4ye group* (j ss 5014 n OavtfU imokef* 65 15 :> 3<3 0) V (6 61 a issc? :> M-44 41 (6 T) `>7 112 0) 11 (14 7) 4# i: v) IV7 (U 31 45*49 M)6l((S1624) 1 i:<n m 35 114 51 i:nu 5> $0-54 AiOm(1i6: 63)i H (|<J 4) 41 (16 ?l lift (16 2) 55-59 5 (15 41 3i:5 (IIiSv 4i>1 31 (16 31 101 U1 7) 60 * :ous :i 41 (16 VI 11(11 7) 42 <14 n 1(4 (16 3) .4 If 144 (8 01 min 7i 2S3R4 1(|145 021) sih (i: v 647 No relationships were demonstrated between tat index and history of chronic cough or sputum, asthma or history or acute chest il+ness. height, weight, and smoking habits (the model in table 3), the overall loss of FEV, associated with one dust index unit (years X mg/m1) was estimated as (MXMl litres. This would be equiva Forced expired volume in one second lent to a loss of 53 ml of FEV, for the mean dust Preliminary analysis indicated different rates of index, additional to the estimated losses caused loss of FEV, because of age between the smoking by age and smoking (26 ml per year in non- ategories, and different mean levels of FEV, smokers, 39 ml per year for cigarette smokers recording to current, pensioner, or leaver employ plus an additional 5-6 ml per year for each ment status. These differences were taken into packet of cigarettes smoked per day throughout nt, account in the regression model, which also took the year). 13 account of height, weight, and lifetime cigarette In currently employed cigarette smokers con vas consumption. sidered separately (the model in table 4), the loss ge Within this framework index of dust exposure associated with dust index was estimated as 84 ent *as significantly inversely related to FEV, mis of FEV, for similar exposure, additional to iits (p<0-025) (table 3). Neither the estimated size the loss caused hy smoking and age. The mean for aor the significance of the regression with dust FEV, loss in this group of men in relation to fe- index was. seriously altered when alternative high dust exposure (40 dust index units or more, ''as models of age and smoking were examined. experienced by only 4-3% of all the men) was te- More detailed analysis examined whether the'" c:t mated at 260 ml. mj effect of dust index varied according to smoking 5). category and job status groups (current workers, Forced vital capacity pensioners, or leavers). Though the observed dif A similar sequence of analysis to that for FEV, ferences in dust effect in these groups could was followed, with qualitatively similar results. have arisen by chance (p--0-45) the numbers of There was a neeative effect of dust index on men in some of the subgroups are small, and the FVC (p<0-l). pattern of positive and negative effects suggested Further analysis of dust effect in the smoking an interaction between dust effect, current and job category subgroups again showed a signi employment at the factory, and cigarette smok ficant adverse dust effect in cigarette smokers ing (table 4). The dust effect was seen principally in currently employed cigarette smokers. After taking into account the effects of age. Table 4 Regression coefficients lor dust index against FEVr Expansion of model of regression fur FF.V t illustrated in table 3 Tible 3 Regression of FEVv Different intercepts far employment and smoking categories allowed but not shown Coefficients and signifn ance of concomitant variables changed little from the model described in table 3. Is not significant at the 10" level Yaneblt Height (cm 1 height (kfl A|(vr) I'non-sinokctv 1 es-smokcr? | other gmokers ' curette hmoker> Ufrtime ciiurctic consumption (1000 picks! Dvti m4r lyejr* % m*;m > KvftrflSUm Cttrfficient 0 0434 -0 0012 (I ll2'4l n -O 04AV --0 03: O 01 54 n Otui r 0 OOOl o2 - 0 144)1 0 1X411 ' n [toot s 0 <HH>) - 0 LHXM o o; (.itdjrptie jmokprj () thtr swttkrrs J| .fTT-- ,~ <t< ' 3 i \1 $' . , !.' tI~I. ' ' 1 -* : n-sirlQi,'. Mfeta 648 C A Souior ndf E/tiemiotogical stm Table J Prevalence of categories of small opacities found by three readers in 818 chest radiographs. Radiographs in which both rounded and irregular opacities were found are also represented here in the rounded and irregular categories Small rounded (syaritirs Reader Category Ofl Or more 3 11 (2 20!;) 15 4 (0 49*,) 17 30 (6 11;> Category HO or more : (0 't.i 2 <0 24\> to<i Small irregu'or ofiotttiet Category 0U or more J: (39I-.I 5) (6 4*\> :9<3 55\l Category HO or more 7 10 36M 46 (3 62!.) (0 9M Both rounded W irrettulor Oflocitlet - 1 Category Oil m mm 4 (0 49%) 0 10 oo*;i 4 (0 4\) currently working at the factory (p<003). The observed differences in dust efTect in these groups could easily have arisen by chance, but an inter action between dust effect; current employment, and cigarette smoking was suggested, broadly similar to that for the FEVt. Other measurements of respiratory function The FEV,/FVC ratio, Tlco, Kco, and Va were not significantly related to index of PVC dust exposure, nor was any sizeable effect indicated. Chest radiographs Small rounded opacities The anticipated differ ences between readers in interpretation of small opacities were apparent (table 5). Reader 17 recorded the greatest prevalence of small rounded opacities; 50 radiographs (61%) with category 0/1 or more, 10 (1-2%) with category I/O or more, the latter consisting of six radiographs with category 1/0 and four with category 1/1. Among these 50 radiographs, there was a strong associa tion between classification by reader 17 as cate gory 1/0 or more and classification by either reader 3 or 15 as small rounded opacities cate- Krr-BEAntR cope - - 03 I-- 15 " - 17 gory 0/1 or more (chi-square test, pCOOOfy, confirming that inter-reader differences in into* pretation of small rounded opacities were diff ences of degree, rather than classification rf unrelated appearances. The readings for readers 3 and 17 showed clear relationships between prevalence of smal rounded opacities and age (p<0 002 and p<0-OOT| respectively). The observed data are set out i| iir 0 fig 2. For reader 3. after age had been taken, . py J Prevalent into account, there was no relationship with dial Oil or more found ' exposure (p=0-83). For reader 17 there was i' r $*.. strong dust effect even after age had been taken Index (p<0 02 into account (p<0 001, 10 dust index unit `in found. increased the estimated prevalence by a fact* Reader 15 c. of about 35%). Observed data are set out in fig 1 showing small : The dust efTect varied according to smoking fications were status (p<002). and was not observed among [` Small irreguh current cigarette smokers although the age effect dear relation- was marked. The reason for these differences was not apparent. Reader 17 recorded 10 radiographs showing small rounded opacities category 1/0 or greater, and in spite of this small number, a significant relationship with both age (p<0 005) and dust I,. - ; I0 i iu - i Fig 2 Prevalence of small rnitn 'ed opacities category Oil or more found by three readersr related to age group. : I, l ' etd t Epikmiological study of respiratory disease in m iers exposed to polyvinylchloride dust 649 d irt >001), inter* differon of lowed small : 0-001 >ut in taken n dust was a taken units factor i fig 3. ioking among effect es was t.| i.* J.i ?. v Dust index lyr * m|/mf) F3 Prevalence of small rounded opacities category Qjtor more found by three readers, related to dust inde x. index (p<0 02) (after adjusting for the other) was found. Reader IS classified only four radiographs as showing small rounded opacities: these classi fications were unrelated to age or dust exposure. Small irregular opacities Analysis showed a clear relationship between prevalence of small irregular opacities category 0/1 or greater and age for all three readers (fig 4) <p<0-00l for each reader). There was no relationship of prevalence of small irregular opacities with dust index for any of the three readers. For reader IS the relationship of small irregular opacities with age could in small part be explained by a positive history of chronic cough or sputum <p<0-03), and by history of chest illness (p<0-03). Reader 17 also found a relationship of small irregular opacities with chronic cough or sputum (p<006). but no relationship with history of chest illness. For both readers, the age effect remained extremely strong even when these symptoms were taken into account. Reader 3 found differences between smoking categories. Prevalence of small irregular opacities was lowest in non-smokers (0-7 %) and highest among other smokers (121%). These were not accounted for by the different age distributions of the smoking groups. There was no dust effect. Neither of the other two readers identified smok ing differences. Relationship of lung function to the presence of small rounded opacities Reader 17 recorded small rounded opacities category 0/1 or greater in 50 radiographs. The lung function of these men was significantly reduced. The FEV, lowing reater, ificant 1 dust ( K :all rv OH coders. 10 im - ? ? *- > 31 I ' <vn Fig 4 Prevalence of small irregular opacities qgtgyory 0/1 or more found by three readers, related to age. 650 C A Soutar etd ` Epidemiologies was reduced by a mean of 206 ml 'p<o-02 after age. height, weight, smoking, cigarette consumption, and dust index had been t.en into account (the less complex model dev rihed in table 3). The FVC was reduced hy a mean of 253 ml (p<001), using the same and FEV,/FVC ratio analysed on the log vale was not significantly reduced. Tlco and Y'i> were measured in 21 of these men, and were r t found to be significantly reduced. Va was re tjced in these 21 men by a mean of 309 ml (p^OS). Relationship of lung function to the pr-n-nce of small irregular opacities Radiographs of 90 men were thought b. one or more readers to show small irregular opacities 0/1 or greater. The lung function of O ise men was significantly reduced. Their mean IEV, was reduced by 205 ml (p<0-01) after adjuring for age, height, weight, smoking category, lifetime cigarette consumption, and dust index (O* model in table 3). The mean FVC was reduce? hy 142 ml. using a similar model (p<0-10). T'~e ratio FEV,/FVC was also significantly reduced (p<00l, by a factor of 0-97). Tlco was r insured in 45 of these men, and was reduced b> a mean of 1-52 ml/min mmHg (p<005). Va aid Kco were not significantly reduced. Autoclave workers The effect of a history of work on-the a.toclaves (where exposure to vinylchloride mono~er may have occurred in the past) was examine: in the respiratory symptoms, lung function, ard chest radiographic abnormality models. A h:-:ory of having been an autoclave worker Lad no demonstrable adverse influence on sy--.ptorns, lung function, or chest radiographic at-ormalities. Thus there was no evidence that apparent PVC dust effects were the result of exposure to vinylchloride monomer during c.toclave working. Clinical readings of chest radiographs The chest radiograph of one man showed advanced diffuse pulmonary fibrosis. Tr.s man had a chest radiograph taken though he was not in the intended study sample. The r: evance of his disease to his work is currently Sting in vestigated. but has not yet been est.-'ished. No cases of lung cancer or active tuS.`:ulosis were detected in the survey. Discussion This study yyjs planned to compare c limp function, chest radiographic appearances, art prevalence of respiratory symptoms in workas in a factory manufacturing PVC with estimafs of personal exposure to respirable PVC dust The random sample was selected from men had previously worked in the factory as well a the current work force, and was weighted ta include a relatively high proportion of thos who had the highest lifetime exposure to PVC dust. These preliminary estimates of exposure were based on factors records and a preliminary inspection of the plants and typical dusts pro duced. Twenty-five per cent of selected mea, thought on this basis to have high or moderate exposures, did not attend for examination Reserves for these men were included, albeit that these were from medium rather than high dust exposure groups, to ensure that sufficient numbers of men with substantial exposures were studied. It is emphasised that the dust exposure est mates used in the analysis were not based on these preliminary estimates but on a detailed occupational history obtained from each maa together with measurements of current personal exposures in the factory. These estimates, though * alone i* of m . exposure *as FVC "but mo volume. The ' dust exposur v variations in | ./'caused dints oon in some " posures. The ' was seen r apparent inti / chance but v ."'of dust effect gories. Respi > * food wTappe: __ and in one be more con ettes.*' It interaction \ po$ure repo efTect of pr contaminate dusty hands direct evidei anism. the best available, may nevertheless have beea Assessmet inaccurate to the extent that previous dust ex in chest rac posures may have been higher than those Classificatio presently experienced. In view of probable over The three all changes in dust levels conclusions about quan part in this titative relationships between dust and disease should be drawn with caution. variability radiographs It was not possible in this study to take fjstently fr- account of the health effects of the components small roun of the PVC powder other than the PVC itself, present stu nor of changes in the formulation occurring readers w ever the years. The "respirable" fraction of air recorded 5 borne dust measured in this survey is suitable chest radio for comparisons with both bronchial and alveolar related to disease, for dust in this size range deposits recorded v substantially either in bronchial or alveolar number of zones. Furthermore, measured exposure to "re* was correl pirable" coal mine dust has been shown to correlate with mucous hypersecretion and loss of The third of small r FEV, in miners.-'1'-' as well as with the radio- these op graphic appearances of pneumoconiosis." The study demonstrated a relationship between - independe each of t estimates of exposure to PVC dust and dyspnoea, lung function, and chest radiological abnormality. X history of moderate exertional dyspnoea was related to dust exposure, though this relationship was apparent only in cigarette smokers. This effect was additional to the effects of smoking fically va sensitive recording the dete' graphic profusior and aging which were, however, the predominant explanatory variables for this symptom It seems unlikely (hat the effect of PVC dust on sy mptoms ;/ V Epidemiological study of respiratory disease in workers exposed to polyvinylchloride dust 651 d 1 tlone is of much clinical importance. PVC dust many cases did not even record their s j exposure was related to reduction of FEV, and presence. On clinical readings of the radiographs s > FVC but not of transfer factor or alveolar there were no cases of advanced pulmonary 4 volume. The mean decline of FEV, related to fibrosis among them, except for one man, not in o dust exposure Ws small, though individual the study population, who did have radiographic s J variations in response might be expected to have evidence of advanced pulmonary fibrosis. Further 3 j caused clinically significant loss of lung func- investigation of the cause of this is being under : I tkm in some of the men with high dust ex- taken. I' ' ` posures. The effect of dust on lung function Thus PVC dust exposure was associated with was seen mostly in cigarette smokers, an both small rounded opacities on the chest radio v [ apparent interaction which could have arisen by graph and a slight average functional defect. The j chance but which was supported by the pattern reduction of FEV, but norma! alveolar volume l of dust effects among the various smoking cate- and transfer factor indicated that the effect was : gories. Respiratory disease has been reported in predominantly obstructive in type, but the > food wrappers cutting PVC film with hot wires." parallel reduction of FVC indicated by the lack i f and in one report these symptoms appeared to of any relationship between dust exposure and i f be more common in workers who smoked.cigar- the ratio between FEV, and FVC suggested a t . ettes.,r It is conceivable that the apparent slight additional element of restriction. The radio interaction between smoking and PVC dust ex- logical and functional abnormalities were them T posure reported in the present study was an selves related, for the 50 men with small rounded ! ` effect of products of combustion of cigarettes opacities also had reductions of FEV,. FVC. and I contaminated with PVC dust from contact with alveolar volume after the effect of dust had been J dusty hands or clothing, though there was no allowed for. While this relationship was not . I direct evidence from this study of such a mech- specific for PVC dust effects, for it was seen - I anism. predominantly among cigarette smokers whose v Assessments of the profusion of small opacities small opacities were not obviously related to dust in chest radiographs according to the TLO U/C exposure, it does tend to suggest that small I Classification are known to vary between readers. rounded opacities may be the result of disease The three experienced readers invited to take of bronchioles, sufficiently distal to be radio- part in this study were each known to show little logically detectable yet sufficiently proximal to variability on repeated readings of the same cause an obstructive defect. The parallel reduc radiographs, but were also known to differ con tions of FVC and V* suggest an additional sistently from each other in the prevalences of~ restrictive defect, which tends to confirm the small rounded opacities they recorded. In the* distal site of the lung damage, the nature of present study the anticipated differences between which might be similar to the cellular reaction readers were again apparent. One reader reported in one case of a PVC worker with recorded small rounded opacities in very few radiographic shadows." chest radiographs, and these were not obviously By contrast, small irregular opacities, related related to age or dust exposure. Another reader to age and in small part to chronic productive recorded small rounded opacities in a larger cough but not to dust exposure, were associated number of men. and presence of these opacities with a more classical obstructive pattern in which was correlated with age but not dust exposure. the FEV, was reduced substantially more than The third reader recorded the greatest prevalence the FVC. There was in addition a reduction of I of small rounded opacities, and it was found that gas transfer factor suggesting the presence of these opacities were related to age and, emphysema or ventilation/perfusion mismatching independently, to dust exposure. We consider Since the later stages of panacinar emphysema each of these readers' assessments to be scienti are usually associated with a diminution rather fically valid, and that the third reader's more than an increase in radiographic lung shadows, sensitive interpretation of the recognition and it is probable that the clinical recognition of ) recording of small rounded opacities enabled small irregular opacities enables the identification I the detection of a relationship between radio- of a type of chronic airflow obstruction associated Jf graphic appearances and dust exposure. The with ventilation/perfusion mismatching. The profusions of these small rounded opacities were pathological basis for the opacities might con almost all of low category (none greater than ceivably be enlarged arteriovenous shunts. I/II. and the slightness of these appearances We conclude that exposure to PVC dust is was corfirmed by the other readers, who in associated with abnormalities of lung function. 652 slight abnormalities of the chest radiograph and complaints of slight dyspnoea. While these results are not unduly alarming, they do indicate that PVC dust exposure should be controlled, and that the men with radiographic abnormalities should be followed clinically to determine future progression or regression of the condition. This study was carried out with the full co operation of the management and workforce of Imperial Chemical Industries Limited to whom uc are grateful for financial support. We are grateful to Or JA Dick, Dr JG Bennett, and Dr DJ Thomas for the .epidemiological radiographic readings, and to Dr A Seaton, Dr M Jacobsen, and Mr J Dodgson for much advice and help. Further details of the results of this work are recorded in Institute of Occupational Medicine Technical Memorandum TM/79/2. References 1 Casula D. CHerchi P, Spiga G. Spinazzula A. Environmental dust in a plant for the production of polwinvlchloride. Ann Inst Super Samtn 1977; 13:189-98. 2 Mapp C. Fabbri L. Rossi A. Moro G, Ccrvi G. Alteration) funzionaii respiratorie da esposizionc cronica a cloruro di vinile monomcro c polimero Med Lav 1973; 69:151-62. 3 Frongia N, Spinazzola A. Bucarelli A. Lesioni polmonari sperimentali da inalazftne prolungata di PVC in amhiente di lavoro. Med Lav 1974; 65:521-42.. 4 Agarvval DK, Kaw JL. Srivastava SP, Seth PK. Some biochemical and histopathological changes induced by polyvinylchloride dust in rat lung Environ Res 1978; 16:533-41. 5 DeHaan RL. 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