Document 93Mrr53gv1vr3op6y1xOxQJve

Occup. Med. Vol. 49, No. 8, pp. 536-539, 1999 Copyright O 1999 Ltpplncott Wiliams 4 WBkins (or SOM Printed In Great Britain. All rights reserved 0962-7480/99 Downloaded from occmed.oxfordjournals.org by guest on May 4, 2011 Mortality due to asbestos-related causes among railway carriage construction and repair workers G. Battista,* S. Belli,1' P. Comba,* C. Fiumalbi,* M. Grignoli,1 F. Loi,s D. Orsi* and I. Paredes* _,, *Unit of Workers Preventive Medicine, University of Sieria, Siena, Italy; tNational Institute of Health (ISS), Rome, Italy; *Occupational Health Service, Local Health Unit, Arezzo, Italy; *Occupational Health Service, Local Health Unit, Siena, Italy The objective of this study was to further clarify the cancer risk associated with asbestos exposure in railway carriage construction and repair. The cohort included 734 subjects employed between 1 January 1945 and 31 December 1969. Vital status was ascertained at 31 December 1997. Mortality was investigated in the time span 1970-97. Forty-two subjects (6%) were lost to follow-up and eight causes of death (4%) could not be ascertained. The overall mortality was not above the expected value. Among neoplastic diseases, excesses were observed for lung [standardized mortality ratio (SMR) = 124; 90% confidence interval (Cl) = 87-172; 26 obs), pleura (SMR = 1,327; Cl = 523-2,790; 5 obs), larynx (SMR = 240; Cl = 95-505; 5 obs), liver (SMR = 241; Cl = 126-420; 9 obs), pancreas (SMR = 224; Cl = 98-443; 6 obs) and multiple myeloma (SMR = 429; Cl = 117-1,109; 3 obs). The observed excess of lung and pleural neoplasms can be causally related to asbestos exposure in the manufacture of railway carnages. A causal rote of asbestos exposure in the raised SMRs from laryngeal and pancreatic neoplasms and multiple myeloma cannot be conclusively proven Key words: Asbestos; laryngeal cancer; lung cancer; multiple myeloma; pancreatic cancer; pleural mesothelioma. Occup. Med. Wol. 49, 538-539, 1999 Received 24 March 1999; accepted in final form 6 July 1999 This study was partially supported by National Research Council Project `Clinical Applications of Oncologic Research'. INTRODUCTION Construction and maintenance of railway carriages in the 1940s through to the 1970s involved extensive use of asbestos in many countries. Initially, asbestos was essen tially used to insulate boilers, mains and gaskets; subse quently, it was employed to insulate the entire carriage. The first report of cases of mesothelioma in railway machinists (t.e., mechanical workers active in construc tion and repair of railway carriages) was presented by Wagner et al.,x followed by several authors from various countries (for a recent review, see Maltoni et al.2) Mancuso3-4 studied a cohort of US retired railway machinists hired between 1920 and 1929 and showed that 61% of cancer deaths among them were due to lung Correspondence to: Prof. G. Battista, Unit of Workers Preventive Medicine, University of Siena, Via dei Tufi, 53ip0 Siena, Italy. Tel: (+39) 0577-586753; Fax: (+39) 0577-586148; email; battistamailsrv.unisl.lt cancer and mesothelioma. Increased mortality from both pleural and lung neoplasms was detected among Italian railway carriage construction workers5 and Swedish rail way maintenance shop workers,6 taking into account a latency time of 20 and 30 years respectively. A casecontrol study by Schenker et cdl detected a relative risk of 7.2 for pleural mesothelioma among US railway workers with previous exposure to asbestos. The present study deals with the cause-specific mor tality experience of a cohort of railway carriage construc tion and repair workers, with the aim of further clarifying the cancer risk associated with asbestos exposure in this occupation, over a 50-year time span. MATERIALS AND METHODS The plant which was studied was in operation from 1906-69, but ceased between 1943 and 1945 due to G. Battista at a/.: RaBway carriage construction and asbestos 537 Downloaded from occmed.oxfordjournals.org by guest on May 4, 2011 wartime destruction. Production included railway and tramway carriages, locomotives, industrial and agricul tural machines; rolling stock was also repaired and even tually demolished in an area of the factory. In the main work areas, forging, pressing, metal con struction, assembling (which included joinery and uphol stery), finishing repair and painting were performed, and were located in large sheds where four to eight carriages could be concurrently processed. The only openings were the accesses for carriages. The use of asbestos as an insulating agent in railway carriages started in the 1940s, with the application of chrysotile boards in specific parts, e.g., around the heating system. Starting from the 1950s, crocidolite-containing mixtures were sprayed on the entire internal surface of the carriage. Insulation workers were employed by specialized companies and wore protective equipment, but they often operated while other workers, with no protective equipment, were engaged in different tasks. Exposure to asbestos could thus be caused both by the work process itself (especially for assemblers, finishers, joiners, uphol sterers, electricians, maintenance workers and cleaners), or by ambient air contamination (for an extensive his torical study on the use of asbestos in Italian railways see Merler et al.8) No measurements of asbestos fibre concentration are available, because at the time this was not recognized as an occupational risk. The cohort, based on company files, included 734 subjects hired between 1 January 1945 and 31 December 1969. Vital status was ascertained at 31 December 1997 from the Registrar Offices of the municipalities of resi dence of cohort members, which also provided informa tion on causes of death. The mortality experience of the cohort was studied for the period 1970-97, since the qual ity of death registration prior to 1970 was not adequately known, and no regional mortality rates were available. Causes of death were coded according to the International Classification of Disease, using the 8th Revision for 1970-79, and the 9th Revision for 1980-94. The observed mortality was contrasted to expected figures obtained by applyingTtiscany Region cause-, sex-, age- and calendar year-specific mortality rates to the cohort's person years, using the OCMAP statistical pack age.9 Confidence intervals (Cl) were computed on the assumption of Poisson distribution; 90% levels were used not only in order to reduce type two statistical error, but also because the causal relation between asbestos expos ure and cancer risk is known a priori, and the hypothesis being tested was only that of an increased mortality. Besides mortality analysis based on death certificates, a `best evidence' approach based on the acquisition of all available clinical and pathological material for every deceased person was undertaken, according to the guide lines provided by Selikoff et al.10 RESULTS The cohort consisted of 734 male workers whose mean age at hiring was 29 years. The vital status of the cohort was ascertained at the end of follow-up (31 December 1997); at that date 449 subjects were alive and 243 were deceased. Forty-two subjects with vital status unknown, corresponding to 6% of the cohort, contributed to the total number of person-years till their last day of employ ment. Forty-four subjects died between 1945 and 1969, and were excluded from the mortality analysis, while the remaining 199 died from 1970 onwards. Eight causes of death were not ascertained, corresponding to 4% of the deceased subjects. The cohort's mortality experience in the years 1970 97 is shown in Table 1. The overall observed mortality was close to the expected value, as a result of a significant increase in the deaths due to some causes and a slight decrease of all other causes. Among neoplastic diseases, excesses were observed for respiratory tract cancer (lung, pleura and larynx), digestive tract cancer (liver and pancreas) and for multiple myeloma. As shown in Table 2, the excess of respiratory neo plasms was evenly distributed between those subgroups with 21-30 years and over 31 years since first exposure. The best evidence procedure provided some further information of interest. Clinical records were available for 109 of the 199 deceased subjects and among them for 54 of the 99 cancer cases, with histological diagnoses in 27out of 54. Four out of the five deaths from malig nant pleural neoplasms were due to confirmed cases of mesothelioma, (three of them with histological diagnoses and one with clinical records only). Of the five subjects, one had been a welder, one a joiner and there were also two painters. The fifth worker had been employed as a joiner, welder and painter, while two more mesothelioma cases, a welder and an electrician, were alive at the end of the study. DISCUSSION The present study showed a significant increase in mortal ity from lung and pleural neoplasms, which is consistent with the established effects of asbestos exposure.11 The excess mortality was observable only after 20 years since first employment, which is in agreement with findings from other authors.12-14 The quality of death registration for these neoplasms in Italy has been previously assessed. Death certification for lung cancer is consistent with clinical data (over 80%), but it underestimates the actual number of cases when compared with autopsy data.15 A national survey has shown that about 75% of established cases of pleural mesothelioma are correctly coded at death;16 an autopsy-based study performed in Trieste has estimated a much higher proportion of false negatives (80%) and 20% of false positives.17 In light of these findings, it can be estimated that misclassification may have, at most, implied some underestimation of lung and pleural cancer mortality in the present cohort; four (out of five) observed deaths from malignant pleural neoplasms, as has been shown, were confirmed by the best evidence procedure. 538 Occup. Med. Vd. 49, 1999 Table 1. Cause specific mortality of railway carriage construction workers Observed deaths Expected deaths All causes Circulatory disease Malignant neoplasms Mouth and pharynx Digestive tract Stomach Intestine and rectum Uver Pancreas Respiratory tract Larynx Lung Pleura Lymphoemopoletic system Multiple myeloma Other malignant neoplasms Respiratory disease Digestive tract disease Violence Other and ill-defined causes Missing causes 199 55 99 3 39 13 6 9 6 36 5 26 5 6 3 15 11 8 6 12 8 199.37 75.11 70.49 1.13 26.80 9.95 6.45 3.74 2.67 23.83 2.08 20.99 0.38 4.27 0.70 14.46 12.77 12.05 12.05 16.90 * SMR = standardized mortality ratio. b 90% Cl ~ 90% confidence Interval of the estimated SMR. SMFT 100 73 140 265 146 131 93 241 224 151 240 124 1,327 141 429 104 86 66 50 71 90% CP 89-112 58-92 118-166 72-686 109-190 77-208 41-184 126-420 98-443 112-196 95-505 87-172 523-2,790 61-277 117-1,109 64-160 48-143 33-120 22-98 41-115 Downloaded from occmed.oxfordjournals.org by guest on May 4, 2011 Table 2. Mortality from malignant neoplasms of respiratory tract by duration of employment and time since first exposure among railway carriage construction workers Time since first exposure (yrs) Duration of employment (yrs) 10 11-20 21-30 37 + Total 10 obs exp SMR p-years 11-20 obs exp SMR p-years 21-30 obs exp SMR p-years 31 + obs exp SMR p-years Total obs exp SMR p-years 0 0.15 - 899 0 0.95 - 2,160 4 3.15 127 2,590 2 4.75 42 1,922 6 9.00 67 7,572 - - 1 0.89 112 1,976 5 3.12 160 2,201 13 4.64 280 1,685 19 8.65 220 5,862 - - - - 4 1.08 370 822 6 4.48 134 1,257 10 5.56 180 2,079 - - - - 1 0.63 160 192 1 0.63 160 192 0 0.15 ~ 899 1 1.84 54 4,135 13 7.35 177 5,614 22 14.49 152 5,056 36 23.83 151 15,705 Key: obs = observed deaths; exp = expected deaths; SMR = standardized mortality ratio; p-years = person years of observation. The increased mortality for laryngeal cancer reported in the present study may in principle be attributed to asbestos exposure,18 even if some authors tend to dis regard this association.19-20 On the basis of a thoroughly designed case-control study, Muscat and Wynder21 sug gest a relative risk of 1.3, allowing for other risk factors of laryngeal cancer. The observed increase in mortality for liver and pan creatic neoplasms requires some comment. Pancreatic cancer has been suggested by some authors to be asso ciated with asbestos exposure,22-24 even if there is aware ness of a possible misclassification due to peritoneal mesothelioma. Recently, though, Kauppinen et al.2S did not confirm this finding in a nation-wide case-control study. While the attribution to asbestos of the reported increase in pancreatic cancer remains problematic, the increase in liver cancer mortality could be disregarded as probably reflecting metastases to the liver from lung cancer, which is certainly in excess in this cohort24 The issue of multiple myeloma in asbestos workers was raised in the 1970s by some authors who reported cases of lymphopoietic malignancies in patients with asbestosis, or in subjects who were heavily exposed to asbestos.26-29 Support for this etiological hypothesis came from some case-control studies performed in the US,30 UK31 and Italy,32 while other case-control studies from the US33-35 and Sweden36 provided no evidence of an association. The small increase in mortality from mul tiple myeloma reported in the present study is consistent with the aforementioned positive studies; it should be stressed, though, that a large cohort study of Italian workers compensated for asbestosis did not show any increased risk for this neoplasm.37 In conclusion, therefore, the present study confirmed the expected causal connection between exposure to asbestos in the manufacture of railway carriages, and occurrence of lung cancer and pleural mesothelioma in railway workers. Raised SMRs from laryngeal and pancreatic neoplasms and multiple myeloma were also G. Battista at a/.: Raftway carriage construction and asbestos 539 Downloaded from occmed.oxfordjournals.org by guest on May 4, 2011 detected, although a causal role of asbestos exposure in such cases could not be conclusively proven. REFERENCES I. Wagner JC, Sleggs CA, Marchand P. Diffuse pleural meso thelioma and asbestos exposure in the Northwestern Cape Province. 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