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K-Z5<75d-600) f R&S 131088 Polyvinyl Chloride Pneumoconiosis: Epidemiological Study of Exposed Workers Giuseppe Mastrangelo, M.D,,* Maurizio Manno, M.D.; Guido Marcer, M.D.; Giovanni Battista Bartolucci, M.O.; Carla Gemignani, M.D.; Giulia Saladino, M.O.; Lorenzo Simonato, M.D.; and Bruno Saia, M.D. Among 1216 workers who were employed in a polyvinyl chloride production factory and who had had no previous dust exposure elsewhere, 20 cases of pneumoconiosis were found. Chest x-ray abnormalities were characterized by limited profusion, irregular type and low gravity. All 20 workers had been exposed to high PVC dust levels. The chest x-ray changes were observed after a minimum ex posure of five years and, in a small percentage of cases, were associated with slight restrictive respiratory function impairments. Moreover, in the whole group of workers 386 cases (31.9%) were found with non-specific x-ray abnor malities mainly related to age and smoking. r olyvinyl chloride (PVC) dust is particularly relevant to a consideration of the anatomical, clinical and radiological signs of pneumoconiosis found in workers ex posed to "inert" dusts because of the high annual produc tion of PVC and the number of exposed workers. Within the framework of a national survey on vinyl chloride hazards to humans, co-ordinated by the Chemical Workers Unions, the authors examined the working population of plants producing PVC in Porto Marghera, Italy. One group of workers was exposed to PVC dust; another group worked in departments polluted only by vinyl chloride monomer (VCM). The characteristics and prevalence of pulmonary radiological abnormalities found are reported and their pathogenic mechanism is discussed in this article. Methods and Population Environmental dust samples were collected and both concentration in air and particle size were measured. In From the Institute ot Industrial Medicine, University of Padova. Padova, Italy 540 the drying, sacking and blending departments, PVC dust concentrations were higher than the TLV (10 mg/m1 of total dust) in about 60% of the samples. In the polymerization departments, no concentration higher than the TLV was found. In the samples taken, particles with diameters of 1 pm to 5 pm constituted 4.5% to 30.9% of total dust weight. All the workers answered the European Coal and Steel Community (ECSC) questionnaire for chronic bronchitis and emphysema,' and were submitted to chest x-ray (ac cording to ILO standards) and spirographic examination (Codart-Expirograph, Bilthoven, Holland). Chest x-ray films were read by two independent physicians utilizing the ILO/UC Pneumoconiosis Classification, 1971.1 For statistical analysis, a consensus reading was used. For each worker examined, present and past working histories were carefully recorded and particular consideration was given to previous dust exposure. Of the total, 1,216 sub jects had had no past exposure to organic or inorganic dusts; 731 had been exposed to PVC dust (employed in drying, sacking and blending of polymer); and 485 had been exposed to monomer alone. Results Table 1 shows the mean and standard deviation of age and of length of exposure, the number of subjects and the percentage of smokers in the two groups; those exposed to PVC dust and those not exposed There are no signifi cant differences in age and smoking habits, but the dura tion of exposure is higher in the workers not exposed to dust. In 20 subjects (1.6%), we diagnosed a typical pneumoconiosis, i.e., chest x-ray changes (irregular opacities or frankly micronodular images) of at least class 1 profusion, according to the ILO/UC classification. The B&S 131089 Table 1. -- Age, Exposure, Number o( Subjects and Percentage ot Smokers in PVC Dust Exposed and Non-Exposed Groups. PVC dust exposed group PVC dust non-exposed group Age (Years) Mean S.D. 37.7 8.8 35.7 8 5 Exposure (Years) Mean S.O. 6.1 4.0 8.6 4 5 No. ol Subjects 731 485 % ot Smokers 73.9 68.7 # mean age of this group was 44.9 ( 5.2) years and the mean length of exposure was 11.6 ( 5.4) years; 16 sub jects (80%) were either smokers or ex-smokers. Table 2 summarizes the distribution of cases in relation to age and length of exposure. In all age groups there is an increase of disease prevalence associated with increasing length of exposure. In the case of x-ray changes, 16 sub jects had class 1/0 profusion; two cases, class 1/1; one case, class 2/1; and one case, class 2/2. In spite of age and the considerable exposure, the majority of cases observed were in a low profusion category, thus indicating a slow evolution of the disease. The changes were characterized by irregular opacities: ten cases were type "s"; three cases, type "t"; six cases, type "p"; and one case, type "r." The opacities were diffused, mainly over median lobe areas. Two subjects showed slight restrictive spirographic impairment All had had jobs which involved high air borne dust levels (mostly drying and sacking) for at least five years. None of the 20 subjects was in a group unex posed to dust None of them had experienced previous occupational exposure to organic or inorganic dusts. We considered the above alterations to be PVC pneumo coniosis. In 388 subjects (31.9%) we found slight chest x-ray alterations consisting of linear or irregular vanishing opacities, or both, classified as class 0/1 profusion; the re maining 808 subjects were class 0/0. Table 3 reports the total population distribution, ex cluding 20 subjects with PVC pneumoconiosis. Results are presented in a two-way table -- each entry reports the number of observations. Samples are classified according to age (three classes) and polyvinyl chloride dust ex posure: "PVC +" represents presence and "PVC -- absence. In the table, "x-ray + " indicates the classes with class 0/1 profusion. To assess the influence of both risk in dicators we performed a two-way analysis of variance for proportions (Snedecor and Cochran) ` The column mean is adjusted for row effects and vice versa. We also tested whether row and column effects were additive or whether interaction was present The results (Table 4) show that both age and exposure were significant factors influenc ing x-ray abnormalities -- since the interaction is not significant, the effects are simply additive The square of a multiple-partial association coefficient for qualitative data was calculated to measure the degree of association between the dependent variable (x-ray changes) and each of the two predictor variables (age and exposure)/ Age and exposure are alternately held cons tant. Age is a most important factor. When exposure is held constant, 33.2% of the x-ray changes are shown to depend upon age; when age is held constant, 6.5% are shown to depend upon exposure. Table 5 summarizes the distribution of cases (same subjects as Table 3) according to smoking habits in workers exposed and not exposed to PVC dust. In Table 6, the two-way analysis of variance for proportions shows that both risk indicators have a significant influence on chest abnormalities. There is no interaction of factors. Habitual smoking plays a major role and, when exposure is held constant, is shown to be responsible for 17.1 % of the changes. When smoking habits are held constant, exposure to PVC dust is shown to be responsible for 8.9% of the x-ray abnor malities. Discussion X-ray changes of at least class 1 profusion, found in 20 subjects, are considered PVC-induced pneumoconiosis. This claim is based on the following: (1) Reading of the chest films was performed by two independent physi cians, who were not informed of the age, job, length of ex posure or clinical history of workers. A consensus reading was required for the pneumoconiosis diagnosis. (2) Special attention was given to the absence of any previous occupational exposure to organic or inorganic dusts. (3) The changes were found in workers who had ex perienced prolonged exposure in departments with demonstrated PVC dust pollution The length of exposure was about 12 years on the average and never less than five. No radiographic signs of pneumoconiosis were found in subjects working in departments free of PVC dust, although the average period of exposure was longer Table 2. -- Distribution ot PVC Pneumoconiosis in Age and Exposure Classes (The percentage on the group of same age and exposure is shown in parentheses). PVC Dust Exposure (Years) <5 5-10 >10 < 30 -- Age (Years) 31-40 41-50 -- 2 (2 4) 2(3 8) -- 5 (8 3) 8(9.0) >50 -- 1 (5.9) 2(9.5) Journal of Occupational Medicine/Vol. 21, No. 8/August 1979 Table 3. -- Distribution of Cases with Class 0/1 and 0/0 Prolusion According to Age and PVC Dust Exposure. PVC + X-ray + X-ray - PVC X-ray + X-ray - Age (Years) < 30 31-40 41-50 >50 20 78 123 35 133 197 108 17 119 158 67 9 541 * R&S 131090 Table 4. -- Two-Way Analysis aI Variance for Proportions (Same cases as in Table 3). Source of Variation Age PVC dust exposure Interaction Error Degrees of Freedom 3 1 3 1188 Sum ot Squares 30 9713 0.7843 0 9882 227.9403 Mean Squares 10 3238 0.7843 0.3294 0 1919 F 53 81" 4.09T 1.72 *P < 0 01 tP <0 05 Table 5. -- Distribution of Cases with Class 0/1 and 0/0 Prolusion According to Smoking and PVC Dust Exposure. PVC + X-ray + X-ray - PVC X-ray + X-ray - Nonsmokers 40 147 25 127 Smokers 216 308 107 226 in these workers (Table 1). Previous experimental data on animals and reports of human lung biopsy indicated the possibility that the im pairments described above can be attributed to PVC dust inhalation In 1970, Szende et al' reported a case of pneumoconiosis in a worker exposed to PVC dust Chest x-ray films showed small patches which became denser toward the hilum. Biopsy revealed multiple granuloma tous centers consisting of foreign amorphous material sur rounded by granulation tissue composed of histiocytes, lymphocytes, plasma cells, eosinophils and foreign body giant cells Such centers were associated with moderate diffuse fibrosis. A histiocytic-macrophage reaction in alveolar septa, observed by frongia et al1' in guinea pigs exposed to PVC dust in a sacking department, developed into lesions with multiple granulomatous centers with giant cells during the course ot exposure. Rats exposed to a similar working environment developed marked thickening of in teralveolar septa with an evolution similar to that in the guinea pigs. Such experimental and pathologic data confirm the results of this epidemiological study. Lung changes are directly relatecl to PVC dust while VCM exposure alone fails to cause these changes Therefore, unlike Lilis et al.' we believe that pulmonary changes are not pathogenically similar to other vinyl chloride induced abnormalities (fibrosis of the liver, scleroderma-like skin changes, peripheral vascular damage) In the present study there was only a 1 6% prevalence of pneumoconiosis in a total population of 1.216 subjects Nevertheless, m workers exposed to effective risk of pneumoconiosis (731 subjects) the prevalence rose to 2.7%. Waxweiler et al* reported pulmonary fibrotic changes associated with respiratory function impairments in 96 subjects exposed to PVC dust. Lilis et al' studied the chest x-ray films and changes in respiratory function of groups of PVC production workers who had experienced exposure of different degree and length. They_ found a 4.3% to 22.7% prevalence of chest x-ray changes (small, linear, reticular and/or rounded opacities) and spirographic impairments related to the duration of exposure and to the presence of chest x-ray changes. As these authors did not employ either the ILO/UC International Classification or any other, no comparison concerning the reported prevalence can be made with the present data Apart from 20 cases of pneumoconiosis, mild non specific alterations (profusion of 0/1 class) were found both in the group exposed to PVC dust and in the group exposed to VCM alone. Such changes are related mainly to age and smoking habits, and the role of exposure is minor. References 1 Commission of the European Communities Notes on the 1%7 ECSC Questionnaire tor Studying Chronic Bronchitis and Pulmonary Emphysema. 1972. A Minette. D. Brille, R van der Lende. F SannaRandaccio. anti U Smidt (Eds) Industrial Hygiene and Medicine Texts No 19. Office tor Official Publications ot the turo|>ean Com munities, Luxembourg. 197.1. 2 lacobson C and Lainhart WS ILO.UC 1971 International classification of radiographs of the pneumoconioses Med Ridtogr Photogr 48 b7. 1972 .1 Snedecor CW and Cochran WC Statistical Methods. Sixth Edi tion Ames the Iowa State University Press. Eighth Printing. 197b. pp 472-SO I 4 Blalock HM Social Statistics. Second Edition New Tork McGraw-Hill Book Company. 1972. pp 458-459 5 S/ende I). Lapis K. Nemes A. and Pinter A Pneumoconiosis caused by the inhalation ot irolyvinvl chloride dust Med Las 61 411-4 it., 1970 b Erongia N, Spina//ola A, and Bucarelh A Lesioni polmonan sperimentali da inala/ione pmlungalu di pnlveri ell PVC m ambiente di lavoro Met/ Lav 65 121-142, 1974 7 Lilis K. Anderson H. Miller A. and Selikotl II Pulmonars changes among vinyl chloride polymerization workers Chest 69 299-101, 197b 8 Waxweiler R|. Stringer W. Falk 11 et al NIOSH, Neoplastic risk among vinyl c hloride pol\ men/ation workers. 1 -1 b Ann ,\1 ,4t:at/ .Sci 271 40-48. 197b Table 6. -- Two-Way Analysis of Variance for Proportions (Same cases as in Table 5). Source of Variation Smokinq PVC dust exposure interaction Error *p <0 01 542 Degrees of Freedom 1 1 1 1192 Sum of Squares 7 8850 1 7847 0 1023 251 9125 Mean Squares 7 8850 1 7847 0,1023 0 2113 F 37 31 " 8 44* <1 Polyvinyl Chloride Pneumoconiosis/Mastrangelo et al