Document nkOZOvMRwnwyL1X9V8bmmzMjG

1.1- .. ...r f/:j.\ol > So* I 4. pp X4| H?4 l**. Pnni.-d -n 0eji Britain THIS m/ite;ml may rc 9 : otov4i i9so>nco Perpj'ron Press Lid t\.' i. \ PROTECTED 3Y Occj"j.n.*nj! Hvgiene Sootis /TITLE 17, u. s. CODE) AN EPIDEMIOLOGICAL-INDUSTRIAL HYGIENE STUDY OF TALC WORKERS J. Gamble; A. Greife and J. Hancock National Institute for Occupational Safety and Health. Appalachian Laboratory for Occupational Safet) and Health. 944 Chestnut Ridge Road, Morgantown. WV 2b505. U S A Abstract--Two-hundred and ninet>-nme (299> miners and millers exposed to talc from Montana. Texas and North Carolina were examined in a cross-sectional studs of respirators systems. lung function and chest X-rays Work histones were taken from personnel records. Personal respirable dust samples were collected for all jobs. Cumulative exposure was calculated by summing the products of the estimated exposure for each job and the length of time worked in that job. The average time worked was 7. 6. and 10 yr and the average exposure (cumulative exposure total time workedl was 12.2.6. and 0 3 mg m' in Montana. Texas, and North Carolina respectively Free silica content of bulk samples was low (below the limit ofdetection in Montana. 1.5",, in North Carolina, and in Texasi No fibres were observed under the light microscope. Under the transmission electron microscope, tremolite and antigorite fibres (0.5-3 pm length) were observed on the Texas talc, acicular particles (aspect ratios 5-100 to I and some diameters less than 0.1 jim) in North Carolina talc, and no fibres in the Montana talc. The differences in age-corrected symptom prevalences (cough, phlegm, and dyspnea) between regions, when compared by both smoking categories and exposure groups were not statistically significant. None of the symptoms showed any consistent association with years worked or cumulative exposure. Symptom prevalence was not elevated compared with blue collar workers and potash miners. There were two cases (less than 1,,) of grade 1 small rounded opacities The prevalence of bilateral pleural thickening among workers 40 yr or older was 7.16. and I4",, in Montana. Texas, and North Carolina, and 0.0. and 10,, in those less than 40 yr of age. No non-smoker had bilateral pleural thickening and there was a slight tendency for the prevalence to increase with exposure. Workers with bilateral pleural thickening had lung function l0-20,, below workers with no pleural thickening. They had also worked twice as long (13 yrl and an average of 13 vr between beginning exposure to talc and the time of the X-ray. TKe prevalence of bilateral pleural thickening was elevated in workers 40 yr or older compared with blue collar workers and potash miners. There also were no demonstrated differences in prevalence when the subjects in this study were compared with workers exposed to New York talc which contains tremolite and anthophyllite. For the entire study population no association of reduced lung function w ith exposure w as demonstrated After adjustments for age. height, and smoking. FEV, and FVC were not delectably different compared with potash miners and blue collar workers: however, flow rates allow lung volumes were' reduced 4 I9",, There was little difference among these three populations in age coefficients for FEV,, FVC. and flow rates by smoking category. Predicted pulmonary function of the study population was elevated compared with New York talc workers. There were no significant increases in symptoms or pneumoconiosis among the study group of talc workers nor significant reductions in lung function; however, the average amount of time worked by the study group was short. Bilateral pleural thickening was significantly increased and was associated with decreased pulmonary function. The prognostic significance of the pleural thickening awaits prospective evaluation. INTRODUCTION Talc is a mineral with a wide variety of uses in paint, paper, ceramics, cosmetics, roofing products, textile material, rubber, lubricants, corrosion proofing compositions, fire extinguishing powders, cereal polishing, water filtration, insecticides, to name a few. Pure talc is a hydrated magnesium silicate, but the talc found in nature has a quite variable chemical composition. The mineral contaminant in talc of most concern is 841 10003004 - T_ *. & V .. jV*'- *15 .. j-. `:'l ~t c *'*?<, `3 <'r. ,i'v--ji*> .Siv'-`-dF .'4" ' J- -' >,I;. '? > /-'T VV-:'-V~ - #.5- y`.< "<fc'v *Z# i.>**-'';jjr-.-'r*<~*..?Si =v : r .-**' fv, - - -. v* ., .i. ': w- m. ... *3/>*?**^-*^Jf?.Qfc3*sjSE*.v.^y>i(fr sj: J Gamble. A. GREirr and J Havcock asbestos. Such contaminated talc can produce a clinical condition resembling that seen on exposure to asbestos. The hazard from exposure to `pure' talc free of asbestos contamination is less well documented. The purpose of this study was to ascertain the effects on the respiratory system (symptoms, lung function, radiographic) of exposure to talc dust thought to contain no asbestos. Talc workers in seven mines and eight mills in Montana. Texas and North Carolina were studied in this cross-sectional study. The mines in Montana and Texas were typical open pit operations, while the underground mine in North Carolina employed square set timbers and stopes. In each mine examined, typical mucking techniques were employed. ANFO (ammonium nitrate and fuel oil) was the most common type of explosive used. Following extraction of the ore. the talc was hand sorted to remove extraneous material, as in Montana, or went directly from the mine to the primary crusher. Froth flotation and heavy metal separation techniques were not used in any facility examined. Follow ing initial crushing, the talc might be calcined, as in the case of ceramic grade talcs, before being ground using dry grinding methods into the final product. Once the talc was ground to the appropriate mesh size, it was sterilized as in the case of pharmaceutical grade talc and then shipped in bags or bulk. The specific questions being addressed in this paper are: (1) What is the prevalence of symptoms and abnormal radiographic findings by exposure categories w ithin each region? What is the association of exposure with reduced lung function? (2) After adjustment for confounding variables, how does the study population compare with other mining and non-mining populations in the prevalence of symptoms, abnormal radiographic findings and mean lung function? METHODS The study of population consisted of workers who mined and milled talc from three regions of the United States: Montana. Texas and North Carolina. Although several different companies may be involved, the results for each region were combined and analysed. Since there were no demonstrated differences among the regions by age. smoking and exposure groups, the combined results of all regions are presented in this paper. Over 90,, of the workers participated in the study. The industrial hygiene portion of the study took place in every facility in w hich the morbidity data were collected. Personal respirable breathing zone samples were collected utilizing a Model G MSA* pump and a 10 mm nylon cyclone. These samples were analysed for respirable dust and percent quartz and cristobalite. The quartz and cristobalite analysis was done by X-ray diffraction (NIOSH. 1977). Time weighted averages (TWA) were obtained for each job classification at each facility. General area dust samples w ere collected on open face cellulose acetate filters and were analy sed by atomic absorption for iron, manganese, calcium, aluminium, zinc and nickel (NIOSH. 1977). From each ore body airborne dust samples were collected on open face cellulose acetate filters and analysed by phase contrast microscopy for the presence of fibres Mention of brand names does not constitute endorsement b\ the L'SPHS An epidemiological industrial hsgiene siud> 84? (NIOSH). Analysis for fibrous tremolite and anthophyllite was done on bulk and airborne dust samples utilizing analytical electron microscopy (NIOSH. undated). Bulk samples from each ore body were analysed for calcite and dolomite by X-ray diffraction (NIOSH. 1977). All workers were administered either a Spanish or English version of the British Medical Research Council respiratory questionnaire by trained interviewers. Non-talc work histories were obtained in the interviews; work experiences at the talc facility were obtained from company records. Standard postero-anterior chest radiograms were read by three `B` readers using the ILO U C 1971 scheme. The films were read independently without know ledge of age, occupation or smoking history. The median of the three readings (i.e. the middle number) was used for analysis. Flow volume curves from a minimum of five forced expiratory manoeuvres w ere obtained and recorded on magnetic tape using an Ohio 800* rolling seal spirometer. Values from the maximum envelope were used for analysis. Sputums were collected on workers >35 >r of age. Personal environmental samples were collected on day shift workers and were used to estimate talc dust exposure for each job. This estimate was then used to calculate cumulative talc dust exposure by multiplying job exposure by time and adding the results. The association of lung function and exposure (cumulative exposure and years worked) was analysed by multiple regression. Years worked was divided into < 5. 5-9, and > 10 yr worked categories for analysis of symptoms and pleural thickening. Cumulative exposure was the estimate of total exposure to respirable particulate over all years employed and was divided into low (<2 mg m~3 x years), medium (2-6 mg m'3 x years) and high (>6mgm'!x years) exposure groups for analysis of symptoms and pleural thickening. Differences by region and department (classified according to whether the majority of work was done in the mine, mill, crayon plant or other) were also estimated. The prevalences of selected symptoms and pleural thickening were compared with mining and non-mining populations after indirect adjustment for smoking and using the age distribution of all populations (Fleiss, 1973). Prediction equations were calculated for each smoking category of the comparison populations. The observed lung function of each worker from the study population was compared with the predicted of the appropriate smoking category of the comparison population. The percent predicted lung function from all smoking categories and regions were then combined. Female prediction equations were available for only the blue collar comparison populations. Percent predicted lung function comparisons with the mining popu lations are therefore for males only. RESULTS Environmental results Respirable dust exposure was highest in Texas and lowest in North Carolina, and mill dust levels were higher than mine dust levels in all regions (Table 1). Montana talc had the lowest concentrations of trace metals of the three regions examined. Concentrations were slightly higher in North Carolina. Texas talc differed Mention of brand names does nol constitute endorsement b> the USPHS 10003006 ^ . ~-., . .v-' :' ~.j ;;frO;%;,' J-t'*1-*; * . v-v-,4 - 4 -W/:;. if.- r WL. r<.- j*rrrx * * ?-\l. . ,^;- ,-.c; ' . . -c. . T '. * **K.'. if ` '.'^i * * ;'. '. J ~ **- - '- :---.-C^V: -f. <--> v r-f :- -.i.-. -- > Vi- . - 'S' .T:.`' -'-- '" >.'.* .. :-.`.vi. -- ..-- - .. .; .. '. v * -, . ,,' . i` -~>v ?;-;>;? :'*'-' " " -_-**-* ^ - - 4' >lr ' :-- HfeisSlc^SjS^^' j^` r, -w *k_v Ot v*iv r ~nir'iTA< 844 J Gamble. A GuFitrandJ Hascocx TaHII 1 DrvicK.KvPHK ( IIVRACTFRI'Ttrs OF Tilt lslC WORMR POPl LAIIOVS BV RIC.Uiv Montana Texas North Carolina M Age Height (cmi Years worked Cumulative exposure [(mg m`* )x>ears] Average exposure Img m" 3I Geometric mean of current respirable dust samples Img m~31 Mine |95,, Cll Mill (95,, CD Non-smokers Ex-smokers pack vears cigarettes dav Smokers pack vears cigarettes dav (SDl ISDI (SDl (SDl (SDl (GSD) r,,i i,,) (SDl (SDl (,,l iSDi (SDl 177 34 9 (115) 175.5 (8 81 6 6 16.3) 5.9 (7.6| 121 (0.94| 0.86 |0.77| 0 66 |0.$5 1 41) 1.1 (0.47 0.921 33 21 15 7 (17.91 23 0 115 0) 45 17.9 116.9| 20.4 111.0) 71 380 (13.7) 173.0 (69) 5.5 (5.7) 11.3 145.11 2.64 (712) 1.08 (0.72) 045 <0.18 0.75) 1 56 (0 96-2.54) 20 27 13.3 (20 7) 12.0 1140) 54 14.3 (19.7) 14.5 111.11 51 43.1 (126) 172.5 <8 3l 10.1 (8 61 3.0 <4.8| 0.28 (033) 0.21 (0.86) 0 14 1007-0.31) 0 26 (0.13-0.51) 21 17 IS 2 (16 5) 21.4 115 7) 62 23.7 |21.8i 20.4 UO.Ol most significantly from the other regions by its extremely large concentration of calcium, as indicated by a much larger percentage of dolomite (13 compared with 3 and 1 %) and a slightly larger percentage of calcite (1 compared with < 1 and 0%) than the other two regions. Silica content of bulk samples of Montana talc was below the limit of detection (<0.8%), 1.45% in North Carolina and 2.230 in Texas. Respirable dust samples revealed the silica content in Montana and North Carolina to be generally below the limit of detection (0.04 mgm'J). The Texas talc had slightly higher levels of respirable silica (0.09 mgm'3) (Table 2). No fibres were detected in any of the regions by fight microscopy utilizing phase contrast techniques. Analysis of bulk samples from each region utilizing analytical transmission electron microscopy revealed no fibres in any samples of Montana talc. Two fibrous minerals were identified in the Texas talc: tremolite and antigorite. Antigorite, a serpentine mineral, was the main constituent. The fibres ofboth minerals ranged from 0.5 to 3.0 pm in dia. and 4 to 30 ^m in length. The morphology of the North Carolina talc was identified as acicular. The acicular particles had aspect ratios ranging from 5-1 to 100-1, with some dia. <0.1 /jm, and may have resulted from mechanical destruction of talc plates. Demographic characteristics All Texas talc workers were male, while about 20% of the Montana and North Carolina workers were female. The North Carolina population had the highest proportion of smokers (62%) and lowest proportion of ex-smokers 117%). The highest proportion of non-smokers (33%) and lowest proportion of smokers (46%) were in Montana. Pack years ranged from 13 to 24 and cigarettes smoked day from 12 to 23 in the three regions. Montana workers were on average 8 yr younger, 3 cm taller, had worked 3.5 yr less and had 2.9 mg m '3 yr more cumulative exposure than the w orkers 10003007 An epidemiological industrial hvgiene siud> Turn 2 Mh\l *mi minfru cmtpnsmos of rilr ssmpi rsm RFt.K Montana Texas North Carolina mg m 1 Iron LOD* Maneanese LOD Calcium LOD Aluminium LOD Zinc LOD Nickel LOD Percent Calcite (range) Dolomite (range) 0.05 0.01 <001 0.01 0 05 0.0? o: 0.1 <001 0.01 <0.01 001 <1 to 0.81 1 10-31 * LOD = Limn of Detection. 0.5 0.1 <0 08 0.08 80 0.2 04 0.2 0.03 008 <0.08 0.08 1 (0 3l 13 |7-20l 0.05 002 <002 002 005 0 02 02 004 <0.02 0.02 <002 0.02 0. 0 11 -4| 845 in North Carolina. Mean values for these parameters in Texas were not demonstrably different from those for Montana and North Carolina. Average exposure (cumulative exposure divided by years worked) was less in North Carolina than in the other two regions (Table 1). There was one case each in Texas and Montana of grade 1 small rounded opacities. This number is too small to analyse further. There were no other radiographic interpretations of pneumoconiosis. Cytology on sputums collected from workers 35 yr of age or older were read as follows: 20o unsatisfactory, 60,, normal cytology or regular metaplastic cells, 20o atypical. Symptoms and radiography (internal comparisons) Tables 3-6 summarize the prevalence of cough, phlegm, shortness of breath and pleural thickening by age, smoking and exposure. Regions were combined for presentation of these results as there were generally no statistically significant differences among the regions. If differences were observed they are noted in the text. The overall prevalence of cough was 190. The prevalence tended to increase with age and smoking (only the difference between non-smokers and smokers was significant). There was no apparent association with either exposure variable (Table 3). The overall prevalence of phlegm was 23 ,,. There was no consistent increase with age. Overall, smokers had a higher prev alence of phlegm than non-smokers. There was no apparent association with exposure (Table 4). The overall prevalence of dyspnea was 5^. Prevalence increased with age in all regions and smoking categories, but the increase with age was significant for only the total population. There was no apparent association with smoking or exposure (Table 5). 10003008 t. - - , * r. , ' ;,v.. . j^Kv>r>.v,, .-.! ' f%-*y t v* .-ef" - - r.> o '**> . '; 75*N45it:.'^jaiv*r***-" -JL.--"//- v _.'_*. :?'V ' (Mi.-:.-. - . 5 SK* > v.- * rv ` .xT**>/:*.-, `vrv--jT*? It" ' MsspgCT ~*"'inln`n >TT % nif' 'Ti< KfhTWrg^.~-C>i.-^ 846 J Gamble. A. GRUtr and J Hancock Table? Pan ALrsrf (",,] or cm <.h* amono ai l talc workers kv ac.i. ami aim. AND r\P**M Kt IaLL KlCilMNA ( miHINI D) Age <40 >40 % 195",, Cl) .95",, Cl) Total (95,, CD Non-smoker Ex-smoker Smoker Total Years worked <5 5-9 > 10 Cumulative exposure Low Medium High 7 13-16) 7 |l-;il 36 (18-351 31 (15-39) 15 15-33) 19 (9-341 30 118-45) 3? (15-33) 10 (5-30) 13 (6-34) 37 (30 35) 19 19 (14-35) 19 (10-31) 31 (10 361 14 (8 3?) 35 (17 ?5i 16 (9 36) Summary: til No demonstration difference among regions by age. smoking or exposure Oil Tendency to increase with age except among smokers, mil Higher prevalence in smokers (iv I No demonstrated association with exposure. * Cough = Answering yes to the question: 'Do yea usually cough on most days for as much as 3 months each year'.r Table 4. Prev alence ( n>OF PHLEGM* AMONG ALL TALC WORKERS SMOK1VG AND EXPOSIRF AGE. Age <40 %(95% Cl) >40 (95% Cl) Total ", (95% Cl) Non-smoker Ex-smoker Smoker Total Years worked <5 5-9 210 Cumulative exposure Low Medium High 13 (5 34) 13 15-39) 33 134-43) 33 (16-30) 7 (1-33) 3' il4 43l 36 115-10) 33(15-31) 11 (5-30I+ 31 (13-331 31 (34-39i+ 33 19 (14-35) 16 18-36) 35 (14-39) 13 17-31) 34(16-34) 19 (11-30) Summary: li) No demonstrated difference among regions by age. smoking or exposure, (in Smokers had highest prevalence, liul No demonstrated association with age or exposure. Phlegm = Answering yes to the question: "Do you usually bring up phlegm from your chest for as much as 3 months each year1' t950,, Cl do not overlap. 10003009 An epidemiological-industrial hygiene study TaRLF 5 PREVALENCE of DYsPNF.A* AMONG ML TALC WORKERS RV AGE. SMOKING AM) FXPOSl RE Age <40 >40 (95% Cll % (950 Cll Total % <95% CIl Non-smoker Ex-smoker Smoker Total Years worked <5 5-9 >10 Cumulative exposure Low Medium High 4 (1-13: 3 (0-161 I 10 5i 2 (0-51+ It (3-271 16 (1-181 6 (0-131 10 (5- IS i+ 6 (2-14) 10 ( 4 20) 3 (1-7) 5 6 (3-101 0(0-61 8 (2 20) 5 (2111 3 (1-8) 7 (2-14) Summary: m No demonstration differences among regions by age. smoking or exposure till Increased prevalence with increased age (ml No demonstrated association with smoking or exposure Dyspnea "Answering yes to the question: 'Do you get short of breath walking with people your own age on level groundv + 95% Cl do not overlap 847 Table 6 Prevalfncf of hilatfral plflral thickening among all talc workers by age. smoking and expose re Non-smoker Ex-smoker Smoker Total Years worked <5 5-9 210 Cumulative exposure Low Medium High Age <40 >40 % (95% Cl) % <95 % CD 0 (0 7) 6 (0 24) 2 t0-7)* 2 (0-6) 0 (0-11) 3 (0 15) 22 (11-36) 11 (5-18) Total ,, (95% C!) 0 (0 6) 4 (0-141 9 (5-15) 5 2 (0-5i: 3 10-101* 23 (12-38)*; 4 tl-IO)+ 5 (1-12) 8 (3-17)+ Summary: (ii No demonstrated differences among regions by age, smoking or exposure, except medium cumulative exposure group in North Carolina had higher prevalence than in Montana dii Tendency to increase with age (significant among smokers) lull No bilateral pleural thickening among non-smokers. (iv| Increasing prevalence with increasing years worked lv| No demonstrated association with cumulative exposure. 95%Confidence intervals do not overlap + 1 with extent 2 pleural thickening I w y t i I 10003010 * '"'Vf% ,._i1- '*' * ` - j **'. f. t. /* ~ ->..- s - `-*..- .V . . /*''*'*. *+* r -Sis* V VE*i^- V .' -^~, t ._ *1 . _ '"ihrtriirrSTiV^ . . rJe, -* v-.:. V'-.- j .'3. tt v-.f_ ** J*' . V .-.V, ' - MX J Gamble. A Grfife and J. Hancock The prevalence of pleural thickening was 4. 13 and 18,, in Montana. Texas and North Carolina respectively, and was significantly less in Montana after adjustment for age or years worked. The number of those with unilateral pleural thickening w as one of six. five of nine, and three of nine in the three regions. There were no radiographic interpretations of pleural calcification. The overall prevalence of bilateral thickening was 50. The prevalence among the medium exposure group was 30o in North Carolina and 0o in Montana. There w ere no other demonstrable regional differences. Prevalence increased with age. but only among smokers. Prevalence was highest among smokers, and no non-smokers had bilateral pleural thickening, but none of the differences were significant. The prevalence was greater (23;) in the group working 10 yr or more, compared with 2.5,, in those working less than 10 yr. but was about the same in the low, medium and high cumulative exposure groups (Table 6). Table 7 compares workers with and without pleural thickening. Those with any pleural thickening were about 10 yr older than those without. Workers with bilateral pleural thickening on average weighed more (11-15 kg), had worked longer (6 yr) and had higher average and cumulative exposures than those with unilateral or no pleural thickening. All pulmonary function values of those with bilateral pleural thickening T MILT COMPARISON i IF XXORKTRS WITH AND XX1THOI T PIFl RXL TIIK KINIM, COMBINED! No PT Unilateral Bilateral n Frequency |95",, CIl Cough (",,) Phlegm r,,l Dvsnnea 1 > Grade 3| Obliteration of costophrcnic angle Unilateral Bilateral Means iSEl Age Height tcml Weieht tkgl Years worked Cumulative exposure [tmg m ' i * vearsil Average exposure img m~ ) 'Laiencv' vears +FEV, FV'C * 100 + FEV, iLi +FVC (Ll Peak flow iL s'11 FEF.0 FEF-, 255 18 t14 23) IS <14-231 5 (3 8| : (0-5) <1 (0-lj 36.4 (0.8) 174.0 (0.5) 76 6 |0.81 6.7 (0.41 5.1 (04) l.l (Oil -- 77.10 |0.7) 3.56 10.051 4 61 (0 061 8.37 |0.I5) 4 10 10.13) 1.40 10.06) 9 :: (4 56i ::(4 56i 11 (0 44) II (0 44| 0(0 29) 46.7 170.1 80 5 6.9 34 (341 (3.1 ( (4.9) (3.:) (0.7) 0.9 (0 3) 4.50(14) 80.30 |3.7| 3 47 (0.191 4 39 (0.331 7.63 (0 56) 4.19 10.49) 143 10.311 15 33 (14-631 33 (14-631 7 tO-30) J3 (3-37) 0 (0-19) 47.7 175.3 91.9 13.4 34.1 (3.3) |3.0) (4.3) (2.3) 34.61 3.3 (3.5) 13.1 (3.3) 73.50 (3.3) 3 08 (0.16) 4.19 (0181 7.03 (045) 3.30 1040) 1.34 (0.18) * Lung fund ion least square means adjusted for differences in sex. age. height, weight and smoking status + Pleural thickening is a significant variable in the linear regression model. 10003011 were reduced compared with those without pleural thickening. Those with unilateral pleural thickening generally had intermediate lung function values. The prevalences of cough and phlegm were not statistically significant and were not adjusted for age and smoking. Symptoms and radiography (external comparisons) Table 8 summarizes the characteristics of the comparison populations. The potash mines were part of the MSHA/NTOSH epidemiological-industrial hygiene study of metal and non-metal underground miners (Attfield. 1979; Sutton et al.. 1979). White male miners from six potash mines were used for comparison. All of the potash mines used diesel engines and had high dust exposures. The New York talc miners and millers were exposed to tremolite and anthophyllite (Gamble et al., 1979a; Dement and Zlmwalde, 1979; Dement et al., 1980). The blue collar comparison population was part of a NIOSH blue collar control study and included male and female workers from North Carolina in such industries as electronics, synthetic textiles, bakeries and bottling plants (Petersen, personal communication). The workers in the comparison populations had generally worked longer in their current industry than had the Montana and Texas talc populations. The mining populations generally were heavier smokers than the study populations and the blue collar workers. The mining comparison groups had occupational exposures in the form of diesel fumes and 'potash' (primarily sylvite, a mixture of KC1 and NaCl, and langbeinite or K. 2Mg2(S04 li) and talc containing asbestiform fibres. Table 9 summarizes the age and smoking adjusted prevalence of cough, phlegm, dyspnea and pleural thickening of the study and comparison populations. There was no demonstrated difference in the prevalence of cough between the study population and the potash or blue collar workers. New York talc workers had an elevated Table 8. Characteristics of comparison, popi lations New York talc : Blue collarj Male Female Potash n Age (SDi Height (cm) ISD) Years worked (SD) Non-smokers (",,) Ex-smokers l,,) Mean pack years (SD) Mean cigarettes dav (SD) Smokers (,,) Mean pack years (SDl Mean cigarettes dav (SDl Current dust levels (mg m'3) Fibres > 5 /im a-"1 i:i 39 (13) 176 (6) 11 (9| 21 31 26 (28) 28 (19) 48 26 (17) 27 III) 0.77 (Mine) 0.87 (Mill i 5.40 (Mine) 4 80 I Mill 1 843 38 (14) 173 (7) 12 (12) 25 23 21 (23) 23 115) 54 23 (19) 23 llll NA NA 597 40 (13) 162 (6) 11 (10) 49 10 9 (10) 16 (12) 42 17 (13) 19 (9) NA NA 875 41 (131 176 (6l 16(13) 20 28 23 (20) 2? (14) 52 25 (23) 2? (12) +345 NA NA = Not Available. Personal samples of respirable dust and light microscope fibre counts from Dimini ft al I19S0) + Personal samples of total dust from Armm> (19791 and Sltton er al. (1979) t Unpublished data from Martin Petersen. 10003012 SI; * ' ' * iV:- ! ' - - '-" T ^ wC-' *-*;LV. ; >^wTV*z- , jr . <: * -*-; . - *. '> . ;.vi r^gg^- T* *.X , TBT'V.'^S,v;< 3I ... > ' '*?.:-*, -*-i/'--*M>--i--Z; *--- lTg' 1*:-V-A^- >' -:-j'WSs^alvl:^- - >- 850 J Gssiblf. A Gunrt and ) Hs.cock Tsui t 9 C>mi'*r sti\ 1 KUi'ini i m (.11. mi 1 i;m. msi-\i s imi mi umi rti 1 mi tint ki mm. wh -m. til Ttl.l WURMRS fliMI-SRI'l) WITH Nl \s Xl'RKTsLI '.s ' S kl RS. Ill l l < nl.HR SS IIR M R.s s\l> Is . T \ Ml MINI RS IIMlIRKIll VI>H stl l> l`.R SI,I S\l) s\|i iKI\(i I Cough Phlegm Dsspnea Bilateral pleural thickening Sludv population Icombinedi (95\ Cli Companion group New York talc |95 Cl 1 Poiash miners \ (95",,Cll 303 116 ;5i :o.t ii6 351 5.8 (4 101 63 |3 9| 36 1 i:s -451 35 5 C* 451 13 3 r i9i *9 |4-I5l 34 1 co :7i 39.5 (37 341 84 16 111 03 10 0.51 Blue collar workers l95CIl 16' 114 301 17 3 114 311 7S (6 IOi 04 toil. Summars: HI Couch Stud> population lest lhan Ne-.i t ork laic, no JilTcrcnl from poiash and blue collar. Oil Phlegm: Siud> population less than New York talc and poiash. no different from blue collar workers, mil Dsspnea. No difference among studs and comparison populations. Its 1 Bilateral Pleural Thickening' Studs population and New York talc workers greater than poiash and blue collar workers. (Difference indicated b> non-oserlap of confidence intersal>> prevalence of cough compared with other populations. There was no apparent difference in the prevalence of phlegm among the studx population and blue collar workers, and the prevalence in both these populations was less than the potash and New York populations. There were no demonstrated differences in the prevalence of dyspnea among the study and comparison populations. The prevalence of bilateral pleural thickening was higher in both talc (study and New York) populations compared with the potash and blue collar populations. Pulmonary function Table 10 summarizes the results of multiple regression models of pulmonary function with the predictor variables race. sex. age. height, smoking status. Region, department, years worked and cumulative exposure were tested for association with lung function. Age and height were significant for all parameters. Race, department, years worked and cumulative exposure were not significant for any of the lung function tests. Sex was not significant for FEFS0 and FEF-5. FVC was reduced in Texas compared with Montana and North Carolina. The effect of smoking was generally as expected. Table 11 summarizes the mean percent predicted pulmonary function of the study population compared with poiash. blue collar workers (male and female) and New York talc workers. Flow rates (peak flow. FEF5n, FEF-S) of the talc workers were reduced compared with the poiash and blue collar workers, but there were no significant differences in FEV^ and FVC. Compared with New York talc workers, all pulmonary function parameters were elevated except percent predicted peak flow. 10003013 An epidemiological-industrial hxgiene studs TxHI I 10 St MM XRX HI Ml I TII'I I Rl tiRrSSK Millin' KiK LI V. H Si In 'S \M1 SI I FC 11 [> IIUM iui xn i) n in six. x(,i. tirn.Hi. sxnikisi, shti x rii.iiix xsn ixrusi ri FEY, Lung function parameter FYC Peak flow FEF,,, FEF-, Department Years exposure Cumulatue exposure Region Montana Texas North Carolina Smoking status Non-smokers Ex-smokers Smokers NS NS NS NS 3 58 (0 061 3 51 lO lOl 3 71 (O.IOl + 3 71 (0 081 3.58 (0.09 > 3.51 10.071 NS NS NS t 4 65 (0061 4.39 (0.1 tl 4.62 10 111 NS 4 62 (0.091 4.51 (O.lOl 4.53 (0.08) NS NS NS NS 8.51 (0161 8 46 (0.271 7.87 (0.2S i 4 8.31 (0 231 8 60 10.251 7 93 (0.201 NS NS NS NS 4 0' 10 I3l 4.63 l0.23i 4 48 (0.24i + 4,55 |0 191 4.52 (0 211 4 12 (0.|7| NS NS NS NS 1 41 1OO6I 1 4> (0.10> 1 55 (0 l1i 1 63 to 091 1 44 (0.10) 1 3" (0.081 Regression model: Lung function = i*0, tracel-/f; (sexl-/>'. (agel-/L lheight 1 -- ^ ismokmg slatusi-/!,, |reeionl-)J- (department l-/>' (xcars exposurel-/! tcumulattxe exposurei. NS = P>005 + P<005>001 ; P<001. Summary: til Age and height were always significant: sex was significant for FEY,. FYC and Peak Flow, ml So exposure xariable was significant Region was significant for FYC (Texas was reducedl. tun Cumulattxeexposure was significant for FYC (P = 002nn model lung function = t. - fi, tsex i- ugol-r- 0, lheightl-(i4 tweighti-^5 tsmoking statusi-r/5. tcumulanxe exposurei /#,,= -4(4i. Comparison of age coefficients by smoking categories showed little difference among the four populations. The New York and blue collar populations showed a greater effect of age than did the study and potash populations (Table 12). DISCUSSION Interpretation of the data from this study has the inherent problems of all crosssectional prevalence studies. The workers examined in this study comprise only those currently working. While there are few studies that have examined ex-workers to determine the effects of selection, significant disease has been observed among older ex hemp workers (Bolhl ys et at.. 1969) and progressive massive fibrosis among ex workers in two silica flour mills (Banks et al.. 1981). In both of these studies there was significant disease among the currently employed workers. The consequences of not examining ex-workers in this study are unknown. The reasons for using several comparison populations are that no comparison population is ideal, and several may help in interpretation of the data. Factors that may alfect the morbidity of a study population (in addition to work exposurei but are not measured include region, socio-economic status and type of employment (for example, mining). These may affect morbidity by selection of particular kinds of individuals, but it is unlikely that all the comparison populations will have biases in the same direction relative to the study population (although the biases in the study group still cannot be estimated). The length of the study group's working history is a relatively short time for the development of occupationally related symptoms, radiographic changes and impaired a--_ seC-T- 'dry-- c-: & rSr- EC'- 10003014 ly.y- ^,uVL' : *r.. - -i A*1*.! --" * -? ,7T' *k - -*^*-`* - * * -c. - - "% t. >' < .' - 4zr*__ - : S'rsSpS raj! 85: J Gasible. A Gkfiff and J Hancock Tablf 11 Mias pfrc nr prfuk ti i> pi i monads h action of am tai c vvdhki rs C( IMP ARM) WITH POT A All MINIRS AND Rl l I COI HR WORK FRA AND A DJI ATI D FOR Adi. HEIGHT AND SMOKING* Percent predicted pulmonarv function (SEl New York talc (males only i n= 119 ' Potash miners (males onlv 1 n = 251 ' Blue collar workers Imalcs and femalesl n=:93 FEV, FVC Peak Flow fefjo FEF-, 106.3 |1 3C 105.7 <1.1|* 95.2 (111 161.1 (39.81 130.5 <4.7 IJ 9S9 ll 0) 996 l08l 93 3 ll.0|t 95 6 C 11+ 88 : (3 11+ 99 7 (10) 101.0 (08) 979 (1 0) 94 1 <: 01+ 84 5 C.41+ * Percent predicted pulmonary function = Ilobserved expected I x 100 + = > 2 SE less lhan 100 X = > 2 SE greater than 100 Summary: ill FEV, and FVC were not demonstrably different from comparison potash and blue collar populations, but elevated compared with New York talc values on FEF.,, and FEF-5 reduced compared with potash and blue collar populations, but elevated compared with New York populations. Table 12. Age coefficients of male stldv and comparison popi lationx (with SEl Study population New York talc Potash Blue collar FEV, (mil Non-smokers Ex-smokers Smokers FVC (mil Non-smokers Ex-smokers Smokers FEFS0 1ml s' `l Non-smokers Ex-smokers Smokers FEF-, (mis'1! Non-smokers Ex-smokers Smokers n Non-smokers Ex-smokers Smokers -:4 isi -35 (5) -41 |5) -6 (5| -33 (6) -:? (6i -51 ill) -49 (15) -73 (111 -43 (7) -: (10) -44 (5) 67 56 i:s -5: l9i -36 111) -54 |6) -55 (12) -43 (13) -50 |8| -66 t:9| -:i <:4i -- 80 (14| -40 till -:: (7i -38 (5) :5 36 58 -38 (3) -33 (3) -40(2) -23 t3l -26 |4I -32 |3) -36 (7) -44 (81 -63 (5) -32 (4) -28 (3) -41 (2) 178 244 451 -30 (3) -36 (3) -39 (2) -24 (31 -25 (3) -25 (2) -43 (6) -58 (8) -71 (51 -38 (4) -40 |3| -50 (2) 207 193 442 lung function that might be caused by exposure to a mineral dust. Significant changes in FEV, and FVC due to exposure to respiratory irritants (such as cigarette smoke, for example) may not become noticeable until after 20-30 yr of smoking. Essentially the same time interval may be required for the development of pneumoconiosis (Cherniack and McCarthy, 1979). The mean ages of the study populations were 10003015 WJJM An epidemiological industrial hsgicne stud) around 40, and mean exposure to talc dust was less than 10 yr. Therefore, if talc dust was to adversely affect FEV, and FVC. the lung function results might not reflect that effect because of the short exposure limes. Estimating past exposure was a problem in this as in other studies w here there was no environmental surveillance. Although dust levels w ere assumed not to hase changed substantially with time, past exposures were probably higher than the calculated estimates and could obscure a true dose-response relation if it existed. Years worked is an exact time period, but it may be a less accurate measure of overall exposure than the calculated estimate of cumulative exposure. Often, years worked and exposure are highly correlated. This was not as true for Texas, but there w as an association of years worked and cumulative exposure in Montana and North Carolina. Age was also correlated with exposure (years worked and cumulative exposure). In this report, both internal comparisons (dose-response relations) and external comparisons were made with another talc population, another mining population and a `non-exposed' blue collar population. For symptoms and pleural thickening the two comparisons supported each other. That is. for symptoms of cough, phlegm and dyspnea there was no dose-response relationship and no excess prevalence in the external comparison. For bilateral pleural thickening there was a dose-response relationship (association with years worked) and the prevalence was increased compared with both non-talc populations. For pulmonary function there was also substantial agreement in the internal and external comparisons. Mean percent predicted pulmonary function after adjustment for age. height and smoking, and the age coefficients by smoking status taken from prediction equations were used for the external comparisons. Age coefficients are thought to be less subject to bias than predicted values (H wcock and Attfikld. 1980). The two methods were consistent in showing a tendency for the study population to have an elevated pulmonary function compared with New York talc workers, with no detectable differences in FEV, and FVC in the other comparisons. Mean flow rates were reduced in the study population compared with potash and blue collar workers, but the age coefficients did not reflect this deficiency. Flow rates at low lung volumes (FEFJ0 and FEF-,S) were slightly reduced compared with tw o of the control populations. FEF,0 was better than 90,, predicted, while FEF-5 w as between 80 and 90o. Air flow at low lung volumes is considered to be measuring changes occurring primarily in the small airways (H y \tt e( al. 1979; Mfad. 1979). A current hy pothesis of the pathophysiology of chronic air flow obstruction is that changes in the lung function seen in disease such as emphysema start in the region of the small airways (Becklake and Permltt. 1979; Macklem, 1972). Tests such as FEF,0 and FEF7} are of interest, because it is difficult to detect pathophy siological changes in the small airways that may be occurring for unknown time periods before they become evident in more routine tests such as FEF, and FVC. While existing data (such as the ability of FEFS0 and FEF-, to detect differences in the young smokers and non-smokers) are compatible with the idea that air flow obstruction begins in the small airway s, there are no available prospective data to prove it. Therefore, the significance of these reductions is only suggestive. Thus, the prognostic significance of reduced flow rates at low lung volumes is not proven and the evidence for reductions in the study population is not convincing. Peak flow was reduced in the study population compared with potash and New - yj.' * t- t. - , ?* * ' v -> 10003016 854 J Gnmbi r. A Ghiice and J Hancock York laic workers but was no different from blue collar workers. Peak flow is most sensitive to changes in large airways, but is also most subject to technician differences and subject effort. The prognostic significance of reduced peak flow is also not know n. The most important finding in this study was the increased prevalence of pleural thickening. Asbestos (particularly anthophyllite) from either occupational or com munity exposure is believed to cause an increased prevalence of pleural thickening (Sargent et ai, 1977) and in some instances, pleural changes have been more common than parenchymal changes (Hlrwitz. 1961). Talc contaminated with asbestos (tremolite and anthophy Hite) seen under the light and electron microscope has also been associated with an increased prevalence of pleural thickening (Gamble er ai. 1979b). But studies of workers exposed to talc without significant asbestos content Have reported higher prevalence of pneumoconiosis than pleural changes (Ri bino et ai, 1977; DeLaide. 1977; Mfssite et ai. 1959; Fine et ai. 1976; Wegm.an et ai. unpublished) and excessive mortality due to non-malignant respiratory disease (Sei.evan et ai. 1979). Radiographic evidence from these Vermont talc millers showed pneumoconiosis on 9 of 11 available chest roentgenograms. Although exposures were It high, the talc w as free of asbestos and free silica (Bolndy et al.. 1979). Pneumoconiosis, . however, was not significant in this study. Pleural abnormalities (unspecified) were found in 90 of Vermont talc workers (Wegm.an et ai. unpublished), compared with 9n w ith small irregular opacities and 12,, w ith small rounded opacities. This is in contrast to this study w here pleural thickening w as observed in 9; of the population, but less than 1 \ had any signs of pneumoconiosis. Pleural thickening is generally considered to take many years to develop. In a study of a Swedish population, mean latency for the development of bilateral pleural plaques after first exposure to asbestos w as estimated at about 30 yr. which was consistent w ith other studies. Pleural plaques were rare before age 40 (Hili frrahl. 1978). However. Ochs and Smith (1976) reported on at least one case where as little a time interval of 1 yr was necessary for the appearance of bilateral pleural thickening in an individual without occupational asbestos exposure. In the study reported here, latency (time r.-( J-"- between first known talc exposure and date of the study) was 13 yr for workers with bilateral thickening and 4.5 yr in those with unilateral pleural thickening, a much shorter time than generally associated with pleural thickening from asbestos exposure. North Carolina also had an increased prevalence in workers less than 40 yr of age. The association of pleural thickening and asbestos exposure may vary considerably in different populations. In a Sw edish study about 1 0 of the men over 40 and less than 0.10o of men less than 40 had bilateral pleural plaques (Hillerdahl 1978). Almost 80,, were current ex-smokers and had had some exposure to asbestos. Fibrosis was rare (4o of those with pleural thickening). Another community type study in Birmingham, England (BTTA and MRCPU, 1972) found that about 1% of those attending chest clinics had pleural plaques (10,, of these were calcified). Unilateral obliteration of the costophrenic angle (not considered to be caused by asbestos) was -?, '<. observed in 360 of those with pleural plaques and there was a definite history of j-X asbestos exposure in no more than 11 ,, of the cases. Much of the pleural thickening i5? was considered to be due to pleural disease (e.g.. emphysema, severe chest wall injury, ix.^' pleurisy). In the study of talc workers reported here, there was no apparent difference between those with and without pleural thickening in the exposure to asbestos or in chest disease. 10003017 \n epidemiological-indu'irul h\cienc siud> 855 In these two community studies the association of pleural thickening and asbestos exposure was quite different. The association of pleural thickening with asbestos may be coincidental, as the prevalence of pleural thickening is quite different in asbestos exposed workers. For example, prevalences of 17.5 and 35c have been reported in asbestos manufacturing plants and shipyard joiners (Weiss and Theodos, 1978; Fletcher. 1971). Two other studies of shipyard and dockyard workers reported prevalences of pleural thickening of around 50 (Flftchi r. 1972; reported in Wf.iss and Thfodos. 1978). It is possible that factors other than asbestos may account for these differences (e g., age distribution, method of reading X-rays, oblique X-rays in addition to PA. different exposures and exposure times, smoking habits, readers, etc). Some of these factors could possibly account for the differences between study and comparison populations seen in this study. Exposure to other dusts have also been associated with pleural abnormalities. Smith (1952) reported finding a pleural calcification among 302 men making mica insulators. 6.30 among miners and millers of tremolitic talc, but zero among 261 asbestos workers. The common feature of exposure of all four groups w as said to be exposure to talc or mica. No asbestos was seen in the NIOSH samples of Montana and North Carolina talc. McCrone (1975) analysed two samples from North Carolina and found 0.1 5,, tremolite-actinolite by polarized light microscopy in one of the samples. Tremolite and actinolite have been reported in the Murphy talc deposits although the quantities were small (Van Horn. 1948).Grexaand Parmentier (1979(report0-50oanthophyllitein `North Carolina' talc and no asbestos in Montana talc. Seven samples from Montana revealed no asbestos (McCrone, 1975) and antigorite was observed in some of the Texas samples (McCrone, 1975). While analysis of the talc from these three regions revealed little or no asbestos, the presence of asbestos as an impurity often occurs. It is not known w hether very low levels of exposure to asbestos for short periods of time is sufficient to cause pleural thickening. Thus, w hile pleural thickening is generally considered to be a signpost of asbestos exposure (Sarc.fnt et al.. 1977), the possibility of other agents causing pleural thickening should be considered. The conclusion of Mcl rman (1966) that factors other than asbestos were either contributory or the sole cause of calcified plaques seems applicable to pleural thickening. The results of this study suggest that talc itself may produce pleural changes. The clinical significance of pleural thickening, pleural plaques and pleural calcification as a result of asbestos exposure remains unclear, but is of concern because the pleural changes were considered to represent a significant exposure to asbestos and may be related to mesothelioma. However, there may be no association of mesotheliomas and pleural plaques even in the presence of asbestos, as no mesotheliomas associated with anthophyllite asbestos exposure have been observed in Finland (Mfi rman et al.. 1974). The suggestion that talc is carconogenic (Bi.fjer and Arlon. 1973) may be due to asbestos contamination of the talc. The characteristics of talc have been poorly reported in the past. Talc free of asbestos contamination does not appear to increase the risk of cancer, and mesothelioma has not been associated with talc exposure (Kleinfeld et al.. 1974; Rihino et al.. 1976; Wagner et al., 1977; RCBTA and MRCPU. 1979; Sflfvan et al.. 1979). Risk of cancer in this study cannot be determined. Among those with bilateral pleural thickening, lung function was 10003018 -* y... \ : * i i. c-- .**- *t~ V#"Vi ^ ---v ,1 ? . Ce; - 7l- J (J \mhi i. A Cki n nd J H \V<H K significantly reduced. The prognostic significance of these obser\ations is unknown and deserves prospective evaluation CONCLUSIONS In ihis cross-sectional stud) of 299 talc workers from Montana. Texas and North Carolina, there was no demonstrated association of symptoms (cough, phlegm, dyspnea) or reduced lung function w it h exposure. The prevalence of symptoms nj. not elevated and there was no demonstrable reduction in FEV, and FVC compared with the control populations. Thus, both internal and external comparisons wereconsisient in confirming the lack of association between morbidity and exposure variables. While there were no demonstrated differences in the symptom prevalences among the three talc regions (despite differences in exposure and talc composition), there were differences in the prevalence of cough and phlegm betw een the study population and the workers exposed to talc containing tremelite and anthophyllite. The only significant effect observed in this study was related to the increased prevalence of bilateral pleural thickening. The excess was considerable in relation to the non-talc comparison populations, but the dose-response relationship was somewhat confounded with age. The comparable results among the talc populations, the lack of a consistent association of pleural thickening with asbestos exposure, and the lack of parenchy mal changes in the talc exposed w orkers suggest talc as an etiological agent in the development of bilateral pleural thickening. While those with bilateral pleural thickening had reductions in lung function and a possible increase in symptoms, the long-term significance is unclear. At least two warnings must be acknowledged. The mean number of years worked is relatively short. Therefore, more lime may be needed to see exposure effects. The suggestion of reduced flow rates at low lung v olumes supports this caution, as they may be early indicators of airways disease. The association of talc exposure w ith bilateral pleural thickening was relatively weak. However, latency was shorter than is commonly found in other studies and the excess is considerable compared with non-talc populations. A prospective study is necessary to answer the questions concerning prognostic significance. Acknoulcil^cmctus -- Wc appreciate ihe assistance and ce-operjiion of the companies and worker- which made the studv possible. We thank the ALOSH medical field team and interpreters who helped collect the data, and Mar>. who tvped the mans drafts. REFERENCES Attmiid. M. 11979 i The effect of exposure to silica and diesel exhaust in underground metal and nor.meul miners Industrial Hvgiene for Mining and Tunneling--Proceedings of an ACGIH Topical Svmposium. November 6-7. 1978. B vx kx, D E.. K. L.. B<m mi i< kt. B A.. At thi-i -i. R B. and Ml ki hvxt. J. A. I I9X| i Silico-ts in silica flour workers, -tin. Her. re.vp. Die. 124, 445 450 Bit kLvkk. M R and Prxvtt it. S. iI979i Evaluation of tests of lung function for 'screening' for earl> detection of chronic obstructive lung disease In The La'V in the Transition Bclnccn Health an,I D.'fasc (Edited bv Mvt kuvt. P. T and Pikvh n. S i Dckker. New York. Bixifr. H. P. and Arlox. R. (1973) A possible occupational and environmental carcinogen J occur. Mai. 15. 92 97 Boi hi vs. A.. BvRHrRU A.. Schii ux<;. R. S F and v vx pt Wufstijxl K P i 1969i Chronic respirators disease in hemp workers Am. J. McJ. 46. 526 537 An epidemiological industrial hygiene study 857 Boinds.M G.. Martin. 1C P. Bi kgfss. W A. and Dfsifnt. J M. 11979) Occupational exposures lo nonasbestiform talc in Vermont In Dusts and Disease (Edited by Levies. R and Dement. J. M I Pathotox Publishers. Park Forest. Illinois. BTTA and N1RCPL: (1972) A surve> of pleural thickening: its relation to asbestos exposure and previous pleural disease Em . Res. 5, 142 -151. Cher suck. R. and McCarths. D S (19791 The Lung m the Transition Between Health and Disease (Edited b) Mvcklem, P T and Permitt. S I. pp 329-342. Dekker. New York DeLai df. A (19771 Talc-related pathology. Bull Acad. Sail Med 161. 405-409 Demest. J M. and Zi mwaldf. R. D (1979 (Occupational exposures to talc containing asbestiform minerals In Dusts and Disease (Edited by Lfmi s. R and Demfst. J. M.|. Pathotox Publishers. Park Forest South. Illinois Demest. J M. Zlmwaide. R D. Gamrie. J. F,, Feuner. W.. DiMfu M. J.. Brows. D. P. and Wagoner, J. K (1980) Occupational exposure to talc containing asbestos Morbidity. Mortalit>. and Environmental Studies of Miners and Millers DHEW (NlOSHl Publication Number 80-115. US Government Printing Office. Washington. DC. Fine, L J.. Peters. M. J. Birgfss. W. A. and DiBtrardinis. L J (1976) Studies of respirators morbidity in rubber workers Part IV Respirators Morbidity in Talc Workers 4rchs enur Hlth 31. 195-200. Fleiss. J L (1973) Statistical Methods lor Rates and Proportions. John Wiles. New York. Flftcher. D. E. (1971) Asbestos-related chest disease in joiners. Proc. R. Soc Med 64. 837 FLETCHrR. D E. (19721 A mortalitv studs of shipvard workers with pleural plaques Br. J. ind Med. 29, 142 145 Gasiri.f, J. F.. Fellnfr. W and DiMio. M J. (!979a) An epidemiologic studs of a group of talc workers. Am. Rei. resp. Dis. 119. 741 753. Gamrle. J. F . Feli.vir, W. and DiMeo. M. J. (1979bI Respirators morbidity among miners and millers of astbestiform talc. In Dusts and Disease (Edited by Lemfn. R. and Dement, J. M l. Pathotox Publishers. Park Forest South, Illinois. Grexa. R W. and Parvientier. C. J. (1979) Cosmetic talc properties and specifications. Cosmetics and Toiletries 94, 29-33. Hancock. J. and Attfifld. M. D. (1980 i Intercept-free method ofestimating the effect ofexposure on FEV,. (Manuscript in preparation.) Hillfrijahi . G. (19781 Pleural plaques in a health survey material--Frequency development and exposure to asbestos Scand. d. resp. Dis. 59, 257-263. Hlrwitz. M. (19611 Roentgenologic aspects of asbestosis. .4m. d. Roentgenology. Radium Therapy, and Suclear Medicine 85, 256-262. Hs att. R E.. Rooartf. J. R.. Mtao. J. and Wii.sox, T. A. 11979) Changes in lung mechanics, flow-volume relations In The Lung in Transition Between Health and Disease (Edited b) MaCKLFsi, P. T. and Pfkmi tt. S ). Dekker. New York. Kifinffld. M.. Mfssitf. J. and Z vki. M H. <1974| Mortalitv experience' among talc workers: a follow-up studs J occup Med 16. 345. Mxcki.fxi. P T. 119721 Obstruction in small airwass--A challenge to medicine, ,4m. J. Med 52. 721-724 McCroni. W. C. (1975) Analssis of Talc bs X-rav Diffraction and Polarized Light Microscopy. USDHEW PHS CDC NIOSH. Contract Number CDC-210-75-0063 with NIOSH Mead, J (1979) Problems in interpreting common tests of pulmonary mechanical function. In The Lung in Transition Between Health and Disease (Edited by Macklfsi. P.T and Persiltt.S). Dekker. New York. Messih. J.. Reddin.G. and Kleisfeld, M. (1959) Pulmonary talcosis. a clinical and ensironmental study. Arch. ind. Hhh 20, 408-413. Mn rsi an, L. O. (1966) Asbestos bodies and pleural plaques m a Finnish series of autopsy cases. Acta Path. Micrnhiol. Scand.. Suppl. 181, 1-107. Mei rman. L. O.. Kixilloto, R. and Hakama. M. (1974) Mortality and morbidity among the working population of anlhophvllite asbestos miners in Finland. Br. J Ind Med 31. 105 112 NIOSH H977) Manual of'Analytical Methods, Second Edition, DHEW, 77-I57-A. NIOSH lundatedl Review and Evaluation of Analytical Methods for Environmental Studies of Fibrous Particulate Exposures. DHEW (NIOSH) Publication Number N-204 Ochs. C. W. and Smith. J. P. (1976) Chronic pleural thickening: some observations on cause and pathogeneses. Milit. Med 141. 77-81. Rfsi ari ii Ciivisuntr he Tiir British Tihirac k Avax ivtuin and thi MRC Pnh mhoinkisis Unit (1979). A survey of the long-term effects of talc and kaolin pleurodesis. Br d. Dis Chest 73. 285-288. Ri hinu C. F.. Scansetti. G.. Piulatto. G. and Gav. G. (1977) Mortality and morbidity among talc miners and millers in Italy Institute of Occupational Health of Turin University. 12 pp Rt hinu C. F.. S( ansi.tti. G.. Phu vttu. G and Rhsiano, C. A. (19761 Mortality study of talc miners and millers d occup. Med. 18. 186. 10003020 v: -, --rv-* -v. ,, 5- ' 4'^- yT.Hr-K T, 3.-- k ri.: L*1 v *1 V * rfr * v'? Trrft' AV.i V*~ wtwuk. :w.-. \*. rsM`;^-5 *. C . - -S-- -< s. . vr:V ;r'r- *" ^ x. ^ " ?*'' '1'v 7% v i * ' -pm :: 'A rt-J 7 i. .T7..' v . - .* T*-? ,,. < f V '' ; '.-mStoS. Z.' .. * -C^?>dv_. -a' TtS'/" - -- ..sd ~. -7-s'. /-..ife.* > -ir:-- : >... *< :: >s; j .Ul'-r/T 858 J Gxxiblf. A Gsi.itandJ Hvmotf, Sxhi.im.E V . J\< nnsiin. G and Gi >rim>xsiis. J S 119771 Pleural plaques a sign-post of asbestos dust inh.tLilion Siiiiiiiumm Ri>cnUic>k<lo<i\ 12. 287-297 Si i i v is. S G . Di mi sr. J M . VViiaisi r. J k and Fki usis. J R (19791 Mortality patterns among miners and nnllcr- of non-asbcxiiform laic preliminary report In Dusts jnJ Discust- (Edited by I.i mi s. R and Dimisi. J M l P.ithotox Publishers. Park ForeM. Illinois Smith. A R i!952i Pleural calcification resulting from exposure to certain dusts -tin J RocmiKiinfoi/i'67. 375 .is; Sittus. G W. Wrrxtx G W. Sent t*. L A and Trahxxt. G. D 11979) Summary report of the environmental results of the MSHA \IOSH silica diesel exhaust studs. Industrial Hygiene for Mining and Tunneling Proceedings of an ACGIH Topical Symposium. 6 7 N'osembet 1978 VasH'irs. E C ll948)Talc Deposits of the Murplv Marble Belt Bulletin Number 56 of the North Carolina Department of Conservation and Development. Raleigh. North Carolina. W vgsir, J. C.. Bt krv. G.. Coukt. T J. Hn L. R J. Potu fs. F D and Smdmuri. J W (1977) Animal experiments with talc. In InhjU-J PariicU'S H (Edited by Wxltox, W H I. pp 647-654 Pergamon. Oxford Whsx. W and Tut him is. P. A 119781 Pleuropulmonary disease among asbestos w orkers in relation to smoking and type of exposure. J. oaup A fed 20. 341 345. DISCISSION* J. C Mr Diisxi.d: In addition to the pleural thickening you observed, was there any evidence of pleural calcification ' J. A. Miri hxm . May 1 answer that'11 reviewed all the films w ith pleural thickening and there were no cases at all of pleural calcification. Most of the pleural thickening was grade 1. but there was one case w here the thickening was considered grade 2. Two of the cases of pleural thickening were extent 2; the rcmtunsler extent I. J. Wii 11vis. Do you have full information on the siee distribution of your talc dust particles ' Dr Dt xust: \Aedo have some information that is not presented in this report. Of course, the respirable dust sampling attempted to simulate those particles which have the possibility of deep lung penetration. In general, the Montana talc had by far the largest particle size with much larger plates. In North Carolina there is a combination of the platy and acicular particles which were identified by electron diffraction and microchemical analysis as being talc with a rather unusual morphology. S F. MrCt t hi.h: In this study land several others'use is made of the standard respiratory questionnaire Among other questions, workmen are asked if they get more short of breath walking on the level than other men of their own age. I have asked this question of thousands of workmen in Australia and at least half answer. 'Gee. Doc. I wouldn't know' In the present study were the men forced to a decision, do you have a 'don't know'category or are American workers a great deal more intelligent than Australians.' Dr Di xii xt: Ve try to administer the same questions to both our exposed and non-exposed populations and hope the level of intelligence is similar and better. The questionnaires are difficult to answer olT-the-cufT. but we employ trained interviewers who are familiar with answering the questions and try to seek the answer in a polite manner Very seldom does a worker answer.`I don't know' A very high percentage answer 'Yes' or No' and. if the answer is equivocal, the question is repeated with the admonitii. o answer 'Yes' or No' M. Jxi tmxix: May I comment on Dr McCullagh'squestion. Whilst it is true that there arc often ambiguous answers and strict protocols have to be used in order to maintain properly recorded answers useful for epidemiological studies, there is ev idcnce from our studies that, if this is done rigorously and conscientiously, then the data obtained may be used sensibly for epidemiological purposes. Coalminers who have been asked these questions are no more or less intelligent than Dr McCullagh's patients. Their responses indicate very clearly that their mortality risk, particularly to the respiratory diseases, can be related to those responxes to the questions particularly those relating to breathlessness and to cough and phlegm. ML N i \xlit>i si: | am surprised at the high prevalence of pleural thickening that you report In a survey of 30 40 pharmaceutical workers exposed to a carefully specified, non-fibrous talc, we observed no more than one or two pleural thickenings. * The paper wax prevented, and questions taken, by Dr J. M Divii xt 10003021 An epidemiological-industrial hygiene study 859 Dr Di mist There are several possible reasons for the difference I think the possibilit) of contamination cannot be ruled out until we look at the talc composition in these facilities o\er a number of sears The possibility that pockets of fibre contamination exist in these operations also cannot be excluded F.DK Liivmi t Tables 7 5 present the pres alence ofcough, of phlegm and of dyspnea by sears ssorked and by cumulanse exposure, but for all three States combined On the other hand. Table 1 reseals important associations betsscen age. duration of employment and dust concentration in the three States Toss hat extent are the 'negatise' findings of Tables 3- 5 a masking of positise associations, within at least one State, bs the interactions shown in Table 1? Dr DtxtEvr: All the regions analysed were looked at separately Admittedly the numbers were small within each region, but the only really significant finding in each of the regions was the pleural thickening J C. Gilson: I would like to make two comments. The first concerns the recording of pleural thickening. The classification does proside a means of measuring the extent of this as well as the width, and I think it is important to make use of this information in order to deal with the kind of question that Dr New house has raised. My second point relates to the respiratory questionnaire. This questionnaire, as many of you know. was originally started here in S W ales by my colleague Dr Fletcher and. of course, it was applied to coal miners Now coal miners do. by virtue of their job. have to walk together often underground under very adverse conditions Also, in this particular area, the coal mines are in relatively steep valleys so miners were constantly walking with their colleagues I have always thought the quest ions were particularly applicable in these circumstances and that they might well be inapplicable where people were walking on the level If we had originally had coal mines in Norfolk this particular questionnaire would never have been developed J C Mr Diinxld: In our studies of Quebec asbestos workers, we found a very much higher prevalence of pleural thickening in one region than in the other, even allowing for exposure and other factors This suggested to us that there might be something other than the asbestos involved, but we found no evidence for this The same went for calcification. m at', t-v Sri .. r LE'-ruf-- ", ' . s ~ ? ._r-- t.'. .' .. ` v ^ - t i` c- f v. i s 10003022