Document e5RGqwXj1LkYrp8RXd4y9GjEm

(Page I of 7> 1190 Asbostos, Construction, and Risk of Cancor Koskinon et aj MD-0Q1094 % r^ Different Measures of Asbestos Exposure in Jt Estimating Risk of Lung Cancer and t ! j ; Mesothelioma Among Construction Workers ! Kari Koskinen, MD Eero Pukkaia, PhD Rami Martikainen, MSc Kari Reijula, MD Antti Karj'aiainen, MD To analyze occupation, experl-evaluated cumulative exposure, and radiographic abnormalities as indicators of asbestos-related cancer risk we followed 16,696 male construction workers for cancer in, 1990-- 2000. We calculated standardized incidence ratios (SIR) in comparison to the Finnish population and relative risks (RR) in a multivariate analysis in comparison to the internal low-exposure category of each indicator. Overall, the risk was increased for mesothelioma (SIR 2.0, 95% CT= 1.0-3.3), but not for lung cancer (SIR. 1.1, 95% Cl = 0.9-1.2). Radiographic lung fibrosis indicated a 2-fold and a high value of the exposure index a 3-fold RR of lung cancer, while there was , no risk among those with pleural plaques. The risk of lung cancer was the highest in insulators (RR 3.2, 95% Cl = 1.4-9.9). Occupation, expert-evaluated cumulative exposure, and lung fibrosis are useful indicators of lung cancer risk among construction workers (J Occup Environ Med, 2002;44:1190-1196) From the Uusimaa Regioaal Institute of Occupational Health, Helsinki. Finland (Dr Koskirsen, Dr Reijula); the Finnish Cancer Registry. Institute for Statistical and Epidemiological Cancer Research, Helsinki. Finland (Dr Pukkaia); and tire Finnish Instilure uf Oceupasionai Health, Department of Epidemiology and Biostatistfcs, Helsinki. Finland (Dr Martikainen, Dr Sarjalainen). Address correspondence to: Dr Aniti Karjulcinen, Finnish insiiltue of Occupational Health, Topeliukscnkatu 41 aA. F1N-0025G Helsinki. Finland; e-mail; antti.karjaiirincn@ttl.11, Copyright by American College of Occupational and Environmental Medicine DOI: 10.1097/0 l.jom,00000441.59147,6* xpost)re to asbestos is known to cause pulmonary fibrosis (asbestosis), pleural plaques and other fibrotic lesions of the pleura, lung cancer, mesothelioma, and possibly some other malignant diseases.1 Ear lier asbestos was widely used as a constiluent of various construction materials in Finland, but average ex posure levels were not as high at the construction sites as in some specific occupational settings of asbestos production or shipyard industries,2,3 Construction workers nevertheless constitute the larges! group of exposed workers.4 In the United King dom, construction and building maintenance is estimated to account for the largest proportion of the cur rent and future mesothelioma burden.5,6 Estimation of the level of risk is needed in the planning of medical follow-up, in providing the exposed workers with information on their individual risk, and in assessing oc cupational diseases. In addition to the cumulative exposure to asbestos, information on occupation and radiographic changes have been used as indicators of risk.7 The exact estimalion of past exposure among construction workers is complicated. The numbers of past jobs and of employers are usually high, and the occurrence and type of past exposure to asbestos were very heterogeneous. For example, in Finland, altogether 250 applications and product names containing asbestos have been iaeritified in the construction industry.3 It is difficult for construction workers l I . j j ! - [ * | 4 -? | * \ ' i . ! JOEM * Volume 44, Number 12, December 2002 1191 themselves to know and recognize al! their past exposures, and evert for an experienced industrial hygienist to assess exactly the cumulative ex posure of a construction worker. However as compared to self- reported exposure, an expert evalua tion seems to give a somewhat better estimate of the risk.8 A screening campaign for benign asbestos-induced occupational dis eases was carried out in Finland in 1990-1992 as part of the Asbestos Program of the Finnish Institute of Occupational Health.9 Various occu pational groups in the construction industry constituted the majority of the screened population.10 The major aims of the screening campaign were to find the asbestos-related occupa tional diseases and to organize their follow-up.9 One of the aims was also to create a database for scientific studies on asbestos-related risks among construction workers in Fin land. This report analyses the signifi cance of occupation, estimated cu mulative asbestos exposure, and ra diographic abnormalities as indicators of asbestos-related cancer risk among those construction work ers who participated in the Finnish asbestos screening campaign in 1990-1992. ' ' Materials and Methods Subjects The study population was selected from among the participants of the Finnish asbestos screening campaign in 1990-1992.i0'u All these men who participated the screening cam paign and indicated that they had been employed mainly in building construction were included. Origi nally the participants of the screen ing campaign had been identified from several registers of construction workers: the Finnish Electrical Workers1 Union, the Construction Union (plumbers and pipe insula tors), the Finnish Metal Workers" Union (construction sheet metal workers), the Central Association of Construction Engineers, and the LEL Employment Pension Fund register covering other occupational groups in the construction industry.*0 The original selection was composed of all those persons who had worked at least 10 years in the construction industry in 1962-1990, had begun their work before 1980, and were aged less than 70 years at the time of the campaign. A preliminary ques tionnaire on job history and willing ness to participate was sent to all the above groups. After exclusion of those who did not respond, did not want to participate, or had worked less than 10 years in a risk occupa tion according to the preliminary questionnaire, altogether 22,583 con struction workers were invited to the screening campaign; 17,335 (77%) of them participated.10 Among this group there were 17,235 (16,696 men and 539 women) who gave their written permission to follow their health status. In this article we report the cancer incidence for those 16,696 men who gave their permission for the follow-up. In this group the mean year of entering work life was 1960. At the time of the screening cam paign, the mean duration of employ ment in construction was 26 years and the mean age of the workers was 53 years. Occupation and Exposure to Asbestos The screening survey included a structured questionnaire interview conducted by a trained occupational nurse. The questionnaire covered smoking habits and a complete job title and industrial sector history. The participants were also asked to indi cate their main type of work for each year of their work career. The alter natives included some specific types of work with known exposure to asbestos and a category of other work (Table 1). As some of the construction workers had also worked in other trades during their career, specific alternatives were given for shipyard, asbestos product manufacture, and car repair work (Table 1). The participants were classified according to their main occupation. In addition, a cumulative exposure index for the work career until the screening visit was calculated by summing up the working years be fore and after the first regulation concerning asbestos work in Finland weighted by the respective estimated exposure levels (Table 1): Exposure index = X weighting factor * duration (years) The weighting factors were esti mated according to the results of past industrial hygiene measurements performed in Finland for some spe cific asbestos work tasks during typ ical construction activities.2,3 Radiology A full-size chest-radiograph {postero-anterior and lateral view) was taken of all participants in the screening. The classification system for the screening campaign was an intermediate form between the com plete and short ILO classification12 with some modifications and addi tions.11 The ILO reference films were used for comparison with every postero-antefior radiograph. The pro fusion of small lung opacities was classified in accordance with the complete ILO system using a 12poiut scale. Right-sided and left sided pleural abnormalities were re corded separately. In this article we report the cancer risk according to the ILO profusion score of small irregular opacities (less than 1/0, at least I/O) and the presence of pleural plaques (yes, no). Smoking A person was classified as a smoker if he had smoked at least 1 cigarette, cigar, or pipeful of tobacco per day for at least 1 year. Ex smokers were persons who had stopped smoking at least 6 months before the screening visit. At the time of the interview, 28% of the male construction workers were cur- 1192 Asbestos, Construction, and Risk of Cancer * Koskinen et at TABLE 1 Exposure Weighting Factors According to Typo of Work and Period of Time Type of main activity Exposure weight ing factor In 1976 and before Construction Installation of new pipes Demolition of old pipes Pipe insulation work Other insulation work Electrical Installation work Other construction work in new buildings Other construction work in building repair Shipyard Any installation work after the hull building phase Ship repair work Asbestos spraying and asbestos insulation work Other shipyard work Asbestos product industry Asbestos product manufacture Asbestos mining Other work in asbestos production Car repair shops Brake or clutch repair work Other work in car repair All other trades 2 5 10 2 1 1 2 S 5 20 1 5 10 2 1 0 0 Exposure weight ing factor in 1977 and after 1 5 2 1 1 1 2 2 6 1 1 5 -- 2 1 0 0 TABLE 2 The Distribution of Smoking Habits by Age in the Study Popuiation (years) < 45 45-59 s 60 Ail N {%) 5868 (100) 8074(100) 4756(100) 16698(100) Never(%} 35 30 25 29 Smoking habits Ex-smoker (%) 30 40 58 42 Smoker (%) 36 30 19 28 rent smokers, 42% ex-smokers and 29% lifetime ttonsmokers (Table 2), Cancer Follow-Up The follow-up for cancer was done in a computer linkage with the Finn ish Cancer Registry, using personal identifier as key. The calculation of person-years started from the date of the screening visit. The calculation of person-years ended at emigration, ai death, or on December 31st 2000, whichever was first. There were 149,607 person-years of follow-up. The numbers of cancer cases and the person-years were counted by five-years age groups and two fol low-up intervals (0--4 years, and 3:5 years since the screening visit). The expected number of cancer cases was calculated by multiplying the num ber of person-years in each stratum by the corresponding average cancer incidence rate in Finland. The stan dardised incidence ratio (SIR) was calculated by dividing the observed number of cases by the expected number of cases. The 95% confi dence interval (Cl) for SIR was cal culated from the Poisson distribu tion. There are no national cancer incidence rates separately for smok ers, ex-smokers, and nonsmokers. Multivariate Analysis of Risk of Lung Cancer In an internal analysis of the de terminants of risk of lung cancer within the construction worker co hort the stratum-specific incidence rates of lung cancer were calculated by dividing the numbers of cases by the accumulated person-years. The incidence rate ratios, hereafter re ferred to as relative risks (RR), of lung cancer were estimated using a log-linear model. Age at start of fottow-up (continuous variable), smoking status, presence of lung fi brosis, presence of pleural plaques, the asbestos exposure index and oc cupation were included in the multi variate model. Univariate analyses (adjusted forage and smoking) were also performed for presence of lung fibrosis, presence of pleural plaques, the asbestos exposure index and oc- JOEM * Volume 44, Number 12, December 2002 1193 TABLE 3 Observed Number of Cases and Standardized incidence Ratio (SIR) with 95% Confidence intervals (Cl) of Cancer Among Male Finnish Construction Workers Lung cancer Mesothei/oma Totai cancer All Smoking Nonsmokef Ex-smoker Smoker Pleural plaques No Yes ILO fibrosis score < 1/0 1/0 Exposure index < 20 20-39 40-89 > SO Occupation Construction technicians Construction carpenters Bricklayers and tile setters Reinforcement concreters etc Insulators Plumbers Electricians Painters and lacquerers Other construction workers Population Obs 16696 249 SIR (95% Cl) 1.07 (0.94-1.20) Obs 13 SIR (95% C!) 1.96(1.04-3.35) Obs 1320 SIR (95% Cl) 1.03(0,96-1.09) 4919 7073 4701 7 0.11 (0.04-0.22) 59 0.4B (0.37-0.62) 133 3.74 (3.21-4.29) 5 2.70 (0.88-6.30) 282 0.80(0.71-0.90) S 2.45 (1,06-4.33) 627 0.96(0,69-1.03) 0 exp 1.51 (0.00-2.44) 411 1.50 (1.36-1,64) 10132 6503 99 0,94(0.85-1.11) 150 1,18(1.00-1.38) 9 4 2.77 (1.27-5,25) 1.19(0-32-3.05) 592 0.99 (0.91-1.07) 728 1.07 (1.00-1.15) 16186 510 217 0.98(0.85-1.11) 13 2.05 (1.09-3.50) 1247 1.03 (0.97-1.08) 32 2.74 (1,88-3,87) 0 exp 0.30 (0.00-12.9) 73 1.20(0.94-1.51) 1610 5736 8443 902 6 0.63(0,24-1,40) 50 0-80(0.60-1.05) 170 1.14 (0.96-1.32) 23 1.78 (1.13-2,67) 0 exp 0.30(0.00-12.3) 3 1.59 (0.33-4,64) 7 1.73 (0,69-3-55) 3 7.02(1.61-22,8) 54 0,96(0.72-1.24) 303 0.94 (0.84-1.04) 849 1.06 (0.99-1.13) 87 1.22(0.98-1.51) 1351 4503 1256 809 334 2106 2135 1267 2935 8 0.43(0.20-0.90) 85 1.00(0.80-1,23) 20 0.83(0.51-1,28) 16 1.03(0.59-1.66) 10 3.03 (1.45-5,56) 21 1.24(0.76-1.68) 9 0.90 [0,41-1.71) 20 1.13 (0.69-1.74) 60 1.40 (1.07-1.80) 0 exp 0.52 (0.00-7.15) 2 0.89(0.11-3.22) 2 3.17(0.38-11,4) 1 2,40 (0.06-13.4) 3 2B.9 (5.97-84.6) 1 1.78(0.04-9,90) 4 9.78 (2.66-25.0) 0 exp 0,53 (0.00-6.97) 0 exp 1,22 (0.00-3.02) 105 1.08(0.83-1.29) 440 0.97(0,68-1.05) 117 0.91 (0.76-1.08) 94 1.14(0.92-1,39) 29 1.55 (1.04-2,22} 102 1.02(0.84-1.23 66 1.02(0.79-1,29) 117 1.20 (0,99-1.42) 250 1.07 (0,94-1.21) Exp - expected number of cancer cases. This parameter is given when no cases were observed. cupation. Similar analyses were per formed for mesothelioma, but due to the low number of cases, not all of the above variables could be in cluded into the models. SAS soft ware was used in the statistical anal yses. Results A total of 1320 cases of cancer were observed among the male con struction workers during the fol low-up (Table 3). The risk was sig nificantly increased for mesothelioma (SIR 1.96, 95% d = 1.04-3.35) but not for lung cancer (SIR 1.07, 95% Cl = 0.94-1.20). The SIR of lung cancer was high est among insulators (SIR 3.03, 95% Cl = 1.45-5.56) (Table 3). The SIR of lung cancer was also significantly increased among those with an ILO small opacity score of at least 1/0. Those with pleural plaques had a slightly, but not significantly in creased SIR of lung cancer. The SIR of lung cancer increased as the expo sure index increased. About 97% of the lung cancers occurred among current or ex-smokers. Table 4 reports the relative risks of lung cancer from the univariate and multivariate internal analyses. The risk estimates from the univariate and multivariate analyses are very similar, except for some occupa tional groups. The RR was 35 (95% Cl = 16-74) among smokers as compared to non smokers and 4,6 (95% Cl " 2.1-10) among ex smokers as compared to nonsmokers. Those with an ILO fibrosis score of at least 1/0 had a 1.9-fold and (hose with the highest value of the expo sure index a 3.3-fold risk of lung cancer. In comparison to construc tion technicians, the RRs were in creased in all the other construction occupations, but in the multivariate analysis statistically significantly in creased estimates were observed only for insulators, construction car penters, and other constmction work ers. There were only 13 cases of me sothelioma. The SIR of mesotheli oma was significantly increased among insulators (SIR 28.9, 95% Cl -- 5.97-84.6) and electricians (SIR 9.78, 95% Cl = 2.66-25.0). There were no cases of mesotheli oma among the current smokers (Ta ble 3). Because of the low number of cases of mesothelioma and lack of cases in several strata, the internal analysis of relative risk included only age, occurrence of pleural plaques, and intensity of exposure (two lowest categories combined). Again the results of the univariate and multivariate analysis were very similar, the risk, increased with in- 1194 Asbestos, Construction, and Risk of Cancer Koskinen et a! TABLE 4 Age-and smoking-adjusted relative risk <of lung cancer (RR) with 95% confidence intervals (Cl) in Finnish construction workers according to a univariate and a multivariate log linear model Univariate analysis Multivariate analysis Pleural plaques No Yes (LO fibrosis score < 1/0 eS 1/0 Asbestos exposure index < 20 20-39 40-89 S: 90 Occupation Construction technicians Construction carpenters Bricklayers and tile setters Reinforcement concreters etc Insulators Plumbers Electricians Painters and lacquerers Other construction workers . RR 1,0 1,3 1,0 2.0 1.0 1.2 1.7 2.7 1.0 2,0 1.6 1.9 5.0 2.4 1,8 2.1 2.3 95% Cl ret {1.0-1.7) ref (1.4-3.0) ref {0.6-2.5) (0.8-3.4) {1.2-6.0) ref (0.9-4.0) (0.7-3,7) (D.8-4.3| (2.0-12.6) (1.1-5.3) (0.7-4.7) (0.9-4.7) (1.1-4.9) RR 9S% Cl 1.0 rdf 1.2 (0.9-1.6) 1.0 ref 1.9 (1.3-2.7) 1.G ref 1.3 (0.6 -2.6) 1.8 (0.9-3.8) 3.3 (1.3-8.3) 1.0 ref 2.1 1.0-4.4 1.6 0,7-3.7 2.1 0.9-4.9 3.7 1.4-9.9 1.S G.6-3.9 2.2 0.8-5.8 1.3 0.9--4.4 2.7 1,3-5.6 Tile following variables were included into the multivariate model: age (continuous variable), smoking, occurrence of pleural plaques, ILO fibrosis score, asbestos exposure index, and occupation. TABLE 5 Age-Adjusted Relative Risk of Mesothelioma (RR) with 95% Confidence Intervals {Cl) In Finnish Construction Workers According to a univariate and a multivariate log linear model Univariate analysis Multivariate analysis Pleural plaques No Yes Asbestos exposure index 0-39 40-88 2:90 RR 95% Cl 1.0 ref 0,7 (0.3-1.5) 1.0 ref 1.9 /Vft"7' --**'--u/ 10.1 (3-4-30.1) RR 95% C! 1.0 ref 0.6 {0.3-1.4) 1.0 ref t n (Q.7-5.2) 10.5 (3.5-31.3) The following variables were included into the multivariate model: age (continuous variable), occurrence of pleural plaques and asbestos exposure index. creasing value of the exposure index, but was lower for those with pleural plaques than for those without plaques (Table 5), Discussion The risk of total cancer and of lung cancer among the male construction workers overall was similar to that of die general male population, but the risk of mesothelioma was significantly increased. Possible healthy worker effort in the case of cancer incidence is much smaller than in mortality studies and is restricted to the very first yean of follow-up. Although the reference population also includes numerous asbestosexposed individuals this can only bias the observed risk estimates slightly downward. The prevalence of smokers among the participants of our study (Table 2) was similar to that reported in a random sample of the general population at the same point of time.! 3 The differences in smoking habits thus have probably not biased the results significantly. We conclude that the risk of lung cancer among construction workers is close to that of the general population. Of the occupational groups, insulators had clearly the highest risk of lung cancer. Their risk of mesothelioma was also higher than among the (yage__6 of ?) a! i I JOEM Volume 44, Number 12, December 2002 1195 other occupational groups, although the number of cases of mesothelioma in each of the groups was small. These observations are well in line with the industrial hygiene data, se, exposure to asbestos was heavy dur ing the installation of pipe and boiler insulation and such tasks were fre quent among insulators during the past decades. All in all, the occupa tion-specific SIRs of lung cancer in our study were similar to those in previous job-title-based follow-up studies in the Nordic countries and in Switzerland.14-17 It must be under lined that for the Finnish part of the Nordic study, there is considerable overlap with the present study and the observed risk estimates are there fore not independent. There have been inter-country differences in the use of different types of asbestos. In Finland, anthophyUite asbestos was widely used, while in other countries chrysotile accounted for a higher proportion of all asbestos used. There is not enough data on use of different types of asbestos in the construction materials to assess po tential differences in exposure pat terns of construction workers in dif ferent countries. Even if the overall risk of cancer or the risk of lung cancer in construc tion workers was similar to that in the general population, cases of as bestos-related disease occur fre quently among construction work ers.5-18 It is obvious that some of the workers in these trades were heavily exposed to asbestos. The identifica tion of persons with a heavy expo sure is a challenge for those involved in the medical and social follow-up or planning of lung cancer screening trials among these workers. Bronchoatveolar lavage and lung tissue asbestos fiber measurements are of ten useful in medicolegal cases, but their use is restricted to cases in which bronchoscopy or surgery are based on clinical indications, and such measurements are therefore not feasible in the exposure assessment of large populations of healthy indi viduals.7'19 Of the indicators tested in our study, the presence of lung fibrosis in chest-rays identified a group with a 1.9-fold risk of lung cancer as compared to those without such changes, while the risk of lung cancer among those with pleura! plaques was only slightly increased. A high value (>90) of the expertevaluated exposure index revealed a group with a 3.3-fokl risk of lung cancer as compared to the group with the lowest value of the index (<20). We defined the cutoff point for the highest exposure category with the aim of including only about 1,000 cohort members with the highest ex posure. That is, only about 6% of the construction workers were classified into this group with the highest ex posure, A previous Swedish study among construction workers found that an expert evaluation of job cat egories was better than self-reported exposure in assessing the exposure and consequent risk of lung cancer.8 Both methods were subject to impor tant misclassification and tended to identify better the use of asbestos cement products than the use of as bestos insulation products. In addi tion to the problems inherent in the identification of asbestos products from among all the construction ma terials handled during the work ca reer of a typical construction worker, even more problems are encountered when assessing bystander exposure from the asbestos handled by other workers at the same work sites. Such exposure may be very important, es pecially from asbestos spraying or pipe or boiler insulation work with friable asbestos lagging.20 We used an exposure index which was de rived from industrial hygiene mea surements (fibers/mL), it must be underlined that the value of the index should not be taken as an absolute value of cumulative exposure in fi ber-years (fibers/mL * years). The reported activities are ones that the respondents reported as their main type of work, and the weighting fac tors describe the exposure level dur ing the most typical exposure situa tion during that type of work. On the other hand it was impossible to esti mate the absolute duration of the specific asbestos-exposing activity during a typical workday. For exam ple, the most typical exposure situa tion in the demolition of old pipes is the removal of the old pipe insula tion, and the average exposure level during the removal of such insulation material was estimated to be 5 fibers/ mL, However, we don't know the typical distribution of the working hours during the demolition of old pipes between the removal of the insulation material and other activi ties, and the variation between the different demolition work sites. In our study, the inclusion of the exposure index and occupation in the same multivariate analysis of relative risk of lung cancer reduced the uni variate risk estimates most markedly for insulators and plumbers. This indicates indirectly that our exposure index identified best the risk caused by pipe insulation products. Interest ingly, the multivariate risk estimates were quite high for all the occupa tions even if the exposure index was included in the model. That is, either the index did not take properly into account all asbestos exposure (eg, indirect bystander exposure), or there are relevant confounding exposures other than asbestos and smoking in these occupations. Overall the simi larity of the results between the uni variate and multivariate analyses in dicates that there was relatively little correlation between the variables. It seems that the different asbestos ex posure indices either capture differ ent aspects of asbestos exposure or that the misclassification is indepen dent among the indices. The practical consequence of these observations would be that combinations of the indices could be used the identify the subgroups with the highest risk of asbestos-related lung cancer. Because of the small number of observed cases, it is difficult to draw firm conclusions on the distribution of the risk of mesothelioma among construction workers. It is interesting nevertheless that the risk seemed to (gsgg ? of 7> 1136 Asbestos, Construction, and Risk of Cancer Koskinen et at be tower among those with pleural plaques and current smokers than among those without plaques and the uon- or ex-smokers. These observa tions would warrant verification in some of the existing large cohorts of asbestos-exposed workers with a rel atively long follow-up. Overall the SIR of mesothelioma was only 2-fold among the construction work ers as compared to the general male population. Yet, most of the male mesotheliomas in the general popu lation arc attributable to occupational exposure to asbestos, and the SIR would have been considerably higher if the comparison would have been made to a truly unexposed popula tion. Such reference rates were not available. In conclusion our data show that subpopulations with a high risk of lung cancer and mesothelioma can be selected from among the long term construction workers based on exposure and radiographic informa tion. Of the indicators of asbestos exposure, pleural plaques did not identify a group with an elevated risk of lung cancer, while lung fibrosis score of at least 1/0 identified a 2-fold and a high value of the expertevaluated exposure index a 3-fold relative risk of lung cancer. The highest risk (RR = 3.7 among insu lators), however, was identified by using the exact job title. Acknowledgment The authors are indebted to Kristian Taskincrt, MSc, and Simo Kaleva, MSc, for their help in building the data flies and to Riiita Rials, MSc, for her help in assessing the exposure levels. Dr Koskinen was supported by a grant from the Finnish Respiratory Assosiation {Hengitysiiitto Heli Ry). The re search was also supported by The Ministry of Social Affairs and Health, Helsinki, Finland. 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