Metal-metal interactions of dietary cadmium, copper and zinc in rainbow trout, Oncorhynchus mykiss

The influence of metal-metal interactions on uptake, accumulation, plasma transport and chronic toxicity of dietary Cu, Cd and Zn in rainbow trout (Oncorhynchus mykiss) was explored. Juvenile rainbow trout were fed diets supplemented with (μg/g) 500 Cu, 1000 Zn and 500 Cd singly and as a ternary mixture at 2.5% body weight daily ration for 28 days. Complex interactions among the metals dependent on the tissue/organ, metals ratios and duration of exposure were observed. While Zn did not accumulate, whole-body Cd and Cu concentrations increased following linear and saturation patterns, respectively. Early enhanced whole-body Cu accumulation in fish exposed to the metals mixture was correlated with reduced Cd concentration whereas late enhancement of Cd accumulation corresponded with elevated Cd concentration. This suggests early mutual antagonism and late cooperation between Cd and Cu probably due to interactions at temporally variable metal accumulation sites. At the level of uptake, Cd and Cu were either antagonistic or mutually increased the concentrations of each other depending on the duration of exposure and section of the gut. At the level of transport, enhanced Cd accumulation in plasma was closely correlated with reduced concentrations of both Zn and Cu indicating competitive binding to plasma proteins and/or antagonism at uptake sites. Compared to the Cu alone exposure, Cu concentrations were either lower (gills and carcasses) or higher (liver and kidney) in fish exposed to the metals mixture. On the other hand, Cd accumulation was enhanced in livers and carcasses of fish exposed to the mixture compared to those exposed to Cd alone, while Zn stimulated Cu accumulation in gills. Chronic toxicity was demonstrated by elevated malondialdehyde levels in livers and reduced concentrations of Zn and Cu in plasma. Overall, interactions of Cd, Cu and Zn are not always consistent with the isomorphous competitive binding theory.     

Metal interactions within the kidney,gill, and digestive gland of the clam,Mercenaria mercenaria,following laboratory exposure to cadmium

Mercenaria mercenaria were exposed to 0.1 g Cd/ml seawater (¹⁰⁹Cd + stable carrier) for either (1) periods of 1 hr to 31 days, or (2) a period of 3 days followed by depuration in clean seawater for 2 to 64 days. Cd accumulated at increasing rates in the kidney, but at decreasing rates in all other organs of the clam during the laboratory exposure period. Measurement of total Cd levels confirmed that¹⁰⁹Cd was accumulated by the clam tissues and not simply exchanged. The overall rate of Cd accumulation was significantly greater (P < 0.05) for the kidney than for the gill, mantle, digestive gland, pericardial gland, adductor, or remaining viscera, but not significantly different among the other organs (P > 0.05). No loss of Cd or other detectable metals occurred even after 64 days depuration. The degree to which Cd accumulated in the kidney, gill, and digestive gland did not correlate with the concentrations of other metals already present in these organs (except with Zn in the digestive gland). Negative correlations between different metal concentrations were never observed. Comparison of metal interaction patterns between the kidney, gill, and digestive gland indicates that each organ relies on different mechanisms for sequestering metals.     

Heavy Metals in the Blue Crab (<Emphasis Type="Italic">Callinectes sapidus</Emphasis>) in Mersin Bay,Turkey

The concentrations of four metals (copper, cadmium, zinc and lead) were quantified in blue crabs (Callinectes sapidus) tissues collected in January, April, June and September at two stations in Mersin Bay, northeastern Mediterranean Sea, using ICP-MS. The metal concentrations in crabs from the two stations differed significantly. The hepatopancreas was the major organ accumulating metals, followed by gill and muscle tissues. Except for lead, the highest concentrations of metals were measured in the hepatopancreas. The hepatopancreas had higher concentrations of all heavy metals (Cu 321.1?±?4.30; Zn 182.2?±?3.40; Cd 48.2?±?2.00) compared to gill (Cu 90.2?±?1.35; Zn 104.3?±?2.30; Cd 22.3?±?3.40) and muscle (Cu 19.1?±?1.10; Zn 55.1?±?3.25; Cd 2.5?±?0.20). Among the metals analyzed, Cu, Zn and Pb were the most abundant in the different tissues while Cd was the least abundant in C. sapidus. Seasonality in the levels of the four metals was determined.The highest concentrations of all metals were observed in the June (Zn 55.1?±?3.25; Cu 19.1?±?1.10; Cd 2.5?±?0.20; Pb 5.1?±?0.18) compared to all other months (Zn 34.1?±?3.23; Cu 11.1?±?1.15; Cd 0.9?±?0.20; Pb 3.1?±?0.21).     

Metal pollution as health indicator of lake ecosystems

As part of a long-term monitoring study of the anthropogenic pollution of the Lake of Balaton (Hungary) the concentrations of toxic metals (Cd2+, Hg2+, Pb2+), as well as of bioelements (Cu2+ and Zn2+) were measured in the muscle, gill and liver of bream (Abramis brama L.) collected in the open water during the autumn of 1999, The highest Cd, Cu, Pb and Zn concentrations were detected in the gill and liver of fish, whereas the highest Hg concentrations were measured in the muscle. The maximum metal concentrations measured in the muscle of bream were generally below maximum permissible levels for human consumption established by the Hungarian Food Directorate. Depending on the sampling site, significantly higher Cd, Hg and Pb concentrations (p < 0.05) were detected in the muscle of fish samples collected from the Western basin, while no significant differences were observed for Cu and Zn. In the muscle and gill an increasing trend of heavy metal (Cd and Cu) load characterizes the individuals of the 2-4 calendar age group (p < 0.05), while for the older specimens the concentration of these elements decreased significantly (p < 0.05). Positive relationships on the whole age scale were found for Cd in the liver, for Pb in the gill, and for Hg both in the muscle and the liver of fish.     

Effects of Cd, Zn and Cd + Zn Combination on ATPase Activitiy in the Gill and Muscle of Tilapia (Oreochromis niloticus)

This study investigated the responses of Na⁺/K⁺-ATPase, Mg²⁺-ATPase and Ca²⁺-ATPase in the gill and muscle of a freshwater fish Oreochromis niloticus exposed to 1 μg/mL of Cd and Zn and their mixture for different periods (0, 7, 14, 21 and 28 days). At the end of experimental periods, the activities Na⁺/K⁺-ATPase, Mg²⁺-ATPase and Ca²⁺-ATPase in gill tissues and only Ca²⁺-ATPase activity in muscle tissues were measured. Gill Na⁺/K⁺-ATPase activity generally decreased following single metal exposures, whereas their combinations increased its activity. Gill Ca²⁺-ATPase activity decreased relative to the control at most exposure times for single exposures of Zn and Cd, as well as for the combined exposure. There was no gill Ca²⁺-ATPase activity after 28 days of exposure to Zn and Cd combined. Mg²⁺-ATPase activity was not affected significantly in gill tissue by exposure to Zn and Cd individually or in combination. Muscle Ca²⁺-ATPase activity also decreased significantly following metal exposure, but not as greatly as in the gill tissue. Tissue protein levels were mostly unaffected by metal exposures. This study showed that certain ATPases are highly sensitive to metal exposure whether the metals are essential or non essential, and suggests using gill tissue Na⁺/K⁺-ATPase and Ca²⁺-ATPase as sensitive biomarkers in metal contaminated waters.     

Influence of metal concentrations in food on metal uptake and accumulation in sawfly larvae

Uptake and accumulation of Cd, Cu, Fe, and Zn by sawfly larvae, Dolerus sp, were studied. Larvae were reared under controlled conditions, allowing their uptake of ingested metals to be calculated after exposure to two different doses of metals. After 10 days of exposure, the concentration of Cd was higher than at the start of exposure, whereas concentration of Cu was higher only in the high dose group. In contrast, the Fe concentration decreased during exposure. Concentrations of Zn in the larvae were the same irrespective of the Zn concentrations in the food. Uptake of the metals, quantified in percent of ingested amounts, was 11% for Cd in both low and high dose groups. The uptake of Zn was 26% at the low dose and 12% at the high dose, while that of Cu was 12% and 19%, respectively. There was a loss in both low and high doses of Fe. The amount of a metal taken up by the larvae was correlated with their growth increment. In conclusion, the concentrations of Cd and Cu in plants influence the concentrations of these metals in plant-eating insects more than the Fe and Zn concentrations.     

Tissue Distribution and Correlation Profiles of Heavy-Metal Accumulation in the Freshwater Crayfish Astacus leptodactylus

The present work details the analysis of heavy-metal and metalloid concentrations in exoskeleton, gill, hepatopancreas, and abdominal muscle tissues of 60 crayfish (Astacus leptodactylus) specimens collected from Lake Hirfanl?, a dam lake located in K?r?ehir (Turkey) with a low metal-contamination profile. Concentrations of 11 metals (aluminum [Al], chromium [Cd], manganese [Mn], cobalt [Co], nickel [Ni], copper [Cu], molybdenum [Mo], silver [Ag], cadmium [Cd], mercury [Hg], and lead [Pb]) and a metalloid (arsenic [As]) were measured by inductively coupled plasma–mass spectrometry, and the relative frequencies of the most abundant isotopes of Cr, Cu, Ag, Cd, Hg, and Pb were evaluated. Three correlation trends were evaluated between the following: (1) different elements in the each individual tissue, (2) individual elements in different tissues, and (3) different elements in different tissues. In addition, correlation rates of growth parameters (weight, cephalothorax length, and total length) with heavy-metal and metalloid concentrations in each tissue were investigated. Our results suggest that substantial differences in metal and metalloid-accumulation levels exist between male and female specimens, with stronger correlations between the heavy-metal concentrations observed in the male cohort. It is notable that correlation trends of Co, Cu, ⁵²As, Cr, and Ni in exoskeleton of the male specimens display strong similarities. Likewise, a very strong correlation is present in Ni–Cd and Ni–Pb accumulations in abdominal muscle of the male specimens; a similar trend is present between Cd and Pb concentrations in the same tissue of female specimens. For correlation rates of different heavy metals and metalloid in different tissues, the strongest positive association observed was between ⁶³Cu in gill and As in hepatopancreas, whereas the strongest negative correlation was between accumulated Ni in abdominal muscle and As in exoskeleton. Strong correlations between metals and metalloid accumulations were observed between exoskeleton and gill. In many cases, metal and metalloid accumulation was negatively correlated with growth parameters. Preferential accumulation of Cr and Cu isotopes was observed in different tissues, suggesting that significant amounts of isotope fractionation occur during heavy-metal accumulation. Relatively low correlation rates were observed between ⁵²Cr/⁵³Cr and ⁶³Cu/⁶⁵Cu concentrations in several tissue types in both male and female cohorts, whereas no such trend was observed between Cd and Pb isotopes.     

Interclonal variation of heavy metal interactions in Salix viminalis

In the complex chemistry of soil, interactions between metals can be expected and these affect the uptake of the metals by the plants. The role of the metal-metal interaction may vary between different plants. This study was performed to investigate if variations exist in the interactions between Cd, Cu, and Zn on toxicity and accumulation of these metals in different clones of Salix viminalis. Two studies were performed. First, to study interaction at uptake, 10 clones with high or low accumulation capacity of Cd, Cu, and Zn, respectively, were treated with 0.3 microM Cd, 0.1 microM Cu, and 3 microM Zn (all three metals at the same time or separately). Second, to study the effect of one of the metals on the sensitivity of the plant to the other metals, three clones with high or low sensitivity to each of the three metals were used in a modified Weibull analysis. Examination of the results shows that interclonal variation exists in effects of metal interaction on metal accumulation and sensitivity exists. The uptake experiment showed that accumulation of Cu was decreased by the other metals, but only in clones with high Cu-accumulating properties because of decreased net uptake of Cu. The accumulation of Zn in roots was increased two- to threefold in all clones in the presence of the other metals because of a decreased translocation of Zn to the shoot. The accumulation of Cd was not changed by the presence of the other metals in any of the clones. The second experiment showed that the effect of interactions between the different metals on metal toxicity was present in all clones but appeared most frequently in the clone with high Zn resistance. Synergistic effects between Cu and Zn in the Zn-resistant clone suggested that this clone had evolved an additional site of toxic action that was absent in the other clones.     

Effect of Cd or Pb Addition to Cu-Contaminated Soil on Tissue Cu Accumulation in the Earthworm,Dendrobaena veneta

Generally, soil heavy metal contamination consists of a mixture of heavy metals. Soil chemical properties and interaction with other pollutants in soil affect the external heavy metal bioavailability. Moreover, interaction with other pollutants accumulated in organisms may change the toxicity of each pollutant. Therefore, the hypotheses was tested that addition of Cd or Pb to Cu-contaminated soil would lead to an increase in tissue Cu accumulation in the earthworm,Dendrobaena veneta,caused by (i) induction of metallothionein by Cd, or (ii) an increase in Cu concentration in soil solution due to the exchange of adsorbed Cu for Pb. Tissue heavy metal concentrations were determined after exposure in contaminated soils for 3 or 21 days. Considerable amounts of Cu, Cd, and Pb were accumulated, indicating that these heavy metals were available for uptake byD. veneta.Both Cd and Pb, however, did not significantly affect tissue Cu accumulation.     

Accumulation of metals and histopathology in Oreochromis niloticus exposed to treated NNPC Kaduna (Nigeria) petroleum refinery effluent

Accumulation of heavy metals and histopathology were observed in Oreochromis niloticus exposed to treated petroleum refinery effluent from the Nigerian National Petroleum Corporation, Kaduna. Analysis of fish metal burden showed that the fish concentrated trace metals a thousand times above the levels existing in the exposure medium. Some metals were preferentially accumulated more than others and the accumulation was, in decreasing order, Pb, Fe, Zn, Cu, Mn, Cr, Ni, and Cd. Whole fish metal burden was lower in fish from which the gill, liver, and kidney had been removed, suggesting that these organs accumulated the metals more than other tissues. Hemorrhaging of fins was observed in all treatment concentrations except that of the control, and fish exposed to 40 and 50% effluent were most affected. Erosion of the caudal fin was also observed in fish exposed to 40 and 50% effluent. Examination of the organs for histopathology revealed damages to the gills. Gills with edematous fused lamellae congested with blood were observed. No histopathological damage was observed in the liver and kidney. The extent of metal accumulation and histopathological damage were directly related to the effluent concentrations.     

Physiological Responses of Hybrid Striped Bass to Aqueous Copper in Freshwater and Saltwater

Copper (Cu) is an abundant trace metal, and although essential at low levels, it is also potentially toxic to aquatic organisms. Mechanisms of toxicity and consequences of exposure vary depending on ionoregulatory status (acclimated to freshwater or salt water). The goal of this research was to examine the responses of hybrid striped bass (Morone chrysops × Morone saxatilis) exposed to Cu in freshwater and 15 g/L salt water. In freshwater, a general dose- and time-dependent pattern of increasing Cu accumulation in gill tissue was evident in fish exposed to aqueous Cu (220 and 447 mg/L) for up to 96 hours. The 96-hour acute median lethal concentration for freshwater-acclimated hybrid striped bass exposed to Cu was 94 mg/L (confidence interval = 62 to 144 mg/L). Plasma osmolality and Na⁺ concentrations decreased in Cu-exposed fish. Freshwater-acclimated hybrid striped bass exposed to aqueous Cu (60 mg/L) for 3 weeks decreased in mass and accumulated Cu in gill, intestine, and liver. In salt water, no mortality occurred, and there were no statistical differences in growth, tissue Cu, or plasma ion concentrations in hybrid striped bass exposed to Cu compared with control fish. Freshwater-acclimated hybrid striped bass were very sensitive to Cu exposure and exhibited responses typical of commonly tested teleost fishes; however, the same sensitivity was not observed in salt water–acclimated fish. An erratum to this article is available at .     

Bioaccumulation of heavy metals in mullet (Mugil cephalus) and oyster (Crassostrea madrasensis) from Pulicat lake, south east coast of India

The accumulation of six heavy metals (Cr, Cd, Cu, Zn, Pb and Ni) in sediment, water and in tissue parts of Mugil cephalus and Crassostrea madrasensis was studied in two locations of Pulicat lake, Southeast coast of India, which receives considerable quantity of effluents from industries located in North Chennai coastal region. The results reveal that the metal concentration in water is decreasing in the following order of Zn > Ni > Cu > Cr > Pb > Cd both in lake and barmouth and highest concentration was observed for Zn (32.5 μg L(-1) in lake and 25.2 μg L(-1) in bar mouth). Metals were highly concentrated in sediments when compared to water and biota. Metals abundance in sediments has following sequential order of Cr > Ni > Zn > Cu > Pb > Cd and the accumulation pattern in barmouth showed minor variation indicating the following pattern of Zn > Ni > Cr > Cu > Pb > Cd. The geoaccumulation index (I(geo)) for Pulicat lake sediments indicate that the sediments are extremely contaminated with Cd and moderately contaminated with Cu and Ni. Bioaccumulation of heavy metals in Mugil cephalus and Crassostrea madrasensis showed marked differences in the accumulation patterns. It is observed that Zn, Cu and Pb are accumulated in elevated concentrations in various parts of the fish and oyster when compared with other metals.     

Effect of Chronic Sublethal Exposure of Major Heavy Metals on Filtration Rate, Sex Ratio, and Gonad Development of a Bivalve Species

The chronic toxic effects of major heavy metals including copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) on the filtration rate (FR), sex ratio, and gonad development of immature blood clams, Tegillarca granosa, were investigated. The FRs were significantly inhibited by Cu, Pb and Cd, with rates generally decreasing with both increasing metal concentrations and exposure time. EC₅₀ values for FR after 28 days of exposure were 12.9, 12.7 and 14.4 μg/L for Cu, Pb and Cd, respectively. Zn exposure had no effect on FR. Sex ratios were significantly altered from controls in favor of an increased proportion of males at metal concentrations of ≥14.2, ≥86 and ≥110 μg/L for Cu, Pb and Cd, respectively; and at ≥1.68 mg/L for Zn. The gonado-somatic index was significantly reduced in clams at all metal exposures, except for the lowest concentration of Cu (7.1 μg/L).     

Heavy Metals in Livers of Waterbirds from Spain

Wetlands tend to accumulate heavy metals from local sources, such as Pb shot used for waterfowl hunting, and from regional sources, such as atmospheric deposition and riverine or marine inputs. We determined concentrations of six heavy metals (Cr, Mn, Cu, Zn, Cd, and Pb) in livers of waterbirds shot by hunters in five Spanish wetlands to study the different factors that can contribute to the accumulation of these metals (sex, age, diet, grit, and Pb shot ingestion). Differences among wetlands were observed only for Cr, Cu, and Cd. Differences among species were observed for all the metals, and Cu was notably higher in pochards (Aythya and Netta genus) than in other waterfowl. Cu, Zn, and Cd concentrations increased with age, and only Pb showed differences related to sex, with males having higher concentrations than females. Most metals other than Pb were correlated with each other. Lead was dependent on Pb shot ingestion. Grit ingestion positively correlated with concentrations of Cr and to a lesser extent with Mn, Zn, and Cd. Ingestion of grit or shot may obscure relationships between metals and diet. Herbivorous species, which had more grit in the gizzard, had higher Cr, Zn, and Cd concentrations. Granivorous birds, which have the highest rates of Pb shot ingestion, had the highest concentrations of Pb. Grit and Pb shot ingestion are both important sources of heavy metals for waterbirds. Lead was the single metal studied whose concentrations exceeded toxicity thresholds. Received: 5 March 2002/Accepted: 12 June 2002     

Individual and Combined Effects of Heavy Metals on Serum Biochemistry of Nile Tilapia Oreochromis niloticus

Changes in serum biochemistry in response to single- and combined-metal exposure were studied in a freshwater fish Oreochromis niloticus. Fish were exposed to 5.0 mg/L Zn, 1.0 mg/L Cd, and 5.0 mg/L Zn+1.0 mg/L Cd mixtures for 7 and 14 days to determine levels of biochemical parameters and metals in blood serum. The individual and combined effects of metals caused an increase in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and in levels of albumin, transferrin, ceruloplasmin, cortisol, glucose, and total protein, whereas they caused a decrease in cholesterol levels. At both exposure periods, increased ALT activity of fish exposed to Cd was higher compared with the Zn and Zn+Cd groups, respectively. The decreased cholesterol level was higher in the Cd alone, and for Cd in combination with Zn, than in Zn alone at 14 days. Zn or Cd levels increased in the blood serum of fish exposed to metals individually or in combination. When fish were exposed to the mixtures of Zn+Cd, concentrations of these metals in their serum were lower than in fish exposed to individual metals. One metal blocks or even antagonizes the gill epithelium absorption of the other and thereby limits the distribution of the metal in blood. The results indicate that biochemical parameters in fish blood can be used as an indicator of heavy-metal toxicity.     

Effects of heavy metals on production of thiol compounds and antioxidant enzymes in Agaricus bisporus

In a pre-experiment, Agaricus bisporus mycelia grown in PDL medium were found to have a substantial ability to tolerate and accumulate heavy metals. In the study, we investigated changes in the contents of soluble protein and thiol compounds as well as the activities of antioxidant enzymes caused by copper, zinc, lead, and cadmium (nitrate salts) in mycelia of A. bisporus during short-and long-term exposure. Results showed that high-level metal concentrations significantly decrease the contents of soluble protein after long-term exposure, Cu and Zn concentrations significantly increase the thiol compounds levels after long-term exposure, while high-level Cd significantly decrease thiol compounds after long-term exposure. Additionally, SOD activities were significantly increased after long-term exposure to metals, especially to Cd. The CAT activities were enhanced after long-term exposure to low-level Cu and high-level Zn, and enhanced after short-and long-term exposure to high-level Pb. The POD activities were significantly increased after long-term exposure to metals, and increased after short-term exposure to Cd and high-level Pb.     

Relationships between surface-bound and internalized copper and cadmium and toxicity in Chlamydomonas reinhardtii

In the present study, the adsorption and uptake of copper (Cu) and cadmium (Cd) in Chlamydomonas reinhardtii were examined to establish fundamental toxicity relationships to glutathione and cell-growth endpoints. Establishing these fundamental relationships of metal accumulation and toxicity metrics is necessary to subsequently implement an algal biotic ligand model. The glutathione response was similar to the response measured from growth endpoints for both internal and adsorbed Cu, indicating that glutathione may be a useful biomarker of toxicity. The glutathione response with Cd contrasted markedly with that observed with Cu and was therefore observed to be a metal-specific biomarker. The density of sites binding metals and the related stability constants for the algal cell surface were also determined. Short exposures to metals (2 h) were conducted, and we determined 6.0 × 10(-6) mol/g sites binding Cu and 2.0 × 10(-6) mol/g sites binding Cd and conditional stability constants as log K' = 7.2 and log K' = 6.7 for Cu and Cd, respectively. Experiments were also conducted to determine the effect on toxicity endpoints of varying nitrate concentrations and different humic acids (HA) in the exposure media. Varying nitrate concentrations did not have an effect on cell growth over 24 h. The surface-adsorbed Cu measurements from the experiments with HA depended on the type and concentration of HA.     

Comparison of different biological methods for the assessment of ecotoxicological risks

To test the effects of heavy metals in river water, we compared the sensitivity of seven different biological test methods, using bacteria (Vibrio fischeri), human FL cells, protozoans (Paramecium spp.), nematodes (Rhabditis oxycerca), aquatic plants (Lemna minor), and fishes (Leuciscus idus melanotus). As test substance we used a representative mixture of 3.0 microg/l As, 2.5 microg/l Pb, 0.8 microg/l Cd, 1.7 microg/l Cr, 3.9 microg/l Cu, 6.7 microg/l Ni, 0.4 microg/l Hg, and 23.0 microg/l Zn, imitating the detectable heavy metal contamination of the Odra estuary (NE Germany/NW Poland). This mixture was defined as normal concentration (NC). Most sensitive was the test with L. minor (exposure time 10 d). The plants already showed phytotoxic effects at the heavy metal concentration found in the Odra estuary. Test systems with human cells, protozoans, and nematodes (exposure time 1-7 d) reacted at concentrations 85-100 times above the NC. Fish toxicity (exposure time 2 d) occurred from 130-fold concentration upwards. In contrast, the standard test carried out with luminescent bacteria (exposure time 30 min) was affected only at > 1000-fold concentrations. This test is therefore not suitable as an early warning system to detect ecological risks. Even the NC of heavy metals measured in the Odra estuary inhibits cells and the growth of aquatic plants. Of the single heavy metals tested, copper produced the strongest effects. Therefore, the reduction of heavy metal emissions, especially of copper-which can amplify the toxicity of other heavy metals-should be a task of highest priority.     

A kinetic model for the relative contribution of waterborne and dietary cadmium and zinc in the common carp (Cyprinus carpio)

In this work, the uptake and whole-body accumulation of Cd and Zn by the common carp from water, diet, and a combination of both was studied using the radioactive tracers 09Cd and 65Zn. A three-compartment pharmacokinetic model was constructed and revealed metal- and exposure route-dependent accumulation profiles. Under the tested exposure conditions in water (0.1 microM Cd and 1 microM Zn), only 0.1 and 0.07%, respectively, of the total Cd and Zn load that passed the branchial surfaces was accumulated by the carp. In contrast, the carp accumulated 20 and 29% of the total ingested Cd and Zn load (mean concentrations in food of newly accumulated metals were 2.24 +/- 0.29 and 19.91 +/- 2.89 nmol/g wet weight, respectively). However, the contribution of the waterborne metals to the whole-body metal accumulation was higher than the metal uptake from food. The constructed model was used to simulate the effect of variable assimilation efficiency (AE) values on the relative importance of dietary Cd and Zn exposure to the overall metal accumulation in common carp. This simulation was performed under a realistic exposure scenario and with Cd and Zn AE values ranging from 5 to 95%. Dissolved Zn levels were higher and Cd levels lower compared to the laboratory experiments. Levels in the midge larvae were much higher. The results show that under these conditions, even at the lowest Cd and Zn AEs, almost 40% of the total body Cd and Zn concentrations originated from dietary Cd and Zn exposure. Taking into account the Cd and Zn AE of the laboratory experiments, respectively, 31 and 55%, more than 85% of the total body Cd and Zn was taken up from the food.