Effects of selected PAHs on reproduction and survival of the calanoid copepod <Emphasis Type="Italic">Acartia tonsa</Emphasis>

The effects of selected polycyclic aromatic hydrocarbons on the marine calanoid copepod Acartia tonsa were tested in laboratory short-term toxicity tests in order to facilitate risk assessment of those compounds to the marine pelagic environment. Photo-induced toxicity of pyrene was also investigated under naturally relevant UV light regimes. Lethal and sublethal effects on egg production rate, hatching and potential recruitment rate were evaluated after 48 h exposure to fluoranthene, phenanthrene and pyrene. The 48 h-median lethal concentrations (LC₅₀) reducing survival by 50% were 594, 2,366 and >640 nM for fluoranthene, phenanthrene and pyrene, respectively, whilst lower concentrations induced different sublethal effects. Median effective concentrations (EC₅₀) affecting the egg production rate and the recruitment rate were 433 and 385 (fluoranthene), 1,245 and 1,012 (phenanthrene) and 306 and 295 nM (pyrene), respectively. An increase in toxicity of pyrene was detected after incubation under UV light, resulting in LC₅₀ values of 201 nM (24 h) and 138 nM (48 h) and EC₅₀ values of 79 nM (egg production rate) and 41 nM (recruitment rate). Finally, a comparison between effective concentrations and worst-case environmental concentrations reported in literature indicated that pyrene may pose a threat to A. tonsa from exposure in the field, and that the risk of adverse effects is high for fluoranthene.     

Metallothionein mRNA Expression and Cadmium Tolerance in Metal-stressed and Reference Populations of the Springtail <Emphasis Type="Italic">Orchesella cincta</Emphasis>

Metal contamination in soil ecosystems is a permanent and often strong selection pressure. The present study investigates metal tolerance in 17 Orchesella cincta (Collembola) populations from metal-contaminated and reference sites, and combines analyses at the phenotypic and molecular level. Metal tolerance was phenotypically assayed by measuring survival times of laboratory cultures during exposure to cadmium. Comparisons of survival curves showed that five out of eight metal-stressed populations tested evolved increased cadmium tolerance (Stolberg, Plombieres, Hoboken, Hygum and Gusum). In addition, the role of the metallothionein (MT) gene in cadmium tolerance of O. cincta was studied by means of quantitative RT-PCR. The constitutive and Cd-induced MT mRNA expression of the laboratory cultures was measured. Results show that the mean constitutive MT mRNA expression of populations from polluted sites was significantly higher than of populations from reference sites. However, no correlation between MT mRNA expression levels after laboratory exposure to cadmium and field cadmium concentrations was observed. Furthermore, no relation between survival rate during exposure to cadmium and MT mRNA expression was detected. Our results suggest that constitutive MT mRNA expression plays a role in early protection against cadmium toxicity, and indicate that mechanisms other then MT up-regulation are involved in tolerance to prolonged exposure to cadmium.     

Detection of exposure effects of mixtures of heavy polycyclic aromatic hydrocarbons in zebrafish embryos

In this study we evaluated the exposure effects of mixtures of five polycyclic aromatic hydrocarbons (PAHs); namely, benzo[a ]anthracene, benzo[a ]pyrene, benzo[b ]fluoranthene, benzo[k ]fluoranthene and chrysene on zebrafish embryos. Supplementation of the exposure media with 0.45% dimethyl sulfoxide and 50 ppm of Tween 20 could guarantee the solubilization and stabilization of the PAHs up to 24 h without affecting the embryos development. The exposure effects were tested by detecting the differential expression of a number of genes related to the aryl hydrocarbon receptor gene battery. Effects were detectable already after 6 h of exposure. After 24 h of exposure, all PAHs, except for benzo[a ]anthracene, acted as potent inducers of the gene cyp1a1 . Benzo[k ]fluoranthene was the major inducer; the effect caused by the mixture at the lower concentration tested (1 ng ml⁻¹) was dominated by its presence. However, in the mixture at the highest concentration tested (10 ng ml⁻¹) it caused less induction and was not dominant. No significant bioaccumulation values were detected on embryos exposed to the PAHs tested in this study; however, the results obtained, indicated that PAHs undergo a very rapid metabolization inside the embryos, and that those biotransformation products yield changes on the expression of genes involved in the aryl hydrocarbon receptor pathway. Future work should focus on identification of the PAH metabolization products and on the effect of these metabolites on toxicity. Copyright © 2016 John Wiley & Sons, Ltd.     

In vivo and in vitro percutaneous absorption of [<Superscript>14</Superscript>C]pyrene in Sprague Dawley male rats: skin reservoir effect and consequence on urinary 1-OH pyrene excretion

The skin reservoir effect of [¹⁴C]pyrene (in vivo and in vitro) on percutaneous absorption was determined in male Sprague Dawley rats. The urinary 1-OHpyrene (1-OHPy) excretion was compared between dermal exposure and intravenous administration. In vivo, the percutaneous absorption flux of [¹⁴C]pyrene (200 μg/cm²; 50 μL/cm² of ethanol) determined by sacrificing batches of rats after different exposure times over 4.5 h was 1.0 ± 0.1 μg/cm² h⁻¹. During exposure, penetration flux was twofold higher than absorption flux, indicating a gradual accumulation of pyrene in the skin. [¹⁴C] skin content at the end of exposure was 16 μg/cm², which decreased gradually over time to 2 μg/cm² 68 h after the end of exposure. The total absorbed dose during exposure was threefold lower than that after exposure, indicating a high contribution of pyrene skin content to the systemic availability of the compound. Similar results were obtained in vitro. The apparent elimination rate of [¹⁴C]pyrene (23 h) contained in the skin after an exposure of 4.5 h was similar to the apparent urinary excretion half life of 1-OHPy (21 h). These values are threefold higher than the urinary excretion half life of 1-OHPy after an intravenous administration of pyrene (0.5 mg/kg). In conclusion, absorbed dose and percutaneous absorption flux were well estimated from the 1-OHPy urinary excretion rate. For risk assessment purposes, the penetration flux rather than the absorption flux should be taken into account for topical pyrene exposure.     

Acute toxicity to Daphnia magna of effluents containing Cd,Zn, and a mixture Cd‐Zn,after metal removal by Chlorella vulgaris

Daphnia magna was used as a test organism for assessing the toxicity remaining in simulated effluents containing cadmium, zinc, and a cadmium‐zinc mixture, after these metals were removed with suspended and immobilized Chlorella vulgaris cultures. The percentage of removal was higher (84.7%) for cadmium in the metal mixture with immobilized cultures. The LC₅₀ value was lower for the residual cadmium (single and in the mixture) in the effluent after treatment with suspended cultures. The acute toxicity response observed in D. magna, indicates that zinc has an antagonistic effect on cadmium toxicity. According to the results, the treatment system can modify the Cd acute residual toxicity. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 160–164, 2000<     

The interaction effects of toxic chemical combinations on chlorella ellipsoidea

The hazardous chemicals that have been released into the aquatic environment may disturb the balance of the aquatic ecosystem. Chemicals do not exist in single pure form, but occur in mixtures in the environment. Consequently, their effects on organisms living in the aquatic environment are primarily due to the combined toxicities. In this study, the interaction effects between chemicals such as copper, cadmium, chromium and pentachlorophenol on the growth of green algae Chlorella ellipsoidea, were investigated using a batch culture. Growth rate was a more sensitive index than standing crop at a given time for detecting the toxicity of chemicals. The EC₅₀ values obtained from dry weight, were higher than those obtained from ATP, chlorophyll-a, chlorophyll-b, carotenoid as growth indices for algal density. The toxicity of each chemical was dependent on the test period. The inhibition rate of PCP and Cu in comparison with the control for the exposure time of 24 hours was higher than that for the exposure time of 48 hours. The inhibition rate of Cr and Cd for 48 hours was higher than that for 24 hours. The toxic intensity of chemicals was, in order, PCP, Cu, and Cr, without exception. The toxicity of Cd was changeable depending upon the indices used. The method modified by Stratton (1983) and the isobologram method were used to determine the modes of interaction effects of the chemical combinations. These two methods led to the same results, with three exceptions. A synergistic effect was observed for combinations between Cr and PCP, between Cu and Cd, and between Cu and Cr; while an antagonistic effect was observed for combinations between Cd and PCP, between Cu and PCP, and between Cd and Cr within some concentration ranges.     

Impact of dietary cadmium sulphide nanoparticles on Danio rerio zebrafish at very low contamination pressure

To address the impact of cadmium sulphide nanoparticles (CdSNPs) of two different sizes (8 and 50 nm), Danio rerio zebrafish were dietary exposed to very low doses: 100 or 40 ng CdSNPs/day/g body weight for 36 or 60 days, respectively. The results obtained using RAPD-PCR genotoxicity test showed genomic alteration since the number of hybridisation sites of the RAPD probes was significantly modified after CdSNPs exposure. In addition, selected stress response genes were either repressed or upregulated in tissues of CdSNPs-exposed fish. Mitochondrial dysfunction was also caused by the presence of CdSNPs in food. Cadmium accumulation in fish tissues (brain and muscles) could only be observed after 60 days of exposure. CdSNPs toxicity was dependent on their size and concentration.     

Cyanobacterial LPS potentiates cadmium toxicity in zebrafish (Danio rerio) embryos

Cyanobacteria are prevalent in the freshwater environment, reaching critical mass in harmful algal blooms. These organisms produce a variety of toxins including endotoxins such as lipopolysaccharides (LPS), which have been previously shown to decrease glutathione‐S‐transferase (GST) activity in zebrafish (Danio rerio) embryos. GST plays a vital role in detoxification response during oxidative stress and provides a first line of defense after toxic heavy metal insult, before increased metallothionein expression. Although some attention has focused on cyanobacterial LPS, little research has focused on effects of concurrent exposures with other toxicants. Because cyanobacterial LPS can alter detoxification enzymes including GST, we hypothesized that cyanobacterial LPS could potentiate metal toxicity. This study investigated the effects of LPS from two cyanobacterial species, Lyngbya spp. and Microcystis aeruginosa, on cadmium toxicity in zebrafish embryos. Forty‐eight‐hour CdCl₂ LC₅₀ values showed that coexposure of cadmium and Lyngbya LPS or Microcystis LPS resulted in significantly increased cadmium toxicity in comparison with cadmium alone. However, increased cadmium toxicity was not due to decreased GST activity as initially hypothesized. In concurrent Microcystis LPS‐cadmium exposures, GST activity was significantly increased in comparison with control embryos at all time points and cadmium concentrations sampled. Concurrent Lyngbya LPS‐cadmium exposures also resulted in increased GST activity at most exposure concentrations. These results indicate that regardless of mechanism, cyanobacterial LPS can potentiate the toxic effects of heavy metals. This represents a significant risk for aquatic organisms exposed to combinations of LPS and metals in the environment. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

The effects of pulse‐exposed cadmium and zinc on embryo hatchability,larval development,and survival of Australian crimson spotted rainbow fish (Melanotaenia fluviatilis)

Effects of 2 h pulse‐exposure of cadmium or zinc on early life stages of Australian crimson spotted rainbow fish (Melanotaenia fluviatilis) were investigated. Ages of embryos used in experiments were 3, 46, and 92 h old. Measured end points included percentage hatch, day of hatch, larval survival time, and spinal deformities. There was a significant concentration‐response of both metals on percentage hatch and spinal deformities. The 3‐h‐old embryos had highest percentage of deformities with 27% for embryos pulse‐exposed to both 3.3 mg/L of cadmium and 33.3 mg/L of zinc. Cadmium 2 h peLC50 (SE) values (n=4) for <24‐h‐, 3–4‐day‐, and 9–10‐day‐old larval rainbow fish were 0.13 (0.01), 0.11 (0.01), and 0.56 (0.11) mg/L, respectively. Zinc 2 h peLC50 (SE) values for the same aged rainbow fish larvae were 0.51 (0.03), 0.56 (0.04), and 1.57 (0.22) mg/L, respectively. For both metals, 9–10‐day‐old larvae were significantly more tolerant than younger ages. Within each of the age groups, larvae were significantly more sensitive to cadmium than zinc. Continuous exposure LC50 (SE) values (n=4) using 9–10‐day‐old larvae were 0.01 (0.00) and 0.27 (0.01) mg/L for cadmium and zinc, respectively. Results show that pulse‐exposed metals at moderate concentrations can significantly affect the early life stages of M. fluviatilis through decreasing percentage hatch of embryos, inducing spinal deformities, and having toxic effects on larvae at relatively low concentrations. Thus, the sensitive early life stages of M. fluviatilis are a suitable model for toxicity testing of metals on Australian species of fish. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 165–173, 2000     

Cadmium toxicity: unique cytoprotective properties of alpha tocopheryl succinate in hepatocytes

Rat hepatocyte suspensions were exposed to toxic concentrations of cadmium (Cd) in the presence and absence of unesterified alpha-tocopherol (T) or alpha-tocopheryl succinate (TS). The exogenous administration of TS completely protected hepatocytes from Cd-induced injury and lipid peroxidation. However, hepatocytes exposed to T were not protected from the toxic manifestations of cadmium even though this treatment resulted in a rapid marked accumulation of cellular T. The rate of cadmium uptake by hepatocytes was not significantly altered by exogenous TS or T treatment. These studies indicate that TS cytoprotection against Cd toxicity results not from alterations in Cd uptake or the accumulation of T but rather from the cellular presence of the intact TS molecule. The data also indicate that the depletion of cellular T is not the critical cellular event that is responsible for Cd-induced injury. Instead it appears that TS possess unique cytoprotective properties that intervene in the critical cellular events that lead to Cd toxicity. Thus, TS administration represents a promising new strategy for the mechanistic study and prevention of tissue damage resulting from Cd exposure.     

The effect of vitamin E exposure on cadmium toxicity in mouse embryo cells in vitro

Heavy metals such as cadmium pose a number of environmental problems in addition to being detrimental to human health. Cadmium is known to be embryotoxic in animal models and to cause brain, limb and craniofacial malformations. Among numerous mechanisms proposed for cadmium toxicity are oxidative stress and lipid peroxidation. Vitamin E has been found to have antioxidant and cytoprotective properties in cultured cells but its effect on cadmium embryonic toxicity has not yet been determined. Epithelial-like cells derived from day-8 whole-mouse embryos were used as a model embryonic tissue. Cadmium toxicity in these cultured cells was found to be both time and concentration dependent. Prior exposure to 50 microM alpha-tocopherol or 25 or 50 microM alpha-tocopherol acetate resulted in a marked reduction in the toxicity of 5 microM CdCl2. The apparent cytoprotective effects may be partly non-specific, however, as a general growth enhancement was observed after vitamin E exposure in the absence of cadmium.     

Toxicity prediction of binary combinations of cadmium, carbendazim and low dissolved oxygen on Daphnia magna

Environmental contamination is often characterised by a combination of stress factors of various sources (biological, physical and chemical). The predictability of their joint effects is an important stage in environmental risk assessment procedures. In this study, the two main conceptual models for mixture evaluation based on the effect of individual compounds, concentration addition (CA) and independent action (IA) and deviations to synergism/antagonism, "dose ratio" and "dose level" dependency were used. The single and combined effects of cadmium, carbendazim and low dissolved oxygen levels were assayed for life-cycle parameters (survival and feeding) of the water flea Daphnia magna Straus. The results of single exposures revealed an increase of acute and chronic toxicity as concentrations of cadmium and carbendazim increases. At low dissolved oxygen levels both survival and feeding parameters were significantly affected (P< or =0.05). In the acute mixture exposure of cadmium and carbendazim a "dose ratio" dependency was observed with a higher toxicity when cadmium was dominant whereas at high concentrations of carbendazim a lower effect on survival was observed. At chronic exposures an antagonistic deviation from IA model was observed for this mixture. The IA model showed to be adequate for toxicity prediction on acute exposure combinations with low DO levels where a synergistic behaviour was observed. However, at sublethal exposures IA and CA models failed by underestimation. Validation from toxicokinetic and toxicodynamic modelling studies should be made in the future as a way to understand toxicological pathways involved in complex mixture/combination exposures.     

The influence of humic acid on the toxicity and bioavailability of selected trace metals

The influence of humic acid (HA) on the toxicity and bioavailability of hexavalent chromium and cadmium was evaluated using a common freshwater invertebrate, Daphnia pulex. The 0.5, 5.0 and 50 mg HA/l concentrations had little influence on either the acute toxicity or the bioavailability of hexavalent chromium. The acute toxicity of cadmium was increased, decreased or not influenced by HA, depending on the concentration of HA and the time point examined. There was a dose-related pattern of binding (a maximal decrease in percent free cadmium followed by metal release from HA) observed with HA and cadmium. The release of cadmium from the HA may have resulted from an associated time dependent decrease in pH.     

Protective effects of puerarin against tetrabromobisphenol a‐induced apoptosis and cardiac developmental toxicity in zebrafish embryo‐larvae

Tetrabromobisphenol A (TBBPA), a brominated flame retardant, is detected commonly in aquatic environments, where it is thought to be highly toxic to the development of aquatic life. In this study, zebrafish embryos and larvae were used to investigate the protective effects of puerarin after exposure to TBBPA. Malformation, blood flow disorders, pericardial edema, and spawn coagulation rates increased, whereas survival decreased significantly after exposure to 0.5 and 1.0 mg L^?1 TBBPA. The measured indices of morphological toxicity improved after treatment with puerarin. TBBPA also induced reactive oxygen species (ROS) production in a dose‐dependent manner. Acridine orange staining results revealed that TBBPA exposure caused cardiomyocyte apoptosis and induced the expression of three proapoptotic genes: P53, Bax, and Caspase9. In contrast, the expression of the antiapoptotic gene Bcl2 was down‐regulated. When genes related to cardiac development were assessed, the expression of Tbx1, Raldh2, and Bmp2b changed after exposure to the combination of TBBPA and puerarin. These results suggest that TBBPA induces cardiomyocyte apoptosis and ROS production, resulting in cardiac developmental toxicity in zebrafish embryos or larvae. Therefore, puerarin regulates the expression of cardiac developmental genes, such as Tbx1, Bmp2b, and Raldh2 by inhibiting ROS production, and subsequently modulates cardiac development after the exposure of zebrafish larvae to TBBPA. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 1014–1023, 2015.     

Consequences of inbreeding and reduced genetic variation on tolerance to cadmium stress in the midge Chironomus riparius

Inbreeding and loss of genetic variation are considered to be major threats to small and endangered populations. The reduction of fitness due to inbreeding is believed to be more severe under stressful environmental conditions. We generated nine strains of the ecotoxicological model organism Chironomus riparius of different inbreeding levels in order to test the hypothesis that the inbreeding level and thus the degree of genome-wide homozygosity influences the life-history under cadmium exposure. Therefore, midge populations were exposed to a gradient of sediment-bound cadmium. The level of genetic variation in the used strains was assessed using microsatellite markers. In the life-cycle tests, inbreeding reduced fitness within C. riparius populations both under control and stressed conditions. However, differences between genetically diverse and impoverished strains were greatest at high cadmium exposure. Overall, inbreeding effects were not only dependent on cadmium concentrations in the sediment, but also on the life-history trait investigated. While some parameters where only affected by inbreeding, others were altered by both, inbreeding and cadmium. For the larval developmental time, a significant interaction was found between inbreeding and cadmium stress. While all strains showed a similar developmental time under control conditions, high rates of inbreeding led to a significantly delayed emergence time under high cadmium concentrations, resulting in longer generation periods and reduced population growth rates as population-relevant effects. The results show, that bioassays with C. riparius are affected by the level of inbreeding within Chironomus test strains. Pollution stress is therefore likely to affect the survival of rare and endangered populations more severe than that of large and genetically diverse ones.     

Inducibility of metallothionein biosynthesis in the whole soft tissue of zebra mussels Dreissena polymorpha exposed to cadmium,copper, and pentachlorophenol

Freshwater mussels Dreissena polymorpha (Pallas, 1771) were exposed to the elevated concentrations of Cd (10, 50, 100, and 500 μg/L), Cu (10, 30, 50, and 80 μg/L), and an organochlorinated pesticide, pentachlorophenol (PCP) (1, 10, and 100 μg/L). Induced synthesis of biomarker metallothionein (MT) and changes in concentrations of cytosolic Cd, Cu, and Zn in the whole soft tissue of mussels were monitored after a 7‐day laboratory exposure to the contaminants. A clear dose‐dependent elevation in the MT concentration was observed after exposure to Cd at doses of 10–100 μg/L, and this increase of MT content was accompanied with a linear increase of cytosolic Cd. Cd concentration of 500 μg/L caused no additional increase of MT and Cd in mussel cytosol, suggesting possible toxic effects due to exceeding cellular inducible/defense capacity. Cu exposure resulted with variable changes in MT concentrations, with no clear linear relationship between MT and Cu concentrations in water, although a progressive dose‐dependent accumulation of Cu in the soluble fraction of mussel tissues was recorded. A decrease of cytosolic Zn was evident at higher exposure concentrations of both metals used. PCP in concentrations applied was unable to induce MT synthesis, but the higher concentrations of PCP influenced the cytosolic metal concentrations. In conclusion, the results obtained confirm the specificity of MT induction in D. polymorpha as an biological response on metal stimulation, especially by cadmium, being more closely correlated to MT than copper within the ecologically relevant concentration range. The strong induction potential of cadmium as well as an absence of MT induction following exposure to PCP as an organic chemical contaminant are supporting evidences for usage of zebra mussel MT as a specific biomarker of Cd exposure in biomonitoring programs. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010.     

Sublethal effects in <Emphasis Type="Italic">Perinereis gualpensis</Emphasis> (Polychaeta: Nereididae) exposed to mercury-pyrene sediment mixture observed in a multipolluted estuary

Sediment-living organisms can be subjected to a multi-pollution condition due to an increase in the diversity of contaminants. Sediment mixtures of Mercury (Hg) and some polycyclic aromatics hydrocarbons like Pyrene (Pyr) are common in heavily industrialized coastal zones. In the present study, greater than (>) and less than (<) probable effect concentration levels (PELs) of Hg and Pyr were assessed using spiked sediments in order to determine combined (Hg?+?Pyr) effects in uptake, metabolization and oxidative balance in the polychaete Perinereis gualpensis at short and medium-term exposure. Hg?+?Pyr significantly influenced the uptake/kinetics of Hg and Pyr metabolite 1-OH-pyrene in polychaete tissues during the exposure time compared with separate treatments of each analyte (p?<?0.05). Both the Hg-only and Pyr-only exposures significantly influenced both enzymatic and non-enzymatic responses respect to control groups (p?<?0.05). The Hg-only treatment showed the worst scenario related to the activation and subsequent inhibition of glutathione S- transferase (GST) and peroxidase (GPx) activities, high levels of Thiol-groups (SH-groups), low antioxidant capacity (ACAP) and enhanced lipid peroxidation (TBARS) in the last days of exposure (p?<?0.05). In contrast, ragworms exposed to Hg?+?Pyr showed a significant increase in both enzymatic and non-enzymatic activity during the first days of exposure and the absence of lipid peroxidation during the whole experiment. Our results suggest different oxidative stress scenarios in P. gualpensis when exposed to >PEL Hg concentration with <PEL Pyr in sediments. Results also reveal the importance of the exposure time, endpoints involved as well as of the contaminant monitoring during the whole experiments in assessing the interactive effects of the contaminant mixture.     

Comparison of the toxicity of inorganic and liver-incorporated cadmium: a 4-wk feeding study in rats

The toxicity of cadmium was examined in rats fed diets containing either tissue-incorporated cadmium or cadmium salt for 4 wk. The test diets contained 30 mg cadmium/kg either as cadmium chloride, or as cadmium incorporated in pigs' livers; the control group was fed a diet containing liver from a pig not treated with cadmium. Over 90% of the cadmium present in the pigs' livers was bound to metallothionein. Analysis of the diet and determination of the food consumption revealed that both cadmium-fed groups were exposed to similar dietary cadmium levels. There was no adverse effect on general health or survival. Feeding cadmium resulted in growth retardation and slightly decreased water intake. Moreover, both cadmium-treated groups showed clear signs of anaemia and increased plasma aspartate and alanine aminotransferase activities. For the group fed cadmium chloride, all of these effects were more pronounced than for the group fed cadmium incorporated in liver. Microscopic examination of the liver and kidneys, however, did not reveal any lesion that could be attributed to the cadmium treatment. After exposure to cadmium the spleen showed decreased extramedullary haematopoiesis, an effect that was also more pronounced after feeding of the cadmium chloride than after feeding liver-incorporated cadmium. The differences in the extent of the toxic effects between the inorganic and the tissue-incorporated cadmium were accompanied by differences in the cadmium concentrations in liver and kidneys: the feeding of cadmium incorporated in pigs' livers resulted in about half the accumulation of cadmium in the rats' livers that took place after intake of a diet containing cadmium chloride. In contrast a much less marked difference in cadmium accumulation was observed in the kidneys. Since humans are usually exposed to tissue-incorporated cadmium these findings deserve further investigation, with special attention to the observed difference in tissue accumulation.