Document mewqknZ8moB6g6VrM7XjNRp0

Environmental Health Perspectives Vol. ii, PP- 15.1-157, 1981 t Epidemiological Study of [ Pneumoconiosis in the Italian j Poly(vinyl chloride) Industry 1 by G. Mastrangelo,* B. Saia,* G. Marcer* and G. Piazzat t \ Among 1216 workers employed in a poly(vinyl chloride) production factory, 20 cases of pneumoconiosis were found. None of these workers had had previous 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. Chest x-ray films were read by two independent physicians utilizing the ILO/UC Pneumoconiosis Classification, 1971. X-ray abnormalities were characterized by limited profusion, irregular type and low gravity; in a small percentage of cases these were associated with slight restrictive respiratory function impair ments, All 20 workers with PVC-induced pneumoconiosis had been exposed to high PVC dust pollution for at least five years. Mild nonspecific 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 (observed in 388 cases, 31.9% of the whole population), are related mainly to age and smoking habits, and the role of exposure is minor. We examined the working population of plants producing polyfvinyl chloride) (PVC) in Porto Marghera, Italy; 1216 workers had no previous dust exposure. Of these 731 were exposed to PVC dust polymer alone while 485 were exposed to vinyl chloride monomer (VCM). In the drying, sacking and blending departments, PVC dust concentra tions were over 10 mg/ms of total dust in about 60% of the samples, whereas in the polymerization departments no concentration over 10 mg/m3 was found. In the samples taken, particles with diame ters of 1 p,m to 6 p,m constituted 4.5 to 30.9% of total dust weight. All the workers had chest x-rays according to ILO standards and a spirographie examination. Chest x-ray films were read by two independent Physicians utilizing the ILO/UC pneumoconiosis classification. For statistical analysis, a consensus reading was used. Mstituto di Medicina del Lavnro, University degli Studi ^'a facciolati 71, Padua, Italy. I*tituto di Radiolngia (I Cattedra) University degli Studi sduv*, Via Giustinian 3, Padua, Italy. October 1981 Table 1 shows that there are no significant differences in age and smoking habits, but the exposure duration is higher in the workers not exposed to dust. Table 1. Group No. of % of Age, yr Exposure, yr subjects smokers (mean SD) (mean - SD) Exposed to PVC dust Not exposed to PVC dust 731 485 73.9 37.7 8.8 6.1 4.0 68.7 35.7 8.5 8.6 4.5 ' Table 2. PVC dust exposure, yr Age distribution of cases* < 30 yr 31-40 yr 41-50 yr > 60 yr <6 5-10 >10 - - 2(2.4) 5(8.3) 1(5.9) - 2(3.8) 8(9.0) 2(9.5) `Values in parentheses are percentages of subjects with PVC pneumoconiosis in each class of age anil exposure. 153 _ ___________ UCC 088250 In 20 subjects we found chest x-ray changes of nt least class 1 according to the II.O/UC classification. The mean age of this group was -14.9 5.2 years and the mean length of exposure was 11.6 5.4 years. Sixteen subjects (80%) were cither 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 the increasing length of exposure. In the case of the x-ray changes, 16 subjects had class 1/0 profusion, 2 cases class 1/1,1 case class 2/1, and 1 case class 2/2. Irregular opacities were prevalent: 10 were type s, three were type t, six were type p and one was type r. They were diffused, mainly over median lobe areas. A chest x-ray of a worker exposed to PVC dust (Fig. 1) for 15 years shows a gross reticular pattern: profusion is class 2/2, type t. In the right hemithorax of the same subject (Fig. 2) there is a mottled reticular pattern. Figure 3 is an enhanced view of the right hemithorax showing the mottled reticular pattern more clearly. Another case of PVC induced pneumoconiosis can be seen in Figure 4. The worker was exposed to PVC dust for 20 years. A fine, dense reticular micronodulution is evidenced. Profusion is class 2/], type p-B, Figure 5 shows the right hemithorax of the same subject; pin-point opacities can he seen. In spite of age and the considerable exposure, the majority of cases were in a low profusion category, indicating the slow evolution of the disease. All had worked in high air-borne dust level environments (mostly drying and sacking) for at least five years. None of the 20 subjects was in a group unexposed to dust and none had experienced previous occupa tional exposure to organic or inorganic dusts. We considered the alterations to be PVC pneumoconio sis. 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; the remaining 808 subjects were class 0/0. Table 3 reports the total population distribution excluding 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 and PVC dust exposure: PVC + represents presence, and PVC absence of PVC; x-ray + indicates the group with Figure 1. Chest x-ray of a worker exposed to PVC dust for 15 years. Profusion class 2/Z; type t. 154 -- Environmental Health Perspectives >- * + ***!*'*&-'-- --- --'-- - Figure 2. Right hemithorax of the same subject as in Fig. 2. Figure 3. Enhanced view of the right hemithorax of Fig. 2, showing the mottled reticular pattern. class 0/1 profusion. To assess the influence of both lisk indicators we performed a two-way analysis of variance for proportions. Table 4 shows that both age and exposure were significant factors influencing x-ray abnormalities. The square of a multiple partial association coefficient for qualitative data was calculated to measure the degree of association between the dependent vari able (x-ray changes) and each of the two predictor variables (age and exposure). Age and exposure are i'vc + X-ray + X-ray - I'VC - X-ray + X-ray - Table 3. Age distribution of subjects < 30 yr 31-40 yr 41-50 yr > 60 yr 20 78 123 35 133 197 108 17 17 46 56 16 119 158 67 9 October 1981 alternately held constant. 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 the cases according to smoking habits in workers exposed and not exposed to PVC dust. Table 6 shows that chest abnormalities are significantly influenced by both risk indicators. Source of variation Age PVC dust exposure Interaction Error Table 4. Degrees of Sum of Mean freedom squares squares 3 30.9713 10.3238 1 0.7843 0.7843 3 0.9882 0.3294 1188 227.9403 0.1919 F 63.81* 4.09b 1.72 *p < 0.01. bp < 0.0!). 155 UCC 088252 I ! Figure 4. Chest x-ray of a worker exposed to PVC dust for 20 years. Profusion class 2/1; type p-s. I i I 1t l iI PVC + X-ray + X-ray - PVCX-ray + X-ray - Table 5. Nonsmokers 40 147 25 127 Smokers 216 308 107 226 li I t t \ v Source of Variation Age PVC dust exposure Interaction Error p < 0.01. 156 Table 6. Degrees of Sum of Mean freedom squares squares 1 7.8850 7.8850 1 1.7847 1.7847 1 0.1023 0.1023 1192 251.9125 0.2113 F 37.31* 8.44* 1.0 i, t1 {; J Figure 5. Right hemithorax of the same subject as in Fig. 4. Environmental Health Perspectives  - " m' Jj t '_>v - Vj ^ , - * ^.1 1 .* ^ j When exposure is held constant, habitual smoking is 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 abnormalities. Our epidemiological study confirms experimental and pathological data already reported regarding the effects of PVC dust. Lung changes are directly related to PVC dust exposure, whereas VCM exposure alone fails to cause these changes. There fore, we believe that pulmonary changes are not pathogenically similar to other vinyl chloride in duced abnormalities, that is fibrosis of the liver, scleroderma-like skin changes, and peripheral vas cular damage. In our study there was only a 1.6% prevalence of pneumoconiosis in the total population, but in the workers exposed to effective risk of pneumoconio sis (731 subjects) the prevalence rose to 2.7%. Apart from 20 cases of pneumoconiosis, mild nonspecific alterations (profusion of 0/1 class) were found 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. K %I October 1981 157 UCC 088254