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FILE NAME Brakes BRK DATE 1990 DOC BRK252 DOCUMENT DESCRIPTION Medical Journal Article - Lung Cancer and Exposure to Diesel Exhaust Among Bus Garage Workers ScandJ Work Environ Health 348-54 Lung cancer and exposure to diesel exhaust among bus garage workers by Per Gustavsson MD Nils Plato MSc Britta Lidstr^mMSc Christer Hogstedt MD,,.2 GUSTAVSSON P PLATO N LIDSTR^ MB HOGSTEDT C. Lung cancer and exposure to diesel exhaust among bus garage workers Scand J W'ork Environ Health 348 5 Mo4 rtality and can- cer incidence was investigated among the 695 bus garage workers employed as mechanics servicemen or hastlers for at least six months in five bus garages in Stockholm between 1915 and 1970. The exposure to diesel exhaust and asbestos was estimated by industrial hygienists A small excess of lung cancer nior- tality was found in the cohort when occupationally active men in Stockholm were used as the reference group A referent study was performed within the cohort six referents being selected for each of the 20 lung cancer cases The lung cancer risk increased with increasing cumulative exposure to diesel exhaust but not with asbestos cumulative exposure The relative risk for lung cancer among the highly exposed men was 2.4 95 % CI 4.5 as compared with those with low exposure The study indicates that exposure to diesel exhaust increases the risk for lung cancer Key terins asbestos epidemiolgy epidemiology humans polycyclic aromatic hydrocarbons PAH epidemiology Exhausts from fueled vehicles have long been considered a potential cancer hazard due to their chemical composition and mutagenic activity in bacterial test systems ) An increased risk for lung cancer was found among railroad workers exposed to diesel exhaust in the United States 2 3 and Canada 4 A small excess of lung cancer was also found among persons with a history of exposure to diesel exhaust in a referent study from the United States 5 while another American referent study was negative in this respect 6 No increase in the occurrence of lung cancer was found for London transport workers 7 nor for employees at a Swedish bus company 8 The carcinogenic activity of diesel exhaust has been supported by several recently completed animal inhalation studies 9-13 The mutagenic and carcinogenic properties of diesel exhaust are probably mainly caused by polycyclic aromatic hydrocarbons PAH and especially the nitroarenes seem to have a high mutagenic potency 14 The present study was initiated to investigate the risk of lung cancer in relation to diesel exhaust and asbestos in a cohort of bus garage workers with varying degrees of exhaust exposure Department of Occupational Medicine Karolinska Hospital 104 01 Stockholm Sweden * Division of Occupational Medicine National Institute of Occupational Health 5-171 84 Solna Sweden Reprint requests to Dr P Gustavsson Department of Oc- cupational holm Medicine cupational Sweden KarolinskaHospital 104 Stock- Subjects and methods Population All the men who had worked as a mechanic service- man or hostler for at least six months in any of five bus garages in Stockholm from 1945 to 1970 were included in the study Altogether 708 individuals were identified from company records Information on name personal identification numiber workplace job type and beginning and end of work periods were collected from the records Life outcome was traced via a computerized register of the living population via death and burial books of the clerical parishes and via Stockholm City archives Underlying causes of death were obtained from Statistics Sweden and cancer incidence data were obtained from the Swedish Cancer Registry Mortality was investigated from 1952 to 1986 and cancer incidence from 1958 to 1984 Seven cohort members were deceased before 1952 and six had emigrated These 13 individuals were excluded from the cohort Life outcome could be ascertained at the end of follow as of 31 December 1986 for all the remaining 695 individuals Exposure assessments powered buses were first introduced in Stock- holm in the beginning of the 1930s During World War If all buses were fueled with generator gas Since 1945 all buses equipped with combustion engines have been diesel fueled The intensity of the exposure to diesel exhaust and asbestos specific for workplace work task and calendar period was assessed by industrial hygienists and structured in aexposure matrix 348 Diesel exhaust Analysis The exhaust exposure exposure assessments assessments based based were on ( the emission of diesel exhaust depending on the number of buses engine sizes engine running time and fuel types ii ventilatory equipment and air vol- ume of the garages and iii job types and work prac- tices Detailed historical data for these parameters were available but only few exposure measurements had been performed No single substance is accepted as a marker of exhaust exposure although several such substances have been proposed eg respirable dust elemental carbon nitrous oxides and PAH 15 16 Thus the available data permitted relative exposures to be estimated but not absolute exposure levels The exhaust exposure level exposure intensity for every work period in the work history was classified on a ratio scale of six degrees The exposure intensity was set at zero for the unexposed work operations and at 1.0 for the lowest exposures greater than zero Each successive degree of the scale corresponded to a 0 % increase in intensity 1.5 2.25 3.38 and 5.06 Cohort and referent techniques were used for the analysis In the cohort analysis the observed mortali- ty was compared with that of a local reference population the population of greater Stockholm A second set of local reference rates was also used with adjustment for occupational activity This standardization for occupational activity was performed in order to reduce the bias from the healthy worker effect 21 Data on occupational activity were recorded in the population and housing census of 1960 and the mortality from 1961 to 1965 among employed and unemployed persons specific for age group sex and cause of death has been published by Statistics Sweden 22 From these data the ratio of the mortality among the employed to that in the general Swedish population was calculated specific for age group sex and cause of death The ratios were subsequently applied to multiplied by the local death rates The obtained rates reflect the local mortality with adjustment for oc- cupational activity The adjustment was specific for cause of death and age but approximate with regard to geographic region and trends in the ratios with calendar time The procedure for the calculation of the adjusted rates has been described elsewhere 23 The reference rates for cancer incidence were based on na- Asbestos tional statistics 24 Personal sampling of asbestos exposure during brake repair in bus garages in Stockholm was performed in 1987 including reconstruction of earlier exposure con ditions Plato N unpublished data These data and the results of exposure investigations from other bus garages 17-20 were used to estimate the exposure to asbestos for the cohort members and the timeweighted annual mean exposures were classified on scale of three degrees 0 1 and 2. Level I corresponded approximately to a level of 0.08 fibers ml- of air Expected numbers of deaths and cancers were computed according to the person method 25 counting years at risk for each individual specific for sex year age classes and year calendar class- es Both the exhaust and asbestos exposure indices were dependent and were recalculated for every year during the allocation of person and the contributions were referred to the appropriate stratum of the respective exposure index 25 and level 2 to 0.16 fibers - ml The occupational mortality analysis program OCMAP 26 was used for the mortality analyses Cumulative exposures and the epidemiology in Link^pingLink^ping EPILIN pro- gram 27 was used for the analysis of cancer incidence response relationships were investigated in a We calculated indices of cumulative exposures to diesel referent analysis A full cohort analysis of inter- exhaust and asbestos by multiplying the exposure level nal response relationships using the Cox propor- by the duration in years for every work period in the tional hazards model 25 was considered However work history The contributions from all work peri- added ods were then for the cumulative exposures to the involvement of two dependent measures of dose exhaust and asbestos exposure indices led diesel exhaust and asbestos for every individual in the to complicated calculations that were not feasible with cohort The exhaust exposure index ranged from the available software A referent analysis to 112 median 13 and the asbestos exposure index matched with regard to age permitted calculation and from 0 to 86 median 19 analysis of cumulative exposures without need for For the referent analysis the exhaust ex- dynamic iterative recalculation of the exposure in- posure index was subdivided into four classes 0 100 10 dices as would have been required in a full cohort de- 10 2200 3a0nd > 30 representing each class by sign Selection of an appropriate number of controls a score value exhaust score of 0 1 2 or maintains validity and causes only a small loss of pre- 3 respectively The asbestos exposure index was sub- cision 25 This design still permitted the use of both divided into the following four classes 0 2200 40 dead and incident cancer cases as end points in 40-60 and 60 the study which was not the case in the analyses for 349 standardized mortality ratio SMR using external reference rates The cases and referents were selected from the co- hort All individuals with a primary form of lung cancer eighth revision of the International Classification of Diseases ICD = 162.1 mesotheliomas not included identified in the register of causes of deaths or in the cancer register were selected as cases Altogether 20 cases were identified 12 were registered in both registers five were registered only in the register of causes of deaths and three only in the cancer register Six referents were selected for every case The refer- ents were drawn at random and without replacement from those being noncases at the time of diagnosis of the case and born within - years of the case according to the method described by Breslow & Day 25 The cumulative exposures of the referents were trun- cated at the time of the diagnosis of the case The relative risk for lung cancer was approximated by the odds ratio calculated by conditional logistic regression 28 with the matched sets kept together The EGRET cpidemiologic graphics estimation and testing program 29 was used and the main results were confirmed with the epilog program 30 The overall mortality in the cohort equaled the expected when the local rates adjusted for occupational activity were used as the reference table ) There were 17 cancer deaths whereas 13.9 would be expected Altogether 73 cases of ischemic heart disease were found whereas 64 were expected Four cases of esophageal cancer were found and 2.1 were expected The observed numbers for other causes of death were close to those anticipated Analysis of the lung cancer mortality by increasing cumulative exhaust exposure indicated no definite evidence for a response relationship and nei- ther was a response trend found for ischemic heart disease table 2 The SMR values for both dis- eases were lowest in the lowest dose category however The analysis by cumulative asbestos dose gave no indication of a response for lung cancer table 3 The analysis of cancer incidence confirmed the niortality findings and no additional excesses were found table 4 Several histological types of lung cancer were represented and also two mesotheliomas but the numbers were too few to permit conclusions regarding excesses of individual types = Table 1. Mortallly among bus garage workers 1952-1958 The referance rates were based on local mortality and on local mor- tality adjusted for occupational activity There were 21 317.5 person of observation 0 observed number of deaths expected number of deaths SMR = standardized mortality ratio 95 % CI = 95 % confidence interval Cause of death Stockholm occupationally active Stockholm general population E SMR 95 CI E SMR 95 CI All malignant tumors 140-209 Esophageal cancer 150 Stomach cancer 151 Bowel cancer 152 151352 153 Rectal cancer 154 Liver cancer 155 Pancreatic cancer 157 Lung cancer 162 Prostatic cancer 185 Bladder cancer 188 Kidney cancer 189 Brain tumors 191 Hematopoletic cancer 200-209 Nervous diseases 320-389 Circulatory diseases 390 458 Ischemic heart disease 410 414 Cerebrovascular diseases 430 438 Respiratory diseases 460-519 Asthma bronchitis emphysema 490 Digestive diseases 520-577 493490 493 Liver curhosis 571 Genitourinary diseases 580-829 Violent death and intoxication E800 E999 Suicide E950 E959 All causes 0-999 Code of the eighth of the International 62 56.0 4. 5 1 4 3 2 a 17 139 6 1 a 4. 6 49 s te 96 90.4 73 64.1 10 117 10 70 4 ve 8 132 5 8.0 2 26 21 234 11 9.8 208 204.3 Diseases Classification of International e 109 84-140 84-140 , . . 122 71-196 : o 123 106 114 37 37 : 6 8 75 80 113 102 o 45-268 o 86-130 86-130 86-130 89-143 89-143 41-157 68-262 68-262 . 20-120 20-145 20-145 9-274 56-137 56-201 68-117 in 60 2.1 51 3.8 2.3 20 44 14.8 5.0 1.9 2.8 1.8 5.1 2.6 104.7 72.8 14.0 115 53 15.6 91 32 25 10.5 235.9 103 193 07 26 26 177 150 46 115 119 52 72 220 117 190 92 100 72 87 75 51 55 63 64 105 88 . 79-132 53-494 32-227 7-147 7-147 48-453 48-453 31-493 5-165 67-184 44-259 1-288 1-288 9-259 60-563 43-255 62-442 62-442 74-112 78-126 78-126 34-132 42-160 20-192 20-192 22-101 18-128 8-230 52-128 52-187 76-101 350 Table 2. Mortality by cumulative exposure to diesel exhaust The reference rates were based on data from occupationally active men in Stockholm O observed number of deaths expected number of deaths SMR = standardized mortality ratio exhaust exposure Index Cause of death 0-10 o E SMR 10-30 o E SMA 30 fe] E SMR All causes 0-999 All malignant tumors 140-209 Lung cancer 162 Ischemic heart disease 410 414 38 38 1 38 38 1 38 38 1 38 38 1 1 # 123 1 # 118 1 # 152 1 # (142 72 # 107 2 # 1243 ? # 127 32. # 23s 428 * Code of the eighth revision of the International Classification of Diseases in parenthaces Index of the cumulative exposure to diesel exhaust the Subjects and Methods section = Table 3. Mortality by cumulative exposure to asbestos The reference rates were based on data from occupationally active man in Stockholm ( observed number of deaths E expected number of deaths SMR = standardized mortality ratio Asbestos exposure index" Cause of death All causes 0-999 0-999 All malignant tumors 140-209 140-209 Lung cancer 182 Ischemic heart disease 410 414 0-20 o E SMR 1 11 1 1 1 1 1 1 111 20-40 o E SMA 1 # # 1 # # 1 ## 1## o 11 11 11 11 40 E 11 11 11 11 SMA 11 11 11 11 International Diseases Code of the eighth revision of the International ClassifiScubajetctison of * Index of the cumulative exposure to the see Subjects and in parentheses Methods section of Incidence Table 4. the bus garage workers among 1958-1984 The reference rates were based on national statis- tics There were 695 person of observation standardized of of O = observed number cases E = expected number cases 95 SMR mortality ratio 95 % CI = % confidence Interval Cancer site E SMR CI All malignant tumors 140-209 Esophagus 150 Stomach 151 Colon 153 Rectum 154 Liver 155 Pancreas 157 Nose and nasal alnuses 960 Lorynu 161 Lung 162 Squamous carcinoms Undifferentiated call carcinoma Adenocarcinoma Prostate 177 Kidney 180 Bladder 181 Malignant matanoma 190 Skin tumors malanoma excluded 191 Nervous systern 193 Hematopoletic organs 200-209 " 58.6 4 12 6 6.7 4 63 . 4.5 2 23 2 35 ' 03 1 12 17 10.6 S 42 7 4.A 2 1.3 15 15.7 3 4.3 . 1 5 2.1 2 2.6 ' 3.2 6 7.5 103 327 90 54 80 85 57 376 15 161 118 160 152 16 70 66 237 78 190 80 53-126 39-537 33-186 17-163 24-226 10-318 6-207 -2095 2-460 14-257 38-275 14-329 17-547 64-158 14-204 18-168 76-554 1-242 1-242 70-015 29-175 Code of seventh in parentheses Including CH of the mesothelioma of Clas ification of Diseases and one case of alveolar The numbers of cases and referents are presented n table 5 and the details of the conditionat logistic egression are presented in table 6. In model 1 the of Tabis 5. Number living and deceased persons with lung can cer cases and referents from the cohort according to the cumulative exhaust exposure RR = relative risk 95 % Cl 05 % confidence interval Casas Referents Tois Crude AR PR from logistic regression Fitted RA from weighted regression 85 Cl exhaust exposure index" 0-10 10-20 20-30 30 5 2 3 10 45 15 18 42 50 17 21 62 " 1.20 1.50 14 " 127 1.56 263 Total 20 120 140 r - 1.34 1.31 1.31 243 1.09-164 1.09-164 1.20-271 1.32-4.47 S ee the Reference celegory for definition of the index exhaust index score was introduced as factors indicator variables 0 and ) The relative risk for lung cancer increased with increasing exposure to diesel exhaust but the confidence intervals were wide figure ) The diesel score was alternatively introduced as an unfactored variable regression model 2 The obtained regression coefficient of 0.32 corresponded to a rela- tive risk of 1.37 interpreted as a 37 % increase in risk for an increase in the dose index score by one unit The 95 % confidence interval 95 % CI for this esti- mate was narrower than that of model , but included a relative risk of unity 351 The asbestos exposure did not seem to influence the lung cancer risk models 3 and 4 There were indications of a response relationship regarding diesel exhaust and lung cancer Com- Tabla Results of the logistic regression RA = relative risk 95 95 % confidence interval Parameter Model I exhaust inderfi 0-10 10-20 20-30 30 Model 2 exhaust score Model 3 Asbestos Index 0-20 20-40 40-60 60 Model 4 Asbestos score B se AR 95 Cl 0.236 0.447 0.969 ~~ 0.922 0.776 0.649 1.0 1.27 1.56 2.63 - 0.21-7.72 0.34-7.16 0.74-9.42 0.318 0.211 1.37 091-207 40 0.511 0.230 0.154 ~ 0.618 0.599 0.789 1.0 1.67 1.26 1.20 - 0.50-5.60 0.32-5.00 0.26-5.64 0.054 0.232 1.08 0.67-166 Explanation of models Model 1 Logit P == B/+ B + B where x 1 when diesel = exposure 10-20 else x 0 = when diesel exposure = 20-30 efse x 0 * t when diesel exposure > 30 alse x = Model 2 Logit P + where x lakes the value of the dissel score 0 1 2 or 3 Models 3 and 4 are analogous replacing the exhaust in- dex with the asbestos index See the Subjects and Methods section for a definition of the Index or score Reforence category 10 10 RR 7 2 eee 4 ---- 4---- 0-10 10-20 20-30 30 exhaust exposure index 1. Estimates of the relative risk AR of lung cancer with logistic regression subdivided by cumulative exposure to diasol exhaust The 95 % confidence intervals shown 352 pare models 1 and 2 in table 6. The confidence inter- vals were wide though since the number of cases in each exposure group was small Rothman has described a method for exploring the response trend in a situation of this type 31 The regression coeffcients ie the logarithms of the relative risks of model I seemed to be nearly linearly correlated with the dieselexhaust index score and a weighted regression was performed with the use of the inverse of the variance of the estimates as weights A regression coefficient of 0.2971 with a standard error of 0.0306 was obtained This figure can be interpreted as an increase in lung cancer risk of 35 % for an increase of one level in the exhaust index score and it corresponds closely to the relative risk of 1.37 obtained in model 2 table 6 The fitted relative risks from the weighted regression and 95 % confidence intervals 31 are shown in table 5 Discussion The overall lung cancer mortality in the cohort was slightly increased SMR 122 In other words an excess of the same magnitude as in other studies of workers exposed to diesel exhaust was found The SMR for lung cancer incidence was higher table 2 The SMR obtained in the mortality analysis was probably the more valid one since it was standardized for geographic variations in the background rate The lung cancer rate in Stockholm is higher than the national average The referent analysis indicated a risk excess among the highly exposed as compared with the lowly exposed workers and a response relationship was present The logistic regression indicated a lung cancer risk that was 2.6 times higher for highly exposed workers than for the lowly exposed workers although with a wide confidence interval When data from all the dose groups were combined in the weighted linear regression a risk excess of 2.4 was found for the highly exposed workers 95 % CI 1.3--4.5 This regression model was thus more effective but also more restrictive since a linear relationship of the logarithms of the relative risks was assumed This condition is met in the material however the observed relative risks corresponded closely to those predicted by the regression table 5 The crude relative risks table 5 were somewhat lower probably because precision was lost when the matching was dissolved The response trend in the SMR analysis was weak The referent analysis utilized both deceased and living lung cancer cases while the cohort analysis was limited to the deceased cases The additional in- cident cases were all highly exposed to diesel exhaust No effect from exposure to asbestos was found The mean asbestos exposure index was 27 and the maximum was 86. These index levels correspond to a cu- mulative asbestos exposure of approximately 2.2 and 6,0 fibers mly...ears respectively Such an exposure would be anticipated to increase the lung cancer rate with in a study this size pleural mesothelioma with cumulative asbestos ex- posures of 2.2 and 3.9 fibers years respectively They were employed by the bus company at 27 and 30 years of age and the tumors occurred at the ages of 63 and 64 respectively One of them was an electrician having worked in the electrical workshop in iN one of the garages Both may have been exposed to asbestos during previous employments Misclassification The exposure estimations were based on job tasks workplace and time periods and the actual exposures to both diesel exhaust and asbestos have probably varied within these subgroups of the cohort However the exposures were classified without knowledge of the life outcome of the individuals and thus the misclassification is independent of the outcome and may only force the relative risk towards unity 31 The classification of the outcome ie the information in the registers of deaths and cancer incidence is generally considered to be accurate 33 and since any misclassification is likely to be independent of the exposure of the individuals it would also tend to underestimate an excess risk Confounding Data on smoking habits were not possible to obtain in this retrospective study and uncontrolled effects from tobacco smoking cannot be ruled out so far as the cohort study is concerned In the referent study however it was not probable that the smoking habits differed substantially between the workers with high and low exposure since both groups belonged to the same occupational category A risk excess of 2.4 is unlikely to be explained even by extreme smoking habits 34 if it is assumed that the group with low exposure had normal smoking habits Risk estimation The results of the study support the assumption that high cumulative exposure to diesel exhaust increases the risk for lung cancer The risk excess among the highly exposed workers was greater than in other studies possibly because of the detailed exposure assessments which gave a good contrast between the workers with high and those with low exposure Total dust levels were measured during bus service and repair in one of the garages in 1981 1982 and 1989. In 1981 personal weighted 8 samples showed a level of 1.2 1.m 4 g Jacobsson un- published data In 1982 during 4 h8of sampling the levels were 0.5 1.m 0 g Bergstr^munpublished data and in 1989 they were 0.3 0.m 9 g Axelsson unpublished data Total dust is also gener- ated from sources other than the diesel engines however and the proportion of inorganic material in the dust was determined by etching of the samples in 1981 and 1989. The proportion varied from 50 to 62 % in 1981 and from 60 to 70 % in 1989 findings indicating that most of the total dust was not generated by the diesel engines Substitution of these approximate data into the jobexposure matrix and into the regression model indicates a doubled lung cancer risk after 20 years of work in bus garages with a total dust level of 0.9 mg The present study supports the view that diesel exhaust constitutes a cancer hazard for exposed warkers The magnitude of the risk excess can only be estimated approximately however due to the limited size of the study group Acknowledgments We thank Ms M S^derholmfor compiling the cohort data and tracing the individuals and Ms A Gustavsson for her computer work We are also grateful to Professor A Ahlbom and Dr L Alfredsson for their valuable discussions regarding the data analysis and their comments on the manuscript The Stockholm Transport Company kindly gave access to the source material and supported the exposure measurements The study was financially supported by the Folksam Insurance Group 1. Lewtas J. Evaluation of the mutagenicity and carcinoge- nicity of motor vehicle emissions in short bioas- says Environ Health Perspect 141 52 2. Garshick E Schenker MB Munoz A et al A case- control study of lung cancer and diesel exhaust exposure 1242-8railroad workers Am Rev Respir Dis 1987 3. Garshick E Schenker MB Munoz A et al A retrospec- tive cohort study of lung cancer and diesel exhaust ex- posure in railroad workers Am Rev Respir Dis 1988 820-5 4. Howe GR Fraser D Lindsay J Presnal B Zhang Yu S. Cancer mortality 1965 7in7relation to diesel fume and coal exposure in a cohort of retired railway work- ers J Natl Cancer Inst 1015 9 5. Hoffetta P. Stellman SD Garfinkel L. Diesel exhaust exposure and mortality among males in the American cancer society prospective study Am J Ind Med 1988 403-15 6. Hall NEL Wynder EL Diesel exhaust exposure and lung cancer a control study Environ Res 1984 7. Waller RE Trends in lung cancer in London in relation to exposure to diesel fumes Environ Int 479 3 8. Edling C Anjou CG Axelson O. Kling H. Mortality exhaust among personnel exposed to diesel Int Arch Oc- cup Environ Health 559 563 9. Brightwell J Fouillet X Cassano AL Gatz R. Duchosal F. Neoplastic and functional changes in ro- dents after chronic inhalation of engine exhaust emis- sions Dev Toxicol Environ Sci 471 88 Heinrich U Pott F Mohr U. Fuhst R K^nigJ. Lung 353 11. 12. 13. 15. 16. 18. 19. 20. 21. 22. tumours in rais and mice after inhalation of PAH emissions Exp Pathol 29 34 Ishinishi N Kuwabara N Nagase M Suzuki T Ishiwa a S Kohno T. Long inhalation studies on effects from heavy and light diesel engines on F344 rats Dev Toxicol Environ Sci 329 48 Iwai K Udagawa T Yamagishi M Yamada H. Long- 25. term inhalation studies of diesel exhaust on F344 SPF rats incidence of lung and lymphoma Dev Tox- icol Environ Sci 349 60 Mauderly JL Jones RK Griffith WC Henderson RF McClellan RO Diesel exhaust is a carcinogen in rats ex- posed chronically by inhalation Fund Appl Toxicol 208 208 2 21 1 27. Pederson TC Siak S The role of nitroaromatic com- pounds in the acting mutagenicity of diesel pac- ticle extracts J Appl Toxicol 54 Steenland K. Lung and diesel exhaust 60 a review Am J Ind Med 1986 177 89 Hammond KS Smith TJ Woskie SR Leaderer BP Bet- tinger N. Markers of exposure to diesel exhaust and cig- arette smoke in railroad workers Am Ind Hyg Assoc 3 516 22 Hickish DE Knight KL Exposure to asbestos during 29. brake maintenance Ann Occup Hyg 17 21 Rohi Langer AM Wolff MS Weisman 1. Asbestos exposure during brake lining maintenance and repair 30 Environ Res 110 28 R^delspergerK Jahn H Br^...ckelB Manke J Paur R 31 Woitowitz HJ Asbestos dust exposure during brake re- pair Am J Ind Med 63 72 32. Kauppinen T Korhonen K. Exposure to asbestos during brake maintenance of automotive vehicles by different methods Am ind Hyg Assoc } 499 504 33. McMichael AJ Standardized mortality ratios and the healthy workers effect scratching beneath the sur- 34 face J Occup Med 165 8 National Central Bureau of Statistics D^dsfallsregister 1961-1970 Registry of deaths 1961 1970 Stock- holm National Central Bureau of Statistics 1982. SCB cupational groups exposed to combustion products Doctoral dissertation Stockholm Karolinska Institute National Board of Health and Welfare The Cancer Registry Cancer incidence in Sweden Stockholmi Na- tional Board of Health and Welfare 1958 1983 Breslow NE Day NE Statistical methods in cancer re- search vol ti The design and analoyf scoihos rt studies Lyon International Agency for Research on Cancer 1987 IARC scientific publications no 82. Marsh GM Preininger M. OCMAP a oriented oc- cupational cohort mortality analysis program Am Stat 1980 Andersson K Anjou CG Brodin G Kling H Samuelsson PJ Datsin ratin cohort search stat dataprogram f^rkohortstudier anv^/ndarhandledningDatain ratin cohort search stat computer programs for cohort studies user manual Link^pingSweden University of Link^ping1982 Breslow NE Day NE Statistical methods in cancer re- search vol 1 The analysis of control studies Lyon International Agency for Research on Cancer 1980 248 7I9ARC scientific publications no 32.j Statistics and Epidemiology Research Corporation EGRET user manual Seattle WA Statistics and Epidemiology Research Corporation 1988 Epicenter Software Epilog user manual Pasadena CA Epicenter Software 1985 Rothman KJ Modern epidemiology Boston MA Little Brown and Co 1986 Doll R. Peto J. Asbestos effects on health of exposure to asbestos London Health & Safety Commission Her Majesty's Stationery Office 1985 Mattsson B. Cancer registration in Sweden Doctoral dissertation Stockholm Karolinska Institute 1984 Axelson O. Aspects on confounding in occupational health epidemiology Letter to the editor Scand J Work Environ Health 1978 98 102 1981 23. Gustavsson P. Cancer and ischemic heart disease in oc- Received for publication 28 June 1989 Journals W1 SC Volume 16 number 5 October 1990 - Scandinavian Journal of Work Environment and Health UCSF LIBRARY Received on 12-09-90 CONTENTS 297 Reviews =Effects of parental occupational exposures on spontaneous abortion and con- genital malformation HK Taskinen Original articles Danish among Fertility male welders JP Bonde KS Hansen AJ Levine abortion among women using video display terminals CV Nielsen Spontaneous abortion LPA Brandt Congenital malformations among children of women working with video display terminals LPA Brandt CV Nielsen Sensory perception In the hands of dentists L Ekenvall BY Nilsson C Falconer Mercury exposure of different origins among dentists and dental nurses 1 Skare T Bergstr^mA Engqvisi JA Weiner Lung cancer and exposure to diesel exhaust among bus garage workers P Gustavs- son N Plato B Lidstrom C Hogstedt Micronuclei in epithallal cells from sputum of uranium workers DP Loomis CM Shy JW Allen G Saccomanno Influence of Indoor climate on the sick building syndrome in an office environ- ment P Skov O Valbj^,rnBV Pedersen the Danish Indoor Climate Study Group Uptake distribution and elimination of pinena in man after exposure by inhala- tion AA Falk MT Hagberg AE L^fEM Wigaeus W Zhiping Book reviews A colour atlas of low back pain Announcements eel lla aa +