Document ykBGn51vrgxvb1YzyzeeJymwX

664 British Journal of Industrial Medicine 1992;49:664-670 Mortality among firefighters from three northwestern United States cities Paul A Demers, Nicholas J Heyer, Linda Rosenstock Abstract To explore whether exposure among fire fighters to fire smoke could lead to an increased risk of cancer, lung disease, and heart disease, the mortality of 4546 firefighters who were employed by the cities of Seattle and Tacoma, WA and Portland, OR for at least one year between 1944 and 1979 were compared with United States national mortalities and with mortalityofpoliceofficersfrom thesame cities. Between 1945 and 1989,1169 deaths occurred in the studypopulation and 1162 death certificates (99%) were collected. Mortality due to all causes, ischaemic heart disease, and most other non-mallgnant diseases was less than expected based upon United States rates for white men. There was no excess risk of overall mortality from cancer but excesses of brain tumours (standardised mortality ratio (SMR) = 2-09, 95% confidence interval (95% Cl) 1-3-3-2) and lymphatic and haematopoetic cancers (SMR = 1-31, 95% Cl = 0-9-1-8) were found. Younger firefighters ( <40 years ofage) appeared to have an excess risk of cancer (SMR = 1-45, 95% Cl 0-8-2-39), primarily due to brain cancer (SMR = 3-75, 95% Cl 1-2-8-7). The risk of lymphatic and haematopoetic cancers was greatest for men with at least 30 years of exposed employment (SMR -- 2-05, 95% Cl 1-1-3-6), especially for leukaemia (SMR = 2-60,95% Cl 10-5-4). Since the end of the second world war the use of synthetic materials for both the structures and interiors of buildings has increased the complexity and toxicity of the smoke generated when these buildings catch fire.12 The potential exposure to suspected or known carcinogens has raised the Department ofEnvironmental Health PA Demers, NJ Heyer, L Rosenstock Department of Epidemiology PADetners Department of Medicine, University ofWashington, Seattle, Washington, USA L Rojenstock concern that firefighters may be at excess risk of cancer. Benzene and polycyclic aromatic hydro carbons are likely encounteredatmost fires and other, less common, exposures may include asbestos, aromatic amines, chlorinated dioxins, and other potential carcinogens." Excesses of brain cancer, cancers of the colon or rectum, malignant melanoma or skin cancer, bladder cancer, leukaemia, and multiple myeloma have been found,'w5 although the results have been far from consistent. Perhaps surprisingly, given a priori suspicions, only one cohort study has noted an excess of lung cancer in firefighters.16 11isplausible thatfirefighterscould also beat excess risk of death due to heart and respiratory disease. Many respiratory irritants, such as hydrogen chloride, nitrogen dioxides, isocyanates, and acrolein, are commonly present in smoke."5 Evidence exists for respiratory dysfunction after acute high exposures12'" although studies designed to look at chronic effects have produced mixed result*.30'" An increased risk of cardiovascular disease due to intense physical and psychological stress after periods ofinactivity or exposure to carbon monoxide and other toxic gases is also plausible.2"5 Most cohort mortality studies, however, have found firefighters to be at the same or lower risk than the general population for both heart and lung disease. Death rates for the general population have been used as the reference in most mortality studies of occupational cohorts. A major bias introduced by using general population rates has been terihed the healthy worker effect.26'25 In many ways firefighters, with their strict physical entry requirements and good employment benefits, typify a population'',m which a particularly strong healthy worker effect would be expected. This may in part account for the low risk of death due to heart and respiratory disease noted in these studies; however, when police, an occupation with similar entrance criteria, have been used as a reference population1'M evidence that firefighters are at increased risk of respiratory disease has been found. Also, a previously reported study ofa sub-population of this same cohort found that the risk of heart disease increased with duration of employment." MortaHa In id Seattle! exposuj expand! in the I same cm the red follow I * Methd i Thestf j employ ; 1944 af i Washi| i exclud ; employ I numbe i of activ 1 used at l Record | were re | was asj preven, , lacked1 fire smi ; firefigh ` samed groupJ The! 31 Dei, collect both if inform h record! Oregoi; motor Index-i considi last kn subseq death j Index.; former don id formed theded Stan TabU 1 \ t 6 Status Current!* Retired T Other aim Deceased! Certificate. Uoknowtf. Total > Yearaof ffi *Per cental Material may be protected by copyright law (Title 17, U.S. Code) 392)49:664-670 Mortality amongfirefightersfrom three northwestern United States cities restern In 1984 we began a retrospective cohort study of with United States white men were calculated using Seattle firefighters to explore the relation between the microcomputer version of the Occupational exposure to fire smoke and mortality." Later we Mortality Analysis Program." Reference rates for expanded the study to include two other major cities United States white men were obtained from the f in the region and to collect data on police from the National Institute for Occupational Safety and same cities as a comparison group. This is a report of Health. White male rates were used because most the results of the expanded mortality study with firefighters from thecities studied were Caucasianand follow up to the end of 1989. . department records did not include information on race. Confidence intervals were calculated using a Methods Poisson distribution. Incidence density ratios The study population consists of all men who were (IDRs) and 95% confidence intervals (95% CIs) for employed as firefighters for at least one year between firefighters relative to police were calculated using jxcess risk of j 1944 and 1979 by the cities of Seattle and Tacoma, Mantel-Haenszel methods with standardisation by matic hydro- ? Washington and Portland, Oregon. Women were five year age groups and time periods and te9t based ires and other, | excluded from the study because they first began confidence intervals." Mortality was examined in ude asbestos, employment as firefighters in the 1970s and their stratified analyses by years of fire combat exposure, is, and other numbers continue to be comparatively small. Years years since firstemploymentas afirefighter, and ageat brain cancer, , of active duty in positions involving fire combat was risk. ant melanoma used as a surrogate measure of exposure to smoke. ukaemia, and Records ofthe Seattle and Portland fire departments 5 although the were reviewed and no time for exposure to fire smoke Results tent. Perhaps i was assigned for years spent in administration, fire Complete follow up was achieved for 98% of the >ns, only one prevention, or support services. Because Tacoma 4401 firefighters (table 1). Between 1945 and 1989, lung cancer in lacked the necessary records to make this distinction, 1169 deaths occurred and 1162 death certificates fire smoke exposure time was assigned for all years of (99%) were collected. The comparison cohort .Iso beat excess firefighter employment. A cohort of police from the consisted of 3676 police officers and complete follow ratory disease. as hydrogen yanates, and in smoke.3"58 function after idles designed oduced mixed cardiovascular psychological Mure to carbon ' 1 i . same cities was also identified for use as a comparison group. The follow up period was from 1 January 1945 to 31 December 1989. Follow up for vital status and collection of death certificates were performed for both the firefighter and police cohorts using information from pension board and department records, the death records of Washington and Oregon, the records of the Washington and Oregon motor vehicle departments, and the National Death up information was attained for 3599 (98%). During the follow up period 714 police deaths were identified and 703 death certificates (98%) were collected. The risk ofdeath due to any cause among firefight ers was less than expected (SMR -- 0-81, 95% Cl 0-77-0-86) due to a lower than expected risk of most types of non-malignant diseases (table 2). A twofold excess of brain tumours was seen (SMR = 2-09, 95% Cl 1-31-3-17). The death certificates listed seven of the tumours as glioblastoma multiforme, o plausible.24"15 >er, have found nr risk than the . lung disease. tion have been dity studies of introduced by een termed the ays firefighters, 1 } j ; ! ^ Index. Those who were lost to follow up were only considered at risk until the date on which they were last known to be alive. Persons lost to follow up subsequent to 1978 were assumed to be alive if no death was identified through the National Death Index. Underlying cause of death was coded by a former Washington state nosologist after informa tion identifying the deceased person as either a former firefighter or police officer was removed from three as astrocytoma, three as other gliomas, five as other or unspecified malignant brain tumours, and four as unspecified brain tumours. Smaller excesses were found for cancers of the lymphatic and haema topoietic tissues (SMR = 1-31, 95% Cl 0-92-1-81) and prostate (SMR = 1-34,95% Cl 0-90-1-91). The number of observed cases of most other cancers, including lung cancer, was similar to expected with only cancers of the bladder (SMR = 0-23, 95% Cl uirements and . population in the death certificate. 0-03-0-83) and kidney (SMR = 0-27, 95%, Cl Standardised mortality ratios (SMRs) compared 0-03-0-97) significantly lower than expected. 'The > worker effect f account for the Table 1 Employment axj vital status andyears offollow up at 1 January 1990 piratory disease hen police, an ; Status S&rnlt Portland Tacoma Total (*) :eria, have been evidence that * ; Currently employed Retired Other alive piratory disease Deceased (ortedstudyofa Certificates collected Unknown status found that the $ Total th duration of ! Years of follow up S10 782 318 516 510 55 2281 54388 458 396 95 509 508 24 1482 41085 217 239 22 144 144 16 638 17379 1285 1417 435 1169 1162 95 4401 122852 (29) (32) (10) (27) (99)* (2) *Per cent ofdeath certificates collected. Material may be protected by copyright law (Title 17, U.S. Code) 666 Table 2 Seattle, Portland, and Tacoma firefighter mortality: 1945-89 Cow* of death (ICD 9 coda) All causes (001-999) All cancers (140-152 2,156-9-165-9,170-175,179-208) Oral and pharyngeal cancers (140-149) Oseophsgcal cancer (150) Stomach cancer (151) Colon cancer (152,153) Rectal cancer (154) ' Biliary passages and liver cancer (155-0-155-1.156) Pancreatic cancer (157) Laryngeal cancer (161) Lung cancer (162) Prostate cancer (185) Kidney cancer (189*0-189-2) Bladder and other urinary cancer* (188,189-3-189-9) Skm cancer (172,173) Brain and nervous system tumours (191,192,237-5-237-9,239-6-239-7) Brain and nervous system cancers (191,192) Unspecified nervous system tumours (237-5-237-9,239-6-239-7) Lymphatfc/hoetnatopoietic cancers (200-208) Lymphosarcoma and rcticutosarcomt (200) Hodgkin's disease (20!) Leukaemia (204-208) Other lymphatic/haeinatopoictic (202,203) Heart diieaw (390-368,402,404,410-414,420-429) Ischaemic heart disease (410-414) Other circulatory disease (401,403,405,415-417,430-438,440-459) Cerebrovascular disease (430-438) Dieases of arteries, vdm and pulmonary circulation (415-417,440-459) Respiratory disease (460-466,470-478,480-487,490-319) Acute upper respiratory infection (460-466) Pneumonia (480-486) Chronic respiratory diseases (470-478,490-519) Emphvscma (492) Asthma (493) COPD and other respiratory disease (470-478,494-519) COPD Chronic obstructive pulmooaiy disease. Demers, Meyer, Rosemtock Death 1169 291 7 6 16 24 8 6 14 2 95 30 2 2 6 22 18 4 37 7 3 15 12 461 394 131 79 48 81 2 22 56 20 3 32 SMR 0-81 0-95 0-82 083 1-07 0*85 0-95 W9 0-89 0-47 096 1'34 0-27 0-23 0*98 2-09 207 2-20 1*31 1-42 105 1-27 140 0-79 0-83 0-96 0-85 1 24 0-89 3-57 0*67 100 1 19 1-05 0 98 f9S%} (0-77-0-86) (0-85-1-07) (0-33-1-66) (0-30-1-80) (0-61-1-73) (0-54-1-26) (0-41-1-87) (0-44-2-59) (0-49-1-49) (0-06-1-701 (0-77-1-171 (0-90-1-911 (0-03-0-971 (0-03-0-83) (0-36-2-13) (1-31-3-17) (1 -23-3-28) (0-60-5-62) (0-92-1-81) (0-57-2-93) (0-22-3-08) (0-71-2-09) (0-72-2-44) (0-72-0-67) (0-74-0-90) (0-80-1-14) (0-67-1-06) (0-93-1-64) (0-71-1-10) (0-43-12-9) (0-42-1-01) (0*76-1-30) (0-72-1-83) (0-22-3-08) (0-67-1 38) risks for death due to heart and circulatory disease were similar to or lower than expected with the exception of diseases of the arteries, veins, and pulmonary circulation, which were somewhat increased(SMR = 1-24,95% CIO-91-1-64). Table 3 presents firefighter mortality relative to that of police and police mortality relative to that of United States white men for causes of death of a priori interest and those found to be in excess as shown in table 2. Hodgkin's disease, asthma, and acute respiratory infections were not included in the table because no deaths due to these causes were found among police. Although the confidence limits were wide, firefighters appear to have a higher risk than police of colon cancer, prostate cancer, brain tumours, "other" lymphatic and haematopoietic cancers, and emphysema. The category of "other" lymphatic and haematopoietic cancer includes multiple myeloma (seven out of 12 firefighter and two out of five police deaths were in this category). Although national rates for the study period were not available,the risk ofmultiple myeloma forfirefighters relative to police was 1-91 (95% Cl 0-4-8-4). Of the brain tumours among police, five were listed on the death certificates as glioblastoma multiforme, two as astrocytomas, and one as a malignant neuroblastoma. Firefighters were at somewhat lower risk than police for deaths due to all causes and circulatory disease and at much lower risk of bladder cancer. The causes ofdeath that were found to be in excess were further analysed by duration of exposed employment (table 4). The risks for lymphatic and haematopoietic cancer, especially leukaemia, and diseases ofthe arteries, veins, and pulmonary circula tion were highest for firefighters with at least 30 yearj of exposure, although the risks do not increase consistently with duration of exposed employment. The risk of leukaemia in firefighters with 30 years of exposed employment remained increased (IDR = 1-80, 95% Cl 0-6-5-4) when comparisons were made with police, whereas the risk of it 11 lymphatic and haematopoietic cancers did not (IDR - 1-14, 95% Cl 0-5-2-6). The risk of mortality from all chronic respiratory disease peaked amongfirefighters with 20 to 29 years ofexposure; the excess risk of emphysema was highest among those with 10 to 19 years of exposure. Lagging exposures by 10 years to allow for a latent period33 increased the risk for 30 or more years of exposure for all lymphatic and haematopoietic neo plasms (SMR =* 2-73, 95% Cl 1-36-4-88), leukaemia (SMR 3-63, 95% Cl 1-46-7-48), diseases Mortalin Came of 4 of the (SMR (SMR furthi (SMR Fireff empU>y| (SMR malign! (SMR pulmoi etnphy: ers alsi (IDR (IDR 4 (IDR police. In gi was hii Oeuseef death fytColun gwisue cancer j and nerve lymphatic/h: ukaemia Phases of die a K gfonary circ gwwuc respt Avkisnphyiana Material may be protected by copyright (aw (Title 17, U.S. Code) (eyer, Rosenstock (95%) (O77-0-86) (0-85-1*07) (033-1*66) (030-1*80) (061-1-73) (0-54-1*26) (0-41-1*87) (0*44-2*59) (0 49-1 49) (0 06-1 70) (0-77-1*17) (090-1-91) (0*03-0-97) (0*03-0*83) (0-36-2-13) (1*31-3*17) (1*23-3 28) (0*60-5*62) (092-1*81) (057-293) (0*22-3*08) (071-209) (0*72-2*44) (0*72-0*87) (0-74-0-90) (0*80-1*14) (067-106) (091-1*64) (071-1*10) (043-12*9) (0-42-1*01) (0-76-1-30) (072-183) (022-308) (067-1-38) risk than police ulatory disease icer. 1 to be in excess m of exposed lymphatic and eukaemia, and nonary drculaatleast 30 years o not increase d employment, hters with 30 lined increased m comparisons the risk of all ncers did not The risk of 'disease peaked ofexposure; the st among those llow for a latent : more years of latopoietic neo;l 1*36-4*88), -7*48), diseases Mortality amongfirefightersfrom three northwestern United States cities 667 Table 3 Seattle, Portland,and Tacomafirefighter mortality compared with police andpolice mortality compared with United States white male rates: 1945-89 Firefighters vpoHee Count ofdetuh Deaths IDR All causes All cancer! Colon cancer Rectal cancer - Biliary passages and liver cancer Trachea, bronchus, and long cancer Prostate cancer Bladder cancer Skin cancer Brain and nervous system tumours Brain and nervous system cancer Lymphatk/haematopoietlc cancers Lymphosarcoma and rcticulosarcoma Leukaemia Other lymphatlc/hfleraatopoiedc Heart diseases Ischaemic heart disease Other circulatory disease Cerebrovascular disease Diseases of the arteries, veins, and pulmonary circulation Respiratory disease Pneumonia Chronic respiratory diseases Emphysema COrD and miscellaneous lung disease 1169 291 24 8 6 95 30 2 6 22 18 37 7 15 12 461 394 131 79 48 81 22 56 20 32 0-87 0-97 1-58 0-69 0-71 0*95 1-43 0*16 M2 1*88 163 1*03 0-83 080 1-40 0-86 088 0*72 0-65 091 Ml 1*04 Ml 1*45 0-89 (95% Cli (0*79-0*95) {0-80-117) (0*73-3*43) (0*30-2*66) (019-2*71) (0*67-133) (0*71-2*85) (0*02-1*24) (027-4*76) (0*82-4*31) (0*70-3*79) (0*62-1*73) (0*30-2*22) (038-1 70) (0*48-4*07) (074-2*00) (0-74-1-04) (054-0-96) (045-092) (0*54-1 52) (0*71-1*73) (046-2-36) (0*65-1*89) (0*54-3*88) (0*47-169) Police v United States white men Deaths SMR (95% Cl) 714 0-87 (081-093) 169 0-95 (0*81-111) 8 0*50 (0-22-099) 5 Ml (0-36-2*59) 4 1-40 (038-3*59) 55 092 (0*69-1*19) 11 2*02 (0*51-1*82) 4 0*91 (0*25-2-34) 4 0-94 (026-2*41) a 1*14 (0-49-2-25) 8 1-36 (0-59-2*69) 21 1*22 (0-75-1*86) 5 1*72 (0*56-402) 11 1*56 (0*78-2*80) 5 0r93 (030*2*17) 269 0*85 (0-75-096) 223 086 (0-75-098) 86 1-25 (1-00-1*55) 59 128 (0*98-1*65) 25 1*24 (070-2*04) 30 0*64 (043-091) 10 060 (0*29-1*11) 20 068 (0*42-1 06) 5 063 (020-1*46) 15 0*83 (0*47-1*37) of the arteries, veins, and pulmonary circulation (SMR = 2*55,95% Cl 1*43-3*38), and colon cancer (SMR 1-69, 95% Cl 0*77-3*20). Lagging also further accentuated the risks for emphysema among firefighters with 20 to29 years ofexposedemployment (SMR = 1-49,95% Cl 0-80-2-56). Firefighters with at least 30 years since their first employment had increased risks for brain tumours (SMR = 2-63), lymphatic and haematopoietic malignancies (SMR = 1*48), prostate cancer (SMR = 1*42), diseases of the arteries, veins, and pulmonary circulation (SMR = 1-33), and emphysema (SMR = l*39)(table5). These firefight ers also had an increased risk for brain tumours (IDR = 3*62, 95% Cl 1*2-11*2), prostate cancer (IDR = 1*58, 95% Cl 0-8-3*2), and emphysema (IDR = 1*48, 95% Cl 0-6-3-9) compared with police. In general, the risk for mortality from most causes was highest among firefighters 65 years ofage or older (table 6). Firefighters under the age of 40, however, had an SMR for all cancers of 1*45 (95% Cl 0*81-2*39) due primarily to a greater than expected number of brain tumours (SMR = 3-75) and lymphatic and haematopoietic malignancies (SMR m. 1 *74). The excess observed for cancer is by contrast with the deficits found for all non-cancer causes of death (SMR =* 0-47). The excess of cancer among firefighters under the age of40 persisted when the comparison was made with police (IDR = 1-51, 95% Cl 0-7-3-5). Discussion We found an excess ofbrain tumours among firefight ers compared with United States white men and police. Previous studies of workers exposed to vinyl chloride, acrylonitrile, and polycyclic aromatic hydrocarbons have noted excesses of braiibfancer." Although it is difficult to quantify, it is likely that &i _Ta_b_le_4__S_e_a_ttl_e,_P_o_rt_la_n_d,_a_n_d_T_ac_o_m_a_fi_re_fi_gh_t_er_m_o_r_ta_lit_y_b_y_d_ur_a_tio_n_o_fe_x_p_ot_e_d _em_p_lo_y_m_e_nt_: _19_4_5_-8_9 <10years 10-19 years 20-29years ^30years ' Cause afdeath Deaths SMR (95% Cl) Dteshs SMR (95% Cl) Deaths SMX (95% Cl) Deaths SMR 195% Cl) Colon cancer Prostate cancer Brain and nervous system tumours Lyrapbatic/haeroatopoietic cancers Leukaemia Diseases of the arteries, veins, and pulmonary circulation Chronic respiratory diseases Emphysema 4 140 (0*4-3*6) 2 054 (0* 1-2-0) 9 0*62 (0*3-1 *2) 9 1*21 (0*6-2*3) 3 242 (05-7*1) 2 M2 (01-4-1) 14 1*23 (07-21) n 1*36 (07-2-4) 5 2*57 (08-60) 8 353 (l*5-7*0) 6 1-24 (05-27) 3 204 (04-5*9) 4 091 (02-2*3) 7 1*46 (006-30) 14 1-06 (0*6-1 *8) 12 205 (1 *1-3*6) 2 M3 (0-1-41) 2 1*04 (01-3-7) 4 073 (0*2-19) 7 2*60 (1 *0-5*4) 4 1-36 (0-4-3-5) 4 0*94 (0*3--2-4) 15 0*79 (0-4-1 *3) 25 1 99 (1 *3-2*9) 2 0-42 (01-1*5) 5 0-82 (03-1-9) 34 I 15 (0-8-I-6) 15 097 (0-5-1-6) 1 0-92 (0*1-51) 3 1*83 (04-5-3) 12 1 35 (07-2*4) 4 0*76 CO-2-1-9) ?| l ! j i 5 i \ Material may be protected by copyright law (Title 17, U.S. Code) rtl--- 668 Demers, Heyer, Rosenstock TableS Seattle, Portland, and Tacomafirefighter mortality by years sincefirst employment: I94S-89 < 20ytun 20-29ytars '? 20years Cause ofdeath Deaths SMR Colon cancer I Prostate auiccr 0 Brain and nervous system tumours 6 Lymphatic/haematopoieoc cancers 3 Leukaemia - *- 3 Diseases of the arteries, veins, and pulmonary 1 circulation Chronic respiratory diseases i Emphysema 0 65] 0-00 2-45 H5 1-50 0-51 0-45 000 (95% Cl) Deaths SMR (0-1-2-9) 3 (0-0-26-6) 0 (0-9-5-3) 2 (0 7-3-2) 2 (0-3-4-4) 1 (0-1-2*8) 4 0-66 0-00 0-73 0-39 0-50 0*91 (01-2*5) 2 (0-0-7-9) 0 0-32 0-00 (95% Cl) Deaths SMR (01-1-9) (60-3-1) (0-1-2*6) (0-1-1-4) (61-2-8) (62-2-3) 20 30 14 27 11 43 0-91 1-42 263 1 48 1-40 1-33 CO-1-1 I) 53 (CKM-8) 20 M2 1-39 (95% Cl) (0-6-14) (1-0-2-0) (1 *4-4-4) (10-2-2) (67-2-5) (1-0-1-8) (0*8-1-5) (0-9-2-2) exposure to polycyclic aromatic hydrocarbons at fires is common whereas exposure to vinyl chloride and acrylonitrile may happen only under certain condi tions. If the excess of brain cancer were due to exposures that were not necessarily present at most fires, this might at least in partexplainourfinding that duration of exposed employment was not associated with increasing risk. We also found an excess risk of leukaemia, which was highest among persons employed 30 or more years in fire combat positions, confirming our earlier finding of an increased risk among Seattle firefight ers." A twofold excess of multiple myeloma relative to police was also found. Other studies have noted an excess of lymphatic and haematopoietic cancers of various histologies11121415 and an excess of these malignancies is plausible given the exposure of firefighters to benzene.'"4 Although exposure to benzene is likely to be short term, measurements have been taken in excess of 100 ppm.'4 Our ability to conclude with certainty an association with exposure to fire smoke is limited by our finding of a similar excess in police. We arc unable to assess whether the excess among police is due to factors held in common between the two occupational groups, to some exposure unique to police, or to chance. Of interest, two other studies that have examined cancer in firefighters v police found firefighters to be at higher risk for leukaemia.1214 We also found an excessofprostate cancer, aneffect ofuncertain significanceand not seen in other studies. The persistence of this excess compared with police makes a diagnostic bias an unlikely explanation. We did not find excess cancers of the skin, bladder, or lung, which have been noted in some other studies of firefighters. Limitedsupportwasfoundforpreviously described excesses of colon cancer when the comparison was made with police, but not with the United States reference group. The inconsistency with previous studies may be due to the small number of deaths found for some sites or to the different methods used and varying time periods examined. As anticipated, many of the results ofthis study ate consistent with the healthy worker effect. One excep tion was deaths due to diseases of the arteries, veins, and pulmonary circulation, which were increased among firefighters with at least 30 years of exposed employment compared with both United States white men and police. This result is difficult to interpret given the heterogeneous nature of conditions in this category. In analyses ofthis cohort performed with follow up through 1083 we found an excess of non-malignant respiratory disease compared with police (IDR = 1'59), as opposed to a deficit when compared with United States rates (SMR -- 0-88)." One other study that compared deaths from lung disease in firefighters with those for police officers found a similar result.14 Although this disparity was also found in the current analysis, the magnitude qf the effect was much reduced. This may be in part Table 6 Seattle, Portland, and Tacomafirefighter mortality by age at risk: 1945-89 Cause ofdeath Colon cancer Prostate ameer Brain and nervous system tumours Lymphstc/haematopoietic cancers Leukaemia Diseases of the arteries, veins, and pulmonary circulation Chrome respiratory diseases Emphysema 18-39 years old 40-64years old ^65 years old Death SMR (95% Cl) Deaths SMR (95% Cl) Deaths SMR I 1-38 (0-1-8-2) 10 0-78 (04-1-4) 13 0-86 0 0*00 (0-0-178) 4 686 (62-2-2) 26 1-46 5 3-75 (1-2-8-7) 11 1-66 (08-3*0) 6 234 5 1-74 (66-4-1) 13 0-96 (05-1-6) 19 1-61 1 0-82 (0* 1-4-6) 5 0-95 (0-3-2-2) 9 1-67 X 1*21 (0-1-6-8) 7 656 (0-2-1-1) 40 1*58 2 Ml (0-1-6*2) 7 636 (04-07) 48 1-36 0 0-00 (0-0-37-2) 3 0-50 (0-0-1-5) 17 1 57 (9534 CD (0-5-1 *5) (1-6-2-1) (0*9-5* 1) (1-0-2-5) (0-8-3-2) (1-1--2'1) (10-1-8) (69-2-5) McrtaHbj accoun use off the risk disease (SMR ' (SMR | Non! founds States employ! 29 year exist bej the fact; with 30. be duej employ] conclusi specific betweei Where diseased emphys Some interpre duration improve may stJ particui all fires!, and with being B, availabi! seen bej andvarij totheu|| AnotS accuracy death o lung did cause oft Inform! lacks dj subsite thatacaf etiologies the expJ obscured Police! populatii omic staj requirent firesmoi by occuj similar," offirefigi of the sri risk est2 Material may be protected by copyright law (Title 17, U.S. Code) iyer, Rosenstock AR (95% Cl) >1 (0-6-1-4) 12 (10-20) >3 (1 -4-4-4) a (1-0-2-2) 10 CO-7-2'5) 13 (1-0-1-8) 12 (0 8-1-5) 19 (0-9-2-2) ed with police planation. We n, bladder, or ther studies of for previously ;r when the t not with the inconsistency to the small ites or to the time periods fthis study are a. One excepjrteries, veins, fere increased ars of exposed United States h is difficult ms nature of with follow up ion-malignant with police 'hen compared 8)." One other mg disease in Beers found a irity was also gnitude of the ty be in part old MR (95% Cl) 86 (0-5-1 -5) 46 (1 -0--2-1) 34 (0-9-5-1) 61 (1 -0-2-5) 67 (O-fc-3-2) 58 (I-1-2-1) 36 (l-O-l-S) 57 (0-9-2-5) Mortality amongfirefightersfrom three nonheocstem United Stales cities 669 accounted for by the increasing availability and stability and their confidence limits are correspond use of respiratory protection since the 1970s. Also, ingly wide. Also, police have rarely been studied and the risk of death due to non-malignant respiratory their occupational exposures and risks for death due II disease among police was higher in the current to various causes have not been well characterised. (SMR = 0-64) than in the earlier analysis An excess or deficit of deaths among police could be (SMR *= 0-48). due to their own unique exposures or characteristics None the less, a raised risk of emphysema was and thus lead to spurious conclusions about firefight found among firefighters compared with both United ers. Potential police exposures include psychological States white men and police. All of these deaths stress and motor vehicle exhausts. The magnitude occurred among subjects at least 30 years after first and health effects of these exposures are not fully employment and was highest among those with 10 to known and their potential for introducing bias 29 years of exposed employment. If a relation does should be borne in mind. exist betweenexposure to fire smoke andemphysema, In conclusion, this study found excesses of brain the fact that the risk was reduced among firefighters cancer and leukaemia among city firefighters from the with 30 or more years ofexposed employment might northwest United States and suggests that they may be due to those most susceptible to disease leaving be at excess risk of dying from emphysema. employment early due to disability. Attempts to draw Exposures to known carcinogens and respiratory conclusions should be tempered by the fact that the irritants are likely to explain these findings; future specificityofdeathcertificatesislowfordifferentiating efforts should be directed towards reducing and between different types of obstructive lung diseases. eliminating these exposures. Whereas the results for all chronic respiratory diseases combined roughly parallel those for This research was funded through a cooperative emphysema, the risks were of lesser magnitude. agreement with the United States Fire Administra Some limitations should be borne in mind when tion of the Federal Emergency Management Agency interpreting the results of this study. Firstly, (BMW 85-K-2089). Paul Demers is supported by a duration of fire combat employment, although an training grant in environmental epidemiology and improvement over total duration of employment, biostatistics from the National Institute for Environ may still be an inadequate measure of exposure, mental Health Sciences (T32 ES07262). We thank particularly for substances that may not be present at the Fire and Police Pension Boards, Departments all fires. Exposure may vary substantially between and Unions of Seattle and Tacoma, Washington and and within fires due to the composition ofthematerial Portland, Oregon, and Rebecca Hubbard. being burned, the temperature of the fire, and availability of oxygen.3 5 Thus the lack of association Requests for reprints to: Linda Rosenstock MD, seen between duration or fire combat employment Occupational Medicine Programme, ZA-66, and various outcomes in this study may in part be due University of Washington, 325 9th Avenue, Seattle, to the use ofa poor surrogate for exposure. WA 98104. Another limitation of this study is the lack of accuracy and specificity of information on cause of 1 Nation*} Research Council. Fir* and smoke: understanding the death on death certificates. In the case of heart and hazard*. Washington DC; National Academy Press. 1986. 2 Birky MM, Clarice FB. Inhalation of toxic product* from fires. lung disease it may be difficult to assign a specific BuUN Y AcadM*d cause of death without a postmortem examination. Information about canceron death certificates usually 3 Brandt-RauF PW, FaUon LF, Tarantini T, Idcma C, Andrews L.Healthhiiardioffire fighters: exposure assessment. Br//d Med 1988;45:606-12. lacks detail and only rarely includes anatomical subsite or histological information. To the extent 4 Trcitman RD, Burgess WA, Gold A. Air contaminants encountered by firefighters. Am 2nd Hyg Assoc J 1980;41: 796-802. \ that a cause ofdeath category contains a wide range of 5 Lowry WT, Juarez L Petty CS, a al. Studies ortoxic gas ! I etiologically unrelated diseases, the relation between the exposure and any one specific disease will be production during actual structural fires in the Dallas area. J Porenstc Set 1985j3<h59-72. \ 6 Bomb RR, Crvunmett WB, Cutie SS, et al. Trace chemin&ct of <> obscured. fire; a source ofchlorinated dioxins. Science 1980j21<fc385-90. 7 Hartxell GE, Psckham SC, Switzer WG. Toadc products from Police were chosen as an alternative reference fires. Am Indust Hyg Assoc J 1983;44:248-55. population because they have a similar socioecon omic state, health benefits, and strict physical entry 8 GoldA, Burgess WA, Oougherty EV. Exposureoffirefighters to loxic air contaminants. Am 2nd Hyg Assoc J 1978;39:534-9. 9 Vena JE, Fiedler RC. Mortality in a municipal workers cohort: * requirements, and are generally free from any major IV. fire fighters. Am J 2ndMed 1987;11:671-84. fire smoke inhalation. Two studies of smoking habits 10 Ebopulo* E, Armstrong BK, Spickett JT, Heyworth F. Mortality of fire fighters in Western Australia. Br J 2nd Med by occupation show that police and firefighters are 1984;41:183-7. similar,35 w although a somewhat greater percentage offirefighters reportedhaving never smoked. Because H Office of Population Censuses and Surveys. 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Am J lad Med 19820:369-73. 24 Radford EP, Levine MS. Occupational exposure to carbon monoxide in Baltimore firefighters. J Occup Med 197608: 628-34. 25 Goldsmith JR, Anmow WS. Carbon monoxide and coronary heart disease: A review. Environ Res 1975;20:236-48. 26 Monion RR. Observationson the healthy worker effect. J Occup Med 198608:425-33. 27 Fox AJ, Collier PF. Low mortality rates in industrial cohort studies due to selection for work and survival in the industry. British Journal of Preventive and Social Medicine 197600; 225-30. 28 Gilbert ES. Some confounding factors in the study ofmortality and occupational exposures. Am J Epidemiol 1982;!16: 177-88. 29 Rosenslock L, Demers P, Heyer NJ, Barnhart S. Respiratory mortality among firefighters. Br J Ind Med 1990;47:462-5. 30 HererN, Weiss N, Demers PjBreslowN.RosenstockL. Cohort morality study of Seattle firefighters: 1945-1983. Am J Ind Med 1990;17:493-504. 31 Marsh GM, Preminger M. OCMAP: a user-oriented occupational mortauty analysis program. American Statistician 1980:34:245. 32 Kleinbaum DG> Kupper LL, Morgenstem H. Epidemiologic research: principles and quantitative methods. New York; Von Nostrend Reinhold, 1982. 33 Checkoway H, Pearce N, Hickey JL, Dement JM. Latencv analysis in occupational epidemiology. Arch Environ Health 1990,45:95-100. 34 Thomas TL, Waxweiier RJ. Brain tumors and occupational riak factors: a review. ScandJ Work Environ Health 1986;12:1-15. 35 Brackbili B, FrazierT, Shilling S. Smoking characteristics ofUS workers 1978-80. Am J IndMed 1988;13:5-42. 36 Stollman SD, Boffette P, Garfinkel L. Smoking habits of800,000 American men in relation to their occupation. Am J Ind Med 1988;13:43-38. Accepted 2 December 1991. Britism cof Postpl blood! Sir,--fi 11-13); the onj gearing concen nancy.' sonertj who ea during' ingperi after he concent her infij noted lopathy specula increase pregnai lead stc our two increase during] f M91 j 1 * M7 V. v \ Ml 5 1tHJf *01 Material may be protected by copyright law (Title 17, U.S. Code)