Effects of Metal (Ag,Cd, Cr,Cu, Zn) Exposures on Some Enzymatic and Non-Enzymatic Indicators in the Liver of <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

Freshwater fish Oreochromis niloticus exposed to 0.05 μg/mL of Cu, Cd, Zn, Ag and Cr for up to 30 days. Only Ag, which exceeded environmentally realistic concentrations by a factor of >100 caused fish mortality within this period. Metals increased aspartate transaminase (AST) activity, while they decreased alanine transaminase (ALT) activity, except Cr exposure. Concentrations of free –SH group decreased whereas protein concentrations did not alter following metal exposures. Detectable metal accumulation occurred in the liver of Cd, Cu and Zn exposed fish. This study emphasized that both enzymatic and non-enzymatic mechanisms may be useful in understanding the degree of metal toxicity in fish liver.     

Exposure to a Mixture of Zinc and Copper Decreases Survival and Fecundity of Discocotyle sagittata (Leuckart) Parasitizing Juvenile Atlantic Salmon, Salmo salar L.

We assessed the effects of zinc and copper on freshwater monogenean ectoparasites (Discocotyle sagittata Leuckart) infecting juvenile Atlantic salmon (Salmo salar L.). Exposure to 47 μg/L zinc and 3 μg/L copper reduced survival and fecundity of adult D. sagittata, while egg hatching success was only reduced at high exposure concentrations (2704 μg/L zinc and 164 μg/L copper). Parasitized salmon had decreased plasma chloride, but this was negated in infected fish exposed to metals. No other effects on Atlantic salmon survival and physiology (plasma osmolality, hematocrit) were noted, suggesting that D. sagittata may be more susceptible to metal toxicity than its host fish.     

Levels of Cadmium, Mercury, and Lead in Magellanic Penguins (Spheniscus magellanicus) Stranded on the Brazilian Coast

Cadmium (Cd), mercury (Hg), and lead (Pb) were determined in samples of liver and breast muscles of first-year Magellanic penguins (Spheniscus magellanicus), from two different areas on the Brazilian coast, 35 on the Rio de Janeiro coast and 12 on the Rio Grande do Sul coast. In both areas, Cd concentrations in muscle samples were <0.025 μg/g. However, the Cd and Hg concentrations found in liver and Hg concentrations found in muscle showed a significant difference between the two regions. The geometric mean of the concentrations was higher in the specimens from Rio de Janeiro (Cd—6.8 μg/g; Hg—liver, 1.6 μg/g, and muscle, 0.4 μg/g wet weight) than in those from Rio Grande do Sul (Cd—2.3 μg/g; Hg—liver, 0.9 μg/g, and muscle, 0.1 μg/g wet weight). The site differences could be related to differences in diet influenced by geographic factors. Brazil’s southeastern coast is highly urbanized, and its coastal waters are contaminated by the waste of agricultural and industrial activities. There is a lack of information on the levels of heavy metals in S. magellanicus, however, their wide distribution and top position in the trophic chain make the use of stranded specimens an attractive source of information for monitoring heavy metals in the South Atlantic coast.     

Metallothionein-Like Protein: Is It an Efficient Biomarker of Metal Contamination? A Case Study Based on Fish From the Tunisian Coast

The aim of this work was to assess the relative importance of natural fluctuations in metallothionein-like protein (MTLP) levels associated with the sexual status of fish versus fluctuations due to metal exposure. In order to see fluctuations due to metal exposure, comparisons were made on the same fish species Scorpaena porcus sampled in polluted and unpolluted sites. The hermaphrodite fish Serranus scriba and Scorpaena porcus, in which sexes are separate, were compared at the unpolluted site to see fluctuations caused by the sexual status. In both species, metals and the MTLP levels were determined in the gills and liver. In these organs, Cd, Cu, and Zn distributions were examined in different fractions: the insoluble fraction (IF) and the cytosol divided into thermolabile compounds (HDF) and the heat stable compounds including MTLP. MTLP levels were higher in the liver (3.09 mg/g in S. porcus, 1.59 mg/g in S. scriba) than in gills (0.13 mg/g in S. porcus, 0.40 mg/g in S. scriba). For Scorpaena porcus, metals and MTLP levels varied with sex, whereas in Serranus scriba, which is a hermaphrodite species, inherent variations were also observed. At the polluted site, MTLP, Cd, and Cu concentrations in the gills of S. porcus increased but the supplementary metals were not associated with the heat stable compounds including MTLP. At this site, hepatic MTLP bound more metals than at the unpolluted site, but its binding capacity was not sufficient to avoid the binding of metals to the insoluble and the heat denaturable fractions. In light of these results and in spite of its hermaphrodism, it is questionable whether to consider S. scriba as a good candidate for biomonitoring based on MTLP. S. porcus could be useful for this purpose only if the MTLP capacity in binding metals is not exceeded. The MTLP could be considered as a biomarker only if it is investigated in relatively unpolluted sites. Received: 10 February 1996/Accepted: 28 October 1996     

First Determination of the Levels of Platinum Group Metals in Manta birostris (Manta Ray) Caught Along the Ghanaian Coastline

Tissues from Manta birostris caught by fishermen from Dixcove in the western part of Ghana were analyzed for their Platinum, palladium and rhodium concentrations (PGM). The use of chondrichthyan fish has permitted the study of trace levels of Platinum group metals (PGMs) which have travelled very far into the sea. The analysis showed that Ghana’s coastline is fairly polluted with these platinum group metals (PGMs). PGM concentration in manta ray recorded a range of (0.15–0.85) μg/g for Pt, (0.033–0.67) μg/g for Pd and (0.007–0.145) μg/g for Rh. Comparing these values to the UK dietary intake of 0.2 μg/day for Pt and Rh and 1.0 μg/day for Pd, its indicates that the values obtained from the analysis for Pt was above the required level. This is the first study to show the accumulation of PGM in chondrichthyan fish, although the sources of this pollution are not clear as manta birostris is migratory and therefore need to be investigated further. The presence of the PGM is very significant, since manta ray meat is consumed in Ghana. This may presents a health risk, due to a possible accumulation of PGMs in humans.     

Alkaline Comet Assay for Genotoxic Effect Detection in Neotropical Fish Prochilodus lineatus (Pisces, Curimatidae)

Toxicants on fish may induce genetic alterations that can be used as genotoxic markers. We evaluated DNA damage using alkaline comet assay applied on erythrocytes after in vivo exposure of Prochilodus lineatus to different concentrations of Cypermethrin (0.300, 0.150, 0.075 and 0.000 μg/L) as a probable chemical mutagen. The results revealed a significantly higher level of DNA damage at all concentrations of Cypermethrin tested compared to control and background level (p < 0.05). We have standardized the technique for one of the most common native fish species that will be useful for biomonitoring genotoxicity in polluted waters of the region.     

Accumulation of Some Heavy Metals Seasonally in Hysterotylacium aduncum (Nematoda) and Its Host Red Sea Bream,Pagellus erythrinus (Sparidae) from Gulf of Iskenderun (North-Eastern Mediterranean)

The Red Sea Bream’s nematode and Sparus aurata, sampled from the Iskenderun Bay, North-eastern Mediterranean in March 2008 were analysed by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES) for their some heavy metal (Cd, Cr, Cu, Fe, Hg, Mn, Mg, Pb and Zn) levels. The metal concentrations of the parasites were compared to different organs (liver, muscle, swimbladder, intestine and skin) of the fish hosts. The highest Cd (0.303 mg/kgg ww) concentrations were found in the muscle, highest Cr (4.932 mg/kg ww), Hg (2.350 mg/kg ww) Pb (22.82 mg/kg ww) concentrations were found in the parasite, highest Cu (7.608 mg/kg ww) and Fe (176.7 mg/kg ww) concentrations were found in the liver, highest Mn (31.24 mg/kg ww) Zn (78.51 mg/kg ww) concentrations were found in the swimbladder for parasitized fish. The highest Cd (0.612 mg/kg ww), Cu (8.261 mg/kg ww) Fe (261.1 mg/kg ww) concentrations were found in the liver, highest Cr (6.123 mg/kg ww) and Pb (9.125 mg/kg ww) concentrations were found in the intestine, highest Hg (2.013 mg/kg ww) Zn (83.30 mg/kg ww) and Mn (41.24 mg/kg ww) concentrations were found in the swimbladder for un-parasitized fish.     

Changes in Selenium, Copper, Cadmium, and Zinc Concentrations in Mullet (Mugil cephalus) from the Southern Basin of Lake Macquarie, Australia, in Response to Alteration of Coal-Fired Power Station Fly Ash Handling Procedures

Selenium, copper, cadmium, and zinc concentrations were measured in mullet (Mugil cephalus) from the southern basin of Lake Macquarie, Australia, in 1997 to determine if improved ash-handling practices at an adjacent coal fired power station, implemented in 1995, had significantly lowered trace metal concentrations in mullet tissues. Mean muscle tissue concentrations of selenium (5.9 ± 0.7 μg/g dry mass), copper (3.6 ± 0.1 μg/g dry mass), and zinc (14 ± 1 μg/g dry mass) are lower than previously reported for mullet analyzed in 1993 (10 ± 2, 21 ± 3, 27 ± 3 μg/g dry mass, respectively). Cadmium concentrations in liver tissues increased from 2.3 ± 0.3 to 6 ± 2 μg/g dry mass. Significant intra-tissue correlations between metal concentrations were found for all tissues except muscle. Strong correlations of selenium, copper, and zinc concentrations were found in liver tissues, indicating a common primary source may exist for these metals, such as fly ash. All trace metals were found to have significant inter-tissue correlations, with strong correlations occurring for selenium between all tissues and for cadmium between all tissues except muscle. Regulation of copper, cadmium, and zinc appears to be occurring in muscle tissue. Selenium concentrations in mullet are still above levels considered to be of concern to human consumers. Trace metal concentrations are below that known to effect the health of fish. Mullet are directly exposed to trace metal concentrations as a result of feeding and the ingestion of contaminated sediment and detritus. Lower metal concentrations found in mullet tissues are attributed to the burial of highly contaminated sediment with material containing lower trace metal concentrations. Little of the variations in trace metal concentrations between mullet was explained by mass, gender, or age. Received: 20 August 2000/Accepted: 22 February 2001     

Metal Concentrations in Two Commercial Fish from Persian Gulf,in Relation to Body Length and Sex

The relationship between sex, size (length and weight) and metal concentrations in the tissues of two commercially valuable fish species (silver pomfret, Pampus argenteus and tiger tooth croaker, Otolithes ruber) from Persian Gulf were evaluated. Concentrations of the metals in fish species ranged as follows: Mn 0.743–11.279; Cd 0.175–2.375; Pb 2.406–11.297; Zn 10.837–80.389; Fe 2.263–86.110; Cu 1.503–6.333 μg/g dry weight, respectively. Metal content in both fish varied with type of metals, organ, and sex. Results showed that, except in a few cases, significant relationships between metal concentrations and fish size were negative.     

Dietary Pb Accumulation in Juvenile Freshwater Rainbow Trout (Oncorhynchus mykiss)

Three different diets amended with lead (Pb) nitrate Pb(NO₃)₂ (7, 77, and 520 μg Pb/g dry weight) and a Pb-free control diet (0.06 μg Pb/g dry weight) were fed to juvenile freshwater rainbow trout for 21 days. Accounting for measured food consumption, the calculated doses per fish were 0.02, 3.7, 39.6, and 221.5 μg/day, for the control, low, intermediate, and high Pb treatments, respectively. The patterns of Pb accumulation over time were determined in various tissues (gills, liver, kidney, intestine, carcass), red blood cells (RBC), and plasma, as well as feeding, growth, hematological, and ionoregulatory parameters. Pb accumulation occurred in a dose-dependent manner in all tissues except the plasma, where accumulation was minimal. Overall, when fed the highest Pb diet, the intestine exhibited the greatest Pb burden (17.8 μg Pb/g tissue wet weight), with high concentrations also found in the kidney (2.4 μg Pb/g tissue wet weight) and liver (1.9 μg Pb/g) at the highest dietary Pb treatment by day 21. The RBCs accumulated a substantial amount of Pb (1.5 μg Pb/g) when compared to the plasma (0.012 μg Pb/g) in the high treatment group. The percentage of Pb retained in the fish decreased with increasing dietary Pb concentrations. Growth, survival, plasma protein, and hematocrit were not significantly affected by dietary Pb. Plasma Ca²⁺ levels decreased at the beginning of the experiment, whereas Mg²⁺ levels decreased during the middle of the experiment in both the intermediate and high dietary treatments. Both the Ca²⁺ and Mg²⁺ levels stabilized by day 21. Branchial Ca²⁺ and Na⁺ influx rates were not affected by dietary Pb, except on day 8 where Na⁺ influx rates were significantly elevated. The results of this study show that Pb does accumulate internally from the diet when present at levels within the range reported in contaminated benthic invertebrates in nature. We further identify the intestine as a potential target site of chronic toxicity of Pb via the diet, and RBCs as a reservoir of dietary Pb.     

Contaminations of Metal in Tissues of Siberian Gull Larus heuglini: Gender, Age, and Tissue Differences

The objective of the present study was to investigate the levels of metals, namely cadmium, lead, and zinc, in Siberian gull (Larus heuglini) (n = 15), in order to: (1) examine the sex and gender related variation in trace metal accumulation, and (2) to determine the significant between metal concentrations in the kidney, liver, and pectoral muscle. The concentrations were different between the tissues of bird as well as among the interaction (sex × age), but this difference (except cadmium in liver and zinc in kidney) between the gender (male and female) and age (adult and juvenile) didn’t exist. Results showed that the metal concentrations in the Siberian gull were decreased in sequence of kidney > liver > muscle. The cadmium, lead, zinc concentration overall means they were measured as 2.2 ± 0.7, 8.8 ± 2.5, and 91.1 ± 37. 1 μg/g for kidney, 1.1 ± 0.2, 5.1 ± 0.8, and 68.3 ± 27.8 μg/g for liver, and 0.8 ± 0.1, 3.4 ± 0.6, and 34.4 ± 23.2 μg/g for pectoral muscle, respectively.     

Comparison of Arsenic and Antimony Contents in Tissues and Organs of Brown Trout Caught from the River Presa Polluted by Ancient Mining Practices and from the River Bravona in Corsica (France): A Survey Study

The present study evaluates the concentrations of arsenic (As) and antimony (Sb) in the intestine, liver, muscle, gonads, gills, and kidney of Salmo trutta subsp. from the Presa River in Corsica (France; n = 10), which crosses an abandoned arsenic mine, and from the Bravona River (reference site; n = 10). Both metalloids were analyzed by means of ICP-MS. The relationships between fish size (length and weight) and metalloid concentrations in their tissues were investigated by linear regression analysis. In all fish samples concentrations of As and Sb (expressed as micrograms per gram fresh weight) were highest in the kidney. Lowest Sb concentrations were found in the muscle, whereas lowest As concentrations were found in the gonads of S. trutta. Two organotropisms were revealed: one for As—kidney (21.4656) > intestine (3.9535) > gills (3.0404) > liver (1.1743) > muscle (0.9976) > gonads (0.8081); and the other for Sb—kidney (0.70067) > gills (0.6181) > intestine (0.2576) > gonads (0.1673) > liver (0.9625) > muscle (0.0753). Results of linear regression analysis in most cases showed a significant negative correlation between metalloid concentration and fish size. Highly significant (p < 0.05) negative correlations were found between fish length and As concentration in the gonads, as well as between fish length and Sb concentrations in the gills. Arsenic concentrations in female fish were significantly higher than those in males in the kidney, gonads, gills, and liver. The same results were found for Sb, except in the liver, where the tendency was reversed.     

Evaluation of Bivalves as Bioindicators of Metal Pollution in Freshwater

The fresh water bivalves, Lamellidens corrianus, Lamellidens marginalis, and Indonaia caeruleus were exposed to chronic concentration of arsenic (0.1719 ppm), cadmium (0.1284 ppm), copper (0.033 ppm), lead (1.50 ppm), mercury (0.0443 ppm) and zinc (1.858 ppm) separately up to 30 days in laboratory. Dry weight of each animal was used to calculate metal concentrations (μg/g) and the metal body burden (μg/individual). It was observed that lead (1235.4 μg/g) and arsenic (37.9 μg/g) concentration were highest in Lamellidens corrianus, zinc (3,032.3 μg/g) was highest in Lamellidens marginalis, while mercury (5.87 μg/g), cadmium (142 μg/g) and copper (826.7 μg/g) was highest in Indonaia caeruleus.     

Investigation of Zinc,Copper, Lead and Cadmium Accumulation in the Tissues of <Emphasis Type="Italic">Sander lucioperca</Emphasis> (L., 1758) Living in Hirfanlı Dam Lake,Turkey

This study, some metals (zinc, copper, lead and cadmium) were analyzed in liver, muscle and gills of Sander lucioperca (Linnaeus, 1758) caught from the Hirfanlı Dam Lake in December 2007. The highest concentrations were found in liver (zinc:32.5 μg/g, lead:10.73 μg/g, copper:5.85 μg/g, cadmium:0.76 μg/g) of Sander lucioperca. It was seen that the accumulation of zinc, lead and cadmium primarily took place in liver followed by muscles and gills. It was observed that copper is mainly accumulated in liver followed by gill and mucsles.     

Distribution of Mercury in Several Environmental Compartments in an Aquatic Ecosystem Impacted by Gold Mining in Northern Colombia

Mercury (Hg) used in gold amalgamation is a major source of contamination in developing countries. Water, sediments, plankton, fish, and human samples from Grande Marsh, a Hg-polluted marsh located in the south of Bolívar, municipality of Montecristo, Colombia, were collected during both the rainy and the dry seasons (2003–2006), at three different sampling sites, and analyzed for total Hg (T-Hg) content. Water, sediment, seston, phytoplankton, and zooplankton T-Hg concentrations were 0.33 ± 0.03 μg/L, 0.71 ± 0.03, 1.20 ± 0.06, 0.52 ± 0.03, and 0.94 ± 0.05 μg/g dry weight (wt), respectively. T-Hg levels in these compartments were highly pair-correlated (p < 0.05), and for all of them, except sediments, greater values were found during the dry season. Significant differences were observed for T-Hg concentrations in fish according to their trophic position. Average highest T-Hg values were found in carnivorous species such as Caquetaia kraussi (1.09 ± 0.17 μg/g fresh wt), Hoplias malabaricus (0.58 ± 0.05 μg/g fresh wt), and Plagioscion surinamensis (0.53 ± 0.07 μg/g fresh wt), whereas the lowest were detected in noncarnivorous species such as Prochilodus magdalenae (0.157 ± 0.01 μg/g fresh wt). In those fish species where seasonal comparisons were possible, specimens captured during the dry season had greater T-Hg levels in muscle. Although the T-Hg mean level for all fish samples (0.407 ± 0.360 μg/g fresh wt) did not exceed the recommended limit ingestion level, risk assessment based on the hazard index suggested that a fish intake of 0.12 kg per day (a small carnivorous specimen) could increase the potential health effects related to Hg exposure in the local human population, whose hair T-Hg median value was 4.7 μg/g, and presented a low but significant correlation with fish consumption (r = 0.250, p = 0.016). In short, Hg pollution from gold mining around Grande Marsh has permeated the food web, and currently levels in fish represent a serious concern for human health.     

Effects of a Chemically Polluted Discharge on the Relationship Between Fecundity and Parasitic Infections in the Chub (Leuciscus cephalus) from a River in Southern England

In fish there is a close association between endocrine and immune function that during seasonal changes in reproductive status can affect the fishes susceptibility to parasitic infection. The effects of endocrine-disrupting pollution on this association are not known. The present study investigates the effects of a chemically polluted (ammoniacal nitrogen, zinc, bromide) discharge in Cranleigh Waters, a river in southern England, on the fecundity and parasitism of chub, Leuciscus cephalus, over an 18-month period. In the polluted site, the gonado-somatic index (GSI) of fish was lower in females and higher in males compared to an unpolluted upstream site, indicating an androgenic effect on reproduction. Parasite species richness, especially the intestinal helminths Proteocephalus torulosus and Pomphorynchus laevis, was increased in fish in the polluted site. However, the occurrence of the two most common parasite species in the river—Myxobulus sp. 1, a gill myxozoan, and Diplostomum sp., a trematode found in the eye—was unchanged between polluted and unpolluted river sites. Nevertheless, there was a significant relationship between GSI and the prevalence of these two parasite species in the unpolluted site but not the polluted site suggesting that endocrine disruption of reproduction did not lead to an increase in host susceptibility. The reasons for this are discussed.     

Relationship Between Gonad Maturation and Heavy Metal Accumulation in the Clam, <Emphasis Type="Italic">Galatea paradoxa</Emphasis> (Born 1778) from the Volta Estuary,Ghana

The relationship between gonadal development and the concentrations of four heavy metals Mn, Zn, Fe and Hg in the tissues of the clam Galatea paradoxa was evaluated at the Volta estuary, Ghana, over an 18-month period. Metal concentrations in the clam tissues were highly variable over the sampling period and seemed to be influenced by the reproductive cycle of the clam. Mn concentrations varied over a wide range from 49 to 867 μg/g and exhibited a significant positive correlation with gonadal development (p = 0.0146, r² = 0.3190). Zn and Fe concentrations ranged from 13 to 59 μg/g and 79 to 484 μg/g, respectively and both revealed negative relationships between gonad development and metal accumulation (Zn (p = 0.0554, r² = 0.0554) and Fe (p = 0.1040, r² = 0.1567)). Hg concentrations ranged from 0.026 to 0.059 μg/g over the sampling period and exhibited a slight positive relationship between gonadal development and metal accumulation (p = 0.0861, r² = 0.1730).     

Metal Concentrations in Tissues of Two Fish Species From Qeshm Island, Iran

The purpose of this study was to determine the concentrations of metals, cadmium, chromium, lead and nickel in Liza vaigiensis and Johnius carutta, in order to: compare metal concentrations between two species with different gender, and to determine the significance between metal concentrations in the gill, liver and muscle. The highest mean concentrations of cadmium, chromium, lead and nickel in different tissues of these two fish species were found in the liver of L. vaigiensis at 0.68, 0.83, 0.37 and 1.42 μg g⁻¹, respectively; while the lowest mean concentrations of cadmium, chromium, lead and nickel were observed in the muscle of J. carutta at 0.16, 0.16, 0.03 and 0.29 μg g⁻¹, respectively. The results showed that the metal concentrations in both species were higher in the females than in the males (except chromium in gill and cadmium in muscle of J. carutta). Also, the results indicated that the metal concentrations were different among fish tissues (one-way ANOVA, p < 0.001), but there was no difference (except lead in gills of J. carutta) between sex (male vs. female).     

Seasonal variation of trace metal concentrations in the digestive gland of the Mediterranean mussel Mytilus galloprovincialis: Comparison between a polluted and a non-polluted site

Seasonal changes in metal (Cu, Fe, Mn, Pb, and Zn) concentrations were observed in the digestive gland of the Mediterranean mussel, Mytilus galloprovincialis, from both a polluted and a non-polluted population. Digestive gland of mussels from the polluted site showed metal concentrations appreciably higher than in non-polluted organisms, especially for Pb (up to 160 g/g d.w.), Mn (up to 300 g/g d.w.), and Fe (up to 8,500 g/g d.w.), whereas the two populations showed maximum mean values, respectively, of 34 and 20 g/g d.w. for Cu and 170 and 120 g/g d.w. for Zn.Over 1 year (1991), differences between maximum and minimum values were moderate only in the unpolluted organisms. During gametogenesis, while the metal concentrations (expressed as g/g dry weight) decreased in the digestive gland, the tissue burden (as g) in that organ remained nearly constant or increased slightly.The apparent decrease in metal concentrations was probably due to the penetration of gonadic tissues into the digestive gland during gametogenesis, which biologically diluted metal concentrations in mussels from both the polluted and unpolluted populations. The effect of mussel size on trace metal concentrations in the digestive gland was demonstrated during different stages of the reproductive cycle. Higher concentrations were found in smaller organisms; however, during the spawning period, due to the fact that this is not a synchronous process within a population, the organisms exhibit a high variability in digestive gland weight which can mask this relationship when digestive gland weight is used as a size-index and as a parameter of the trace metal digestive gland burden.     

Accumulation of Environmental Contaminants in Wood Duck (<Emphasis Type="Italic">Aix sponsa</Emphasis>) Eggs,with Emphasis on Polychlorinated Dibenzo-<Emphasis Type="Italic">p</Emphasis>-Dioxins and Polychlorinated Dibenzofurans

We measured polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), organochlorine pesticides, and mercury in wood duck (Aix sponsa) eggs collected near a North Carolina (USA) bleached kraft paper mill. Samples were taken a decade after the mill stopped using molecular chlorine. Using avian toxic equivalency factors, 2,3,7,8-tetrachlorodibenzo-p-dioxin toxicity equivalent (TEQ) concentrations were 1–30 pg/g fresh wet weight in eggs (n = 48) collected near the mill in 2002–2005 and were significantly higher than those from a reference site (<1 pg/g) 25 km away. Geometric mean wood duck egg TEQs (6 pg/g) were one-fifth those measured at this site prior to the cessation of molecular chlorine bleaching. Concentrations of mercury in wood duck eggs from nests of the Roanoke River sites ranged from 0.01 to 0.14 μg/g (geometric mean, 0.04 μg/g) and were significantly higher than those from the reference site, where concentrations did not exceed 0.04 μg/g (geometric mean, 0.02 μg/g). All concentrations were lower than those associated with adverse effects in birds. The congener profiles, lack of contamination in reference site eggs, and decline in contaminant concentrations after process changes at the mill provide strong evidence that mill discharges influenced contamination of local wood duck eggs. Collectively, the results indicate that the wood duck is an effective sentinel of the spatial and temporal extent of PCDD, PCDF, and mercury contamination.