Document B15G10ednx19Oo599L2M4XM4

,V . .. EWIROXMENTAL RESEARCH 5, 210-216 (1972) ENV. t-- 'IS APR 979 K. V'A Nelson 3. N. Kestan FILE Prevalence of PfeofqlXZalcification in Persons Exposed to jffsbestospust, and in the General Hon in the Same District M. Navrahl and F. Trippe Institute of Hygiene and Epidemiology, Department of Industrial Hygiene and Occupational Diseases, Srobdrova 48, Prague 10; and District Hospital, Department of Lung Diseases, Xymburk, Czechoslovakia Received Kovember 17, 1971 It is of interest whether pleural calcification is primarily the result of long years of exposure to asbestos dust or whether there are factors other than ex posure to dust We have investigated persons working for a long period in a plant processing asbestos products (chrysotile), persons without occupational exposure to dust but living in the vicinity of the plant and consanguineous relations of patients with pleural calcifications. We have also studied a large population above the age of 40, in the district in which the plant is situated. Comparison of the groups disclosed that prevalence of pleural calcifications was closely related to opportunity for expo sure to asbestos dust either occupational)v~ni~ huTi--jly ^ reighb^rhiwi mptact. as contrasted with tbe unexposed population. The prevalence in the group with direct or indirect asbestos exposure was 5.3, 5.8, 3.52; whereas in the unexposed population it was 0.342. These results indicate that asbestos is primarily responsible for pleural findings, but that some pleural disease may be the result of the other factors, still not known. Ihe identification of other causes is hampered by the long period which need elapse from the onset of the process to the radiological appearance of the pleural change. Soon after the demonstration of the fibrogenic properties of asbestos clinical evidence appeared demonstrating pleural changes in persons with long work exposure in asbestos mines or factories. The unusual finding of pleural calcifica tion was attributed, in the fifties, solely to the effect of asbestos [Cartier (4), Lynch and Cannon (12;]. Later, when unexplained findings of the same char acter were made in the populations not known to be exposed to asbestos, the etiology seemed less certain [Jacob and Bohlig (9); Anspach (1); Anspach, Roitzsch, and Clauswitzer (2); Bohlig (3)]. Epidemiological studies of populations designed to investigate possible ex posures to asbestos dust led in the sixties and later to sharp differentiation of both points of view. In the first instance, are Finnish, Canadian, American and other investigators who believe that occupational or noaoccupational exposure to asbestos provide the background for pleural findings [Kiviluoto (10, 11); Raunio (16); Cartier (5.i; Selikoff (19); Zolov, Bourilkov, and Babaljov (21); Rubino, Concina, and Scansetti (18)]. In the second group are authors who describe regional concentrations of pleural calcification with no evident contact with asbestos and who. for this reason, reject an asbestos etiology. Prominent in this second group are Czechoslovak workers [Hromek (S); Marsova (13); 1972 by Academic Press, Inc. 210 ASARCO ALV 0002337 212 NAVRATTL AND TMPPE Age 31-40 41-50 51-60 61-70 71 and above Total No. of persons 190 245 1S2 126 12 755 % 25.2 32.5 24.0 16.7 1.6 100.0 In this employed group we found 42 persons with pleural calcifications (5.32); 23 of them had simultaneous X-ray signs of asbestosis, 19 had only isolated ''findings of pleural calcification. Appendix No. 2 The age distribution of persons with pleural calcifications ascertained within the entire period of studies, i.e., during 16 years, was as follows: Age 31-10 41-50 51-60 61-70 71 and above Total No. of persons 1 4 19 16 2 42 % 2.4 9.6 45.0 3S.1 4.9 100.0 The stated age limits relate to the time when we ascertained signs of pleural calcifications for the first time and thus these age limits do not mean the present age of the patients. Till the present day already 6 of the recorded persons have been recorded as deceased. It is important that only one of the patients in which we ascertained pleural calcification for the first time in 1959 was below the age of 40 (36 years). The absolute majority of persons with pleural findings ranges within the age groups of 51-60 years and 61-70 respectively. The second group, with less intimate exposure, may be divided into two subgroups: a. The population living in the neighborhood of the factory (those over the age of 20). This group includes individuals who are not and never were em ployed at the factory. b. Blood relations of factory employees, older than 20 years. Asbestos air pol lution in the vicinity of the factory may have been heavier 20, 30 and more years ago. At present, environmental dust concentrations and chrysotile content in the airborne dust in the vicinity of the factory, are lower because of improved industrial hygiene practice in the last 15 years (Simecewk, Internal Hygienic Report 1969). Blood relations may be assumed to have some increased exposure by virtue of their daily contact with employees, who may have come home with con taminated work clothes. There were 155 persons in the neighborhood group. Pleural calcifications were present in 9 (5.82). Five were also blood relatives of employees. It was quite difficult to investigate blood relatives of exposed factory em ployees. In some cases, we found it necessary to ask physicians from other ASARCO ALV 0002338 5>V. 214 NAVRATTL AND TRIPPE calcifications in the groups with direct or indirect exposure to asbestos dust were so numerous as to strongly affect the prevalence of pleural findings in the population as a whole. Among the factory employees, there were 42 cases of pleural calcifications against an "expected" 2.75 (based on the unexposed gen eral population); in the neighborhood group there were 9 cases against an expected 0.53, and in the family group there were 4 instances as compared with expected 0.39. These results lead to the conclusion that the direct and indirect exposure to asbestos dust is associated with an increased incidence of pleural calcifications. It is also of interest that the relationship of prevalence of pleural calcifications between the general population group and the other three is statistically sig nificant at the 12 level. DISCUSSION This report, reviewing the experiences of several different population groups, supplements our previous observations limited to exposed persons (14). They also tend to confirm results of English, Canadian and American authors, con cerning effects in occupationally exposed populations (5,6,19). It should be noted that in our group of the general population, without any known asbestos exposure, 0.342 showed quite typical findings. According to Finnish and other workers (10, 11, 16, 21) one could expect even here minimal but nevertheless definite asbestos exposure in some cases, as by airborne asbestos. However, from the point of quantitative effect, such asbestos exposure probably represents a very low hazard in terms of pleural changes in the general popula tion living and working far from possible asbestos sources. Parenthetically, serpentine and amphibole minerals are not found in the soil of the region studied, with almost only sedimentary deposits found. Although most cases of pleural calcification in this investigation were related to direct or indirect asbestos exposure, some had no such history. The question might properly be asked whether the causes in such cases were the same as in other series in which asbestos exposure could not be identified (8, 13, 17). We are not able to give a clear answer. Comparison of the results in the several studies shows considerable variation (Table 2). It is difficult to say whether TABLE 2 Prevalence or Plecr.il Calcifications in General Population* Author No. of persons Pleural examined calcifications % Rous and Student fIT i 0760 644 c:5o Iiroraet (so 9571 273 2.70 Marsovi (13) 44549 241 0.54 This study S133 28 0.34 Zolov, Bourilkov, and Babaljov (21/ 3323 135 4.6G Kiviluoto (11/ 35000 77 0.23 * Review of published inves'izations. * Certain environmental asbestos exposure is presumed. ASARCO ALV 0002339 1 ASARCO ALV 0002340