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A vial equilibration technique was used to estimate the fugacity capacities of food and feces samples for 1,2,3,4-tetrachlorobenzene (TCB). The method was calibrated using different volumes of n-octanol and by comparing the measured and predicted fugacity capacity (Zoct) of n-octanol for TCB. The vial equilibration technique showed linearity with increasing amounts of n-octanol added to the vial. However, the measured Zoct was on average 8.5 times lower than the literature estimate and interpreted to be influenced by co-solvent effects. The ratio of fugacity capacities of food/feces was 2.9 and was consistent with the ratio estimated using Zt calculation methods (4.3) which considers partitioning capacity of both lipids and non-lipid organic matter. These results provide experimental support to the use of lipid equivalent approaches as opposed to lipid normalization when estimating the partition capacity of biological samples containing low lipid contents.

Ring doves were provided contaminated food spiked with [(13)C]-2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) over a period of 63 days. Animals were sacrificed after 0.33, 0.5, 1, 2, 4, 8, 18, 36 and 63 days following access to contaminated food. At each time point, chemical concentrations in blood, liver, brain, gonad, adipose and remaining whole carcass was determined. Whole body concentrations of PCB 153 increased linearly with time over the experiment indicating that the birds did not reach steady state with their food after 63 days. Tissue/plasma concentration ratios were plotted as a function of time to determine time to inter-tissue steady state for fast and slowly perfused tissues. Liver, brain and gonad achieved steady state concentrations with plasma in less than 3 days, whereas fat and carcass tissues required 9.7 and 11.5 days, respectively. The results indicate that inter-tissue distribution kinetics for PCBs in birds is relatively rapid and completed within a little over a week following exposure to a contaminated diet.

Organochlorine pesticide and total polychlorinated biphenyl (PCB) concentrations were measured in largemouth bass from the Tombigbee River near a former DDT manufacturing facility at McIntosh, Alabama. Evaluation of mean p,p'- and o,p'-DDT isomer concentrations and o,p'- versus p,p'-isomer proportions in McIntosh bass indicated that DDT is moving off site from the facility and into the Tombigbee River. Concentrations of p,p'-DDT isomers in McIntosh bass remained unchanged from 1974 to 2004 and were four times greater than contemporary concentrations from a national program. Total DDT in McIntosh bass exceeded dietary effect concentrations developed for bald eagle and osprey. Hexachlorobenzene, PCBs, and toxaphene concentrations in bass from McIntosh also exceeded thresholds to protect fish and piscivorous wildlife. Whereas concentrations of DDT and most other organochlorine chemicals in fish have generally declined in the U.S. since their ban, concentrations of DDT in fish from McIntosh remain elevated and represent a threat to wildlife.

To assess geographic distributions of elements in the Arctic we compared essential and non-essential elements in the livers of polar bears (Ursus maritimus) collected from five regions within Canada in 2002, in Alaska between 1994 and 1999 and from the northwest and east coasts of Greenland between 1988 and 2000. As, Hg, Pb and Se varied with age, and Co and Zn with gender, which limited spatial comparisons across all populations to Cd, which was highest in Greenland bears. Collectively, geographic relationships appeared similar to past studies with little change in concentration over time in Canada and Greenland for most elements; Hg and Se were higher in some Canadian populations in 2002 as compared to 1982 and 1984. Concentrations of most elements in the polar bears did not exceed toxicity thresholds, although Cd and Hg exceeded levels correlated with the formation of hepatic lesions in laboratory animals.

An Avian BioAccumulation Model (ABAM) of persistent organic pollutant (POP) uptake and elimination in adult life-stage of birds was validated by simulation of concentrations of DDE, dieldrin, mirex, and HCB in herring gull eggs in Lake Ontario for the years 1985, 1990, and 1992. These chemicals represented a range of whole-body half-lives of 82-265 days in the gull. Dietary intake of POPs by a female gull was simulated by a dynamic bioenergetics model which included dependence on temperature, photoperiod, egg production, and feeding chicks. Concentrations in the two main prey fish of the gull in Lake Ontario were used for POP exposure. Clearance from the female was based on a two compartment toxicokinetic model. Egg concentrations were estimated from egg/whole body female concentration ratios. Simulated concentrations were compared to measured concentrations in gull eggs from 4 different colonies in the northern part of Lake Ontario. Simulations using a diet of 81% fish and 19% uncontaminated food resulted in the best fit with least variance among predicted and measured data. The mean ratio of predicted to measured concentrations in eggs was 1.0 +/- 0.27 among chemicals, years, and colonies for this exposure scenario. This result was in excellent agreement with field assessments of herring gull diet composition in Lake Ontario of 80-82% fish. The ability to perform accurate a priorisimulations for the range of test conditions employed in the validation constituted a rigorous test of the soundness of the model's structure and parameterization. With species-specific adjustments, ABAM can be regarded as a general model for lipophilic POPs bioaccumulation in birds.

Monitoring of environmental contaminants in Canadian Arctic polar bears (Ursus maritimus) typically has used superficial adipose tissue samples collected as part of controlled native subsistence hunts. However, little attention has been paid to the compositional difference in contaminants that may exist among the major adipose depots that are routinely collected. To address this knowledge gap, we investigated the profiles and concentrations of chlorinated hydrocarbon contaminants (CHCs), including major polychlorinated biphenyl (PCB) congeners and organochlorine (OC) pesticides and metabolites, in six major adipose depots (i.e. superficial, inter-muscular and intra-abdominal regions) obtained from adult male polar bears in the vicinity of Resolute Bay, Canadian high Arctic. Concentrations and congener patterns of PCBs (20 congeners) and OCs (14 compounds; chlordanes and dichlorodiphenyltrichloroethanes and metabolites, chlorinated benzenes, hexachlorocyclohexane isomers, octachlorostyrene and dieldrin) were found to be relatively uniform throughout the adipose tissue of male polar bears. The only exception was the inter-muscular adipose depot from the cervical region, which was characterized, compared to other major depots routinely sampled, by lower proportions of higher-chlorinated and recalcitrant congeners such as CB170/190, 180, 194 and 206, and higher contribution of the lower-chlorinated PCBs, CB47, 74 and 99. No difference in the OC makeup and concentrations was found among the adipose depots investigated. In view of this, we conclude that the determination of CHCs in adipose tissue of polar bears from any major depots, with the potential exception of the fat under the neck muscles, would give a representative picture of the overall CHC composition and concentrations in polar bear fat for purpose of trend monitoring.

Twenty-five essential and nonessential elements were analyzed in Arctic seabirds to study the influence of phylogeny, tissue, Arctic region, and diet on avian element accumulation and to identify co-occurrence among metals. Muscle and liver concentrations were positively correlated, generally being higher in liver than in muscle, and generally did not differ by sex. Zinc showed the highest absolute concentrations in all samples (mean, 11.2-26.7 microg/g in muscle, depending on species and area), followed by copper (5.2-7.5 microg/g), arsenic (0.5-5.4 microg/g), selenium (1.0-5.8 microg/g), rubidium (1.4-2.2 microg/g), and cadmium (0.04-1.2 microg/g). Mercury levels ranged from 0.05 to 0.8 microg/g in muscle. The concentrations varied among species (dovekie [Alle alle], black guillemot [Cepphus grylle], thick-billed murre [Uria lomvia], black-legged kittiwake [Rissa tridactyla], northern fulmar [Fulmaris glacialis], ivory gull [Pagophila eburnean], Thayer's gull [Larus thayeri], and glaucous gull [Larus hyperboreus]), and between the northern Baffin Bay (Canada) and the Barents Sea, depending on the element. Whereas some elements (e.g., mercury and zinc) increased in absolute and standardized concentrations with trophic level in the northern Baffin Bay, most elements showed no relationship with trophic level or other dietary descriptors. In absolute concentrations, nonessential elements differed between regions, whereas essential elements differed among species but not within a species across the two regions. Standardized concentrations (element pattern) of both essential elements and nonessential elements generally did not differ between regions but was highly species specific and, thus, determined by the phylogenetic element regulation capacity. The usefulness of multivariate ordination in element wildlife studies is illustrated, which provides additional insight regarding element co-occurrence in wildlife, allows inclusion of species with low sample number, and reduces the possibility of type II errors created by low sample size.

Herring gull egg homogenates collected between 1971 and 1982 from a colony in central Lake Ontario (Scotch Bonnet Island) and from a colony in central Green Bay, Lake Michigan (Big Sister Island) were archived in the Canadian Wildlife Service Specimen Bank. Pooled samples (N = 10) were exhaustively analyzed in 1993 for a wide range of individual chlorinated hydrocarbon contaminant (CHC) compounds: DDT, mirex and chlordane compounds and metabolites, chlorobenzenes (CBzs), dieldrin, chlorostyrenes (CSs), hexachlorocyclohexanes (HCHs), polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), and 87 PCB congeners, including the TCDD-like non-ortho and mono-ortho congeners. PCBs and DDTs were the dominant residues in eggs from both Lake Ontario (31-242 mg kg(-1) and 9-64 mg kg(-1)) and Green Bay (34-133 mg kg(-1) and 14-91 mg kg(-1)). SigmaPCBs declined by a factor of 4-5 and DDTs a factor of 4-7 at both colonies between 1971 and 1982. Lake Ontario eggs had significantly higher residues of 2,3,7,8-TCDD (0.2-2.0 microg kg(-1)), HCBz (0.1-4.7 mg kg(-1)), OCS (0.03-0.45 mg kg(-1)), three HpCSs (0.13-0.97 mg kg(-1)), mirex and mirex photodegradation products (2.1-9.2 mg kg(-1)) than Green Bay eggs. HCBz levels in Lake Ontario eggs declined a factor of 40, TCDD and chlorostyrenes a factor of 8-10, and mirex a factor of 4 between 1971-1978. Green Bay eggs had slightly higher levels of chlordane-related compounds, dieldrin and beta-HCH than Lake Ontario eggs. There were no consistent or strong trends in residue levels of these pesticides, PCDDs (except TCDD) and PCDFs in either lake, indicating that rates of input and removal of these CHCs in the lakes were much closer in the early 1970s than was the case for the other compounds.

Perfluoroalkyl substances are globally distributed anthropogenic contaminants. Their production and use have increased dramatically from the early 1980s. While many recent publications have reported concentrations of perfluorooctane sulfonate (PFOS) and other perfluoroalkyl acids (PFAs) in biotic and abiotic samples, only limited work has addressed temporal trends. In this study we analyzed archived polar bear(Ursus maritimus) livertissue samples from two geographic locations in the North American Arctic, collected from 1972 to 2002. The eastern group, taken from the vicinity of northern Baffin Island, Canada, comprised 31 samples, and the western group, from the vicinity of Barrow, Alaska, comprised 27 samples. Samples were analyzed for perfluorocarboxylic acids (PFCAs) from carbon chain length C8 to C15, perfluorohexane sulfonate, PFOS, the neutral precursor perfluorooctane sulfonamide (PFOSA), as well as 8:2 and 10:2 fluorotelomer acids and their alpha,beta unsaturated acid counterparts. Concentrations of PFOS and PFCAs with carbon chain lengths from C9 to C11 showed an exponential increase between 1972 and 2002 at both locations. Doubling times ranged from 3.6 +/- 0.9 years for perfluorononanoic acid in the eastern group to 13.1 +/- 4.0 years for PFOS in the western group. PFOSA showed decreasing concentrations over time at both locations, while the remaining PFAs showed no significant trends or were not detected in any sample. The doubling time for PFOS was similar to the doubling time of production of perfluoroctylsulfonyl-fluoride-based products during the 1990s.

Polybrominated diphenyl ethers (PBDEs) were determined in adipose tissue of adult and subadult female polar bears sampled between 1999 and 2002 from sub-populations in Arctic Canada, eastern Greenland, and Svalbard, and in males and females collected from 1994 to 2002 in northwestern Alaska. Only 4 congeners (BDE47, 99, 100, and 153) were consistently identified in all samples. BDE47 was the major PBDE congener representing from 65% to 82% of the sum (sigma) PBDEs. Age was not a significant covariate for individual PBDEs or sigmaPBDE. Higher proportions of BDE 99, 100, and 153 were generally found in samples from the Canadian Arctic than from Svalbard or the Bering-Chukchi Sea area of Alaska. Geometric mean sigmaPBDE concentrations were highest for female polar bear fat samples collected from Svalbard (50 ng/g lipid weight (lw)) and East Greenland (70 ng/g lw). Significantly lower sigmaPBDE concentrations were found in fat of bears from Canada and Alaska (means ranging from 7.6 to 22 ng/g lw).

A suite of chlorinated hydrocarbon contaminants (CHCs) including organochlorine pesticides (OCPs) and by-products, polychlorinated biphenyls (PCBs), and methyl sulfone (MeSO2) PCB and p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE) metabolites were determined in adipose tissue of 107 adult and sub-adult polar bears, almost exclusively females, sampled between 1996 and 2002 from populations spanning Arctic and Subarctic regions of Alaska, Canada, East Greenland, and Svalbard. The East Greenland and Svalbard populations of polar bears were distinguished by higher proportions of dichlorodiphenyldichloroethane (DDT)-related compounds, nonachlors, oxychlordane, and higher-chlorinated and persistent PCB congeners (hepta- to nona-chlorinated). Conversely, Alaska, the westernmost population of the North American Arctic, was characterized by higher proportions of relatively volatile compounds such as hexachlorocyclohexanes (HCHs) and pentachlorobenzene (PnCBz), lower-chlorinated PCB congeners (tri- to penta-chlorinated), and lower proportions of oxychlordane. Geometric mean (GM) with 95% confidence limits (CL) SigmaHCH concentrations were highest in Alaska male polar bear fat samples (GM 593; CL 363-909 ng g-1 lipid weight), SigmaDDT concentration were highest in East Greenland female samples (GM 309; CL 249-490 ng g-1 l.w.), and Sigma42PCB (GM 5972; CL 4637-9129 ng g-1 l.w.) and SigmaMeSO2-PCB (GM 198; CL 162-279 ng g-1 l.w.) concentrations were highest in female samples collected from Svalbard. The distribution of Sigma-chlordane-related compounds (SigmaCHL), SigmaCBz, mirex, and dieldrin was relatively uniform among the populations of polar bears investigated. The present 1996-2002 data of female polar bear fat samples was compared to spatial assessments of female polar bear fat samples collected between 1989 and 1993 from comparable populations. The two-point temporal comparisons showed a general decrease for age-adjusted mean concentrations of SigmaCHL, p,p'-DDE, Sigma42PCB, SigmaMeSO2-PCB and 3-MeSO2-p,p'-DDE over a period of approximately 10 years. However, concentrations of dieldrin were comparatively unchanged. Comparisons of present 2001-2002 concentrations in fat of female polar bears from Western Hudson Bay showed great consistency with temporal trends (1991-1999) previously reported for the same region, i.e. the apparent non-decreasing trend of SigmaCHL, beta-HCH, SigmaHCH and dieldrin, and the apparent declining trend for SigmaPCB. However, present concentrations of alpha-HCH and SigmaCBz were elevated, and SigmaDDT was notably lower in Western Hudson Bay samples compared to the last measurements in fat samples collected in 1999, which was not in accord with reported temporal trends for this region. As a result of their relatively high degree of contamination, East Greenland and Svalbard polar bears are at higher health risk of contaminant exposure among Arctic and Subarctic populations. In addition to continued biomonitoring, further research on health and population status is needed to evaluate the impact from chronic exposure of polar bear populations to CHCs and their metabolites.

This review summarizes and synthesizes the significant amount of data which was generated on mercury (Hg) and persistent organic pollutants (POPs) in Canadian Arctic marine biota since the first Canadian Arctic Contaminants Assessment Report (CACAR) was published in 1997. This recent body of work has led to a better understanding of the current levels and spatial and temporal trends of contaminants in biota, including the marine food species that northern peoples traditionally consume. Compared to other circumpolar countries, concentrations of many organochlorines (OCs) in Canadian Arctic marine biota are generally lower than in the European Arctic and eastern Greenland but are higher than in Alaska, whereas Hg concentrations are substantially higher in Canada than elsewhere. Spatial coverage of OCs in ringed seals, beluga and seabirds remains a strength of the Arctic contaminant data set for Canada. Concentrations of OCs in marine mammals and seabirds remain fairly consistent across the Canadian Arctic although subtle differences from west to east and south to north are found in the proportions of various chemicals. The most significant development since 1997 is improvement in the temporal trend data sets, thanks to the use of archived tissue samples from the 1970s and 1980s, long-term studies using archeological material, as well as the continuation of sampling. These data cover a range of species and chemicals and also include retrospective studies on new chemicals such as polybrominated diphenyl ethers. There is solid evidence in a few species (beluga, polar bear, blue mussels) that Hg at some locations has significantly increased from pre-industrial times to the present; however, the temporal trends of Hg over the past 20-30 years are inconsistent. Some animal populations exhibited significant increases in Hg whereas others did not. Therefore, it is currently not possible to determine if anthropogenic Hg is generally increasing in Canadian Arctic biota. It is also not yet possible to evaluate whether the recent Hg increases observed in some biota may be due solely to increased anthropogenic inputs or are in part the product of environmental change, e.g., climate warming. Concentrations of most "legacy" OCs (PCBs, DDT, etc.) significantly declined in Canadian Arctic biota from the 1970s to the late 1990s, and today are generally less than half the levels of the 1970s, particularly in seabirds and ringed seals. Chlorobenzenes and endosulfan were among the few OCs to show increases during this period while summation operatorHCH remained relatively constant in most species. A suite of new-use chemicals previously unreported in Arctic biota (e.g., polybrominated diphenyl ethers (PBDEs), short chain chlorinated paraffins (SCCPs), polychlorinated naphthalenes (PCNs), perfluoro-octane sulfonic acid (PFOS) and perfluorocarboxylic acids (PFCAs)) has recently been found, but there is insufficient information to assess species differences, spatial patterns or food web dynamics for these compounds. Concentrations of these new chemicals are generally lower than legacy OCs, but there is concern because some are rapidly increasing in concentration (e.g., PBDEs), while others such as PFOS have unique toxicological properties, and some were not expected to be found in the Arctic because of their supposedly low potential for long-range transport. Continuing temporal monitoring of POPs and Hg in a variety of marine biota must be a priority.

Total mercury (THg), methylmercury (MeHg) and 22 other trace elements were measured in ice algae, three species of zooplankton, mixed zooplankton samples, Arctic cod (Boreogadus saida), ringed seals (Phoca hispida) and eight species of seabirds to examine the trophodynamics of these metals in an Arctic marine food web. All samples were collected in 1998 in the Northwater Polynya (NOW) located between Ellesmere Island and Greenland in Baffin Bay. THg and MeHg were found to biomagnify through the NOW food web, based on significant positive relationships between log THg and log MeHg concentrations vs. delta15N muscle and liver . The slope of these relationships for muscle THg and MeHg concentrations (slope=0.197 and 0.223, respectively) were similar to those reported for other aquatic food webs. The food web behavior of THg and delta15N appears constant, regardless of trophic state (eutrophic vs. oligotrophic), latitude (Arctic vs. tropical) or salinity (marine vs. freshwater) of the ecosystem. Rb in both liver and muscle tissue and Zn in muscle tissue were also found to biomagnify through this food web, although at a rate that is approximately 25% of that of THg. A number of elements (Cd, Pb and Ni in muscle tissue and Cd and Li in seabird liver tissue) were found to decrease trophically through the food web, as indicated by significantly negative relationships with tissue-specific delta15N. A diverse group of metals (Ag, Ba, La, Li, Sb, Sr, U and V) were found to have higher concentrations in zooplankton than seabirds or marine mammals due to bioconcentration from seawater. The remaining metals (As, Co, Cu, Ga, Mn, Mo and Se in muscle tissue) showed no relationship with trophic position, as indicated by delta15N values, although As in liver tissue showed significant biomagnification in the seabird portion of the food web.

Chiral polychlorinated biphenyls (PCBs) were measured in an arctic marine food web from the Northwater Polynya (NOW) in the Canadian Arctic to examine potential biotransformation of chiral PCB atropisomers. Organisms under investigation included pelagic zooplankton, Arctic cod (Boreogadus saida), seabirds, and ringed seals (Phoca hispida). Previous studies using achiral methods (e.g., biomagnification factors) have shown that chiral PCB congeners biomagnified in the NOW food web, but provided little information about biotransformation of PCBs except in extreme cases (i.e., high biotransformation). In this study, highly nonracemic enantiomeric fractions (EFs) were observed in several seabird species and ringed seals, but racemic EFs were found in prey (zooplankton and fish). This suggests stereoselective and species-specific biotransformation of individual PCB stereoisomers by birds and mammals. These results are consistent with previously reported biotransformation activity of chiral organochlorine pesticides, alpha-hexachlorocyclohexane, and chlordane within these organisms. This study demonstrates the utility of using chiral analysis of PCBs to investigate biotransformation within biota of arctic food webs.

Statistical analysis of organochlorine contaminants (OCs) in marine mammals has shown that, for most OCs, the European Arctic is more contaminated than the Canadian and U.S. Arctic. Recently, comparison of OC concentration ranges in seabirds, arctic cod (Boregadus saida), and zooplankton, found no difference between these regions. To address these inconsistencies, marine food web OC data from the European (central Barents Sea (CBS)) and Canadian Arctic (Northwater Polynya (NOW)) were simultaneously statistically analyzed. In general, concentrations of OCs were greater in seabirds and ringed seals (Phoca hispida) from the CBS as compared to the NOW; consistent with circumpolar trends observed in marine mammals. In contrast, levels of OCs were generally similar in zooplankton and arctic cod between the CBS and NOW. The main exception is HCH which had greater levels in the NOW across all trophic levels because of the greater proximity to sources in eastern Asia. The lack of differences in OC concentrations in zooplankton and Arctic cod from the European and Canadian Arctic suggest that regional differences in OC contamination in the Arctic have evened out. Reduced regional differences were not observed in marine mammals or seabirds because they are long-lived and also acquire contaminants from maternal transfer and hence reflect levels from the past when the European Arctic was more contaminated than the Canadian Arctic. In addition, seabirds may reflect exposure from other areas. This study highlights the potential problem of comparing spatial trends by using means and confidence intervals as compared to simultaneous statistical analysis of raw data. Differences in the spatial trends of OCs between trophic levels in the Arctic are important for consideration when assessing regional differences in spatial and temporal trends of discontinued and current-use contaminants.

Previous studies have reported alarmingly high levels of organochlorines (OCs), particularly polychlorinated biphenyls (PCBs), in free-ranging polar bears (Ursus maritimus). In this study plasma concentration of PCBs ranged from 14.8 to 200 ng/g wet weight. The aim of the study was to investigate associations between OCs and lymphocyte proliferation after in vitro stimulation with different mitogens and antigens. In 1998 and 1999, 26 and 30 free-ranging polar bears from Svalbard and Churchill, Canada, respectively, were recaptured 32-40 d following immunization with inactivated tetanus toxoid and hemocyanin from keyhole limpets (KLH) to sensitize lymphocytes. At recapture, blood was sampled for determination of plasma levels of PCBs and organochlorine pesticides (OCPs) and lymphocyte proliferation after in vitro stimulation with specific mitogens--phytohemagglutinin (PHA), pokeweed mitogen (PWM), concanavalin A (Con A), lipopolysaccharide (LPS), and purified protein derivative of Mycobacterium avium subsp. paratuberculosis (PPD)--and antigens: tetanus toxoid and KLH. The combinations of sum(PCBs) (sum of 12 individual PCB congeners), sum(OCPs) (sum of 6 OCPs), and their interactions contributed up to 15% of the variations in the lymphocyte responses. By using multiple regression analyses, followed by classical mathematic function analyses, thresholds for immunomodulation were estimated. Depending on the lymphocyte proliferation response studied, the estimated thresholds for significant immunomodulation were within the concentration ranges 32-89 ng/g wet weight (ww) and 7.8-14 ng/g ww for sum(PCBs) and sum(OCPs), respectively. Thus, this study demonstrated that OC exposure significantly influences specific lymphocyte proliferation responses and part of the cell-mediated immunity, which also is associated with impaired ability to produce antibodies (Lie et al., 2004).

Basic physical-chemical properties of five bromine and chlorine containing mixed halogenated dimethyl bipyrroles (HDBPs) were determined using established methods. Subcooled liquid vapour pressures (P(o)(L,25)), aqueous solubilities (S(w,25)), and octanol/water partition coefficients (K(ow)) were determined using the gas chromatography-retention time, generator column, and slow-stirring methods, respectively. Henry's Law constants (H25) were estimated using experimentally-derived P(o)(L) and S(w,25) data. Values of all four properties were generally similar to those reported for other polyhalogenated aromatic compounds [P(o)(L,25) = (7.55-191) x 10(-6) Pa; S(w,25) = (1.0-1.9) x 10(-5) g/l; log K(ow) = 6.4-6.7; H25 = 0.0020-0.14 Pa m3/mol]. The effect of replacing a chlorine with a bromine atom significantly decreased P(o)(L,25) (log P(o)(L,25) = -0.4197 (# bromine atoms) - 2.643, p<0.01) and H25 (log H25 = -0.508 (# bromine atoms) + 0.394, p<0.02). There were no significant effects of bromine/chlorine substitution on S(w,25) or K(ow). A simple Level I equilibrium partitioning model predicted the environmental behaviour of HDBPs to be similar to a tetrabrominated diphenyl ether. Only slight differences in behaviour amongst HDBP congeners were predicted since substitution of a bromine for a chlorine (Cl/Br substitution) atom had less effect than H/Cl or H/Br substitution on P(o)(L,25), S(w,25), H25, and K(ow).

This study was undertaken to assess if high levels of organochlorines (OCs) are associated with decreased ability to produce antibodies in free-ranging polar bears (Ursus maritimus) and thus affect the humoral immunity. In 1998 and 1999, 26 and 30 polar bears from Svalbard, Norway, and Churchill, Canada, respectively, were recaptured 32-40 d following immunization with inactivated influenza virus, reovirus, and herpes virus and tetanus toxoid. Blood was sampled at immunization and at recapture for determination of plasma levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), serum immunoglobulin G (IgG) concentrations, and specific antibodies against influenza virus, reovirus, and herpes virus, tetanus toxoid, and Mannheimia haemolytica. The OCs alone contributed with up to 7% to the variations in the immunological parameters. The combination of sigma PCBs (sum of 12 individual PCB congeners), sigma OCPs (sum of 6 OCPs), and biological factors accounted for 40-60% of the variation in the immunological parameters. Negative associations were found between sigma PCBs and serum immunoglobulin G (IgG) levels and between sigma PCBs and increased antibody titers against influenza virus and reovirus following immunization. In contrast, a positive association was registered between sigma PCBs and increased antibodies against tetanus toxoid. sigma OCPs also contributed significantly to the variations in the immunological responses. OCs did not have the same impact on the antibody production against M. haemolytica. The present study demonstrated that high OC levels may impair the polar bears ability to produce antibodies and thus may produce impaired resistance to infections.

Organochlorine contaminants (OCs) were determined in liver and fat of seven species of seabirds (Alle alle, Uria lomvia, Cepphus grylle, Rissa tridactyla, Pagophila eburnea, Larus hyperboreus, and Fulmaris glacialis) collected in May/June 1998 from the Northwater Polynya in northern Baffin Bay. OC concentrations ranged over an order of magnitude between seabird species and OC groups, with PCBs having the highest concentrations followed by DDT, chlordane, HCH and ClBz. Positive relationships between delta15N (estimator of trophic level) and OC concentrations (lipid basis) were found for all OC groups, showing that trophic position and biomagnification significantly influence OC concentrations in Arctic seabirds. Concentrations of a number of OCs in particular species (e.g., HCH in P. eburnean) were lower than expected based on delta15N and was attributed to biotransformation. P. eburnea and F. glacialis, which scavenge, and R. tridactyla, which migrate from the south, were consistently above the delta15N-OC regression providing evidence that these variables can elevate OC concentrations. Stable isotope measurements in muscle may not be suitable for identifying past scavenging events by seabirds. OC relative proportions were related to trophic position and phylogeny, showing that OC biotransformation varies between seabird groups. Trophic level, migration, scavenging and biotransformation all play important roles in the OCs found in Arctic seabirds.

Halogenated dimethyl bipyrroles (HDBPs) recently have been identified as a group of environmentally persistent naturally produced bioaccumulative organohalogens. The ability of these compounds to activate the aryl hydrocarbon receptor (AhR) signaling pathway in vitro was examined. Induction of cytochrome P4501A (CYP1A), measured as ethoxyresorufin-O-deethylase (EROD) activity, and porphyrin accumulation were monitored after exposure of chick embryo hepatocytes to three individual HDBP congeners and two HDBP mixtures. All HDBP congeners and mixtures tested caused induction of EROD activity. Induction equivalency factors, calculated as the ratio of the effective concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to induce 10 and 50% of the maximal EROD induction to that of the HDBP congener or mixture ranged from 0.0004 to 0.05. Halogenated dimethyl bipyrroles also caused porphyrin accumulation, which increased with exposure time of the hepatocytes and molar bromine content of the HDBP congener or mixture. Heptacarboxylporphyrin III and corproporphyrinogen III were the most abundant porphyrins observed after an exposure period of 48 h. The individual HDBP congeners and mixtures also inhibited binding of [3H]TCDD to chicken and mouse AhR. Binding of [3H]TCDD to chicken AhR was inhibited approximately 20% by tetra- to hexabrominated congeners at concentrations of 20 to 40 microM; binding to mouse AhR was inhibited 40 to 50% by tri- and tetrabrominated dimethyl bipyrroles (DBPs) at 10 microM. The relative affinity of the hexabrominated DBP congener (vs TCDD) for binding to chicken AhR was estimated to be 0.000017. The results of this work illustrate that HDBPs act as agonist ligands for the AhR in the same manner as many anthropogenic organohalogens.

Sixty-four adult captive American kestrels (Falco sparverius) were exposed to a dietary source of halogenated dimethyl bipyrroles (HDBPs), a group of organohalogens proposed to have a natural origin. Adult kestrels were assigned to four treatment groups that were administered a different dose of HDBPs [high, 140 microg/(bird x d); medium, 4.3 microg/(bird x d); low, 0.13 microg/(bird x d); control, 0 microg/(bird x d)]. Exposure began prior to pairing and continued during breeding until approximately 28 d after hatching of the final eggs. Juvenile and adult kestrels accumulated HDBPs in carcass tissue, plasma, and liver. In addition, HDBPs were transferred to yolks during egg development. Low dietary absorption efficiencies (0.011-0.029) indicated that HDBPs were effectively cleared from kestrels either from increased elimination, metabolism, or a combination of the two processes. Reproductive and morphological endpoints examined for HDBP-induced changes included egg volume, egg mass, eggshell thickness, egg fertility, clutch size, liver and whole body mass, antebrachium, central retrice, tarsus, ninth primary, and wing cord lengths. Few statistically significant dose-dependent effects were observed. Hepatic tissue samples from selected individuals underwent histomorphological evaluation. Although the hepatic function was not evaluated specifically in these birds, no clinical signs suggestive of liver disease or gross hepatic anomalies were observed. Only minor histomorphological changes were detected in the hepatic tissue. The lack of serious effects suggests that HDBPs are not an acute reproductive threat to avian populations.

Recently, there has been an increase in studies focusing on an emerging class of organic contaminants, hydroxylated PCBs (OH-PCBs) and chlorinated phenolic compounds (CPCs) in the environment, particularly in northern regions of Europe and Canada. Since information for fish from the Great Lakes are scarce, we determined the blood plasma concentrations of OH-PCB congeners, pentachlorophenol (PCP), 2,3,4,5-tetrachlorophenol (TCP), and 4-hydroxyheptachlorostyrene (4-OH-HpCS) for lake trout (Savelinus namaycush) collected from two of the Great Lakes, Lake Ontario and Lake Superior, and two regional lakes, Lake Champlain and Lake Opeongo. PCP was the dominant CPC in lake trout (105-658 pg/g of plasma). Detectable concentrations of 2,3,4,5-TCP and 4-OH-HpCS were found in all lake trout (2.6-101 and 0.4-27 pg/g, respectively). Highest concentrations were found in trout from Lake Ontario and Lake Superior. Sixteen OH-PCBs were quantified, with 4-OH-CB187 having the highest concentration in all samples (10-173 pg/g of plasma). Unexpectedly, highly chlorinated OH-PCBs such as 4'-OH-CB199 (mean 21.4 and 74.4 pg/g), 4,4'-diOH-CB202 (18.3 and 27.7 pg/g), and 4'-OH-CB208 (24.5 and 34.7 pg/g) were found in lake trout from Lake Ontario and Lake Superior, respectively. Future studies to delineate the sources and impacts of CPCs in the Great Lakes catchment are needed.

A toxicokinetic model was developed to describe polychlorinated biphenyl (PCB) accumulation by herring gull (Larus argentatus) embryos during development. The model consists of two components, a bioenergetics model that predicts the lipid mass balance of embryo and yolk compartments with time and an empirical toxicokinetic model that describes PCB partitioning between lipid compartments in the egg. The model was calibrated using data on PCB and lipid partitioning between embryo and yolk + albumen at four time points during incubation in herring gull eggs injected with a PCB mixture, combined with data sets on herring gull embryo growth rates and bioenergetic demands with time. The model was validated using independent data consisting of maternally exposed, field-incubated Lake Superior herring gull eggs that varied in incubation ages over the range of 8.5 d to pipping age (26-28 days). PCB concentrations in 6-9 d embryos were nearly an order of magnitude less than predicted by equilibrium lipid partitioning between the embryo and yolk + albumen compartments of the eggs. PCB concentrations in embryos were adequately predicted by equilibrium partitioning, however, for eggs incubated for 23-28 d. An empirical relationship was developed to account for the apparent nonequilibrium behaviour of PCBs during early development. The model was sensitive to the mass of yolk lipids and the mass of PCBs deposited to fresh eggs and much of the variability in embryo PCB concentrations could by explained by accounting for variability in these input parameters. Consistent with experimental data for other avian species, the model predicts that the highest PCB concentrations in the embryo/chick occur during pipping or soon after when yolk lipids have been completely resorbed by the embryo.

For the first time, organochlorine (OC) contaminants were measured in blubber biopsies from free-ranging St. Lawrence River Estuary beluga whales (Delphinapterus leucas), to compare contaminant levels to those previously measured in dead stranded belugas. PCBs, DDTs, toxaphene and chlordane-related compounds were the major OC contaminants detected in 44 belugas biopsied in 1994-1998. SigmaPCB (the sum of 104 congeners) ranged from 2080 to 128,000 ng/g lipid in males (n=34; minimum estimated ages 8-22 years), and from 148 to 44,100 ng/g lipid in females (n=10; minimum estimated ages 7-22 years). The concentrations of PCBs and OC pesticides in the blubber of these whales overlapped those observed in stranded belugas from an earlier study, and demonstrated comparable age and sex-related trends. However, lower proportions of mirex, HCB, DDTs, and many of the highly chlorinated PCBs occurred in the biopsy samples compared to results for blubber from stranded carcasses. Most major OC compounds were present at lower concentrations in the biopsies, but this does not appear to be solely related to age differences between the two groups, or to emaciation in the stranded whales. Nor does it appear to be associated with the use of superficial biopsies, and the possible stratification of lipids and OCs in the blubber layer. Nevertheless, given these possible confounding factors, and the uncertainty in age estimates for the biopsied whales, the results point to the need for careful interpretation of biopsy results when comparing with data taken from the full depth of the blubber mantle in stranded whales. Taken together, results from both biopsied whales and previously studied stranded belugas indicate that PCB and OC pesticide contamination of St. Lawrence beluga whales may occur across a broader range of levels than previously thought, at least for males which formed the largest group in this study, possibly due to different degrees of dietary exposure. It also appears that measuring contaminant concentrations only in stranded whales, may overestimate OC levels in the population as a whole, especially for highly chlorinated OCs.

The influence of diet properties and feeding rate on the uptake and elimination of polychlorinated biphenyls (PCBs) was investigated in ring doves (Streptopelia rissoria). Elimination rates of PCBs were determined in birds dosed with an Aroclor mixture (1242:1248:1260, 1:1:1) and allowed to depurate on uncontaminated high-lipid or low-lipid/high-fiber diets for 105 days. Uptake rates for seven additional PCBs not found within the above Aroclor mixtures were studied in the same birds by feeding high- or low-lipid PCB-spiked diets for 15 days. The two diet treatments contributed to differences in feeding rates, fecal egestion rates, and total fat volume of the birds. Uptake rate constants of PCBs were higher for the low-lipid diet group, whereas PCB assimilation efficiencies were similar between the two groups. Whole-body elimination rates of Aroclor PCBs were most strongly influenced by the chlorine substitution pattern of the congeners, such that PCBs containing an open meta-para site on one of the phenyl rings were rapidly cleared from the animal. Whole-body elimination rates for persistent PCBs could only be determined for PCB 28; other congeners exhibited negligible elimination over the depuration period. For the latter compounds, fecal elimination rates were estimated using the excreta/carcass distribution coefficient and excreta production rates. For PCB 28, the fecal elimination rate was similar to the whole-body elimination rate, suggesting that fecal elimination of persistent PCBs dominates whole body elimination of these compounds. Diet treatment effects were less evident for PCB elimination rates compared to uptake rates. Steady-state biomagnification factors were estimated to range from 1.0 to 5.1 for rapidly cleared PCBs and from 27 to 97 for persistent congeners.

Geographical distribution of brominated diphenyl ether (BDE) flame retardants in the North American Great Lakes ecosystem in 2000 was determined by analysis of herring gull eggs (13 egg pools) from a network of 15 monitoring colonies scattered throughout the lakes and connecting channels. sigmaBDEs were found at concentrations ranging from 192 to 1,400 microg/kg, mean of 662 +/- 368 microg/kg (wet weight of egg contents). Highest concentrations were found in northern Lake Michigan and Toronto harbor (1,000-1,400 microg/kg) and lowest in Lake Huron and Lake Erie (192-340 microg/kg). The distribution suggested that input from large urban/ industrial areas through air or water emissions contributes local contamination to the herring gull food web in addition to background levels from regional/global transport. The congener composition was similar among sampling sites. Major congeners were BDE-47 (43%), BDE-99 (26%), BDE-100 (13%) BDE-153 (11%), BDE-154 (4%), BDE-183 (2%) and BDE-28 (1%). Temporal trends of BDE contamination, 1981-2000, were established by analysis of archived herring gull eggs (10 egg pools) from colonies in northern Lake Michigan, Saginaw Bay, Lake Huron and eastern Lake Ontario. BDE-47, -99 and -100, and BDE-153, -154 and -183 concentrations were grouped separately for analysis because these two groups had different trends and are primarily associated with the Penta BDE and Octa BDE flame retardant formulations, respectively. SigmaBDE47,99,100 concentrations were 5-12 microg/kg (wet weight) in 1981-1983 and then increased exponentially (p < 0.00001) at all three sites to 400-1,100 microg/kg over the next 17 years. Doubling times were 2.6 years in Lake Michigan, 3.1 years in Lake Huron and 2.8 years in Lake Ontario. SigmaBDE154,153,183 concentrations generally increased but varied in an erratic fashion among sites and decreased as a fraction of sigmaBDE over time. Concentrations of sigmaBDE154,153,183 were 100-200 microg/kg in eggs from all three colonies in 2000. Therefore, most of the dramatic increases in sigmaBDE concentrations observed over the past 20 years in the Great Lakes aquatic ecosystem seem to be connected with the Penta BDE formulation, which is mainly used as a flame retardant in polyurethane foam in North America. If present rates of change continue, concentrations of sigmaBDEs will equal or surpass those of sigmaPCBs in Great Lakes herring gull eggs in 10-15 years.

Concentrations of polychlorinated biphenyls (PCBs), hydroxylated metabolites of PCBs (HO-PCBs) and octachlorostyrene (4-HO-HpCS), and pentachlorophenol (PCP) were determined in umbilical cord plasma samples from three different regions of Québec. The regions studied included two coastal areas where exposure to PCBs is high because of marine-food-based diets--Nunavik (Inuit people) and the Lower North Shore of the Gulf of St. Lawrence (subsistence fishermen)--and a southern Québec urban center where PCB exposure is at background levels (Québec City). The main chlorinated phenolic compound in all regions was PCP. Concentrations of PCP were not significantly different among regions (geometric mean concentration 1,670 pg/g, range 628-7,680 pg/g wet weight in plasma). The ratio of PCP to polychlorinated biphenyl congener number 153 (CB153) concentration ranged from 0.72 to 42.3. Sum HO-PCB (sigma HO-PCBs) concentrations were different among regions, with geometric mean concentrations of 553 (range 238-1,750), 286 (103-788), and 234 (147-464) pg/g wet weight plasma for the Lower North Shore, Nunavik, and the southern Québec groups, respectively. Lower North Shore samples also had the highest geometric mean concentration of sum PCBs (sum of 49 congeners; sigma PCBs), 2,710 (525-7,720) pg/g wet weight plasma. sigma PCB concentrations for Nunavik samples and southern samples were 1,510 (309-6,230) and 843 (290-1,650) pg/g wet weight plasma. Concentrations (log transformed) of sigma HO-PCBs and sigma PCBs were significantly correlated (r = 0.62, p < 0.001), as were concentrations of all major individual HO-PCB congeners and individual PCB congeners. In Nunavik and Lower North Shore samples, free thyroxine (T4) concentrations (log transformed) were negatively correlated with the sum of quantitated chlorinated phenolic compounds (sum PCP and sigma HO-PCBs; r = -0.47, p = 0.01, n = 20) and were not correlated with any PCB congeners or sigma PCBs. This suggests that PCP and HO-PCBs are possibly altering thyroid hormone status in newborns, which could lead to neurodevelopmental effects in infants. Further studies are needed to examine the effects of chlorinated phenolic compounds on thyroid hormone status in newborns.

Lipophilic organochlorines (OCs) are ingested by mammals through their foods and are generally stored in adipose tissue depots. For some species, such as polar bears, the size of these depots can fluctuate seasonally by several-fold. However, the effect of these fluctuations on the fate of stored OCs in an animal with such labile lipid depots is unknown. We determined the whole body burden and tissue concentrations of OCs in free-ranging polar bears categorized by age (cubs-of-the-year, yearlings and adults) and sex before and after a fast averaging 56 days. Adipose tissue, plasma, and milk samples were analysed for sum of chlorobenzenes (sigma-ClBzs), hexachlorocyclohexanes (sigma-HCHs), chlordanes (sigma-CHLORs), dichlorodiphenyltrichloroethane compounds (sigma-DDTs) and polychlorinated biphenyls (sigma-PCBs). Decline in body mass during fasting ranged from 0.2 kg/day for cubs-of-the-year to 0.9 kg/day for sub-adult and adult males. Although all bears showed a decline in both lipid and lean mass during fasting, patterns of OC whole body burden changes were not consistent among compounds and bear classes. The burdens of sigma-DDTs declined by 11-50% for most bears during fasting, those of sigma-CHLORs declined by 67% during fasting in sub-adult and adult males but remained constant for all females, indicating male-specific metabolism of sigma-CHLORs. As fat depots became depleted, OC concentrations in the remaining adipose tissue varied; sigma-DDTs and sigma-HCHs declined while those of sigma-CHLORs and sigma-PCBs generally increased. Thus. within a 3-4 month fast, most polar bears were able to significantly rid their adipose tissue of sigma-DDTs and sigma-HCHs. Burdens of sigma-CHLORs (except males), sigma-ClBzs and sigma-PCBs remained constant for all classes of bears, therefore there was no significant excretion or metabolism during the fast of the specific congeners in these compound classes typically found in polar bears. The ratio of plasma/adipose tissue and milk/adipose tissue OC concentrations was the same for before and after the fast indicating that OC concentrations in polar bears are probably at a steady state among various body compartments. Concentrations of sigma-CHLORs and sigma-PCBs in milk almost doubled during the fast. As a consequence of this rise in milk OC concentrations, the whole body concentrations of these compounds increased in nursing cubs. Since developing young may be susceptible to the effects of environmental contaminants, the increased exposure of nursing cubs to OCs during a fast by their mothers is noteworthy.

To examine the influence of diet and age on organochlorine contaminant (OC) concentrations in two closely related ringed seal (Phoca hispida) populations enantiomeric fractions (EFs) of chiral contaminants and stable isotopes of nitrogen (delta15N) and carbon (delta13C) were measured along with OCs in ringed seals collected from the east and west side of the Northwater Polynya. Seals from these two locations were feeding at the same trophic level based on delta15N values in muscle but had slightly different sources of carbon based on delta13C measurements in muscle. After removing the influence of age, sex, and blubber thickness, OC concentrations did not vary between ringed seals from the east and west side of the polynya. SigmaPCB, SigmaDDT, and Sigmachlordane were found to increase with age for both male and female seals. The inclusion of older (>20 years) female seals, which may have a reduced reproductive effort, may influence the relationships in females. Stable isotopes failed to describe OC concentrations in ringed seals suggesting that diet was not a major factor in variation of OC concentrations within this ringed seal population. Cis- and trans-chlordane, oxychlordane, and heptachlor epoxide were all nonracemic in the ringed seal blubber but did not vary with age, sex, or collection site. Alpha-HCH appeared racemic (enantiomeric fraction = 0.50 +/- 0.01) in the seals, although this EF is different than those previously observed in their prey species, and was found to vary significantly with age. EF values in the ringed seals varied considerably from other Arctic marine mammals and seabirds, providing addition evidence that the type(s) and characteristic(s) of the enzymes involved in biotransformation of chiral OCs vary between these organisms.

The molecular structures of four unknown bioaccumulating halogenated compounds, C10H6N2Br3Cl3, C10H6N2Br4Cl2, C10H6N2Br5Cl, and C10H6N2Br6 were characterized using isotope exchange positive chemical ionization (IE-PCI) mass spectrometry (MS) and identified by comparison to synthesized standards. NH3 and ND3 were used as reagent gases for the IE-PCI-MS experiment. The shift in mass of the quasimolecular ion between the NH3 and ND3 PCI obtained spectra indicated the number of exchangeable hydrogens attached to the two nitrogen atoms in C10H6N2Br4Cl2, and thus the type of amines present (primary, secondary, or tertiary). 19 compounds (13 amines of varying degree of substitution; six containing no nitrogen) were used as reference compounds and controls in the experiment to validate the IE-PCI technique. The results of the IE-PCI-MS indicated the presence of two tertiary amine functional groups. The molecular structures of the four hexahalogenated compounds were then proposed to be 1,1'-dimethyl-3,3',4,-tribromo-4',5,5'-trichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole, 1,1'-dimethyl-3,3',4,4',5-pentabromo-5'-chloro-2,2'-bipyrrole, and 1,1'-dimethyl-3,3',4,4',5,5'-hexabromo-2,2'-bipyrrole and subsequently synthesized. Comparison of retention times and electron capture negative ionization (ECNI) full scans on various gas chromatography (GC) columns between the synthesized bipyrroles and the corresponding unknown compounds in biota indicated that three of the unknown compounds--possible marine natural products--were the proposed halogenated dimethyl bipyrroles. The placement of the halogen atoms on the fourth compound, C10H6N2Br3Cl3 could not be unequivocally determined since the synthesized standard could not be fully characterized.

Concentrations of four possibly naturally produced organohalogens--1,1'-dimethyl-3,3',4-tribromo-4,5,5'-trichloro-2,2'-bipyrrole (DBP-Br3Cl3), 1,1'-dimethyl-3,3',4,4'-tetrabromo-5,5'-dichloro-2,2'-bipyrrole (DBP-Br4Cl2), 1,1'-dimethyl-3,3',4,4',5-pentabromo-5'-chloro-2,2'-bipyrrole (DBP-Br5Cl) and 1,1'-dimethyl-3,3',4,4',5,5'-hexabromo-2,2'-bipyrrole (DBP-Br6)--were quantitated and the extent of their magnification through an entire Arctic marine food web [measured as integrated trophic magnification factors (TMFs)] were calculated. The food web consisted of three zooplankton species (Calanus hyperboreus, Mysis oculata, and Sagitta sp.), one fish species [Arctic cod (Boreogadus saida)], four seabird species [dovekie (Alle alle), black guillemot (Cepphus grylle), black-legged kittiwake (Rissa tridactyla), and glaucous gull (Larus hyperboreus)], and one marine mammal species [ringed seal (Phoca hispida)]. Trophic levels in the food web were calculated from ratios of stable isotopes of nitrogen (15N/14N). All halogenated dimethyl bipyrrole (HDBP) congeners were found to significantly (P<0.02) biomagnify, or increase in concentration with trophic level in the invertebrate--fish--seabird food web. DBP-Br4Cl2 (TMF= 14.6) was found to biomagnify to a greater extent than DBP-Br3Cl3 (TMF = 5.2), DBP-Br5Cl (TMF = 6.9), or DBP-Br6 (TMF = 7.0), even though the Kow of DBP-Br4CI2 was predicted to be lower than those of DBP-Br5Cl and DBP-Br6. None of the four HDBP congeners in ringed seals followed the general trend of increasing concentration with trophic level, which was possibly due to an ability of the seals to metabolize HDBPs.

The bioaccumulation and toxicokinetics of 42 polychlorinated biphenyls (PCBs) was determined in male American kestrels exposed to an Aroclor-contaminated diet for 120 d followed by a 348-d depuration period. The birds were housed under ambient outdoor temperatures to permit normal fluctuations in body weight during the study. Whole body PCB clearance, plasma/fat distribution coefficients, and plasma PCB clearance constants were determined for individual PCBs to calibrate a two-compartment rate constant model in order to describe PCB elimination in the birds. Plasma/fat partition coefficients (K(PF)) averaged 0.0060 +/- 0.0001 for all congeners of study, were not dependent on chemical hydrophobicity, and did not change in summer versus winter sacrificed animals. Plasma clearance constants (k'pc) for PCBs were observed to be dependent on both chlorine substitution patterns and congener hydrophobicity. Polychlorinated biphenyl congeners categorized as readily cleared congeners contained vicinal meta-para hydrogen substituents on at least one phenyl ring, while slowly cleared congeners were chlorine hindered at these positions. A general equation was derived to predict plasma clearance constants for all tri- to octachlorobiphenyls based on the presence of an open meta-para site on one of the phenyl rings and from the n-octanol-water partition coefficient of the chemical. The equation was validated by comparing predicted versus measured relative biomagnification factors of PCBs determined in birds at the end of the dosing period. The two-compartment model calibrated for PCB elimination in American kestrels may be used to describe PCB toxicokinetics in wild birds provided that seasonal fluctuations in the fat content of the modeled population is known.

Eggs from 21 resident great blue heron (Ardea herodias) rookeries were monitored from 1983 to 1998 along the coast of British Columbia, Canada, for contamination with polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs). Dominant congeners (1,2,3,7,8-PnCDD, 1,2,3,6,7,8-HxCDD, 2,3,7,8-TCDD, 2,3,7,8-TCDF, 1,2,3,7,8,9-HxCDD and 2,3,4,7,8-PnCDF) fell markedly in the early 1990s after pulp mills changed from molecular chlorine bleaching to alternative bleaching technologies, and the use of chlorophenolic wood preservatives and anti-sapstains was severely restricted. Strong positive linear regressions between prey fish and heron egg contaminant levels suggested that local dietary uptake was an important route of exposure for herons. Toxic equivalent concentrations (TEQs) sufficient to produce embryotoxicity in great blue heron chicks were measured in eggs from 1985 to 1991 at some colonies. Despite reduction in PCDD/Fs, estimated TEQs remained elevated throughout the 1980s at some urban colonies due to contributions from PCBs.

Concentrations of hexachlorocyclohexane (HCH) isomers (alpha, beta, and gamma) and enantiomer fractions (EFs) of alpha-HCH were determined in the Northwater Polynya Arctic marine food web. Relative food web structure was established using trophic level models based on organic delta 15N values. Concentrations of HCH in the samples collected, including water, sediment, benthic invertebrates (four species), pelagic zooplankton (six species), Arctic cod, seabirds (seven species), and ringed seal, were in the range previously reported for the Canadian Arctic. The relative proportion of the HCH isomers varied across the food web and appeared to be related to the biotransformation capacity of each species. For invertebrates and fish the biomagnification factors (BMFs) of the three isomers were > 1 and the proportion of each isomer and the EFs of alpha-HCH were similar to water, suggesting minimal biotransformation. Seabirds appear to readily metabolize gamma- and alpha-HCH based on low BMFs for these isomers, high proportions of beta-HCH (62-96%), and high EFs (0.65-0.97) for alpha-HCH. The alpha- and beta-HCH isomers appear to be recalcitrant in ringed seals based on BMFs > 1 and near racemic EFs for alpha-HCH. The beta isomer appears to be recalcitrant in all species examined and had an overall food web magnification factor of 3.9. EFs of alpha-HCH and the proportion of beta-HCH in sigma-HCH in the food web were highly correlated (r2 = 0.92) suggesting that EFs were a good indicator of a species capability to biotransform alpha-HCH.

The influence of maternal versus dietary sources of polychlorinated biphenyls (PCBs) deposited to eggs of ring doves (Streptopelia risoria) was investigated. Mature birds that lay a clutch of two eggs every 12 to 15 d were fed a diet of pellets spiked with 2,2',4,4',5,5'-hexacholorobiphenyl (unlabelled isotope designated as [12C]PCB153) for 25 d. The birds were subsequently switched to a diet containing isotopically labeled [U-13C12]PCB153 at similar concentrations for an additional 63 d. The toxicokinetics of [12C]PCB153 and [13C]PCB153 were followed in egg and carcass samples with time. Isotopic ratios of PCB153 in yolk lipids were identical to those in carcass lipids after introduction of diet 2, and they did not resemble those of the food at the time of egg formation. The data indicate that the PCB composition of eggs directly reflects the composition of maternal tissues, not the diet, at the time of yolk formation. Egg yolk:carcass lipid concentration ratios for the two isotopes were significantly less than one, averaging 0.33+/-0.02 (mean +/- standard error). Lipid normalized egg:maternal tissue contaminant concentration ratios for persistent organochlorine chemicals in the literature were reviewed for other avian species. The results provide a preliminary data set that suggests egg:maternal tissue contaminant concentration ratios vary among species, particularly among species that invest different quantities of lipids to a clutch of eggs. The results support the hypothesis that dilution of contaminants in egg lipids relative to maternal lipids is related to the reproductive strategy employed by the species.

Persistent organic pollutants (POPs) and stable isotopes of nitrogen (delta 15N) were measured in zooplankton (6 species), a benthic invertebrate (Anonyx nugax), Arctic cod (Boreogadus saida), seabirds (6 species), and ringed seals (Phoca hispida) collected in 1998 in the Northwater Polynya to examine effects of biological and chemical factors on trophic transfer of POPs in an Arctic marine food web. Strong positive relationships were found between recalcitrant POP concentrations (lipid corrected) and trophic level based on stable isotopes of nitrogen, providing clear evidence of POP biomagnification in Arctic marine food webs. Food web magnification factors (FWMFs), derived from the slope of the POP--trophic level relationship, provided an overall magnification factor for the food web but over and underestimated biomagnification factors (BMFs) based on predator--prey concentrations in poikilotherms (fish) and homeotherms (seabirds and mammals), respectively. Greater biomagnification in homeotherms was attributed to their greater energy requirement and subsequent feeding rates. Within the homeotherms, seabirds had greater BMFs than ringed seals, consistent with greater energy demands in birds. Scavenging from marine mammal carcasses and accumulation in more contaminated winter habitats were considered important variables in seabird BMFs. Metabolic differences between species resulted in lower than expected BMFs, which would not be recognized in whole food web trophic level--POP relationships. The use of sigma POP groups, such as sigma PCB, is problematic because FWMFs and BMFs varied considerably between individual POPs. FWMFs of recalcitrant POPs had a strong positive relationship with log octanol--water partition coefficient (Kow). Results of this study show the utility of using delta 15N to characterize trophic level and trophic transfer of POPs but highlight the effects of species and chemical differences on trophic transfer of POPs that can be overlooked when a single magnification factor is applied to an entire food web.

The Northwater Polynya (NOW) is a large area of year-round open water found in the high Arctic between Ellesmere Island and Greenland. NOW has high biological productivity compared with other arctic marine areas, and supports large populations of several seabird species. Seven species of seabirds, dovekie (Alle alle, DOVE), thick-billed murre (Uria lomvia, TBMU), black guillemot (Cepphus grylle, BLGU), black-legged kittiwake (Rissa tridactyla, BLKI), ivory gull (Pagophila eburnea, IVGU), glaucous gull (Larus hyperboreus, GLGU) and northern fulmar (Fulmaris glacialis, NOFU) were collected in May and June 1998 to determine chlordane concentrations in liver and fat and to examine species differences, relationships with stable isotopes of nitrogen, and enantiomeric fractions (EFs) of chiral components. sigma CHLOR concentrations varied over an order of magnitude among species, from a low of 176 +/- 19 ng/g (lipid corrected) in TMBU liver to a high of 3190 +/- 656 ng/g (lipid corrected) in NOFU liver. Lipid-corrected concentrations of chlordane did not vary between sex for any species or between fat and liver except for the DOVE, that had fat concentrations that were significantly greater than the liver. delta 15N values described a significant percentage of the variability of concentrations for most chlordane components, although less than what has been reported for whole food chains. Slopes of delta 15N versus concentration of chlordane components and sigma CHLOR were similar with the exception of those which were metabolized (trans-chlordane) or formed through biotransformation (oxychlordane). The relative proportions of chlordane components in seabirds were related to phylogeny; the procellariid (NOFU) had the greatest percentage of oxychlordane (> 70%), followed by the larids (BLKI, IVGU and GLGU; 40-50%) and the alcids (DOVE and BLGU; 10-20%). The exception was TBMU, an alcid, where oxychlordane made up > 40% of its chlordane. EFs of chiral components failed to predict concentration or trophic level, but did identify biotransformation differences between species and chlordane components. TBMU appeared to have a greater capacity to metabolize and eliminate chlordane, based on high proportions of oxychlordane, the highest EFs for oxychlordane and heptachlor epoxide, and a delta 15N-sigma CHLOR value which was well below the relationships developed for all seabird species.

Samples of Calanus hyperboreus, a herbivorous copepod, were collected (n = 20) between April and July 1998, and water samples (n = 6) were collected in May 1998, in the Northwater Polynya (NOW) to examine persistent organic pollutants (POPs) in a high Arctic marine zooplankton. Lipid content (dry weight) doubled, water content (r2 = 0.88) and delta15N (r2 = 0.54) significantly decreased, and delta13C significantly increased (r2 = 0.30) in the C. hyperboreus over the collection period allowing an examination of the role of these variables in POP dynamics in this small pelagic zooplankton. The rank and concentrations of POP groups in C. hyperboreus over the entire sampling was sum of PCB (30.1 +/- 4.03 ng/g, dry weight) > sum of HCH (11.8 +/- 3.23) > sum of DDT (4.74 +/- 0.74), sum of CHLOR (4.44 +/- 1.0) > sum of CIBz (2.42 +/- 0.18), although these rankings varied considerably over the summer. The alpha- and gamma-HCH and lower chlorinated PCB congeners were the most common POPs in C. hyperboreus. The relationship between bioconcentration factor (BCF) and octanol-water partition coefficient (Kow) observed for the C. hyperboreus was linear and near 1:1 (slope = 0.72) for POPs with a log Kow between 3 and 6 but curvilinear when hydrophobic POPs (log Kow > 6) were included. Concentrations of sum of HCH. Sum of CHLOR and sum of CIBz increased over the sampling period, but no change in sum of PCB or sum of DDT was observed. After removing the effects of time, the variables lipid content, water content, delta15N and delta13C did not describe POP concentrations in C. hyperboreus. These results suggest that hydrophobic POP (log Kow = 3.86.0) concentrations in zooplankton are likely to reflect water concentrations and that POPs do not biomagnify in C. hyperboreus or likely in other small, herbivorous zooplankton.

In this study, we identified the main hydroxylated polychlorinated biphenyls (OH-PCBs) and other chlorinated phenolic compounds and we determined their relative concentrations in whole blood from 13 male and 17 female Inuit from northern Quebec, Canada, and from a pooled whole blood sample from southern Quebec. We also determined concentrations of polychlorinated biphenyls (PCBs). Total OH-PCB concentrations were variable among the Inuit samples, ranging over 2 orders of magnitude (0.117-11.6 ng/g whole blood wet weight). These concentrations were equal to and up to 70 times those found for the southern Quebec pooled whole blood sample. Geometric mean concentrations of total OH-PCBs were 1.73 and 1.01 ng/g whole blood for Inuit men and women, respectively, and 0.161 ng/g whole blood for the southern population pool. There are limited data available for comparison, but the levels of OH-PCBs in Inuit are higher than those previously reported in the literature for other populations. There was a significant correlation (p < 0.005) between OH-PCBs and PCBs (r = 0.84) and both correlated significantly (p < 0.005) with age (r = 0.68 and 0.78, respectively). The ratio of OH-PCBs to PCBs was lower in Inuit (0.11) than in the southern Quebec pool (0.33). There is no apparent explanation for the difference. There was considerable variability in the congener pattern of the identified OH-PCBs. The main metabolite, 4-OH-CB109 (4-OH-2,3,3',4', 5-pentachlorobiphenyl), constituted 12-62% of the total OH-PCBs in the samples. Pentachlorophenol (PCP) was the dominant phenolic compound in blood, constituting 46% (geometric mean) of the total quantitated chlorinated phenolic compounds. PCP concentrations in Inuit blood ranged from 0.558 to 7.77 ng/g on a wet weight basis. All but two Inuit samples had lower concentrations than the southern Quebec pool (6.29 ng/g). The possible role of OH-PCBs in mediating PCB-induced adverse effects needs to be investigated further.

Geographical and temporal trends of total PCBs (SigmaPCBs) and hexachlorocyclohexanes (SigmaHCHs) have been examined in polar bear (Ursus maritimus) adipose tissue and ringed seal (Phoca hispida) blubber along a transect from Alaska to Svalbard and northern Norway/western Russia. PCB concentrations in polar bear show a strong west to east trend with higher levels in east Greenland, Svalbard. In ringed seal, highest PCB levels were found at two sites near the Russian coast. SigmaHCHs levels in ringed seals and polar bear show the reverse trend coinciding with much higher levels of SigmaHCHs in seawater in the North American Arctic. Some of these geographical differences may reflect dietary differences especially in the case of PCBs. Levels of SigmaPCBs in polar bears in the eastern Canadian Arctic appear to have increased from the 1970s to the 1980s but are now on the decline. SigmaPCBs and SigmaHCHs levels showed no significant change from the mid-1980s to 1990s in ringed seal blubber from three locations in the eastern Canadian Arctic.

The human placental JEG-3 and JAR choriocarcinoma cell lines have been used as placental models for the study of aromatase (CYP19) activity and endocrine functions. In the present study, 21 organochlorines (OCs) mediated decreases in aromatase activity and protein and DNA content and increases in the percent lactate dehydrogenase (LDH) leakage in JEG-3 cells. These effects were highly variable among the types of OC and their treatment concentrations. Lowest observed effective concentrations reached 0. 001 microM for several OCs. Aromatase activity decreases and OC-mediated cytotoxicity were related. Thus, it was not possible to clearly assess the capacity of the OCs to modulate aromatase activity. Similar to 1,4-naphthoquinone, the most cytotoxic OCs contained a hydroxyl (4'-OH-2,4,6-trichlorobiphenyl and tris(4-chlorophenyl)methanol) or methylsulfonyl- (3- and 4-MeSO(2)-2, 2',5,5'-tetrachlorobiphenyl and -2,3',4',5-tetrachlorobiphenyl, and 3'- and 4'-MeSO(2)-2,2',3,4,5'-pentachlorobiphenyl and -2,2',4,5, 5'-pentachlorobiphenyl) functional group. Modulation of aromatase activity and LDH leakage were less for 3,3',4,4', 5-pentachlorobiphenyl and benzo[a]pyrene and insignificant for five alkyl-substituted trichloro-dibenzofurans and 2,3,7, 8-tetrachloro-dibenzo-p-dioxin (up to 10 microM). Cytotoxicity-related effects were influenced by the cell density and the presence of 10% fetal calf serum in the medium during compound incubation. Similar cytotoxic effects were observed for the JAR cell line. The involvement of an apoptotic mechanism of cytotoxicity in OC-treated JEG-3 cells was suggested by the binding of APO2.7 (an antibody specific to apoptotic cells), DNA fragmentation, and trypan blue staining. JEG-3 and JAR cells appear too sensitive toward OC-mediated cytotoxicity for use as in vitro bioassays to evaluate the potential modulation of aromatase activity. However, these cell lines may prove useful for examining the capacity of xenobiotics to modulate placental toxicity., (Copyright 1999 Academic Press.)

Osprey (Pandion haliaetus) eggs were collected from 1991 to 1997 at nests (n = 121) upstream and downstream of bleached kraft pulp mills and at reference sites in the Fraser and Columbia River drainage systems of British Columbia, Washington, and Oregon. Blood samples were collected from nestling ospreys during the 1992 breeding season on the Thompson River. Samples were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and -dibenzofurans (PCDFs). Mean concentrations of 2,3,7,8-TCDD were significantly higher in eggs collected in 1991 at downstream compared to upstream nests near pulp mills at Kamloops and Castlegar, British Columbia. There were no significant temporal trends in 2,3,7,8-TCDD, -TCDF or other measured compounds at a sample of nests monitored between 1991 and 1994 downstream of the Castlegar pulp mill, despite changes in bleaching technology (CIO2 substitution). However, by 1997 concentrations of 2, 3,7,8-TCDD and -TCDF were significantly lower than previous years in nests sampled downstream at both Castlegar and Kamloops. An unusual pattern of higher chlorinated PCDDs and PCDFs was found in many of the osprey eggs collected in this study, and considerable individual variation in the pattern existed among eggs from the same site. For example, eggs from four different nests at one study area (Quesnel) on the Fraser River had concentrations of 1,2,3,4,6,7,8-HpCDD ranging from <1 to 1,100 ng/kg and OCDD from <1 to 7,000 ng/kg wet weight. Higher mean concentrations of HpCDD and OCDD were found in eggs from the Thompson River, a tributary of the Fraser, compared to the Columbia River, and concentrations were generally higher at nests upstream of pulp mills. In plasma samples, 1,2,3,4,6,7,8-HpCDD and OCDD were the main compounds detected, with no significant differences measured between samples upstream versus downstream or earlier versus later in the breeding season. Use of chlorophenolic wood preservatives by lumber processors was considered the main source of higher chlorinated PCDD/Fs throughout the systems, based on patterns of trace PCDFs in eggs and significant correlations between egg concentrations of pentachlorophenol and both HpCDD (r = 0.891, p < 0.01) and OCDD (r = 0.870, p < 0.01).

Adipose tissue samples from polar bears (Ursus maritimus) were obtained by necropsy or biopsy between the spring of 1989 to the spring of 1993 from Wrangel Island in Russia, most of the range of the bear in North America, eastern Greenland, and Svalbard. Samples were divided into 16 regions corresponding as much as possible to known stocks or management zones. Concentrations of dieldrin (DIEL), 4,4'-DDE (DDE), sum of 16 polychlorinated biphenyl congeners (sigma PCB), and sum of 11 chlordane-related compounds and metabolites (sigma CHL) were determined. In order to minimize the effect of age, only data for adults (320 bears age 5 years and older) was used to compare concentrations among regions. Concentrations of sigma PCB were 46% higher in adult males than females, and there was no significant trend with age. Concentrations of sigma CHL were 30% lower in adult males than females. Concentrations of sigma PCB, sigma CHL, and DDE in individual adult female bears were standardized to adult males using factors derived from the least-square means of each sex category, and geometric means of the standardized concentrations on a lipid weight basis were compared among regions. Median geometric mean standardized concentrations (lipid weight basis) and ranges among regions were as follows: sigma PCB, 5,942 (2,763-24,316) micrograms/kg; sigma CHL, 1,952 (727-4,632) micrograms/kg; DDE, 219 (52-560) micrograms/kg; DIEL, 157 (31-335) micrograms/kg. Geometric mean sigma PCB concentrations in bears from Svalbard, East Greenland, and the Arctic Ocean near Prince Patrick Island in Canada were similar (20,256-24,316 micrograms/kg) and significantly higher than most other areas. Atmospheric, oceanic, and ice transport, as well as ecological factors may contribute to these high concentrations of sigma PCB. sigma CHL was more uniformly distributed among regions than the other CHCs. Highest sigma CHL concentrations were found in southeastern Hudson Bay, which also had the highest DDE and DIEL concentrations. In general, concentrations of sigma CHL, DDE, and DIEL were higher in eastern than western regions, suggesting an influence of North American sources. Average sigma PCB concentrations in bears from the Canadian Arctic were similar to those in 1982-84, while average sigma CHL and DDE concentrations were 35-44% lower and DIEL was 90% lower. However, the significance of these temporal trends during the 1980s is not conclusive because of the problems of comparability of data.

During 1989-1991, we assessed developmental abnormalities in embryos and hatchlings from eggs of the common snapping turtle (Chelydra serpentina serpentina). Eggs were collected and artificially incubated from eight sites in Ontario, Canada and Akwesasne/New York, USA. In eggs from the same clutches we measured 20 organochlorine pesticides, 48 polychlorinated biphenyl (PCBs) congeners including 6 non-ortho PCBs, 8 polychlorinated dibenzodioxins (PCDDs), 14 polychlorinated dibenzofurans (PCDFs) and total mercury. We found a significant increase in abnormal development with increasing polychlorinated aromatic hydrocarbon exposure in eggs, particularly PCDD and PCDF concentrations. In contrast, the risk of abnormality was not significantly higher as toxic equivalent concentrations increased in eggs. We also found significant 7-ethoxyresorufin O-deethylase and Cytochrome P4501A responses in livers of hatchling turtles from Lake Ontario relative to hatchlings from a clean, inland site whereas we did not find any evidence of porphyria in the hatchlings from either site.

The present study examined the utility of an immunoblot method for quantitation of cytochrome P450 isozymes in archived liver samples as a bioassay of exposure to halogenated hydrocarbons. Hepatic microsomes were prepared from 44 archived polar bear (Ursus maritimus) liver homogenates that had been stored at approximately -40 degrees C for 9-10 years and analyzed on blots probed with antibodies to rat cytochromes P450 1A1 and P450 2B1. The results revealed a positive correlation between cytochrome P450 1A and total polychlorinated biphenyl (PCB) levels in the archived liver samples, suggesting that cytochrome P450 1A was induced in polar bears by environmental exposure to PCBs.

Common snapping turtle (Chelydra serpentina serpentina) eggs from five sites within the Great Lakes basin, and from a reference site in north-central Ontario were collected during 1981-1991 and analyzed for four organochlorine pesticides, polychlorinated biphenyls (PCBs) including six non-ortho PCBs, polychlorinated dibenzodioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). The pattern of geographic variation was consistent over time in eggs with Cootes Paradise/ Hamilton Harbour and Lynde Creek eggs on Lake Ontario containing the highest concentrations and most PCDD and PCDF congeners among all sites. Eggs from Cranberry Marsh on Lake Ontario contained organochlorine concentrations similar to those from Big Creek Marsh and Rondeau Provincial Park on Lake Erie except PCDDs and PCDFs which occurred at higher concentrations and more congeners were detectable in Cranberry Marsh eggs. Concentrations of most contaminants in turtle eggs from Algonquin Park, the reference site, have significantly decreased in the past decade. Dieldrin concentrations, however, increased in Algonquin Park eggs from 1981 to 1989. Significant decreases in concentrations of hexachlorobenzene, mirex and PCBs occurred between turtle eggs collected in 1981/84 and 1989 at Big Creek Marsh and Rondeau Provincial Park, whereas there was no significant change in concentrations of p,p'-DDE and dieldrin. In Lake Ontario eggs, concentrations of PCBs, p,p'-DDE and dieldrin increased significantly between 1984 and 1991. Differences were also found in patterns of temporal variation in contamination between herring gulls (Larus argentatus) and snapping turtles which were attributed to differences in diet. Elevated and continued contamination in turtle eggs from Lake. Ontario is probably due to a combination of local sources of chemicals and consumption of large migratory fish that spawn in wetlands inhabited by these turtles.

Bald eagle (Haliaeetus leucocephalus) eggs were collected during incubation, 1990-1992, from 16 nests near three bleached-kraft pulp mills, from six nests in the Fraser River estuary and from seven nests at a reference site on the Pacific coast of Canada. Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were present in all eggs in a qualitatively similar pattern among sites. Mean concentrations of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) were significantly higher in eggs collected from near three kraft pulp mill sites in the Strait of Georgia (44, 45, 84 ng/kg) than from the reference area in Johnstone Strait (15 ng/kg). There were few differences among sites in mean organochlorine pesticide levels, indicating the diffuse distribution of those chemicals and the domination of atmospheric inputs. Mean concentrations of total polychlorinated biphenyls (PCBs) were highest in eggs from the Strait of Georgia (4.86 mg/kg) and the PCB congener pattern was significantly different between that area and both the lower Fraser valley and Johnstone Strait. Mean mercury concentrations, which were mainly methyl-mercury, were significantly higher in eggs collected from the lower Fraser Valley (0.258 mg/kg) and Johnstone Strait (0.294 mg/kg) compared to the Strait of Georgia (0.188 mg/kg). Individual and regional variation in concentrations of organochlorine pesticides, PCBs and mercury in eagle eggs were thought to be influenced mainly by dietary differences. Toxicologically, in 1990, mean TCDD-toxic equivalents (TEQs) in bald eagle eggs were about two-fold greater than a lowest-observed-effect level, suggested elsewhere for this species, of 210 ng/kg TEQs. In the Strait of Georgia, PCCDs and PCDFs made a greater contribution to TEQs than non-ortho and mono-ortho PCBs, whereas the reverse was true for eggs outside the strait. Mean eggshell thickness was less than the pre-1947 value at all sites, although there was no significant relationship between eggshell thickness and DDE concentrations. Levels of other organochlorine pesticides and mercury were below those considered to be toxic.