Great Lakes Sport Fish Consumers Research Articles

Polychlorinated biphenyls and incident coronary heart disease-related outcomes in Great Lakes fish consumers

BackgroundExposure to polychlorinated biphenyls (PCBs) has been linked to risk factors for cardiovascular disease such as increased inflammation, accelerated atherosclerosis, diabetes, and sex hormone dysregulation. Furthermore, there is increasing evidence suggesting associations between internal dose of PCBs and cardiovascular outcomes. ObjectivesThe purpose of this study is to investigate longitudinal associations of PCBs with coronary heart disease (CHD)-related outcomes in a cohort of Great Lakes sport fish consumers. MethodsThe Great Lakes Sport Fish Consumer cohort was established in the early 1990's. Eight hundred nineteen participants were followed from 1993 to 2017. Serum PCBs were measured in 1994/1995 (baseline), in 2001, and in 2004, while health history questionnaires were administered in 1996, 2003, 2010, and 2017. Cox models were used to prospectively investigate associations of total PCBs and PCB groupings, based on aryl hydrocarbon receptor activity, with incident self-reported physician diagnosis of coronary heart disease (CHD), myocardial infarction (MI), and angina pectoris. ResultsA 2-fold increase in phenobarbital-type PCBs was associated with a 72% increase in likelihood of self-reported incident diagnosis of CHD (HR=1.72, 95% CI: 1.06–2.81; p=0.0294). Similar results were observed for total PCBs (HR=1.68, 95% CI: 1.05–2.69; p=0.0306) and mixed methacholine/phenobarbital type (mixed-type) PCBs (HR=1.60, 95% CI: 1.02–2.52; p=0.0427), but not methacholine-type PCBs. PCBs were not strongly associated with risk of MI or angina. ConclusionsThis study presents evidence that exposure to PCBs increases the risk of developing coronary heart disease. Given the large number of risk factors and causal pathways for CHD, future research is required to better understand biological mechanisms of action for PCBs on CHD.

Associations of PCB and PBDE congeners with thyroid hormones in Great Lakes sport fish consumers

TPS 634: Health effects of pops, voc and other chemicals, Johan Friso Foyer, Floor 1, August 27, 2019, 3:00 PM - 4:30 PM Thyroid hormones play an essential role in regulating many physiologic functions including growth, reproduction, and metabolism. Consequently, disruption of thyroid homeostasis by pollutants such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) may result in clinical or subclinical disease. Individual congeners of PCBs and PBDEs may show strong correlation with each other given shared chemical structure and usage patterns; consequently, past evaluation of thyroid hormone disruption in Great Lakes sport fish consumers (GLSFC) predominantly focused on summary measures of total PCB body burden. However, newer statistical methodologies can better account for collinearity among exposures. This investigation focused on data collected in 2005 from male GLSFC, and used weighted quantile sum (WQS) regression to investigate associations of PCB congeners, PBDE congeners and DDE, with endogenous thyroid hormones, triiodothyronine (T3), total thyroxine (T4), free forms of T3 and T4 (FT3 and FT4), reverse T3 (rT3), thyroxine binding globulin-bound T4 (TBG-T4), albumin-bound T4 (alb-T4) and thyroid-stimulating hormone (TSH). The cohort of 367 males were 30 to 81 years of age (mean = 60 years), without diagnosed thyroid disease and were not using thyroid, sex steroid or corticosteroid medications. We found significant associations with many hormone outcomes. Free T4 was inversely associated with PCB congeners, predominately PCB170 and 178, and positively associated with PBDE153 and 99. Similarly, total T4 was inversely associated with PCB146, 170 and 178, and positively associated with PBDE153 and 99. Reverse T3 was positively associated with PBDE47, 99 and 153. Alb-T4 was positively associated with PBDE47 and 100 and TBG-T4 was inversely associated with PBDE47, 100 and 153. In conclusion, recent developments in the analysis of multiple correlated exposures can expand our understanding of the impact of individual exposures on hormone dysregulation in historical data sets and identify which specific congeners may play a role in determining health outcomes.

Organochlorine Exposure and Body Mass Index Trajectory in Adults

PURPOSE: Since the publication of the “obesogen hypothesis”, there has been considerable interest in the role of chemical exposures in the development of obesity and diabetes. A substantial body of literature supports an effect of persistent organic pollutants (POPs) on diabetes risk. However, studies on the obesogenicity of POPs have not been conclusive for a number of reasons, including the predominance of cross sectional studies which are potential subject to reverse causality. METHODS: This study examined data from a cohort of 505 frequent and infrequent Great Lakes sport fish consumers collected from 1994-2010 to explore the hypothesis that exposure to POPs is related to obesity in adults. Polychlorinated biphenyls (PCBs) and p,p’-dichlorodiphenyldichloroethylene (DDE) were measured at baseline and the effect of individual PCB congeners and DDE on the rate of BMI change or BMI trajectory in the cohort was estimated using longitudinal models adjusting for age, age*time, sex, smoking status and education. RESULTS: Baseline BMI significantly modified associations of PCB congeners with BMI trajectory. In persons of normal BMI at baseline, PCB congeners were positively associated with BMI trajectory, with significant associations for PCBs 180, 182/187 and 201. In persons who were obese at baseline, PCB congeners were inversely associated with BMI trajectory, with associations reaching significance for PCBs 74, 118, and 138/163 and 180. DDE (quartile 4 versus quartile 1) was inversely associated with BMI trajectory and this association was not modified by baseline BMI. Conclusions: Associations of PCBs with the rate of BMI change over up to 17 years of follow up were modified by baseline BMI status. PCB congeners 180, 182/187 and 201 were significantly associated with greater rates of BMI change only in persons of normal weight at baseline. Additional longitudinal investigations are needed to better understand these complex interactions.

Uterine leiomyomata in a cohort of Great Lakes sport fish consumers

Diet and endocrine disrupting persistent organic pollutants (POPs) have been associated with gynecologic conditions including uterine leiomyomata (UL), endometriosis, and ovarian cysts. Great Lakes sport fish consumption is a source of exposure to POPs such as p,p′-diphenyldichloroethene (DDE) and polychlorinated biphenyls (PCBs). This study was designed to examine retrospectively the effects Great Lakes sport fish consumption on the incidence of UL and to examine the effects of DDE and PCB serum levels on prevalent UL in women participating in the Great Lakes Fish Consumption Study. We hypothesized that associations of exposures with UL would be modified by breastfeeding status. Years of sport fish consumption, demographic, health, and reproductive data were assessed by survey. In a subgroup, serum was collected and tested for DDE and PCB levels. Effects of years of Great Lakes sport fish and sport fish consumption were modeled using time-dependent Cox proportional hazards regression and effects of POP exposures on UL were modeled using multiple logistic regression. Years of sport fish consumption were associated with UL, with an incidence rate ratio of 1.2 (95% CI 1.0–1.3) for each 10-year increment of fish consumption. Summary measures of POP exposures in the overall group were not associated with UL. In the subgroup of women who never breastfed and in whom PCB measurements were available, however, UL was significantly associated with PCBs and groupings of estrogenic, antiestrogenic, and dioxin-like PCBs. These findings support the possibility that PCB exposures from fish consumption may increase the risk of UL and highlight the importance of additional studies exploring biologic pathways by which they could be acting.

Diabetes and Exposure to PCBs, DDE, Polybrominated Diphenyl Ethers in Frequent and Infrequent Great Lakes Sport Fish Consumers

Diabetes and Exposure to PCBs, DDE, Polybrominated Diphenyl Ethers in Frequent and Infrequent Great Lakes Sport Fish Consumers

Organochlorine Exposure and Incidence of Diabetes in a Cohort of Great Lakes Sport Fish Consumers

BackgroundStudies have demonstrated ubiquitous human exposure to persistent organic pollutants (POPs) such as p,p′-diphenyldichloroethene (DDE) and polychlorinated biphenyls (PCBs). Although there is considerable evidence that POP exposures are associated with prevalent diabetes, these studies do not establish causality because the cross-sectional study design does not allow for assessment of temporality of the exposure–disease association. Prospective studies, however, have been lacking.ObjectivesThis study was designed to determine whether POP body burdens are related to incidence of diabetes in a cohort of Great Lakes sport fish consumers.MethodsThe cohort was established in the early 1990s and followed through 2005. We tested serum for DDE and PCB congeners and assessed diabetes diagnosis, demographics, and fish consumption. Associations of diabetes with exposures were examined prospectively in participants without diabetes in 1994–1995, followed through 2005. Annual percent changes in DDE and PCB-132/153 from 1994 to 2005 were examined by diabetes status.ResultsDDE exposure was associated with incident diabetes. Incident diabetes was not associated with mono-ortho PCB-118, total PCBs, or years of sport fish consumption. Annual percent change in DDE and PCB-132/153 did not differ significantly by diabetes status.ConclusionsThis study demonstrates an association between DDE exposure and incident diabetes. The findings of an association of DDE with incident diabetes and the lack of effect of diabetes on annual percent change in POPs do not support the hypothesis that associations of POPs with diabetes are attributable to reverse causality. Additional studies should address the biological pathways by which DDE could affect glucose homeostasis.

Prevalence of diabetes and body burdens of polychlorinated biphenyls, polybrominated diphenyl ethers, and p,p′-diphenyldichloroethene in Great Lakes sport fish consumers

Recent studies have demonstrated ubiquitous exposure to persistent organic pollutants (POPs) such as p,p′-diphenyldichloroethene (DDE), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). Although several studies have noted associations of dioxins, PCBs and DDE with diabetes, the results have not always been consistent, with few examining effects of PBDEs or simultaneous exposures. The purpose of this study was to determine whether POP body burdens are related to diabetes in a cross section of Great Lake sport fish consumers. The cohort, which was established in the early 1990s, was recontacted in 2004–2005. Serum was collected and tested for DDE, PCBs, PBDEs, hemoglobin A1c and lipids, and diabetes diagnosis, demographics and fish consumption were assessed by self report. Associations of diabetes with exposures were examined in cross sectional data from 2004 to 2005. DDE exposure and dioxin-like mono-ortho PCBs were associated with diabetes, but the association of dioxin-like mono-ortho PCBs with diabetes did not remain significant after control for DDE exposure. Neither the sum of PCBs or years of sport fish consumption were associated with prevalent diabetes. There was a non-significant association of PBDEs with diabetes only in those with hypothyroid disease. The current study confirms previous cross sectional associations of DDE exposure with diabetes. Future studies should address biologic pathways by which selective POPs affect glucose homeostasis.

Fish ingestion and congener specific polychlorinated biphenyl and p, p'-dichlorodiphenyldichloroethylene serum concentrations in a great lakes cohort of pregnant African American women

A cohort of low income, city dwelling, pregnant African American Women (delivered from 1994–1999) was assembled to identify factors related to organochlorine exposure through consumption of Great Lakes resources. The cohort is known as the Great Lakes Cohort of Pregnant African American Women (GLCPAAW). Pregnant women from metropolitan Chicago, IL area clinics were administered a questionnaire on diet, demographics, and health history. Weight, height, and serum lipids were measured at delivery along with serum organochlorines such as PCBs and DDE. Congener specific concentrations of PCBs and p, p'-DDE found in the maternal serum are reported. Dominant PCB congeners found in the serum of the pregnant women at delivery included PCB 101, 118, 138, 153, and 180. The high prevalence and magnitude of PCB 101 (greater than the limit of detection in > 80% of the women in the cohort) are unique characteristics of this cohort. Great Lakes fish has been identified as a source of exposure to organochlorines in several studies. Spearman correlations and robust regression models were utilized to identify the impact of Great Lakes fish ingestion on cohort serum organochlorine concentrations. Several potential confounders of the relationship between serum organochlorines and Great Lakes fish consumption were identified. Covariates related to organochlorines in correlations as well as regression models included age, body surface area, fish ingestion, lipids, parity, race and smoking. Lower chlorinated PCB congeners do not follow the same trends as the higher chlorinated congeners and DDE. The higher chlorinated PCB congeners (PCB 138, 153, and 180) and DDE were correlated with age while the lower chlorinated congeners were not. PCB 153 and 180 regression models included age as a significant covariate. None of the higher chlorinated congeners correlated to race, while both lower chlorinated congeners were correlated to race. Race was also significant in both lower chlorinated congeners' regression models. PCB 101, a lower chlorinated congener seldom found in human serum, is readily found in the cohort. Airborne PCB exposure as well as diminished metabolism of PCB 101 in African Americans may explain the increased presence of PCB 101 and it's correlation with race. High end sport fish consumers (≥ 1meal per week) carried elevated levels of DDE and higher chlorinated PCB congeners (138, 153, and 180) compared to non-sport fish eaters. Unexpectedly, DDE was correlated more consistently with fish ingestion and age (a marker of bioaccumulation) in comparison to PCBs. Small correlations were found between serum PCBs and fish ingestion (Spearman correlation = 0.19 for total PCBs and fish meals per year). Additionally, Serum PCBs in low end Great Lakes sport fish consumers were not higher than non-consumers. These findings suggest the women of the cohort are being exposed to PCBs through other routes in addition to Great lakes sport fish. One major route of exposure may be Chicago air. The observed trends amongst individual PCB congeners has important ramifications because lower chlorinated congeners or their metabolites may be mediators of toxicity. Organochlorine exposure through Great Lakes fish ingestion was clearly identified in high end fish consumers while associations with race, metabolism, and possible airborne exposures pose new questions.

Temporal changes in PCB and DDE levels among a cohort of frequent and infrequent consumers of Great Lakes sportfish

A variety of environmentally persistent contaminants of the Great Lakes Basin are able to bioaccumulate in the aquatic food chain and pose a threat to the health and reproductive success of people and wildlife that depend on locally caught fish as a source of dietary protein. Exposure to polychlorinated biphenyls (PCBs) and 1,1-bis(4-chlorophenyl)-2,2-dichloroethene (DDE) has been linked to higher rates of cancer, reproductive problems, and endocrine disorders. To investigate the effects of exposure to persistent contaminants of the Great Lakes Basin, the health departments of five Great Lakes states formed a health-assessment consortium. Between 1988 and 1994, the consortium collected demographic and fish consumption information from 2548 licensed charter boat captains, 182 anglers, and 1667 referents. Between 1994 and 1995, a subset of 619 participants in this study provided additional fish consumption information and donated blood samples that were analyzed for PCBs and DDE. Follow-up studies conducted between 2001 and 2005 re-assessed fish consumption rates and blood levels of PCBs and DDE in 293 of these individuals. While there was a trend for increasing overall fish consumption among most participant groups, sportfish and Great Lakes sportfish consumption decreased significantly in the captains over the study period. Serum DDE concentrations, which were highest in men in the captain and angler groups, declined in 90% of study participants. Mean DDE levels fell from 5.6 to 3.2 μg/L. Total PCB levels declined in 80% of participants with the mean concentration falling from 4.2 to 2.8 μg/L. Annual declines in serum DDE and PCB concentrations averaged 4.6% and 3.5%, respectively.

Polybrominated diphenyl ethers (PBDE) in serum: Findings from a US cohort of consumers of sport-caught fish

Polybrominated diphenyl ethers (PBDEs) have been used as flame retardants in foams, fabrics and plastics, and are common contaminants of household air and dust and bioaccumulate in wildlife, and are detectable in human tissues and in fish and animal food products. In the Great Lakes Basin sport fish consumption has been demonstrated to be an important source of PCB and DDE exposure. PBDEs are present in the same sport fish but prior to our study the contribution to human PBDE body burdens from Great Lakes sport fish consumption had not been investigated. This study was designed to assess PBDE, PCB and 1,1-bis(4-chlorophenyl)-2,2-dichloroethene (DDE) serum concentrations in an existing cohort of 508 frequent and infrequent consumers of sport-caught fish living in five Great Lake states. BDE congeners 47 and 99 were identified in the majority of blood samples, 98% and 62% respectively. summation operatorPBDE levels were positively associated with age, hours spent outdoors, DDE, summation operatorPCB, years of sportfish consumption, and catfish and shellfish intake, and negatively associated with income and recent weight loss. Other dietary components collected were not predictive of measured summation operatorPBDE levels. In multivariate models, summation operatorPBDE levels were positively associated with age, years consuming sport fish, shellfish meals, and computer use and negatively associated with recent weight loss. Having summation operatorPBDE levels in the highest quintile was independently associated with older age, male gender, consumption of catfish and shellfish, computer use and spending less time indoors. summation operatorPCB and DDE were strongly associated suggesting common exposure routes. The association between summation operatorPBDE and summation operatorPCB or DDE was much weaker and modeling suggested more diverse PBDE sources with few identified multi-contaminant-shared exposure routes. In our cohort Great Lakes sport fish consumption does not contribute strongly to PBDE exposure.

Chronic exposure to dioxin-like compounds and thyroid function among New York anglers

Experimental studies suggest that dioxin-like compounds influence thyroid function, although human studies have presented equivocal results. Great Lakes sportfish consumers represent a population with greater potential for exposure to dioxin-like compounds than non-consumers. Thirty-eight licensed anglers participating in a dioxin exposure study, consumers and non-consumers, conducted as part of the New York Angler Cohort Study, donated blood and completed questionnaires regarding demographic, clinical, and sportfish consumption data. Sera were analyzed for polychlorinated dibenzo- p-dioxins (PCDDs), dibenzofurans (PCDFs), coplanar biphenyls (PCB), and PCB IUPAC #153, in addition to thyroid stimulating hormone (TSH), total and free thyroxine (T 4 and fT 4), total triiodothyronine (T 3), and lipids. An inverse linear association between serum fT 4 and the sum of dioxin-like congener concentrations (∑DIOXs) in serum ( B = −0.3, 95% CI = −0.5, −0.1) was identified adjusting for PCB #153 and serum lipids ( R 2 = 0.3, p = 0.02, n = 37). The results of this study are preliminary but suggest an inverse association between dioxin-like compounds and fT 4.

Profiles of ortho-polychlorinated biphenyl congeners, dichlorodiphenyldichloroethylene, hexachlorobenzene, and Mirex among male Lake Ontario sportfish consumers: the New York State Angler Cohort Study

Great Lakes sportfish consumption is a recognized human exposure source to environmental organochlorine compounds. Using data collected as part of the New York State Angler Cohort Study, 203 males were considered with regard to history of Lake Ontario sportfish consumption and sera levels of 57 ortho-substituted polychlorinated biphenyl (PCB) congeners, dichlorodiphenyldichloroethylene, hexachlorobenzene, and Mirex. Consumption of six species of highly contaminated Lake Ontario sportfish during the years 1980 to 1990 was considered. Exposure was weighted by average annual frequency of consumption, whole-fish PCB estimates, and meal size to determine a continuous index of exposure. This index was dichotomized to compare “consumers” to “nonconsumers” in several procedures. Recovery and lipid-adjusted serum values for PCB congener IUPAC Nos. 138+163 (rsp=0.3), 183 (rsp=0.3), 187 (rsp=0.4), and 188 (rsp=0.3) and Mirex (rsp=0.4) were significantly correlated with the index of fish consumption (P<0.001). A logistic regression model, using forward stepwise selection procedures (α in/out=0.002/0.004), was employed to account for high intercorrelations among organochlorine predictor variables. Mirex was the sole statistically significant predictor variable of “consumer/nonconsumer.” A one-unit increase in log Mirex was associated with a 92.0% increase in the odds of having reported sportfish consumption (OR=1.92, 95%CI=1.43, 2.58). Age, body mass index, cigarette smoking, water/wildfowl consumption, and year of sampling were considered covariates. The results of this study support the premise that long-term dietary consumption of Lake Ontario sportfish, even at comparatively low levels, contributes significantly to the body burden of organochlorine compounds in western New York anglers and sportsmen.

Serum PCB and DDE Levels of Frequent Great Lakes Sport Fish Consumers—A First Look

Great Lakes (GL) sport fish consumption is a potential human exposure route for polychlorinated biphenyls (PCBs) and dichlorodiphenyl dichloroethene (DDE). Because of fish tissue contamination, frequent consumers of Great Lakes sport caught fish (GLSCF) may be at risk for PCB and DDE accumulation. To examine this problem, the Health Departments of Wisconsin, Illinois, Indiana, Ohio, and Michigan formed a health assessment consortium. Participants were contacted by telephone to complete a detailed demographic and fish consumption survey. Frequent and infrequent GLSCF consumers were identified, and a participant subset was then asked to donate blood for PCB and DDE analysis. Analysis of variance (ANOVA) was done to study exposure group mean differences, while correlation and regression analyses were performed to examine relationships between demographic characteristics, GLSCF consumption, PCB, and DDE body burdens. A total of 4206 individuals participated in the study. Of these, 2542 were habitual GLSCF consumers (mean greater than 35 meals/year males; greater than 27 meals/year females), while 1664 did not eat GLSCF. A subset of 538 participants donated blood and included 439 frequent and 99 infrequent GLSCF consumers. PCB levels were significantly higher in the group of GLSCF consumers (geometric mean: 4.8 ppb males, 2.1 ppb females) when compared to their referents (geometric mean: 1.5 ppb males, 0.9 ppb females), while DDE levels were also higher for GLSCF consumers. PCB and DDE body burdens varied by exposure group, gender, and great lake (Michigan, Huron, Erie). PCB and DDE levels were significantly correlated to age, body mass index, and sport fish and Great Lakes sport fish consumption histories. Regression analysis identified years of consuming sport caught fish as the most robust predictor of PCBs (r2=25%), while age was the best predictor of DDE levels (r2=21%). This study corroborated previous findings relating frequent GLSCF consumption to a higher body burden for PCBs and DDE.

Profiles of Great Lakes critical pollutants: a sentinel analysis of human blood and urine. The Great Lakes Consortium.

To determine the contaminants that should be studied further in the subsequent population-based study, a profile of Great Lakes (GL) sport fish contaminant residues were studied in human blood and urine specimens from 32 sport fish consumers from three Great Lakes: Lake Michigan (n = 10), Lake Huron (n = 11), and Lake Erie (n = 11). Serum was analyzed for 8 polychlorinated dioxin congeners, 10 polychlorinated furan congeners, 4 coplanar and 32 other polychlorinated biphenyl (PCB) congeners, and 11 persistent chlorinated pesticides. Whole blood was analyzed for mercury and lead. Urine samples were analyzed for 10 nonpersistent pesticides (or their metabolites) and 5 metals. One individual was excluded from statistical analysis because of an unusual exposure to selected analytes. Overall, the sample (n = 31) consumed, on average, 49 GL sport fish meals per year for a mean of 33 years. On average, the general population in the GL basin consume 6 meals of GL sport fish per year. The mean tissue levels of most persistent, bioaccumulative compounds also found in GL sport fish ranged from less than a twofold increase to that of PCB 126, which was eight times the selected background levels found in the general population. The overall mean total toxic equivalent for dioxins, furans, and coplanar PCBs were greater than selected background levels in the general population (dioxins, 1.8 times; furans, 2.4 times; and coplanar PCBs, 9.6 times). The nonpersistent pesticides and most metals were not identified in unusual concentrations. A contaminant pattern among lake subgroups was evident. Lake Erie sport fish consumers had consistently lower contaminant concentrations than consumers of sport fish from Lake Michigan and Huron. These interlake differences are consistent with contaminant patterns seen in sport fish tissue from the respective lakes; GL sport fish consumption was the most likely explanation for observed contaminant levels among this sample. Frequent consumers of sport fish proved to be effective sentinels for identifying sport fish contaminants of concern. In the larger study to follow, serum samples will be tested for PCBs (congener specific and coplanar), DDE, dioxin, and furans.

Consortium for the Health Assessment of Great Lakes Sport Fish Consumption.

Consortium for the Health Assessment of Great Lakes Sport Fish Consumption.

Organochlorine accumulation by sentinel mallards at the Winston-Thomas sewage treatment plant, Bloomington, Indiana

Farm-raised 12-month-old female mallards (Anas platyrhynchos) were released at the Winston-Thomas sewage treatment plant, Bloomington, Indiana. Five mallards were sacrificed at the start of the study and at approximately 10-day intervals through day 100. Concentrations of polychlorinated biphenyls (PCBs) in carcasses increased linearly with time of exposure and exceeded 16 μg/g wet weight by day 100; PCBs in breast muscle exceeded 3.9 μg/g by day 100. These PCB values are among the highest recorded for wild or sentinel waterfowl. PCB concentrations in breast muscle (26–523 μg/g lipid weight) were 50–1,000 times greater than human consumption guidelines for edible poultry in Canada (0.5 μg/g lipid weight) and 9–176 times greater than consumption guidelines for edible poultry in the United States (3.0 μg/g lipid weight). Additionally, PCB concentrations in carcass and breast muscle exceeded the threshold of the Great Lakes Sport Fish Consumption Advisory ‘do not eat’ category (1.9 μg/g wet weight) by day 20 and day 50, respectively. Hepatic cytochrome P450-associated monooxygenases including BROD (benzyloxyresorufin-O-dealkylase), EROD (ethoxyresorufin-O-dealkylase), and PROD (pentoxyresorufin-O-dealkylase) were induced over 5-fold compared to reference mallards. BROD, EROD, and PROD were each significantly correlated to total PCBs and to the toxicity of selected PCB congeners, relative to 2,3,7,8-tetrachlorodibenzo-p-dioxin.