Evaluation of Cardiovascular Outcomes among U.S. Workers Exposed to 2,3,7,8-Tetrachlorodibenzo-p-dioxin Geoffrey M. Calvert, David K. Wall, Marie Haring Sweeney, and Marilyn A. Fingerhut Division of Surveillance, Hazard Evaluations and Field Studies, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, Cincinnati, Ohio Some animal studies and some human studies suggest that exposure to 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) may be associated with adverse effects on the cardiovascular system. As part of a cross-sectional medical study comparing workers employed 15 years earlier in the manufacture of 2,4,5-trichlorophenol or one of its derivatives at two U.S. chemical plants with an unexposed comparison group, we examined the association between TCDD exposure and various cardiovascular outcomes. A total of 281 workers and 260 unexposed referents participated. The workers had substantial exposure to TCDD, as demonstrated by significantly elevated mean serum TCDD concentration of 220 pg/g of lipid, compared with 7 pg/g of lipid among the referents. No significant association was found between TCDD exposure and any of the cardiovascular outcomes including myocardial infarction, angina, cardiac arrhythmias, hypertension, and abnormal peripheral arterial flow. Although our study had sufficient statistical power to detect an elevated risk for cardiac arrhythmias, hypertension, and abnormal peripheral arterial flow, it had low power (approximately 50%) to detect an elevated risk for myocardial infarction and angina. Our review of the literature suggests that our negative findings are consistent with those from other cross-sectional medical studies. Although several mortality studies of TCDD-exposed cohorts found significantly increased risks for cardiovascular disease mortality, similar increased risks were not observed in other mortality studies. The data available do not provide definitive conclusions but indicate that further examination of the association between TCDD exposure and cardiovascular disease should be pursued. - Environ Health Perspect 1 06(Suppl 2):635-643 (1998). http://ehpnetl.niehs.nih.gov/docs/1998/Suppl-2/ 635-643calvert/abstract.html Key words: dioxin, cardiovascular diseases, cross-sectional study Introduction Dioxins are produced as unwanted continues to be widespread. Among the contaminants during the combustion or health concerns is cardiovascular toxicity. production of chlorinated compounds. Animal studies indicate that exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin high doses of TCDD can produce effects (TCDD) is considered the most toxic of the on the cardiovascular system. These effects dioxin congeners. Concern about the toxic- include ventricular dilatation (1), cardiac ity of this and other dioxinlike congeners edema (1,2), valvulitis (2), myocardial This paper is based on a presentation at the International Symposium on Dioxins and Furans: Epidemiologic Assessment of Cancer Risks and Other Human Health Effects held 7-8 November 1996 in Heidelberg, Germany. Manuscript received at EHP28 May 1997; accepted 18 August 1997. The authors thank C. Mueller, B. Connally, and many other NIOSH personnel. The study was partially funded by the Agency for Toxic Substances and Disease Registry. Address correspondence to Dr. G.M. Calvert, National Institute for Occupational Safety and Health, 4676 Columbia Parkway, R-21, Cincinnati, OH 45226. Telephone: (513) 841-4448. Fax: (513) 841-4489. E-mail: jac6@cdc.gov Abbreviations used: 2,4,5-T, 2,4,5-trichlorophenoxyacetic acid; APAF, abnormal peripheral arterial flow; BMI, body mass index; Cl, confidence interval; ECG, electrocardiogram; HDL, high-density lipoprotein; ICD-9, International Classification of Disease, 9th revision; mm Hg, millimeters of mercury; OR, odds ratio; RR, risk ratio; SE, standard error; SMR, standardized mortality ratio; TCDD, 2,3,7,8-tetrachlorodibenzo-p-dioxin TCP, 2,4,5-trichlorophenol. degeneration (3), preatherosclerotic lesions in the aorta (4), and altered cardiac contractility (5-8). Evidence for TCDD effects on the cardiovascular system in humans is con- flicting. Case reports of TCDD-exposed individuals have described myocarditis (9), myocardial infarctions (10,11), ectasia of the coronary arteries (12), and rapidly pro- gressive atherosclerosis (13,14). Four mor- tality studies of TCDD-exposed cohorts reported significantly elevated risks for car- diovascular disease mortality (15-18), whereas several others have not observed such elevations (19-22). Although several cross-sectional medical studies have also examined the association between TCDD exposure and effects on the cardiovascular system (23-27), statistically significant associations were found only in the study of U.S. Air Force Ranch Hand personnel responsible for spraying TCDD-contami- nated Agent Orange in Vietnam (27). The Ranch Hands Study found statistically sig- nificant associations between TCDD expo- sure and peripheral pulse abnormalities of several arteries, medical record-verified hypertension, and one type of electrocar- diogram (ECG) abnormality. In addition, findings from cross-sectional medical studies suggest that TCDD exposure may be associated with several risk factors for cardiovascular disease, including disorders of lipid metabolism (27-29), and glucose intolerance (30). In this paper we report the cardiovascular findings from the largest cross-sectional morbidity study of TCDD-exposed industrial workers. These workers formerly were involved in production of 2,4,5- trichlorophenol (TCP) or one of its deriva- tives. Data were collected and analyzed to determine if TCDD exposure is associated with an increased risk for myocardial infarction, angina, cardiac arrhythmia, hypertension, and abnormal peripheral arterial flow. Materials and Methods In 1987, a cross-sectional medical study was undertaken to examine the long-term health effects of occupational exposure to chemicals and materials contaminated with TCDD. Details of the study design have been previously described (31). In summary, this study compared living individuals (workers) employed more than 15 years earlier in the production of TCP or one of its derivatives, which were Environmental Health Perspectives * Vol 106, Supplement 2 * April 1998 635 CALVERT ETAL. substances contaminated with TCDD, with an unexposed comparison group. The workers were employed in one of two plants in Newark, New Jersey, and Verona, Missouri. Four hundred ninety workers were employed at the New Jersey facility from 1951 through 1969 in the produc- tion of TCP or one of its derivatives. At the facility in Verona, Missouri, 96 indi- viduals were involved in the production of TCP or one of its derivatives. Production took place for approximately 4 months in 1968 and from April 1970 to January 1972. Both plants produced a variety of other chemicals, none of which are known or suspected cardiotoxins. To constitute the referent (comparison) group, one indi- vidual with no self-reported occupational exposure to TCDD-contaminated sub- stances was sought from within the resi- dential neighborhood of each worker; this individual matched the worker in age (within 5 years), race, and gender. The study protocol was approved by the National Institute for Occupational Safety and Health Human Subjects Review Board and informed consent was obtained from each of the participants. Information on worker and referent health status was collected through a com- prehensive set of standardized interviews and medical examinations. A lifetime med- ical history was elicited from each partici- pant using interviewer-administered questionnaires. To reduce observer bias, all individuals conducting the medical histo- ries, examinations, and tests were blind to the exposure status (worker or referent) of the participant. An interviewer-adminis- tered lifetime occupational history was elicited from each participant separate from the medical history. Duration of each job and length of occupational exposure to spe- cific substances were recorded beginning with the participant's 16th birthday. Blood was obtained from the participants after fasting and analyzed for TCDD (32), total cholesterol, triglyceride, high-density lipoprotein (HDL) cholesterol, and glucose. Two participants (one worker and one referent) did not have their blood drawn. The medical examination consisted of a general physical examination (includ- ing blood pressure measurement in each arm while the participant was seated), Doppler examination of the peripheral pulses, chest X-ray, and ECG (Marquette Microcomputer Augmented Cardiograph II (Marquette Electronics, Milwaukee, WI). The computer interpretations of the ECG were reviewed blindly by board-certified cardiologists, who made corrections where appropriate. The Doppler examination of the peripheral pulses involved measuring of ankle and arm pressures using a standard Baumonometer blood pressure bag and cuff and a Doppler ultrasonic instrument (Model 1010-LA, Parks Medical Elec- tronics, Aloha, OR) while the participant was supine. The examination was divided into two parts: resting examination and postocclusion examination. The resting examination involved bilateral blood pressure measurement at the brachial artery (arm blood pressure) and at the ankle (either the posterior tibial artery or the dorsalis pedis artery). The postocclusion examination involved inflat- ing blood pressure cuffs that were placed around the participant's calves bilaterally to a pressure approximately 50 mm Hg higher than the maximal brachial pressure. After 5 min, both cuffs were deflated simultaneously and ankle blood pressures were measured bilaterally at both 1 and 2 min postocclusion. Generally, the dorsalis pedis artery blood pressure was measured at resting and postocclusion rather than the posterior tibial because of the dorsalis pedis ease of measurement. Measurement of the brachial blood pressure was repeated 3 min postocclusion. Normally, ankle blood pressure should equal or slightly exceed arm blood pressure (33). The resting index has been derived to represent this relationship and was calcu- lated by dividing the resting ankle pressure by the maximal resting brachial pressure. A resting index value of 0.97 or greater is con- sidered normal. A value less than 0.97 is consistent with abnormal peripheral arterial flow (APAF) (33). Because the resting index may not detect all cases of APAF, the postocclusion exam was included in our study. Including the postocclusion exam increases the sensi- tivity of detecting APAF (33). Normally, the ankle blood pressure at 1 min post- occlusion should equal or slightly exceed the arm blood pressure. The recovery indices have been derived to represent this relationship. The recovery index 1 min postocclusion was calculated by dividing the ankle pressure at 1 min postocclusion by the maximal resting brachial pressure. The recovery index 2 min postocclusion was calculated similarly using the ankle pressure at 2 min postocclusion. A recovery index value of 0.97 or greater is considered normal. A value less than 0.97 is consistent with APAF (34). Case Definitions A participant was defined as having a history of myocardial infarction if the individual met one of two criteria. The participant either had to have reported that a physician had diagnosed this condi- tion or had to have ECG evidence for a previous myocardial infarction. Similarly, a participant was defined as having a his- tory of cardiac arrhythmia if the partici- pant reported that a physician had ever diagnosed this condition, or if the partici- pant had ECG evidence for an arrhythmia (an irregularity of heart rhythm including premature ventricular contractions, pre- mature supraventricular contractions, ectopic beats, presence of a pacemaker, atrial fibrillation, atrial flutter, bradycardia [under 50/min], tachycardia [over 100/min] but excluding normal sinus rhythm). A participant was defined as hav- ing hypertension if one of the following three criteria was satisified: a) a self- reported history of physician-diagnosed hypertension; b) the lowest of two brachial artery systolic pressure readings taken while the participant was in sitting posi- tion exceeded 140 mm Hg (this is also the case definition for current systolic hyper- tension); or c) the lowest of two brachial artery diastolic pressure readings taken while the participant was in sitting posi- tion exceeded 90 mm Hg (this is also the case definition for current diastolic hyper- tension). A participant was defined as having APAF if either the resting index, the recovery index 1 min postocclusion, or the recovery index 2 min postocclusion was less than 0.97 in either leg. Finally, angina was defined as a self-reported his- tory of physician-diagnosed angina. Participants were excluded from an analy- sis if they could not recall whether they had the disease of interest, if the self- reported onset of the disease of interest preceded the date of first exposure to sub- stances contaminated with TCDD, or if the examination or test was not performed on the participant. Analysis of Data To evaluate the association between TCDD exposure and each of the cardio- vascular outcomes and to evaluate for the presence of participation bias, unadjusted odds ratios (OR) were calculated and tested for significance using a chi-square test for association. To evaluate the association between TCDD exposure and each of the cardio- vascular outcomes of a priori interest Environmental Health Perspectives * Vol 106, Supplement 2 * April 1998 636 CARDIOVASCULAR OUTCOMES AMONG TCDD-EXPOSED WORKERS (myocardial infarction, angina, arrhythmia, hypertension, current systolic hypertension, current diastolic hypertension, APAF), logistic regression analyses were performed. The confounders that were examined in the regression analyses are described in detail elsewhere (29) and included years since last occupational TCDD exposure, age, race, gender, alcohol consumption his- tory, employment at the New Jersey versus Missouri plant, body mass index (weight in kilograms divided by height squared in meters [BMI]), use of antihypertensive medications during the 2 weeks preceding the physical exam, cigarette consumption history, current diabeties, serum triglyc- eride concentration, serum total cholesterol concentration, serum HDL cholesterol concentration, family history of heart dis- ease, occupational exposure to agents asso- ciated with cardiovascular effects (carbon monoxide, methylene chloride, lead, and carbon disulfide), and presence of pedal edema on physical exam. In each model, the linearity assumption was checked for all continuous variables. Variables found to be nonlinear were strati- fied based on a priori cutpoints. Variables determined to be nonlinear in one or more models included BMI, triglyceride, HDL cholesterol, lipid-adjusted TCDD, half- life-extrapolated lipid-adjusted TCDD, and unadjusted TCDD. Separate regression analyses were conducted using lipid-adjusted serum TCDD concentrations, half-life-extrapolated lipid-adjusted serum TCDD concentrations, or unadjusted serum TCDD concentrations. The half-life-extrapolated lipid-adjusted TCDD concentration is the estimated TCDD concentration when occupational TCDD exposure ceased and was calculated as described previously (35) to reflect the 7- year estimated half-life of the serum TCDD concentration (36). Because findings were similar for the analyses using the three dif- ferent TCDD measurements, we report only the models using the lipid-adjusted TCDD concentrations. The workers were stratified into two groups based on lipid- adjusted serum TCDD concentrations: the quartile with the workers having the highest TCDD concentrations (238-3400 pg/g of lipid), and the three quartiles of workers with lower serum TCDD concentrations (< 138 pg/g lipid). Eight workers were exduded from these analyses because serum TCDD concentrations were not obtained. OR are provided, indicating the risk for the outcome of interest among each group of exposed workers compared to that for the unexposed referent group. Potential confounders were retained in the final model if they created a meaningful difference in the coefficient of the exposure variable (more than a 15% difference) or if they were statistically significant for the outcome (p< 0.05). No significant interac- tions with TCDD exposure were observed. All models appeared to have adequate fit (37). All analyses were carried out using SAS procedures (SAS Institute, Cary, NC). Results Of the 586 workers at the two plants who were eligible for the study, 400 (68.3%) were living and could be located. A total of 142 (24.2%) workers were deceased and 44 (7.5%) could not be located. All 400 work- ers from the two plants who were living and could be located were invited to participate in the study; 281 (70%) were examined. A total of 938 referents were invited to partic- ipate in the study, of whom 260 (28%) were examined. Descriptive information on the study cohort is provided in Table 1. Workers were found to have a statistically signifi- cantly elevated mean serum lipid-adjusted TCDD concentration (worker, 220 pg/g lipid [range, not detected, 3400 pg/g lipid; median, 68 pg/g lipid]; referents, 7 pg/g lipid [range, not detected, 20 pg/g lipid]; p< 0.001). Half-life-extrapolated lipid- adjusted serum TCDD concentrations were also elevated among workers (mean, 1900 pg/g lipid; median, 476 pg/g lipid). Overall, there were no statistically signifi- cant differences or a consistent pattern of differences between workers and referents for any demographic characteristics (age, race, gender, education, income) except for alcohol-years (alcohol-years are the average number of alcoholic drinks consumed per day multiplied by the number of years alcohol was consumed) . Referents were found to have a statistically significantly higher mean lifetime alcohol consumption (workers, 41.4 alcohol-years; referents, Table 1. Characteristics of the study population by lipid-adjusted serum TCDD group. Referents Workers with lower serum TCDDa Workers with higher serum TCDDb All workers, (n= 260) (n= 208) (n= 65) (n= 281 )c Mean age, years (SD) 56.0 (10.5) 53.2 (9.6)* 61.4 (10.0)* 55.4 (10.3) White, % 88.9 88.0 92.3 88.9 Male, % 93.5 93.3 100* 95.0 Current drinker, % 63.1 64.4 63.1 64.4 Former drinker, % 23.9 27.9 26.2 27.1 Mean alcohol-years (SD) 62.1 (115.1) 40.9 (64.3)* 41.4 (60.3)* 41.4 (63.4)* Current smoker, % 32.3 37.5 23.1 33.8 Former smoker, % 46.5 41.4 55.4 44.5 Mean pack-years (SD) 29.0 (32.4) 26.4 (28.3) 24.5 (24.8) 25.8 (27.3) Plant 1, % 0 76.9* 83.1* 79.0* Body mass index > 29, % 28.9 28.4 30.8 29.2 Use of antihypertensive medication, % 21.9 19.2 20.0 20.6 Family history of heart disease, % 50.6 51.9 53.2 52.5 Family history of hypertension, % 47.1 48.5 36.9 45.8 Current diabetic, % 6.2 8.2 15.4* 9.6 Serum triglyceride 2 250 mg/dl, % 7.3 8.2 6.2 7.5 Serum HDL > 35 mg/dl, % 86.9 84.6 80.0 82.9 Serum total cholesterol ?240 mg/dl, % 32.3 37.5 24.6 33.8 Mean serum lipid adjusted TCDD, pg/g lipid (SD) 7 (2) 59 (59)* 730 (675)* 220 (434)* "Serum TCDD < 238 pg/g lipid. bSerum TCDD ? 238 pg/g lipid. cThe number of all workers is greater than the sum of the two subsets of workers (workers with lower and higher serum TCDD concentrations) because the group of all workers includes the eight workers for whom serum TCDD was not measured. *p< 0.05 unexposed referent group versus the group of exposed workers. Environmental Health Perspectives * Vol 106, Supplement 2 * April 1998 637 CALVERT ET AL 62.1 alcohol-years), which was attributed to seven referents with extremely high alcohol- year values. This was not considered an important difference because alcohol-years was found not to be a confounder in any of the analyses. Finally, workers in the quar- tile with the highest serum TCDD con- centrations were older and had a higher prevalence of diabetes mellitus compared to the referent group. Table 2 provides the results of the unadjusted analyses of the cardiovascular outcomes among workers and referents. Workers were not found to have a signifi- candy elevated risk for any of the cardiovas- cular outcomes. Findings were similar when workers, stratified by lipid-adjusted serum TCDD concentration, were compared with the referent group. Table 3 provides the results of logistic regression analyses for each of the cardio- vascular outcomes. These analyses revealed that even after controlling for important confounders, TCDD exposure was not associated with an increased risk for myocardial infarction, angina, arrhythmia, hypertension, current systolic hyperten- sion, current diastolic hypertension, or APAF. Even when the models were sepa- rately fitted with various parametric rela- tionships for the lipid-adjusted serum TCDD concentration (linear, quadratic, log-transformed), TCDD was not signifi- candy associated with any of the outcomes of interest. Furthermore, the findings for angina, current diastolic hypertension, and APAF are similar even after eliminating those variables (diabetes, triglycerides, and HDL cholesterol) found by some investiga- tors to be possibly affected by TCDD exposure (i.e., potential intermediate vari- ables). We found that age, gender, BMI, cigarette smoking, current diabeties, and a family history of heart disease were signifi- cant risk factors for two or more of these outcomes of interest. Discussion Our data do not support an association between long-term, high-dose TCDD exposure and any of several adverse cardio- vascular outcomes. Although our data are consistent with other cross-sectional med- ical studies and some mortality studies of TCDD-exposed populations, data from four mortality studies suggest that TCDD exposure may be associated with an increased risk for cardiovascular disease mortality (15-18). Two mortality studies of workers employed at pesticide-producing chemical plants showed positive dose-response associations between TCDD exposure and cardiovascular disease mortality (16,18). Flesch-Janys et al. (16) found significant trends between TCDD exposure and both cardiovascular disease (codes 390-459 from the International Classification of Disease, 9th revision [ICD-9]) and ischemic heart disease mortality (ICD-9 codes 410-414). Those with the highest predicted half-life- extrapolated serum TCDD concentrations (345-3890 pg/g lipid) had the highest risk ratio (RR) for cardiovascular disease (RR= 1.96; 95% confidence interval [CI ]= 1.15, 3.34) and ischemic heart disease (RR= 2.48; 95% CI= 1.32, 4.66). Hooiveld et al. (18) also found that those with the highest predicted half-life-extrapolated serum TCDD concentrations (121.5 pg/g lipid or higher) had the highest risk for cir- culatory system disease mortality (RR= 2.44; 95% CI = 1.34, 4.46) and ischemic heart dis- ease mortality (ICD-9 codes not provided) (RR= 3.70; 95% CI = 1.75, 7.80). A study of Air Force personnel (the Ranch Hands Study) responsible for spray- ing Agent Orange, a TCDD-contaminated herbicide mixture, in Vietnam from 1962 to 1971 found an elevated risk for circula- tory system disease mortality among non- flying enlisted personnel (ICD-9 codes not provided) (standardized mortality ratio [SMR] = 1.6; 95% CI= 1.05, 2.35) but not among the entire cohort in the Ranch Hands Study (SMR= 1.05; 95 % CI = 0.76, 1.42) compared to a nonexposed compari- son group of Air Force veterans (17). Among the personnel in the Ranch Hands Study, the nonflying enlisted personnel had the highest current serum dioxin concentrations (27). Another mortality study of a TCDD- exposed cohort found an increased risk for cardiovascular disease (15). Bertazzi et al. (15) studied the mortality of citizens in the Seveso region of Italy exposed to TCDD after an explosion at a trichlorophenol plant. For this study the Seveso region was divided into three zones named zones A, B, and R. Zone A had the highest TCDD contamina- tion, zone R the lowest. Zone A males and females had an increased risk of death from nonmalignant disease of the circulatory sys- tem (ICD-9 codes 390-459) (males: SMR= 1.75, 95% CI= 1.0-3.2; females: SMR = 1.89, 95% CI = 0.8-4.2). Zone R females also had a slightly increased risk of death from nonmalignant disease of the cir- culatory system (SMR= 1.15; 95% CI= 1.0-1.3). In addition, Zone R males had a statistically significant increased risk for death from chronic ischemic heart disease (ICD-9 codes 412, 414) (SMR= 1.61; 95% CI = 1.2-2.2) and Zone R females from hypertensive heart disease (ICD-9 codes 401-405) (SMR= 1.62; 95% CI= 1.0-2.8). Zone B residents did not have an increased risk of death from any disease of the circula- tory system. Because the increased risk for cardiovascular disease mortality was observed principally within the first 5 years after the explosion, Bertazzi et al. (15) emphasized the role of disaster-related stres- sors. However, in light of the findings of Flesch-Janys et al. (16) and the Ranch Hands Study (17), the suggestion that stress was responsible for the Seveso findings needs to be reconsidered. Several mortality studies of TCDD- exposed occupational cohorts did not find a significantly elevated risk for cardiovascu- lar disease (19-22). However, comparison of findings across studies is difficult because of lack of consistency in the types of cardiovascular diseases that were reported. Furthermore, some of these studies are limited by small sample size (19,20) and lack of detailed exposure- response analyses (20,22). On the other hand, it should be noted that the SMRs for cardiovascular disease approached or exceeded 1.00 in many of these studies (19,21,22), suggesting the absence of a healthy worker effect. Because employed workers are healthier than the general pop- ulation, the SMR for cardiovascular disease in employed populations is generally lower than 1 (38,39), although this differential disappears with longer follow up (39). The absence of a healthy worker effect in these TCDD-exposed cohorts may suggest a pos- sible association between TCDD exposure and cardiovascular disease. Several cross-sectional medical studies have also examined the association between TCDD exposure and effects on the cardio- vascular system (23-27). Statistically sig- nificant associations were found only in the U.S. Air Force Ranch Hands Study (27). Although the overall conclusion from the study was that there was no apparent asso- ciation between cardiovascular disease and TCDD exposure, an elevated risk was observed for peripheral pulse abnormalities of four leg arteries, medical record-verified hypertension, and nonspecific ST- and T- wave changes on ECG. It should be noted that the personnel participating in the U.S. Air Force Ranch Hands Study had lower serum TCDD concentrations (median 12.5 pg/g lipid, range 0-618 pg/g lipid) (27) than the workers we studied. The Environmental Health Perspectives * Vol 106, Supplement 2 a April 1998 638 CARDIOVASCULAR OUTCOMES AMONG TCDD-EXPOSED WORKERS CD C-c 00 00 0 - Co o Co o Co 6)c 6~4 CV C)J - CY) cq CR UP U-N C o c0 CD C) Co C) a) - ~- - C-~ '- C I. c C--i4 CV -cr - ,~W= 6 6D O CO O) OR OR LP Ot C-_ - Con CoOa Cm C-_ Co C co Co o- C) LC) C) C14 CD LC- C . CD Co Co CO -.j Co) Co4: Co mC CO SR cn d 6o 6o o~ Co Co ,D LP 00 Co o Co a) . C) - CV) C)- W Co 6 c 6: 6~c oo~ ? r-. Co U CD C-. CD C-- C- C-_ n Cr C7) CD *j C.D *-7 CV) CD O a LC) . -. Co co Co 6 6 6 CV)- CC CoL) Co C ,* CliN CD CD Co OC) C-X r-S L N C' c I. a _i C. D Co Cos? s o14 ,Co o o 6o- (o C_ L _ I C C) 6~ C) CS C) C-N cs o- Co C( O C=) ' N C) Co CD 6 6 CD C=D r.. C:) d' - a Co C C)- '0R CV) Cro _cl O: m Oa CD~~~~~r O * CN C) Wiz - ~Co1 C) q er C1) W Co LCo- CD - nj Co,- _ C= C - Cd o 0 m0 (C 6 00 6 C-- r- r- C) _n R )a )aW _ _7 Sz Co- ci CD 4 ) 0 'CN '0w CDoC-- Co- ~0 CL ~~ ~~~~~0 0, 0 0 CL) ~~ ~ ~~~~~c, -c 00 -~ C,) C~ t 0 0, C.0 " -0~o 0 C C - o ~ ~ ~ ~ ~ C 0 C ) 0 , 0 C o . t 0 ,~~CL CL 0 CD 3 o 0 , 0 C CD CDC) . 2 CC +-COI ?-4t-o -W r_ ~ ~ 0 -CE . 0 CD cc, cc _C.- 0 C.)C ~~0,C0 ~ 20 42,) 0, - 0, W - t - ~ C- _ = C C )0. CC C1) C C) CC C - t" C 0C.) - CD ~ 0 - CD Co U -) Co )- C c, > , . w. Eo E4 -c E E C. CC) M CD m -5 CC 0 . C C0 C.) C) S~ - t ) 1 C) 0 oD CD CD -E CD 0-m 0, , Environmental Health Perspectives * Vol 106, Supplement 2 * April 1998 a) C co o (N = 11 = CZ -) C) E L- W CO m an c CD CD 11 _e 0 Q)C) C o -c Z = W X (2 C CD . E 6 og o ,- C o -o O C z E. ,o 6 D 0CD . _0 ? =- Z3 o (c C) C) E CD cn mo o 0 11 - Co _C" *x5 CD Co- a CO =a C) z CD 0, -~0, E. Zo az Q) Co CD C0 Z O __ X u O 0 W E 0 C; r z *-5D E O Z o) CD cl 0) E E 0, 0 C1) ?5 I- -c CO h- CD -I cm 0 CD E C) U) tO m CR m CO N C) Co i_ Co CM LC- )C- CDCN el -_ 639 r- a? - a LO iz LO R CALVERT ET AL. Table 3. Parameter estimates from adjusted logistic regression models for myocardial infarction, angina, arrythmia, hypertension, and APAF. Beta SE OR 95%07 Cl Myocardial infarctiona Workers with serum TCDD < 238 pg/g lipid Workers with serum TCDD ? 238 pg/g lipid Age, per year Per pack-year Current alcohol drinker Former alcohol drinker Family history of heart disease Employed at New Jersey plant No. observations, 521 Hosmer and Lemeshow Goodness-of-Fit Test Angina Workers with serum TCDD <238 pg/g lipid Workers with serum TCDD ? 238 pg/g lipid Age (greater than 55 years) HDL cholesterol (greater than 35 mg/dl) Current diabeties Family history of heart disease No. observations, 522 Hosmer and Lemeshow Goodness-of-Fit Test Arrhythmiaa Workers with serum TCDD <238 pg/g lipid Workers with serum TCDD ?238 pg/g lipid Age (greater than 55 years) No. observations, 527 Hosmer and Lemeshow Goodness-of-Fit Test Hypertensionb Workers with serum TCDD < 238 pg/g lipid Workers with serum TCDD ? 238 pg/g lipid Age, per year BMI (greater than 29) Male gender Family history of hypertension No. observations, 506 Hosmer and Lemeshow Goodness-of-Fit Test Current systolic hypertension Workers with serum TCDD < 238 pg/g lipid Workers with serum TCDD ? 238 pg/g lipid Age, per year BMI (greater than 29) Caucasian race Family history of hypertension No. observations, 506 Hosmer and Lemeshow Goodness-of-Fit Test Current diastolic hypertension Workers with serum TCDD < 238 pg/g lipid Workers with serum TCDD ? 238 pg/g lipid Triglyceride (> 250 mg/dl) BMI (greater than 29) Current alcohol drinker Former alcohol drinker Male gender No. observations, 514 Hosmer and Lemeshow Goodness-of-Fit Test Abnormal peripheral arterial flow Workers with serum TCDD < 238 pg/g lipid Workers with serum TCDD ? 238 pg/g lipid Age, per year Per pack-year (square root) Serum cholesterol (per mg/mi) Current cigarette smoker Former cigarette smoker Caucasian race Current diabeties No. observations, 527 Hosmer and Lemeshow Goodness-of-Fit Test 0.13 0.08 0.07 0.02 -0.91 0.30 0.97 0.48 0.70 0.79 0.02 4.7 x 10-3 0.57 0.57 0.36 0.68 1.14 1.09 1.07 1.02 0.40 1.35 2.63 1.61 0.29, 4.49 0.23, 5.06 1.03,1.11 1.01, 1.03 0.13,1.23 0.44,4.15 1.30, 5.33 0.43, 6.06 4.35 with 8 degrees of freedom (p= 0.82) -0.06 -0.40 1.56 -0.71 1.54 1.29 0.38 0.53 0.44 0.44 0.43 0.40 0.95 0.67 4.76 0.49 4.64 3.58 0.45, 1.98 0.24,1.89 2.00,11.36 0.21, 1.16 1.99, 10.85 1.67, 7.86 10.24 with 8 degrees of freedom (p= 0.25) -0.03 -0.26 0.82 0.28 0.42 0.28 0.98 0.77 2.27 0.56, 1.70 0.34, 1.78 1.31, 3.93 0.66 with 4 degrees of freedom (p= 0.96) 0.29 0.05 0.06 1.03 1.16 0.47 0.21 0.30 0.01 0.21 0.46 0.20 1.34 1.05 1.06 2.81 3.20 1.59 0.89, 2.02 0.58, 1.89 1.04, 1.08 1.85, 4.28 1.29, 7.94 1.08, 2.34 11.34 with 8 degrees of freedom (p= 0.18) 0.09 0.18 0.11 0.92 -1.54 0.69 0.26 0.34 0.01 0.25 0.38 0.24 1.09 1.20 1.12 2.51 0.22 2.00 0.65, 1.83 0.61, 2.34 1.09, 1.15 1.52, 4.13 0.10, 0.45 1.24, 3.23 5.83 with 8 degrees of freedom (p= 0.67) 0.30 -0.03 0.78 0.77 1.04 0.60 1.68 0.22 0.33 0.36 0.22 0.43 0.47 0.74 1.35 0.97 2.19 2.16 2.83 1.82 5.35 0.88, 2.09 0.51, 1.87 1.09, 4.40 1.40, 3.32 1.21, 6.62 0.73, 4.56 1.23, 23.28 1.51 with 7 degrees of freedom (p= 0.98) -0.15 0.17 0.04 0.22 7.1xlO-3 0.80 0.40 -1.00 0.93 0.28 0.39 0.01 0.06 3.0x 10-3 0.69 0.63 0.41 0.39 0.86 1.19 1.04 1.24 1.01 2.23 1.49 0.37 2.55 0.50, 1.51 0.55, 2.55 1.01, 1.07 1.11, 1.39 1.00,1.01 0.58, 8.59 0.43, 5.15 0.17, 0.82 1.19, 5.47 5.90 with 8 degrees of freedom (p= 0.66) half-life-extrapolated serum TCDD concen- trations were also lower (median among per- sonnel in the Ranch Hands Study having dioxin concentrations above background- 130 pg/g lipid; range not provided) (40). The Ranch Hands Study found that among the participants with a normal pulse examination in 1985, those with a current serum lipid-adjusted TCDD concentration greater than 10 pg/g lipid in 1992 had increased risk for abnormalitiesof the femoral pulse (RR= 3.35; 95% CI = 0.95, 11.8), popliteal pulse (RR=4.86; 95% CI= 1.80, 13.10), dorsalis pedis pulse (RR= 1.70; 95% CI =0.96, 2.99), and posterior tibial pulse (RR = 2.80; 95% CI= 1.39, 5.65) (27). In contrast, our study of workers who had higher serum TCDD concentrations compared to the those in the Ranch Hands Study did not find evidence of peripheral arterial disease. One explanation for this difference in find- ings may involve the techniques used to examine the lower extremity arteries. Our study used pressure indices whereas the Ranch Hands Study used Doppler wave- form morphology. Pressure indices are the preferred noninvasive test for assessing the presence of peripheral arterial disease (41). Although Doppler waveform morphology can be useful as a supplemental test, interpretation of the test can be difficult and is prone to error due to Doppler equip- ment problems, poor operator technique, and certain pathologic and physiologic conditions (42). In future studies, con- sideration should be given to including both techniques for assessing peripheral arterial disease. In addition, the Ranch Hands Study found a significant association between current lipid-adjusted TCDD concentra- tion and both medical record-verified hypertension (RR for a 2-fold increase in TCDD = 1. 14; 95% CI = 1.02, 1.28) and presence of nonspecific ST- and T-wave changes on ECG (RR for a 2-fold increase in TCDD = 1.20; 95% CI = 1.03, 1.40) (27). Several other cardiovascular outcomes examined in the Ranch Hands Study were found not to be associated with serum lipid-adjusted TCDD con- centration. These included hypertension detected on examination, medical record- verified myocardial infarction, medical record-verified heart disease (not further specified), and other types of ECG abnormalities (excluding nonspecific ST-and T-wave changes). The U.S. Air Force Ranch Hands Study, therefore, does not provide definitive conclusions Environmental Health Perspectives * Vol 106, Supplement 2 * April 1998 Beta, parameter estimate. SE, standard error; pack-year, smoking one pack of cigarettes daily for 1 year. &Includes those with self-reported and/or ECG diagnosis of the outcome. bincludes those meeting any of the three criteria: self-reported hypertension, current systolic hypertension, or current diastolic hypertension. 640 CARDIOVASCULAR OUTCOMES AMONG TCDD-EXPOSED WORKERS because of inconsistent findings for related outcomes. No statistically significant associations were observed in any of the other cross- sectional medical studies that reported cardiovascular outcomes (23-26). It should be noted that these other studies may have been limited by small sample size, and except for the study by Zober et al. (26), lack of detailed exposure-response analyses. Among 204 male 2,4,5-tri- chlorophenoxyacetic acid (2,4,5,-T) pro- duction workers, Suskind and Hertzberg (23) found no increased risk for self- reported hypertension, self-reported coro- nary artery disease, ECG findings, or atherosclerotic changes (not specified) on chest X-ray. Similarly, when Moses et al. (24) examined 116 male 2,4,5-T produc- tion workers with chloracne and compared them with workers not affected by chlor- acne, she found no increased risk for self- reported angina or self-reported myocardial infarction and no difference in the physical examination of the cardiovascular system. Bond et al. (25) found no increased associ- ation with self-reported hypertension among 27 workers involved in the produc- tion of TCP or among 87 workers involved in 2,4,5-T production. Finally, Zober et al. (26) did not find increased morbidity due to ischemic heart disease or other disorders of the circulatory system among 158 men who were exposed to TCDD after an uncontrolled decomposition reaction involving a TCP unit. Cross-sectional medical studies may be less suitable for investigating severe or fatal disease such as cardiovascular disease because affected individuals often are not capable of participating in this type of study (43). We considered this participa- tion bias as a possible explanation for why our study and other cross-sectional med- ical studies did not find an association between TCDD exposure and cardiovas- cular disease morbidity. For this explana- tion to be true, one would expect to see elevated cardiovascular disease mortality among the cohorts studied. The plants studied by Suskind and Hertzberg (23), Moses et al. (24), Bond et al. (25), and the two plants described here were included in a large cohort mortality study of U.S. workers involved in the produc- tion of TCDD-contaminated substances (21). This study by Fingerhut et al. (21). did not find an elevated risk for heart dis- ease mortality (ICD-9 codes 390-398, 402-404, 410-414, 420-429) (SMR= 0.96, 95% CI = 0.87-1.06), even among those with the highest durations of exposure (SMR= 0.87 among those with 15 or more years of exposure) (44). Findings were sim- ilar for ischemic heart disease (ICD-9 codes 410-414) (SMR= 103) (44). Among workers at the two plants we studied, the SMRs for heart disease and ischemic heart disease were 1.07 and 1.06, respectively (44). These results suggest that participa- tion bias may not be responsible for the findings in our study or in several other cross-sectional studies. Furthermore, to assess the potential magnitude of participation bias in our study, a telephone interview was attempted with all the workers who would not consent to an examination, a 10% random sample of the referents who refused all participa- tion, and all of the referents who provided lifetime occupational histories but refused to be examined. Of the 1 15 nonconsenting workers (excluding 2 who resided outside the United States and 2 who died between the first and this subsequent vital status determination) and 129 nonconsenting referents, 68 (57%) and 100 (78%), respec- tively, agreed to be interviewed by tele- phone. These individuals were asked questions similar to those asked in our med- ical study. The proportions of examined and nonconsenting workers reporting histories of myocardial infarction or angina were not statistically significantly different (Table 4). Similar results were found for the referents (Table 5). These results further suggest that participation bias may not be responsible for our study findings. We were unable to com- pare hypertension or cardiac arrhythmia because the questions asked about these conditions in the medical study differed from those asked in the telephone interview. A possible limitation in this study is the low statistical power for examining some of the outcomes of interest. Although our study had sufficient power (80% or more) to detect a 1.5-fold elevation in risk for car- diac arrhythmias, hypertension, and APAF, our study had low power (approximately 50%) for detecting a similar elevation in risk for myocardial infarction and angina. Although cross-sectional medical studies provide little evidence to support an associ- ation between TCDD exposure and cardio- vascular disease, these studies have found associations with several risk factors for car- diovascular disease. Among the risk factors found to be associated with TCDD expo- sure were decreased HDL cholesterol serum concentrations (27,29), increased serum triglyceride concentrations (27-29), and glucose intolerance (30). There is some ani- mal evidence to suggest that a TCDD- induced metabolic imbalance can lead to some of these risk factors. Enan et al. (45) found that TCDD-exposed guinea pigs have reduced glucose-transporting activity in the plasma membranes of adipose tissue and pancreas. In adipose tissue, reduced transmembrane glucose transport leads to suppressed lipoprotein lipase activity, and in the pancreas, to suppressed insulin pro- duction and release. These effects can lead to hypertriglyceridemia (lipoprotein lipase is responsible for metabolizing triglycerides absorbed from the gut) and glucose intoler- ance (insulin is needed for the metabolism of glucose), respectively, both of which are risk factors for cardiovascular disease. In Table 4. Comparison of self-reported history of physician-diagnosed myocardial infarction and angina between examined and nonconsenting workers. Number of examined Number of nonconsenting workers workers Outcome Yes No Excludeda Yes No Excludeda Unadjusted OR (95% Cl) Myocardial infarction, 25 254 3 7 61 0 0.86 (0.33, 2.29) self-reported Angina, self-reported 24 256 1 2 66 0 3.09 (0.68, 12.54) &Participants were excluded from the analysis if they could not recall whether they had the disease of interest. Table 5. Comparison of self-reported history of physician-diagnosed myocardial infarction and angina between examined and nonconsenting referents. Number of examined Number of nonconsenting referents referents Outcome Yes No Excludeda Yes No Excludeda Unadjusted OR (95% Cl) Myocardial infarction, 14 254 2 9 91 0 0.58 (0.23, 1.51) self-reported Angina, self-reported 22 237 1 6 94 0 1.45 (0.54, 4.15) &Participants were excluded from the analysis if they could not recall whether they had the disease of interest. Environmental Health Perspectives * Vol 106, Supplement 2 * April 1998 641 CALVERT ETAL. support of this hypothesis, two animal studies have shown that TCDD causes suppressed lipoprotein lipase activity (4,46). Because the origin and metabolism of HDL is not as well understood com- pared with that of other lipoproteins, the mechanism by which TCDD affects HDL metabolism cannot be determined at this time. 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